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SINGH, SHATRUPA. "AUGMENTATIVE ROLE OF PLANT GROWTH PROMOTING BACTERIA (PGPB) IN MODULATING RESPONSES AGAINST MITIGATION OF SALT STRESS IN TRIGONELLA FOENUM-GRAECUM." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18463.
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An experiment was conducted to evaluate the role of plant growth promoting bacteria (PGPB)
in mitigating salinity stress in Trigonella foenum graecum. Plants were subjected to three
different levels of salinity viz 0, 70 and 150 mM NaCl (electrical conductivity value 0.01, 7.67
and 15.50 mS cm-1
, respectively) using a completely randomized design experiment. PGPB
showed positive effects in mitigation of salinity stress in fenugreek plants and elevated various
growth responses viz. shoot and root length, shoot and root dry weight, leaf area and number
of leaves as compared to uninoculated plants. Microbial inoculation significantly enhanced the
physiological responses viz. photosynthetic rate, stomatal conductance, transpiration and
internal CO2 as compared to uninoculated plants. Biochemical aspects like carotenoids,
chlorophylls, nitrogen and protein content were also increased in the microbial inoculated
plants as compared to uninoculated plants. PGPB was very effective than in mitigating salinity
stress in fenugreek plant. The findings of this study revealed that PGPB inoculation can help
the plants to overcome the deleterious effects of salinity stress in fenugreek plants.
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Hamzaoui, Soufiane. "Heat stress responses in dairy goats and effects of some nutritional strategies for mitigation." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/285552.
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En la presente tesis se han llevado a cabo 4 experimentos con cabras lecheras bajo condiciones de estrés por calor (HS) para medir la respuesta bajo las condiciones de estrés (Exp. 1 y 2) y para evaluar el aceite de soja y el propilenglicol como suplementos alimenticios (Exp. 3 y 4). En los Exp. 1 y 2, 8 cabras lecheras de raza Murciano-Granadina, a final (Exp. 1) y a mitad (Exp. 2) de lactación fueron expuestas a diferentes condiciones ambientales, utilizando jaulas metabólicas en una cámara climática. El diseño experimental fue de efecto cruzado (2 periodos de 28-35 d y 4 cabras por grupo) y las condiciones fueron: 1) temperatura neutral (TN, 15 a 20ºC día-noche) y 2) estrés por calor (HS, 12-h d a 37ºC y 12-h noche a 30ºC). La humedad se mantuvo al 40% y luz-oscuridad fue constante (12-12h). Diariamente, se midió la temperatura rectal, la frecuencia respiratoria (0800, 1200 and 1700 h) y la producción de leche, mientras que la composición de la leche y los parámetros sanguíneos fueron evaluados semanalmente. Se determinó los coeficientes de digestibilidad y el balance N y se registró el comportamiento mediante cámaras de video. Además, se realizaron tratamientos con insulina (4.6 µg/kg BW), epinefrina (2 µg/kg BW) y glucosa (0.25 g/kg BW) y se tomaron muestras de sangre para analizar insulina, NEFA y concentraciones de glucosa. En comparación con las cabras TN, las cabras HS experimentaron una mayor temperatura rectal, frecuencia respiratoria, consumo de agua y evaporación de agua. La ingesta de las cabras HS decreció un 21 y 29% en los Exp. 1 i 2, respectivamente. La leche de las cabras HS mostraron un menor porcentaje de grasa, proteína y lactosa. En comparación a las cabras TN, las cabras HS disminuyeron la concentración y la presión sanguínea del CO2 debido al jadeo y mantuvieron el pH sanguineo al bajar la concentración de HCO3–. Las cabras TN y HS tuvieron niveles similares de NEFA en sangre después de la inyección de insulina, pero después de la administración de epinefrina los valores de NEFA fueron mayores (P < 0.05) en las cabras TN que en las HS. Las cabras HS secretaron menos (P < 0.05) insulina que las cabras TN en respuesta al test de tolerancia de glucosa. Las cabras TN y HS presentaron una similar frecuencia alimentaria, aunque la duración de cada ingesta fue menor en las cabras HS que en las TN. Por otra lado, las cabras HS tuvieron una mayor frecuencia de bebida, aunque no hubo variación en la duración.
En los Exp. 3 i 4, se utilizaron 8 cabras lecheras multíparas a mitad de lactación de raza Murciano-Granadinas en un diseño de cuadrado latino 4 x 4 con 4 periodos de 21 d cada uno (14 d de adaptación, 5 d de medidas y 2 d de transición entre periodos). Las cabras fueron asignadas a 4 grupos con un diseño factorial 2 x 2. Los factores fueron la suplementación o no suplementación con aceite de soja (Exp. 3) y propilenglicol (Exp. 4) en condiciones de TN o HS iguales a lo mencionado en Exp. 1 y 2. Se evaluó la ingestión, la producción lechera, la composición de la leche y los metabolitos sanguíneos. Desde el punto de vista de salud humana, el HS mejoró el perfil de ácidos grasos de la leche debido a la disminución de los ácidos grasos saturados y el aumento de los ácidos grasos monoinsaturados sin afectar la grasa. El aceite de soja incrementó (P < 0.05) las NEFA en sangre en un 50%, la grasa de la leche en un 30% y el ácido linoleico conjugado en un 360%. La respuesta al aceite de soja fue de la misma magnitud en cabras TN y HS. Por el otro lado, la suplementación con propilenglicol aumentó los niveles de glucosa (P < 0.05) e insulina (P < 0.10), pero disminuyó (P < 0.10) la ingestión y la grasa en leche. Además, los niveles de NEFA y BHBA fueron menores en las cabras suplementadas con el propilenglicol.
En conclusion, el HS disminuyó la producción lechera entre un 3 y 10% con una marcada reducción en la proteína de la leche. El tejido lipídico de las cabras HS se volvió insensible a las hormonas lipolíticas, secretando el páncreas menor cantidad de insulina al inyectarle glucosa. El HS no afectó el número de acercamientos al comedero, pero sí redujo su duración. La suplementación con aceite de soja en condiciones HS y TN incrementó de forma similar la grasa de la leche, el ácido trans-vacénico y el ácido linoleico conjugado. Finalmente, el propienglicol incrementó el nivel de glucose e insulina sanguíneo, pero no alteró la proteína de la leche<br>In the current thesis 4 experiments were carried out using dairy goats under heat stress (HS) to measure responses to HS (Exp. 1 & 2) and to evaluate soybean oil and propylene glycol as feed supplements (Exp. 3 & 4). In Exp. 1 & 2, 8 Murciano-Granadina dairy goats in late (Exp. 1) and mid (Exp. 2) lactation were exposed to different ambient conditions, using metabolic cages in a climatic chamber. Experimental design was a crossover (2 periods of 28-35 d and 4 goats each), and conditions were: 1) thermal neutral (TN, 15 to 20°C day-night), and 2) heat stress (HS, 12-h day at 37°C and 12-h night at 30°C). Humidity was maintained at 40% and light-dark was constant (12-12 h). Rectal temperature and respiratory rate (0800, 1200 and 1700 h) and milk yield were recorded daily, whereas milk composition and blood parameters were evaluated weekly. Digestibility coefficients and N balance were determined and behavior was recorded by video cameras. Moreover, challenges with insulin (4.6 µg/kg BW), epinephrine (2 µg/kg BW) and glucose (0.25 g/kg BW) were done and blood samples were collected for the analysis insulin, NEFA and glucose concentrations. Compared to TN goats, HS goats experienced greater rectal temperature, respiratory rate, water intake, and water evaporation. Intake of HS goats decreased by 21 and 29 in Exp. 1 and 2, respectively. Milk of HS goats contained lower fat, protein and lactose. Panting reduced concentration and pressure of CO2 in blood of HS goats, but they were able to maintain their blood pH similar to TN group by lowering HCO3– in blood. The TN and HS goats had similar blood NEFA after insulin injection, but NEFA values were greater (P < 0.05) in TN than HS goats after epinephrine administration. The HS goats secreted lower (P < 0.05) amounts of insulin than TN goats in response to the glucose tolerance test. Furthermore, TN and HS goats had similar eating bouts, but the duration of each bout was lower in HS than in TN. On the other hand, HS had greater number of drinking bouts with no change in drinking bout durations.
In Exp. 3 & 4, 8 multiparous Murciano-Granadina dairy goats at mid lactation were used in a replicated 4 × 4 Latin square design with 4 periods; 21 d each (14 d adaptation, 5 d for measurements and 2 d transition between periods). Goats were allocated to one of 4 treatments in a 2 x 2 factorial arrangement. Factors were supplementation or not with soybean oil (Exp. 3) or propylene glycol (Exp.4, and TN or HS conditions similar to Exp. 1 & 2. Feed intake, milk yield, milk composition, and blood metabolites were evaluated. From the point of view of human health, HS improved milk fatty acid profile by decreasing saturated fatty acids and increasing monounsaturated fatty acids with no effect on milk fat content. The soybean oil increased (P < 0.05) on average blood NEFA by 50%, milk fat by 30%, and conjugated linoleic acid by 360%. The response to soybean oil was with the same magnitude in thermo-neutral and heat stress conditions. On the other hand, the supplementation with propylene glycol increased blood glucose (P < 0.05) and tended to increase (P < 0.10) blood insulin, but dry matter intake and milk fat decreased (P < 0.10). Furthermore, blood NEFA and β-hydroxybutyrate acid decreased (P < 0.05) by propylene glycol.
In conclusion, heat stress decreased milk yield by 3 to 10% with a marked reduction in milk protein. Lipid tissue of heat-stressed dairy goats became insensitive to lipolytic hormones and their pancreas secreted lower insulin when glucose was injected. Heat stress had no effect on eating bouts, but the time of each eating bout was shorter. The supplementation with soybean oil increased milk fat, trans-vaccenic acid and conjugated linoleic acid similarly in thermo-neutral as well as in heat stress conditions. Although propylene glycol increased blood glucose and insulin, no change in milk protein was observed.
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Mian, Afaq Ahmad. "Improving salt stress resistance in cereals." Thesis, University of York, 2010. http://etheses.whiterose.ac.uk/1191/.
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Salinity is a complex environmental stress that affects growth and production of agriculturally important crops world-wide. Tolerance to salt stress is variable for different plants and involves integration of various physiological and biochemical mechanisms. This thesis investigates the role in salt tolerance of various transporter genes in important agricultural cereal crops, i.e. rice and barley. Transgenic lines overexpressing OsTPKa, OsTPKb and OsAKT1 were generated using Agrobacterium mediated rice transformation, while for OsAKT1 a loss of function mutant was also isolated. Transgenic and mutant plants were characterized to study the role of these genes in rice. For barley, transgenic lines overexpressing HvHKT2;1 were obtained and studied for its role in barley salt tolerance. Transgenic rice plants overexpressing TPKa did not show any growth phenotype under salt stress conditions, however, the performance of TPKa overexpressors was better at different K+ stress conditions compared to control lines. In contrast, transgenic lines overexpressing TPKb showed improved growth under all K+ and Na+ stress conditions, suggesting that TPK channels plays a crucial role in K+ nutrition and in maintaining a higher K+/Na+ ratio under different K+ and Na+ stress conditions. Characterization of rice AKT1 mutants and overexpressors showed the involvement of the AKT1 channel in Na+ uptake at low [K+]ext or high [Na+]ext concentrations and both overexpression and loss of function resulted in reduced growth under these conditions. On the other hand, data from experiments with barley HKT2;1 overexpressing lines showed improved growth under salt stress conditions possibly via Na+ exclusion or accumulation of excessive Na+ in the shoots. Overall, the findings point to two important aspects of salt tolerance: firstly, the contribution of TPKa and TPKb to K+ homeostasis, particularly that of TPKb in maintaining ion homeostasis during different K+ and Na+ stress conditions. Secondly, a role of AKT1 and HKT2;1 in Na+ uptake at the root soil boundary is inferred. These findings reconfirm the idea that maintaining a high K+/Na+ ratio is crucial for salt tolerance in both rice and barley. In barley, HvHKT2;1 overexpressors showed improved salt tolerance via Na+ redistribution from shoot to root and accumulation of Na+ in older leaves. The transgenic lines overexpressing TPKs and HKT2;1 and the information gained from this study could be used in future breeding programs or to generate multiple overexpressors to study the additive or synergistic effects of traits that will add to the present knowledge of ion transport in rice and barley.
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Crowley, Cara Leilani. "Bile salt induced stress response pathways." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289231.
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Our lab has shown that the bile salt found in the highest concentration in human fecal water, sodium deoxycholate, induces apoptosis in several cell types including Jurkat cells as well as human colonic epithelial cells. We have also found that cells within the normal appearing flat mucosa of patients with a history of colon cancer are relatively resistant to apoptosis induced by NaDOC. The current studies test the hypothesis that sodium deoxycholate induces multiple stress response pathway s that protect against apoptosis. I have tested this hypothesis by developing and analyzing cell lines that are resistant to sodium deoxycholate-induced apoptosis and focusing on two stress-response proteins known to be activated by sodium deoxycholate, poly(ADP-ribose) polymerase (PARP) and the redo-sensitive transcription factor nuclear factor-kappa B (NF-κB). I found that PARP is protective against NaDOC-induced apoptosis, and by independently inhibiting the individual subunits of NF-κB, I found that the p65 subunit is protective, while the p50 subunit is not. Development and subsequent characterization of the NaDOC-resistant HCT-116 cell lines identified several proteins that may be responsible for the development of apoptosis resistance. These proteins will be further tested in future studies.
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Unruh, Ellen M. "Heat stress detection and mitigation in feedlot cattle." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38179.
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Master of Science in Biomedical Sciences<br>Department of Clinical Sciences<br>Robert L. Larson<br>Bradley J. White<br>Feedlot cattle frequently endure high environmental temperature-humidity index conditions in the summer months within cattle feeding regions of North America. Heat stress develops when the total heat gain (combined effects of environmental and metabolic factors) exceeds an animal’s heat loss capabilities. The objective of my research was evaluating heat mitigation strategies and developing a practical method to identify animals that are of greatest risk of heat stress; thus improving animal welfare and performance.
A number of heat abatement strategies have been utilized in US feedlots including shade, sprinklers, nutritional modifications, and misters. A literature review was performed using published journal articles demonstrated significant benefits of providing shade to feedlot cattle. Sprinkling the pen surface may be just as beneficial as sprinkling or misting cattle. Sprinkling the ground not only cooled the ground which increased the thermal gradient between lying cattle and the ground, but also provided increased thermal conductivity and better heat flow down that gradient.
A study was performed to develop a noninvasive, remotely applied, practical method to identify animals at risk for heat stress. Infrared thermography images were obtained during the morning hours and pant scores obtained in the afternoon hours. Data mining techniques were employed to evaluate accuracy of potential classification methods to identify heat stress events in the afternoon based on the known morning data. Using infrared technology as a diagnostic test was not accurate for predicting heat stress events in the study presented.
Finally a retrospective study of Kansas feedlot performance, medical and weather data was performed. Findings indicate that diagnostic counts of bovine respiratory disease are associated with elevated ambient temperature two days prior. In conclusion, heat stress in beef feedlot animals is an important area of research. Heat mitigation methods such as shade have been proven to be effective at reducing heat stress in beef feeder cattle. Further research is needed to evaluate the use of infrared technology to predict heat stress events in the feedlot setting.
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Verbruggen, Nathalie. "Proline accumulation after salt-stress in arabidopsis thaliana." Doctoral thesis, Universite Libre de Bruxelles, 1992. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212895.
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Moser, Chase. "Experimental evolution of «Chlamydomonas reinhardtii » under salt stress." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94916.
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Abstract The environment is now changing much faster than in recent geological time, causing increasing population extinctions. Experiments have shown that extinction can be avoided by adaptation through natural selection leading to evolutionary rescue. I first determined the response of Chlamydomonas to stressful environments by growing populations over a range of salinity. The population growth is halved at 5 g/L salt (NaCl), and 8 g/L is lethal. In this experiment, the genetic correlation between environments increases with environmental similarity. I then manipulated the genotypic diversity in experimental populations and cultured them by serial transfer at 5 g/L salt. The outcome of adaptation is not influenced by initial genetic variation. Instead, populations adapted mainly through the spread of new beneficial mutations. These results suggest that populations have a greater chance of adapting when new environments are similar to current conditions and that adaptation is sometimes dominated by the spread of new mutations, even in the presence of a substantial amount of standing genetic variation.<br>Résumé Notre environnement change maintenant beaucoup plus rapidement que dans le passé géologique récent, précipitant l'extinction de plus en plus d'espèces. Des chercheurs ont démontré que, grâce à l'adaptation par la sélection naturelle, des espèces peuvent éviter l'extinction, un processus nommé sauvetage évolutif. J'ai d'abord étudié la capacité de Chlamydomonas à croitre dans des environnements dont la salinité augmente. J'ai trouvé que 5 g/L de sel diminue la croissance de moitié tandis que 8 g/L est suffisant pour empêcher toute croissance. Ici, la corrélation génétique entre environnement augmente avec la similarité des environnements comparés. J'ai ensuite soumis des populations contenant différentes quantités de diversité génétique initiale à une salinité de 5 g/L. La diversité génétique initiale ne semble pas influencer la capacité d'adaptation. Cependant, les populations semblent plutôt s'adapter en utilisant de nouvelles mutations dont l'effet est bénéfique. Ces résultats suggèrent que les populations s'adapteront plus facilement à des environnements similaires aux conditions présentes. De plus, ce processus sera dominé par la fixation de nouvelles mutations, même dans des populations contenant de la diversité génétique.
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Shafiq-ur-Rehman. "Physiological responses of acacia seeds to salt stress." Thesis, Coventry University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363856.
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Crane, Andrew John. "The spectral detection of salt stress in cotton." Thesis, University of Portsmouth, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292358.
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Stergiopoulos, Konstantinos. "Functional genomics of salt stress in 'Drosophila melanogaster'." Thesis, University of Glasgow, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433614.
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Fancy, Nurun Nahar. "Role of S-nitrosylation in plant salt stress." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29509.
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Salinity stress is one of the main challenges for crop growth and production. The estimated loss of crop yield due to salinity stress is up to 20% worldwide each year. Plants have evolved an array of mechanisms to defend themselves against salinity stress. A key aspect of plant responses to salinity stress is the engagement of a nitrosative burst that results in nitric oxide (NO) accumulation. A major mechanism for the transfer of NO bioactivity is S-nitrosylation which is a modification of the reactive thiol group of a rare but highly active cysteine residue within a protein through the addition of a NO moiety to generate an S-nitrosothiol (SNO). S-nitrosylation can result in altered structure, function and cellular localisation of a protein. Our findings suggest that S-nitrosylation is a key regulator of plant responses to salinity stress. Glutathione (GSH), a tripeptide cellular antioxidant, is S-nitrosylated to form S-nitrosoglutathione (GSNO), which functions as a stable store of NO bioactivity. Cellular GSNO levels are directly controlled by S-nitrosoglutathione reductase (GSNOR), thereby, regulating global SNO levels indirectly. The absence of this gene results in high levels of SNOs. In Arabidopsis, previous research has shown that loss-of-function mutation in GSNOR1 results in pathogen susceptibility (Feechan et al., 2005). In our study, we investigated salt tolerance in gsnor1-3 plants. We have found that this line is salt sensitive at various stages of their life cycle. Interestingly, classical salt stress signalling pathways are fully functional in gsnor1-3 plants. We have also explored non-classical pathways involved in salt tolerance. Autophagy is a cellular catabolic process which is involved in the recycling and degradation of unwanted cellular materials under stressed and non-stressed conditions. We have demonstrated that gsnor1-3 plants have impaired autophagy during salt stress. An accumulation of the autophagy marker NBR1 supports the lack of autophagosome formation. We hypothesised that S-nitrosylation might regulate upstream nodes of autophagosome formation. Our study demonstrated that at least one key player involved in autophagosome biogenesis is regulated by S-nitrosylation. ATG7, an E1-like activating enzyme, which regulates ATG8-PE and ATG12-ATG5 ubiquitin like conjugation systems, is S-nitrosylated in vitro and in vivo. S-nitrosylation of ATG7 impairs its function in vitro. We showed that S-nitrosylation of ATG7 is mediated by GSNO. Interestingly, ATG7 is also transnitrosylated by thioredoxin (TRX), another important redox regulatory enzyme. We suggest that similar mechanisms might exist in planta. Finally, work in this study revealed that S-nitrosylation of Cys558 and Cys637 cause the inhibition of ATG7 function. In aggregate, this study revealed a novel mechanism for the redox-based regulation of autophagy during salt stress.
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Pessarakli, Mohammed, K. B. Marcum, and David M. Kopec. "Growth Responses of Desert Saltgrass under Salt Stress." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/216374.
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Saltgrass (Distichlis spicata), clonal accession WA-12, collected from Wilcox, Arizona was studied in a greenhouse to evaluate its growth responses in terms of shoot and root lengths, shoot fresh weight, and shoot and root dry weights under control and salt (sodium chloride) stress conditions. Plants were grown under control (no salt) and three levels of salt stress (100, 200, and 400mM NaCl equivalent to 6250, 12500, and 25,000 g Lᴮ¹ sodium chloride, respectively), using Hoagland solution in a hydroponics system. Plant shoots (clippings) were harvested weekly, oven dried at 60 °C, and dry weights recorded. At each harvest, both shoot and root lengths were measured and recorded. At the last harvest, plant roots were also harvested, oven dried, and dry weights were determined and recorded. The results show that the shoot and root lengths decreased with increasing the salinity levels, however, both shoot fresh and dry weights significantly increased at 200mM NaCl salinity compared with the control or the 400mM NaCl level. Root dry weights at both 200mM and 400mM NaCl salinity levels were significantly higher than the control.
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Morales, Arturo Jason. "Physiological Assessment of Chenopodium quinoa to Salt Stress." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2205.
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The physiological responses to salt stress were measured in Chenopodium quinoa. In a greenhouse experiment, salt water was applied to the quinoa varieties, Chipaya and KU-2, and to the model halophyte Thellungiella halophila to assess their relative responses to salt stress. Height and weight data from a seven-week time course demonstrated that both cultivars exhibited greater tolerance to salt than T. halophila. In a growth chamber experiment, three quinoa cultivars, Chipaya, Ollague, and CICA 17 were hydroponically grown and physiological responses were measured with four salt treatments. Tissues collected from the growth chamber treatments were used to obtain leaf succulence data, tissue ion concentrations, compatible solute concentrations, and RNA for real-time PCR. Stomatal conductance and fresh weight were measured to determine the degree of stress and recovery. The expression profiles of SOS1, NHX1, and TIP2, genes involved in salt stress, showed constitutive expression in root tissue and up-regulation in leaf tissue in response to salt stress. These data suggest that quinoa tolerates salt through a combination of exclusion and accumulation mechanisms.
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Drake, Arly Marie. "EFFECT OF PLANT GROWTH REGULATORS ON CREEPING BENTGRASS GROWTH AND HEALTH DURING HEAT, SALT, AND COMBINED HEAT AND SALT STRESS." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1546450732510932.
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Lima, Leonardo Warzea. "Selenium and sulfur : mitigation in plant stresses /." Jaboticabal, 2016. http://hdl.handle.net/11449/138897.
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Orientador: Priscila Lupino Gratão<br>Coorientador: André Rodrigues dos Reis<br>Banca: Tiago Tezotto<br>Banca: Tiago Santana Balbuena<br>Abstract: Plants do not have specific defense mechanisms to counteract the diverse range of abiotic stresses and pollutants into the environment, and its survival depends on the flexibility and adaptability of its own natural defense mechanisms. Furthermore, the maintenance of cellular homeostasis depends on several interlinked and complex mechanisms, while the cellular defense system does not follow a specific pattern of action and may differ due to various factors such as plant species, exposure time to the stress, plant developmental stage, different organs and tissues analyzed. In the light of these considerations, this dissertation aimed to highlight and investigate the role of Sulfur and Selenium against different plant stresses, through the enzymatic and non-enzymatic plant responses and other related defense mechanisms. In the first chapter the author characterize the general biochemical mechanisms of the antioxidant cell defense, specifically the reactive oxygen species (EROs) formation and its chemical singularities and the induced oxidative stress, the enzymatic antioxidant defense system, specifically the superoxide dismutase (SOD) and Catalase (CAT) enzymes, the non-enzymatic mechanisms against the stress, including the Ascorbate-Glutathione cycle, the GSH (reduced glutathione), the phytochelatins and also proline formation. The plant nutritional status during the stress is crucial in order to maintain a proper defense response. In view of this, the chapter two is a publis... (Complete abstract click electronic access below)<br>Resumo: As plantas não possuem mecanismos de defesa específicos para combater a diversidade de estresses abióticos e poluentes do ambiente, e sua sobrevivência depende da flexibilidade e adaptação dos seus próprios mecanismos de defesa naturais. Além disso, a manutenção da homeostase celular depende de vários mecanismos interligados e complexos, enquanto o sistema de defesa celular não segue um padrão específico de ação e pode ainda variar devido a vários fatores tais como a espécie do vegetal, o tempo de exposição ao estresse, o estágio de desenvolvimento da planta e também nos diferentes órgãos e tecidos analisados. Com base nessas considerações, esta dissertação teve como objetivo destacar e investigar o papel do Enxofre (S) e do Selênio (Se) contra diferentes estresses nas plantas, através das respostas enzimáticas, não enzimáticas e também outros mecanismos de defesa relacionados. No primeiro capítulo, o autor caracteriza os mecanismos bioquímicos gerais da defesa celular antioxidante, especificamente a formação das espécies reativas de oxigênio (EROs) e suas singularidades químicas e o estresse oxidativo induzido, o sistema de defesa antioxidante enzimático, especificamente as enzimas Superóxido Dismutase (SOD) e a Catalase (CAT), os mecanismos não-enzimáticas contra o estresse, incluindo o ciclo Aascorbato-Glutationa, a GSH (glutationa reduzida), as fitoquelatinas e também a formação de prolina. O estado nutricional da planta durante o estresse é crucial a fim de manter uma re... (Resumo completo, clicar acesso eletrônico abaixo)<br>Mestre
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Lima, Leonardo Warzea [UNESP]. "Selenium and sulfur: mitigation in plant stresses." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138897.
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Previous issue date: 2016-05-18<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>As plantas não possuem mecanismos de defesa específicos para combater a diversidade de estresses abióticos e poluentes do ambiente, e sua sobrevivência depende da flexibilidade e adaptação dos seus próprios mecanismos de defesa naturais. Além disso, a manutenção da homeostase celular depende de vários mecanismos interligados e complexos, enquanto o sistema de defesa celular não segue um padrão específico de ação e pode ainda variar devido a vários fatores tais como a espécie do vegetal, o tempo de exposição ao estresse, o estágio de desenvolvimento da planta e também nos diferentes órgãos e tecidos analisados. Com base nessas considerações, esta dissertação teve como objetivo destacar e investigar o papel do Enxofre (S) e do Selênio (Se) contra diferentes estresses nas plantas, através das respostas enzimáticas, não enzimáticas e também outros mecanismos de defesa relacionados. No primeiro capítulo, o autor caracteriza os mecanismos bioquímicos gerais da defesa celular antioxidante, especificamente a formação das espécies reativas de oxigênio (EROs) e suas singularidades químicas e o estresse oxidativo induzido, o sistema de defesa antioxidante enzimático, especificamente as enzimas Superóxido Dismutase (SOD) e a Catalase (CAT), os mecanismos não-enzimáticas contra o estresse, incluindo o ciclo Aascorbato-Glutationa, a GSH (glutationa reduzida), as fitoquelatinas e também a formação de prolina. O estado nutricional da planta durante o estresse é crucial a fim de manter uma resposta de defesa adequada. Em vista disso, o capítulo dois apresenta uma revisão sobre a participação de Enxofre (S) na defesa contra o estresse. Este nutriente tem um papel importante em processos fundamentais, tais como o transporte de elétrons, estrutura, regulação, produção de oxigênio fotossintético, resistência a estresses abióticos e bióticos e no metabolismo secundário. Além disso, alguns elementos químicos são considerados benéficos para as plantas, no qual o Selênio (Se) é o mais relevante. No capítulo três, o autor descreve o papel do Se na amenização do estresse induzido pela contaminação por metais pesados, suas poderosas características antioxidantes, a melhoria da atividade de enzimas antioxidantes e também dos mecanismos globais de defesa. O capítulo quatro consiste em um projeto científico conduzido pelo autor. O objetivo deste estudo foi investigar se o Selênio, sob a forma de selenito (Na2SeO3), é capaz de evitar a absorção, translocação e concentração de cádmio (CdCl2), em diferentes tecidos no tomate, indicando os possíveis mecanismos para amenizar o estresse, bem como também analisar o estado geral dos frutos através das análises nutricionais, peso seco, pigmentos e concentração de Prolina livre. Os resultados demonstram que efeito atenuante do Se em tomateiro submetido ao Cd poderia estar relacionado com a restrição da absorção e translocação de Cd2+, aumentando a concentração de micronutrientes nos frutos e, finalmente, aumentando a concentração de prolina livre nos frutos.<br>Plants do not have specific defense mechanisms to counteract the diverse range of abiotic stresses and pollutants into the environment, and its survival depends on the flexibility and adaptability of its own natural defense mechanisms. Furthermore, the maintenance of cellular homeostasis depends on several interlinked and complex mechanisms, while the cellular defense system does not follow a specific pattern of action and may differ due to various factors such as plant species, exposure time to the stress, plant developmental stage, different organs and tissues analyzed. In the light of these considerations, this dissertation aimed to highlight and investigate the role of Sulfur and Selenium against different plant stresses, through the enzymatic and non-enzymatic plant responses and other related defense mechanisms. In the first chapter the author characterize the general biochemical mechanisms of the antioxidant cell defense, specifically the reactive oxygen species (EROs) formation and its chemical singularities and the induced oxidative stress, the enzymatic antioxidant defense system, specifically the superoxide dismutase (SOD) and Catalase (CAT) enzymes, the non-enzymatic mechanisms against the stress, including the Ascorbate-Glutathione cycle, the GSH (reduced glutathione), the phytochelatins and also proline formation. The plant nutritional status during the stress is crucial in order to maintain a proper defense response. In view of this, the chapter two is a published review about the participation of Sulfur (S) on the stress defense. This nutrient has a role in fundamental processes such as electron transport, structure, regulation and it is also associated with photosynthetic oxygen production, abiotic and biotic stress resistance and secondary metabolism. Moreover, few chemical elements are considered benefic to plants, while Selenium (Se) is the most relevant. In the chapter three the author describes the role of Se to detoxify the stress induced by heavy metal contamination, its powerful antioxidant characteristics and the improvement of the antioxidant enzymes activity and overall defense mechanisms. The chapter four consists of a scientific project conducted by the author. The aim of this study was to investigate whether Selenium, under the form of selenite (Na2SeO3), may avoid the uptake, translocation and concentration of Cadmium (CdCl2), in different tomato tissues, indicating possible mechanisms to counteract the stress, as well as to analyze the fruits overall status through the nutritional analyses, dry weight, pigments and proline concentration. The results demonstrate that alleviating effect of Se in tomato under Cd contamination could be related to restriction of Cd2+ uptake and translocation, enhancing micronutrient concentration in fruits and, finally, enhancing fruit proline concentration.<br>CAPES: 445978/2014-7
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Krell, Andreas. "Salt stress tolerance in the psychrophilic diatom Fragilariopsis cylindrus." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980889235.
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OROZCO, SERGIO OROZCO. "WELLBORE STABILITY IN SALT ZONES: USING STRESS TRANSFER TECHNIQUES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=22966@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>BOLSA NOTA 10<br>A estabilidade de poços através de zonas de sal é um aspecto relevante em ambientes de perfuração offshore no Brasil. O fluxo convencional no planejamento de um poço de petróleo não reconhece a natureza complexa do estado de tensões in-situ em torno destes corpos de sal. Portanto, é necessária
uma avaliação fiável das tensões in-situ considerando tanto a escala de campo (global) quanto as principais estruturas presentes no overburden. Neste trabalho, a análise de estabilidade de poços é realizada em três etapas. Primeiro, é realizada uma análise numérica a escala global para avaliar as tensões in-situ considerando a geometria de um corpo de sal. A seguir, são introduzidas as tensões in-situ em um modelo local, chamado subestrutura, através de duas técnicas de transferência de tensões propostas, denominadas as técnicas do Inverso Ponderado da Distância (IPD) e do Gradiente de Tensões (GT). O termo subestrutura é definido como uma linha curva no espaço composta por um conjunto de pontos, se assemelhando a uma seção ou trajetória completa de um poço. Finalmente, a janela operacional do poço é calculada acoplando os resultados de tensões da modelagem numérica com equações elásticas. Neste trabalho as técnicas IPD e GT são também utilizadas para transferir tensões em
submodelos localizados dentro de um modelo global, visando realizar futuros estudos de submodelagem de estabilidade de poços. O termo submodelo consiste em uma malha de elementos finitos de um tamanho menor e um refinamento maior em relação ao modelo global.<br>Wellbore Stability drilling through salt zones is an important current endeavor in many areas offshore of Brazil. The conventional well design workflow does not recognize the complex nature of the stress field near these salt bodies. Therefore, a reliable assessment of the in-situ stresses must be carried out
considering a field (global) scale of the problem and the presence of major structures in the overburden. The proposed stability analysis is carried out in three stages. Firstly, a global finite element analysis is employed to evaluate the in-situ stresses at a global scale considering the geometry of a salt body.
Secondly, the global scale in-situ stresses are introduced in a local model, that we call substructure, by using two proposed stress transfer techniques called the Inverse Distance Weighted Technique (IDWT) and the Stress Gradient Technique (SGT). We define Substructure as a set of points forming a section or
a complete trajectory of an oil well. Finally, optimal mud weights are calculated combining numerical stress results with analytical elastic equations. These two stress transfer techniques are also proposed to be used to transfer stresses to submodels inside a global model domain for submodeling wellbore stability
purposes. The term submodel is defined as a finite element mesh with a smaller size relative to the size of the global model.
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Roosens, Nancy. "Proline biosynthesis related to salt stress in higher plants." Doctoral thesis, Universite Libre de Bruxelles, 1999. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211926.
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Brígido, Clarisse Cordeiro. "Tolerance of chickpea mesorhizobia to acid and salt stress." Doctoral thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/14546.
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The main objectives of this thesis were to evaluate the tolerance of a collection
of native Portuguese chickpea rhizobia to abiotic stresses, namely acidity and
salinity, and to investigate the molecular bases of acidity and salinity tolerance.
Additionally, the evaluation of the symbiotic performance of ACC deaminasetransformed
strains under salinity was performed. The involvement of the
chaperone ClpB in the response to abiotic stresses and in the symbiosis with
chickpea was investigated by gene deletion in a Mesorhizobium strain.
Chickpea rhizobia were assigned to several Mesorhizobium species. In both
stress conditions, tolerant and sensitive rhizobia were found, including
moderately acidophilic isolates. The analysis of the expression of the chaperone
genes dnaK and groESL suggests their involvement in acid tolerance. ACC
deaminase-transformed rhizobia strains showed an improvement of their
symbiotic performance under salinity. The characterization of the ClpB knockout
mutant indicated that ClpB is involved in the nodulation process; RESUMO:Os principais objetivos desta tese foram a avaliação da tolerância a stresses
abióticos, nomeadamente acidez e salinidade, de uma coleção de rizóbios
portugueses nativos de grão-de-bico, e investigar as bases moleculares da
tolerância a ambos os stresses. Adicionalmente, avaliou-se a eficiência
simbiótica de estirpes transformadas com o gene da ACC desaminase em
condições de salinidade. Investigou-se ainda o envolvimento da chaperone
ClpB na resposta a stresses abióticos e na simbiose com grão-de-bico através
da deleção do gene.
Os rizóbios de grão-de-bico pertencem a diferentes espécies de
Mesorhizobium. Encontraram-se rizóbios tolerantes e sensíveis a ambos os
stresses, incluindo isolados moderadamente acidófilos. A análise da expressão
dos genes de chaperones dnaK e groESL sugere o seu envolvimento na
tolerância à acidez. Estirpes de rizóbio transformadas com o gene da ACC
desaminase apresentaram uma melhoria da sua eficiência simbiótica em
condições salinas. A caracterização do mutante ClpB de Mesorhizobium
indicou que esta chaperone está envolvida no processo de nodulação.
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Kang, Ren. "Appliance-level demand side management for power network stress mitigation." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:1daf3825-1836-4bdb-89cb-763ecccca010.
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Power networks are under increasing pressure to maintain operation within permissible voltage and current limits with higher penetrations of renewable energy. This thesis aims to develop and evaluate a practical and economical way to control key domestic appliances to alleviate stress caused by high level of renewable energy penetration. The first objective in this thesis is to develop a network stress identification technique that does not rely on communication infrastructure. Traditionally, there is an emphasis on using centralized control strategies for demand side management (DSM) involving a central brain which collects information from each individual device and sends out commands to them which schedules their operation. This approach relies heavily on communication infrastructure and introduces security challenges, which are not problems for distributed or decentralised control. Whilst the latter two approaches have the virtue of scalability and flexibility, they require a good network model or good estimation of network condition without real time communication for effective control. A tap change detection approach via local voltage measurement has been developed and validated to enable the domestic smart appliance to perceive the network stress in three different levels across the power network without any real-time communication. The second objective is to explore the economic benefits associated with the usage of electric hot water tanks (EHWTs) as an alternative to home batteries or electric vehicles for demand response. To do this, an optimization approach for sizing of the EHWT is proposed. Real-world hot water usage data is analysed and applied, revealing four typical hot water usage patterns and 100-litre as the most common optimal tank size for UK consumer. Finally, since increasing PV generation has risen voltage concerns in various locations across the UK, such as in Cornwall, this thesis investigated to what extend intelligent EHWTs can be used to alleviate the LV network stress caused by the high level of PV penetration. A Monte-Carlo simulation is carried out on real UK LV networks, showing that the presence of intelligent EHWTs could improve both the voltage and current performance of the LV network and allow 50% more PV installations beyond the network's original capacity.
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Wibowo, Anjar Tri. "Epigenetic response and adaptation to salt stress in Arabidopsis thaliana." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/78172/.
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High soil salinity is a major environmental stress that adversely affects crop production throughout the world. It is now estimated that half of the world’s cropland is affected by salt stress. To cope with various environmental stresses, plants are able to spatially and temporally regulate gene expression through changes in DNA methylation and chromatin conformation, known as epigenetic modifications. Recent studies indicated that epigenetic modifications induced by environmental stress can be inherited over several generations, despite a genomewide epigenetic resetting of epigenetic imprints that takes place during plants reproduction. In this thesis, I evaluated in Arabidopsis thaliana the effect of multigeneration salt stress treatments on the genome-wide dynamics of DNA methylation and tolerance to high salinity. My results show that the immediate progenies of stressed plants displayed better germination and survival rate under high salinity, but contrary to current theories this effect is lost in the following non-stressed generation. Genome-wide DNA methylation analysis revealed that stress induced discrete de novo methylation and demethylation changes on epigenetically labile regions of the plant genome. These acquired tolerance and methylation marks are likely under parent-of-origin control as a result of a robust epigenetic reprogramming that takes place in the male germline. Stress-induced methylation marks identified are associated with transcriptional changes of stress responsive genes and correlated with antisense long-non coding RNA expression. Overall this work establish for the first time a link between differential DNA methylation, gene expression and shortterm adaptation to stress in plants.
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Kader, Md Abdul. "Salt stress in rice : adaptive mechanisms for cytosolic sodium homeostasis /." Ultuna : Dept. of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200657.pdf.
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Dadkhah, Ali Reza. "Ecophysiology of sugar beet (Beta vulgaris L.) under salt stress." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246614.
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Lauer, Nathan T. "Physiological and Biochemical Responses of Bald Cypress to Salt Stress." UNF Digital Commons, 2013. http://digitalcommons.unf.edu/etd/454.
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Bald Cypress (Taxodium distichum (L.) Rich.) is native to freshwater wetlands of Florida. The vitality of cypress within coastal freshwater wetlands is threatened by saltwater intrusion. Biomarkers to detect sub-lethal salinity stress were developed using a controlled greenhouse study. Cypress saplings maintained at elevated salinities of 4 and 8‰ exhibited a decrease in maximum quantum yield (MQY) and an increase in non-photochemical quenching (NPQ). Cypress leaves exhibited an increase in Na+, H2O2, and free proline content compared to plants maintained in freshwater. These biomarkers were used to detect salinity stress within a population of cypress associated with the lower St. Johns River where saltwater intrusion is occurring. Cypress in a basin swamp exhibited signs of salinity stress with low MQY and elevated NPQ values compared to Cypress at other sites. Cypress leaves at the basin swamp also had the highest Na+, lipid peroxidation, and proline content compared to plants at other sites. Detached Cypress leaf experiments were conducted to explore the mechanisms of salt tolerance. Detached cypress leaves were first exposed to elevated NaCl concentrations for 24, 48, or 72 hours. Elevated salinity caused a decrease in leaf transpiration for all times tested. Total peroxidase activity exhibited an increase in response to salt stress after 48 hours. Enhanced peroxidase activity was found to be associated with the induction of a ~37 kDa peroxidase isoform. Treatment of leaves with clofibrate caused an increase in activity of the ~37 kDa peroxidase. Pre-treatment of leaves with brefeldin A (BFA) blocked the induction of the ~37 kDa peroxidase associated with salt stress. Pre-treatment of Cypress leaves with diphenyliodonium (DPI) blocked the decrease in transpiration associated with salt stress, suggesting that H2O2 is enzymatically produced within the stomata in response to salt stress
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Pessarakli, Mohammad, David M. Kopec, and Jeff J. Gilbert. "Growth Responses of Selected Warm-Season Turfgrasses under Salt Stress." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008. http://hdl.handle.net/10150/216638.
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Use of low quality/saline water for turf irrigation, especially in regions experiencing water shortage is increasing. This imposes more salt stress on turfgrasses which are already under stress in these regions. Therefore, there is a great need for salt tolerant turfgrasses to survive under such stressful conditions. This study was conducted in a greenhouse, using hydroponics system, to compare growth responses of three warm-season turfgrasses, bermudagrass (Cynodon dactylon L.), cv. Tifway 419, seashore paspalum (Paspalum vaginatum Swartz), cv. Sea Isle 2000, and saltgrass (Distichlis spicata L), accession A55 in terms of shoot and root lengths and DM, and canopy green color (CGC) under salt stress condition. Whole plants, stolons, and rhizomes were grown in Hoagland solution for 4 months prior to initiation of salt stress. Then, plants were grown for 12 weeks under 4 treatments (control, 7000, 14000, and 21000 mg/L NaCl) with 4 replications in a RCB design trial. During the stress period, shoots were clipped bi-weekly for DM production, shoot and root lengths were measured, and CGC was evaluated weekly. The bi-weekly clippings and the roots at the last harvest were oven dried at 60o C and DM weights were recorded. Shoot and root lengths and shoot DM weights decreased linearly with increased salinity for bermudagrass and paspalum. However, for saltgrass these values increased at all NaCl levels compared with the control. For bermudagrass and paspalum, the highest values were obtained when the whole plants were used, and the lowest ones resulted when the rhizomes were used. The reverse was found for saltgrass. For the control plants, the measured factors were higher and the canopy colors were greener for bermudagrass and paspalum compared with saltgrass. The canopy color changed to lighter green for bermudagrass and paspalum as NaCl salinity increased, but saltgrass maintained the same color regardless of the level of salinity.
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Pessarakli, Mohammed, David M. Kopec, and Jeff J. Gilbert. "Growth Responses of Selected Warm-Season Turfgrasses under Salt Stress." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2009. http://hdl.handle.net/10150/216660.
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Use of low quality/saline water for turf irrigation, especially in regions experiencing water shortage is increasing. This imposes more salt stress on turfgrasses which are already under stress in these regions. Therefore, there is a great need for salt tolerant turfgrasses to survive under such stressful conditions. This study was conducted in a greenhouse, using hydroponics system, to compare growth responses of three warmseason turfgrasses, bermudagrass (Cynodon dactylon L.), cv. Tifway 419, seashore paspalum (Paspalum vaginatum Swartz), cv. Sea Isle 2000, and saltgrass (Distichlis spicata L), accession A55 in terms of shoot and root lengths and DM, and canopy green color (CGC) under salt stress condition. Whole plants, stolons, and rhizomes were grown in Hoagland solution for 4 months prior to initiation of salt stress. Then, plants were grown for 12 weeks under 4 treatments (control, 7000, 14000, and 21000 mg/L NaCl) with 4 replications in a RCB design trial. During the stress period, shoots were clipped bi-weekly for DM production, shoot and root lengths were measured, and CGC was evaluated weekly. The bi-weekly clippings and the roots at the last harvest were oven dried at 60o C and DM weights were recorded. Shoot and root lengths and shoot DM weights decreased linearly with increased salinity for bermudagrass and paspalum. However, for saltgrass these values increased at all NaCl levels compared with the control. For bermudagrass and paspalum, the highest values were obtained when the whole plants were used, and the lowest ones resulted when the rhizomes were used. The reverse was found for saltgrass. For the control plants, the measured factors were higher and the canopy colors were greener for bermudagrass and paspalum compared with saltgrass. The canopy color changed to lighter green for bermudagrass and paspalum as NaCl salinity increased, but saltgrass maintained the same color regardless of the level of salinity.
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Wu, Xiao. "Design of a Tritium Mitigation and Control System for Fluoride-salt-cooled High-temperature Reactor Systems." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452249907.
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Peng, Licheng. "Mitigation of Oxygen Stress and Contamination-free Cultivation in Microalga Cultures." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34189.
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Microalgae are promising candidates for biofuel production, CO2 biomitigation, and production of a variety of value-added products. However, high production costs and large energy consumption have been a major concern hindering the commercialization of microalgal products and processes. In addition, biological contamination and oxygen stress are two of the major contributors to these challenges. The objective of this project was twofold: 1) developing a novel strategy for control of biological contamination to enable non-sterile cultivation of microalgae such as N. oleoabundans, and 2) developing advanced deoxygenation mechanisms to reduce oxygen accumulation in the culture.
It was found that addition of appropriate amount of NaHCO3 could effectively inhibit the growth of protozoa while its inhibition on microalgae was much less and could be alleviated by increasing pH to an appropriate level. It was also found that adding 160 mM NaHCO3 in media or decreasing incident light intensity to 100 W/m2 would help alleviate the oxidative stress to cells at 400% of air saturation. The feasibility of contamination-free non-sterile cultivation of freshwater green alga N. oleoabundans was verified using long-term continuous cultivation in a 15-liter TPBR with non-sterile medium and aeration. Furthermore, localized oxygen removal using hydrophobic hollow membranes was found to effectively reduce dO2 and increase lipid accumulation. These results have the potential to be translated into low-cost cultivation of freshwater microalgae processes for production of value-added microalgal products. At a more fundamental level, the mechanisms of the inhibition of NaHCO3 on microalgae and protozoa were discussed. Efforts were also made to simulate the effects of incident light intensity on light distribution, cell growth kinetics, and lipid accumulation of N. oleoabundans under non- sterile cultivation conditions.
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Tsiantis, Miltiades S. "Regulation of V-ATPase gene expression by ionic stress in higher plants." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337540.
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Wei, Wenxue. "Physiological and molecular mechanisms of salt tolerance in barley (Hordeum vulgare L.)." Thesis, University of Wolverhampton, 2002. http://hdl.handle.net/2436/93525.
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Kalifa, Ali. "Salt stress, and phosphorus absorption by potato plants cv. 'Russet Burbank'." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29727.pdf.
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Ferreira, Thalita Montoril. "Biochemical and physiological responses of sorghum plants submitted to salt stress." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17086.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior<br>The plants are frequently exposed to environmental stresses, which cause imbalances in physiological and biochemical metabolism. This work aimed to study the physiological and biochemical changes of plant forage sorghum (Sorghum bicolor) genotype CSF18, depending on the time of salt stress. The seeds were sown in vermiculite moistened with distilled water, in a greenhouse conditions, and after seven days, the seedlings were transferred to trays with Hoagland solution diluted 1:2. After seven days, treatment was established stress saline (75 mM NaCl), one group of plants kept in nutrient solution in the absence of salt (control). Samples were collected at 0, 5, 10 and 15 days after the initiation of stress. We evaluated the growth, gas exchange, contents and chlorophyll fluorescence, the concentration of organic solutes (proline, N-amino solutes, soluble carbohydrates, soluble proteins and polyamines free) and inorganic (Na+, Cl- and K+), as well as the activity of ribonuclease (RNase). We also determined the activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaicol peroxidase (GPX), as well as the levels of H2O2, ascorbate and glutathione in leaves and roots. Salinity reduced plant growth, being observed reductions in leaf area, and fresh and dry weights of shoots and roots. This was related to a reduction in net photosynthesis rate, even with the transpiration rate and stomatal conductance is not affected. The salinity increased contents of Na+ and Cl- in plant tissues, but the K+ decreased. The levels of organic solutes in leaves and roots increased, particularly at five and ten days of stress. The polyamines putrescine and spermidine were found at very low levels in both leaves and roots, while spermine was not detected in any analyzed portion of the plant. Although putrescine increased in salt stress, some must have contributed to the osmotic adjustment, however, their participation in oxidative protection was suggested. The salinity increased the activity of SOD, APX and GPX and the redox state of ascorbate, especially in the leaves, and this is related to the maintenance of H2O2 levels and increased protection against oxidative damage. The CAT showed the main enzyme remover H2O2 in the leaves while the roots that role was played by GPX. The RNase activity in leaves, stems and roots of sorghum increased in stress conditions, but their role in protection against the deleterious effects of salinity is not yet fully understood. In general, the data show that the antioxidative system (enzymatic and non-enzymatic) can play a key role in the acclimation of sorghum plants to salt stress, and that the reduction of plant growth was probably due to inhibition of biochemical phase of photosynthesis, caused by accumulation of toxic ions, Na+ and Cl-, reducing the relation K+/Na+ at levels harmful to the metabolism<br>As plantas estÃo freqÃentemente expostas a estresses ambientais, os quais causam desequilÃbrios no metabolismo fisiolÃgico e bioquÃmico. Este trabalho teve por objetivo estudar as alteraÃÃes fisiolÃgicas e bioquÃmicas de plantas de sorgo forrageiro [Sorghum bicolor (L.) Moench], genÃtipo CSF 18, em funÃÃo do tempo de exposiÃÃo ao estresse salino. As sementes foram semeadas em vermiculita umedecida com Ãgua destilada, em casa de vegetaÃÃo e, apÃs sete dias, as plÃntulas foram transferidas para bandejas com soluÃÃo nutritiva de Hoagland diluÃda 1:2. ApÃs sete dias, foi estabelecido o tratamento de estresse salino (NaCl a 75 mM), sendo um grupo de plantas mantido em soluÃÃo nutritiva na ausÃncia de sal (controle). As coletas foram realizadas aos 0, 5, 10 e 15 dias apÃs o inÃcio do estresse. Avaliou-se o crescimento, as trocas gasosas, os teores e a fluorescÃncia da clorofila, os teores de solutos orgÃnicos (prolina, N-aminossolÃveis, carboidratos solÃveis, proteÃnas solÃveis e poliaminas livres) e inorgÃnicos (Na+, Cl- e K+), bem como a atividade da ribonuclease (RNase). TambÃm foram determinadas as atividades das enzimas catalase (CAT), dismutase do superÃxido (SOD), peroxidase do ascorbato (APX) e peroxidase do guaicol (GPX), bem como os teores de H2O2, glutationa e ascorbato em folhas e raÃzes. O estresse salino reduziu o crescimento das plantas, sendo observadas reduÃÃes na Ãrea foliar, e nas matÃrias fresca e seca da parte aÃrea e das raÃzes. Isto foi relacionado com a reduÃÃo na taxa de fotossÃntese lÃquida, mesmo com a taxa de transpiraÃÃo e a condutÃncia estomÃtica nÃo sendo afetadas. A salinidade aumentou os teores de Na+ e Cl nos tecidos das plantas, porÃm, diminuiu os de K+. Os teores de solutos orgÃnicos em folhas e raÃzes aumentaram, principalmente aos cinco e dez dias de estresse. As poliaminas putrescina e espermidina foram encontradas em nÃveis muito baixos tanto em folhas como raÃzes, enquanto a espermina nÃo foi detectada em qualquer dos tecidos analisados. Embora a putrescina tenha aumentado em condiÃÃes de estresse salino, pouco deve ter contribuÃdo para o ajustamento osmÃtico, contudo, foi sugerida sua participaÃÃo na proteÃÃo oxidativa. A salinidade aumentou a atividade das enzimas SOD, APX e GPX e o estado redox do ascorbato, especialmente nas folhas, sendo isto relacionado com a manutenÃÃo dos nÃveis de H2O2 e com o aumento da proteÃÃo contra os danos oxidativos. A CAT mostrou-se a principal enzima removedora de H2O2 nas folhas, enquanto nas raÃzes esse papel foi desempenhado pela GPX. A atividade da RNase, em folhas, colmos e raÃzes de sorgo aumentou em condiÃÃes de estresse, porÃm seu papel na proteÃÃo contra os efeitos deletÃrios da salinidade ainda nÃo està totalmente esclarecido. Em geral, os dados mostram que o sistema antioxidativo (enzimÃtico e nÃo-enzimÃtico) pode desempenhar papel fundamental na aclimataÃÃo das plantas de sorgo ao estresse salino e que os efeitos deletÃrios da salinidade no crescimento das plantas, devem-se, provavelmente, à inibiÃÃo da fase bioquÃmica da fotossÃntese, causada pelo acÃmulo de Ãons tÃxicos, Na+ e Cl-, reduzindo a relaÃÃo K+/Na+ a nÃveis prejudiciais ao metabolismo.
34
Serra, Sara <1979>. "Salt stress responses in pear and quince: physiological and molecular aspects." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1620/1/Serra_Sara_Tesi_.pdf.
Full textAbstract:
The productivity of agricultural crops is seriously limited by salinity. This problem is rapidly increasing, particularly in irrigated lands. Like almost all the fruit tree species, Pyrus communis is generally considered a salt sensitive species, but only little information is available on its behavior under saline conditions.
Previous studies, carried out in the Department of Fruit Tree and Woody Plant Science (University of Bologna), focused their attention on pear and quince salt stress responses to understand which rootstock would be the most suitable for pear in order to tolerate a salt stress condition. It has been reported that pear and quince have different ability in the uptake, translocation and accumulation of chloride (Cl-) and sodium (Na+) ions, when plants were irrigated for one season with saline water (5 dS/m).
The aim of the present work was to deepen these aspects and investigate salt stress responses in pear and quince. Two different experiments have been performed: a “short-term” trial in a growth chamber and a “long-term” experiment in the open field.
In the short-term experiment, three different genotypes usually adopted as pear rootstocks (MC, BA29 and Farold®40) and the pear variety Abbé Fétel own rooted have been compared under salt stress conditions. The trial was performed in a hydroponic culture system, applying a 90 mM NaCl stress to half of the plants, after five weeks of normal growth in Hoagland’s solution. During the three-weeks of salt stress treatment, physiological, mineral and molecular analyses were performed in order to monitor, for each genotype, the development of the salt stress responses in comparison with the corresponding “unstressed” plants. Farold®40 and Abbé Fétel own rooted showed the onset of leaf necrosis, due to salt toxicity, one week before quinces. Moreover, quinces displayed a significant delay in premature senescence of old leaves, while pears emerged for their ability to regenerate new leaves from apparently dead foliage with the salt stress still running. Physiological measurements, such as shoots length, chlorophyll (Chl) content, and photosynthesis, have been carried out and revealed that pears exhibited a significant reduction in water content and a wilting aspect, while for quinces a decrease in Chl content and a growth slowdown were observed.
At the end of the trial, all plants were collected and organs separated for dry weight estimation and mineral analyses (Cu, Fe, Mn, Zn Mg, Ca, K, Na and Cl). Mineral contents have been affected by salinity; same macro/micro nutrients were altered in some organs or relocated within the plant. This plant response could have partially contributed to face the salt stress. Leaves and roots have been harvested for molecular analyses at four different times during stress conditions.
Molecular analyses consisted of the gene expression study of three main ion transporters, well known in Arabidopsis thaliana as salt-tolerance determinants in the “SOS” pathway: NHX1 (tonoplast Na+/H+ antiporter), SOS1 (plasmalemma Na+/H+ antiporter) and HKT1 (K+ high-affinity and Na+ low-affinity transporter). These studies showed that two quince rootstocks adopted different responsive mechanisms to NaCl stress. BA29 increased its Na+ sequestration activity into leaf vacuoles, while MC enhanced temporarily the same ability, but in roots. Farold®40, instead, exhibited increases in SOS1 and HKT1 expression mainly at leaf level in the attempt to retrieve Na+ from xylem, while Abbé Fétel differently altered the expression of these genes in roots. Finally, each genotype showed a peculiar response to salt stress that was the sum of its ability in Na+ exclusion, osmotic tolerance and tissue tolerance.
In the long-term experiment, potted trees of the pear variety Abbé Fétel grafted on different rootstocks (MC, BA29 and Farold®40), or own rooted and also rootstocks only were subjected to a salt stress through saline water irrigation with an electrical conductivity of 5 dS/m for two years. The purposes of this study were to evaluate salinity effects on physiological (shoot length, number of buds, photosynthesis, etc.) and yield parameters of cultivar Abbé Fétel in the different combinations and to determine the salt amount that pear is able to tolerate over the years. With this work, we confirmed the previous hypothesis that pear, despite being classified as a salt-sensitive fruit tree, can be cultivated for two years under saline water irrigation, without showing any salt toxicity symptoms or severe drawbacks on plant development and production. Among different combinations, Abbé Fétel grafted on MC resulted interesting for its peculiar behaviors under salt stress conditions.
In the near future, further investigations on physiological and molecular aspects will be necessary to enrich and broaden the knowledge of salt stress responses in pear.
35
Serra, Sara <1979>. "Salt stress responses in pear and quince: physiological and molecular aspects." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1620/.
Full textAbstract:
The productivity of agricultural crops is seriously limited by salinity. This problem is rapidly increasing, particularly in irrigated lands. Like almost all the fruit tree species, Pyrus communis is generally considered a salt sensitive species, but only little information is available on its behavior under saline conditions.
Previous studies, carried out in the Department of Fruit Tree and Woody Plant Science (University of Bologna), focused their attention on pear and quince salt stress responses to understand which rootstock would be the most suitable for pear in order to tolerate a salt stress condition. It has been reported that pear and quince have different ability in the uptake, translocation and accumulation of chloride (Cl-) and sodium (Na+) ions, when plants were irrigated for one season with saline water (5 dS/m).
The aim of the present work was to deepen these aspects and investigate salt stress responses in pear and quince. Two different experiments have been performed: a “short-term” trial in a growth chamber and a “long-term” experiment in the open field.
In the short-term experiment, three different genotypes usually adopted as pear rootstocks (MC, BA29 and Farold®40) and the pear variety Abbé Fétel own rooted have been compared under salt stress conditions. The trial was performed in a hydroponic culture system, applying a 90 mM NaCl stress to half of the plants, after five weeks of normal growth in Hoagland’s solution. During the three-weeks of salt stress treatment, physiological, mineral and molecular analyses were performed in order to monitor, for each genotype, the development of the salt stress responses in comparison with the corresponding “unstressed” plants. Farold®40 and Abbé Fétel own rooted showed the onset of leaf necrosis, due to salt toxicity, one week before quinces. Moreover, quinces displayed a significant delay in premature senescence of old leaves, while pears emerged for their ability to regenerate new leaves from apparently dead foliage with the salt stress still running. Physiological measurements, such as shoots length, chlorophyll (Chl) content, and photosynthesis, have been carried out and revealed that pears exhibited a significant reduction in water content and a wilting aspect, while for quinces a decrease in Chl content and a growth slowdown were observed.
At the end of the trial, all plants were collected and organs separated for dry weight estimation and mineral analyses (Cu, Fe, Mn, Zn Mg, Ca, K, Na and Cl). Mineral contents have been affected by salinity; same macro/micro nutrients were altered in some organs or relocated within the plant. This plant response could have partially contributed to face the salt stress. Leaves and roots have been harvested for molecular analyses at four different times during stress conditions.
Molecular analyses consisted of the gene expression study of three main ion transporters, well known in Arabidopsis thaliana as salt-tolerance determinants in the “SOS” pathway: NHX1 (tonoplast Na+/H+ antiporter), SOS1 (plasmalemma Na+/H+ antiporter) and HKT1 (K+ high-affinity and Na+ low-affinity transporter). These studies showed that two quince rootstocks adopted different responsive mechanisms to NaCl stress. BA29 increased its Na+ sequestration activity into leaf vacuoles, while MC enhanced temporarily the same ability, but in roots. Farold®40, instead, exhibited increases in SOS1 and HKT1 expression mainly at leaf level in the attempt to retrieve Na+ from xylem, while Abbé Fétel differently altered the expression of these genes in roots. Finally, each genotype showed a peculiar response to salt stress that was the sum of its ability in Na+ exclusion, osmotic tolerance and tissue tolerance.
In the long-term experiment, potted trees of the pear variety Abbé Fétel grafted on different rootstocks (MC, BA29 and Farold®40), or own rooted and also rootstocks only were subjected to a salt stress through saline water irrigation with an electrical conductivity of 5 dS/m for two years. The purposes of this study were to evaluate salinity effects on physiological (shoot length, number of buds, photosynthesis, etc.) and yield parameters of cultivar Abbé Fétel in the different combinations and to determine the salt amount that pear is able to tolerate over the years. With this work, we confirmed the previous hypothesis that pear, despite being classified as a salt-sensitive fruit tree, can be cultivated for two years under saline water irrigation, without showing any salt toxicity symptoms or severe drawbacks on plant development and production. Among different combinations, Abbé Fétel grafted on MC resulted interesting for its peculiar behaviors under salt stress conditions.
In the near future, further investigations on physiological and molecular aspects will be necessary to enrich and broaden the knowledge of salt stress responses in pear.
36
Attumi, Al-Arbe. "Effects of salt stress on phosphorus and sodium absorptions by soybean plants." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ44119.pdf.
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Elias, Demetra. "Characterization of ES147, a salt stress regulated protein kinase from Lophopyrum elongatum." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ59271.pdf.
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Abdelkader, Amal Fadl. "Salt stress in wheat (Triticum aestivum) and its impact on plastid development /." Göteborg : Göteborg University, 2007. http://www.loc.gov/catdir/toc/fy0714/2007423862.html.
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Attumi, Al-Arbe. "Effect of salt stress on phosphorus and sodium absorptions by soybean plants." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20242.
Full textAbstract:
The radiotracer methodology was combined with the Hoagland solution culture of growing soybean in a greenhouse to investigate the absorptions of phosphorus (P), calcium (Ca), and sodium (Na) as a function of salinity. Salt stress was varied by using zero to 120 mM NaCl. The research was initiated because of a need to increase soybean production in the saline soils of the semi-arid regions of the world. Although P absorption increased with time at each concentration of NaCl, increasing its concentrations ([NaCl]) to 120 mM reduced P uptake considerably. The addition of inorganic P (Pi) to the salt medium improved P absorption significantly (P < 0.0001) in stem, petiole, and roots. Polynomial regressions showed the relationship between 22Na activity and [NaCl] for leaves and petiole to be cubic (R2 = 1) while in the stem a quadratic relationship prevailed. A maximum of P and Na absorption was observed at 40 mM NaCl. The relationship between 32P activity and increasing [NaCl] was linear for the roots (a positive slope) and the stem (a negative slope). 45Ca and 32P dual labelling part of the experiments failed to produce results because an unexpectedly high degree of tissue quenching which prevented from obtaining the minimum counting requirements for separation. Shoot fresh and dry weights decreased linearly with increasing [NaCl] as did the root fresh and dry weights. Leaf chlorophyll content during the last week of the final harvest showed a linear relationship with time. Chlorophyll increased with time linearly when the growth medium contained zero and 40 mM NaCl; whereas a negative slope was obtained for 80 and 120 mM NaCl. It seems that P fertilization of the soil could ameliorate the salt effect. 22 Na uptake results indicated that there is a mechanism for exclusion of Na from soybean plant parts.
40
Alm, David Michael. "Comparison and interaction of heat and salt stress in cultured tobacco cells." Virtual Press, 1986. http://liblink.bsu.edu/uhtbin/catkey/445616.
Full textAbstract:
Cultured tobacco cells (Nicotiana tabacum L., cv Wisconsin-38) were subjected to temporary sub-lethal heat and salt shock treatments to determine the effects of these treatments on various physiological parameters after subsequent lethal heat or salt stresses. Tobacco cells developed a tolerance to a non-permissive temperature stress (54C for 14 min) when pretreated with heat shock of 38C for 2h but not when pretreated at 42C for 2h. Cells pretreated at 38 (2h) exhibited less than 30% normal growth when the 54C stress came immediately after the 38C treatment. Tolerance to the 54C stress developed with increased interval between shock and stress with cells exhibiting 95% normal regrowth when the 54C stress was administered 8h after the 38C shock. The developement of heat tolerance was inhibited if heat shock was done in the presence of a non-injuring level of EGTA (.0.5mM). Cells treated with EGTA during heat shock grew normally at 23C but not after a 54C heat stress. EDTA (0.5mM) had little effect on the acquisition of tolerance to heat stress.Wisconsin-38 cells developed a tolerance to a non-permissive salt stress (2% NaCl for 16h) when pretreated at a lower salt level (1.2% NaCl) for 3h. Cells heat shocked at 38C exhibited increased tolerance of the lethal salt stress up to 8h. Conversely, cells heat shocked at 42C exhibited immediate tolerance to lethal salt stress and this tolerance decayed over eight hours. The heat shock-induced acquisition of salt tolerance was inhibited by both EGTA and EDTA.Proteins synthesized during heat and salt stress treatments were labeled with [35S]-methionine and/or [3H]-leucine and separated using Sodium dodecylsulfate polyacrylamide gel electrophoresis. Fluorographic analysis of the gels indicate that a number of proteins are produced in response to heat shock. Similar analysis of proteins from salt shocked cells indicates that no salt shock proteins are produced in response to a brief low-level sodium chloride shock.
41
Chevrot, Thierry. "Pressure effects on the hot-salt stress-corrosion cracking of titanium alloys." Thesis, Cranfield University, 1994. http://dspace.lib.cranfield.ac.uk/handle/1826/7745.
Full textAbstract:
Benefiting from good specific mechanical properties, exceptional oxidation resistance, and high temperature capability, Titanium Alloys are used in Gas Turbine Engines, especially in the early stages of the compressor. However they are subject to stresscorrosion cracking in the laboratory when subjected to stresses and contaminated with salts at elevated temperatures. The lack of in-service failures of titanium components due to Hot-Salt Stress-Corrosion Cracking (HSSCC) is not yet understood. The parameters influencing the HSSCC of titanium alloys (temperature, load, stress and temperature cycling, quantity and kind of salt, air velocity, water vapour or oxygen content of the atmosphere, composition, texture, and microstructure of the alloy, surtace conditions), cannot account for the lack of in-service failure. After an examination of the service conditions within a typical gas turbine engine compressor, it was considered that the high pressures prevailing may extend the life of titanium alloys subjected to HSSCC. This work used a unique high temperature, high pressure, servo-hydraulic facility in order to carry out hot-salt stress-corrosion testing on titanium alloy 1M! 834 at high pressure. The results obtained show that high oxygen partial pressures extend significantly the life of 1M! 834 subjected to HSSCC. Continuous thermogravimetric measurements both in oxidising and salt-corroding environments were carried out to study the kinetics of the hot-salt attack of IMI 834. Basic metallography revealed the formation of channels which extend deep into the metal during the initial stages of hot-salt-corrosion. Theoretical thermodynamic studies highlighted the role of alloying elements and vapour phase metallic chlorides in the mechanisms of the HSSCC of titanium alloys. A new model for the hot-salt stress-corrosion of titanium alloys is proposed. It is based on the establishment of a self sustaining cycle where vapour phase metallic chlorides act as hydrogen carriers and can diffuse quickly into the material through channels.
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Seebaruth, Khemnandanee. "A microstructural study of hot salt stress corrosion cracking in titanium alloys." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308326.
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Story, Geraint-Wyn. "Development of a non-invasive screen for salt stress in Arabidopsis thaliana." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612986.
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Foust, Christy Marie. "Seeking Generalities in Salt Stress Effects on Herbivores: A Multi-Species Approach." UNF Digital Commons, 2010. http://digitalcommons.unf.edu/etd/377.
Full textAbstract:
Stress has been identified as one of the primary factors influencing the structure of food webs, but few conclusions about the effects of stress on community dynamics have emerged. This study examined generalities that exist between salt stress and insect herbivore responses. Ambient salinity was artificially increased by adding 1.3 kg/m2 of salt to six different plant species: Avicennia germinans, Baccharis halimifolia, Batis maritima, Borrichia frutescens, Iva frutescens, and Spartina alterniflora. By performing a multiple species examination, stress responses were examined to determine if consistencies within and between plant type, ambient salinity conditions, and host plant species (among other criteria) existed, allowing for generalizations to be made about stress and herbivore interactions. Herbivore responses were determined by direct visual counts and indirect visual evidence of insects (e.g. galls, stem boring, and leaf mining). A metaanalysis was then performed on the data to determine the factors that may result in consistent responses to salt stress. No differences were found between insect feeding guilds. Herbivory increased in the presence of that added salt in high ambient salinity conditions, increased on experimental Spartina plants, and decreased on experimental Iva plants. These findings suggest that stress is generally a more important factor for plants in areas of already high ambient salinity. Results have been disparate in various studies, likely due to the difficulty in making comparisons between different field sites and experimental designs. This study addresses these issues, and ultimately finds that consistencies can be found among multiple species within communities.
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Zhou, Maoqian 1961. "Nitrogen fixation by alfalfa as affected by salt stress and nitrogen levels." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277231.
Full textAbstract:
The growth and Nitrogen fixation by one low salt tolerant alfalfa (Medicago sativa L.) and two germination salt tolerant selections inoculated with were investigated at two salt levels (0, -0.6 Mpa) and two N rates (1, 5ppm) using a system which automatically recirculates a nutrient solution. The high level of salinity (-0.6 Mpa osmotic potential of culture solution) resulted in substantial reduction in the N fixation percentage and total fixed N. The effect of salinity was more pronounced for later cuttings than for the earlier cutting. The N fixation percentages were substantially decreased by increasing N level and the reduction was enhanced by time. The N treatment levels did not exhibit a significant effect on total fixed N. Cultivars did not differ in either growth or N fixation. However, the interaction of N and salinity significantly decreased the percentage and amount of N fixation.
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Al-Bahrany, Abdulaziz Maatook 1960. "Physiological and biochemical responses of short staple cotton (Gossypium hirsutum L.) to salt stress." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184634.
Full textAbstract:
Three cotton (Gossypium hirsutum L.) germplasms (DP62, 84027, and 84033) were used to investigate the physiology of salt tolerance. Lines 84027 and 84033 were developed from the parental line DP62 and showed superior vigor under varying NaCl conditions (0.5 to 2.0 M) during germination and emergence. Proline levels increased in the leaves of all germplasms in response to increasing salinity. Varietal differences in proline levels did not reflect their variation in salt tolerance. Several physiological characteristics were also evaluated under non-saline condition in the greenhouse. There were no significant differences among germplasm sources for all parameters measured. However, salinity reduced transpiration rate, increased leaf diffusive resistance and leaf temperature for all lines. Ribosomal-RNA levels in all germplasms were evaluated after seeds were stressed for 24 hrs in various concentrations of NaCl and then germinated under normal conditions for 72 hrs. Ribosomal-RNA levels were inversely related to salt concentrations. Line 84033 followed by line 84027 had highest ribosomal-RNA content than the parental line DP62 when averaged over the four salt concentrations. Sodium content (ppm/g FW) and Cl⁻ content (ppm/g FW) were evaluated in microsomal and cell walls fractions as well as a cytoplasmic fraction which consisted of vacuoles, mitochondria, and plastids. The Cl⁻ ion exhibited a greater consistency in a concentration shift from one fraction to another as a function of time than did the Na⁺ ion. As a result, there may be a correlation between the drop in ribosomal-RNA and the amount of Cl⁻ in the microsomal fraction. Other parameters measured in the germinating seed were soluble protein (globulin), insoluble proteins (prolamin and glutelin) and fiber percentage. Variations within the germplasms were shown to exist. This study shows that even among lines that have been selected for salt tolerance from a single variety, the possibility exists that each of these lines may have a different mechanism to cope with salt stress.
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Benothmane, Faycal. "Mycorrhizal Colonization and Growth Characteristics of Salt Stressed Solanum Lycopersicum L." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19908.
Full textAbstract:
The present study aimed to examine the effects of root colonization in tomato, Solanum lycopersicum L. cv. Moneymaker, by the arbuscular mycorrhizal (AM) fungus, Glomus intraradices Shenck and Smith, on alleviating salt stress. I postulated that AM symbiosis increases tomato plant performance to salt stress. Two greenhouse experiments were done according to a randomized factorial experimental design. The results showed a significantly higher level of AM root colonization that also occurred earlier in salt than non-salt treated plants. There were also positive interactions between root colonization levels and the alleviation of salt stress; these contributions resulted initially on higher root fresh mass (FM), later on shoot FM, and DM, and higher phosphorus and unchanged potassium concentrations in roots. The effects observed in salt-treated plants were significant when root colonization levels were significantly different than those observed in non-salt treated plants. This suggests a relationship between the level of root colonization and the alleviation of salt stress in plants. The attempt to use molecular techniques to detect early root colonization was quite successful in detecting the presence of G. intraradices in AM plants. However, it was not possible to detect the presence of the AM fungus as early as by classical root staining. This was observed presumably because sampling methods were different. In general, the results support the hypothesis that AM root colonization contributes to some extent to salt resistance of tomato plants.
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Wang, Lijun. "Physiological response of Kentucky bluegrass under salinity stress." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1492.
Full textAbstract:
Salinity is a major abiotic stress in plant agriculture which reduces seed germination, vegetative growth, and flowering, and limits crop productivity world-wide. Salinity causes water deficit, ion toxicity, and nutrient deficiency in plants, which can result in cellular damage, growth reduction, and even death. Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season species in cool-arid climates; however it has relatively poor salt-tolerance. Thus the development of Kentucky bluegrass genotypes with increased salt tolerance is of interest to turf breeders. One impediment to selection towards this goal is finding an efficient and accurate method to evaluate the salt tolerance. The objective of this study was to examine physiological responses to salt stress and to evaluate the genetic diversity among the accessions used in the research. Salt-tolerant accessions PI371768 (768) and PI440603 (603) and salt-sensitive varieties Midnight and Baron were exposed to four levels of salinity imposed by irrigating with salt solutions of 0 dS m-1 (control), 6 dS m-1, 12 dS m-1, and 18 dS m-1 or 24 dS m-1. Soil salinity was measured using Acclima Digital TDT sensors and grass response to the stress was measured using turf quality ratings, stomatal conductance, leaf water potential and electrolyte leakage. In general, turfgrass quality, stomatal conductance, and leaf water potential decreased while electrolyte leakage increased under salinity stress. Midnight and Baron exhibited greater changes in these measurements, indicating more sensitivity compared to 768 and 603. The 6 dS m-1 treatment had little effect on the salt-tolerant accessions. Salt tolerance of 603 and 768 was confirmed and likewise, salt sensitivity of Baron and Midnight was confirmed. The genetic similarity of all cultivars used in this study was very high.
All of the evaluation measurements were highly correlated, with water potential and electrolyte leakage being the most reliable and accurate methods due to the low standard deviations. Due to more repeatable methods and less user error, electrolyte leakage and turfgrass quality are recommended methods for screening salt tolerance of turfgrasses.
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Sudiro, Cristina. "Unveiling salt-tolerance mechanisms in Italian rice varieties." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3425725.
Full textAbstract:
Plant tolerance to salinity stress involves complex physiological traits, metabolic pathways, and molecular and gene networks (Gupta and Huang, 2014, Int J Genomics). Salinity impacts plants by causing osmotic stress and ion toxicity. Salt stress also causes the production of excessive reactive oxygen species (Munns and Tester, 2008, Annu Rev Plant Biol). Salt-stress perception and signalling are required for appropriate responses to these insults. Key components of the signalling pathways induced by salt stress are Ca2+ (Knight et al., 1997, Plant J), NO and the recently re-evaluated H2O2.
Cereals are overall considered to be salt sensitive and, among them, rice is the most sensitive one.
Two Italian rice cultivars, Vialone Nano (VN) and Baldo (B), were selected for their contrasting salt sensitivity, being VN more sensitive and B more tolerant. The analysis of the salt-stress responses in these varieties was performed both in plants and in suspension cell cultures established from their seeds.
At the whole plant level, morphological, physiological and molecular analyses showed B being able to rapidly respond to the stress, by developing of an adaptive programme that allowed growth to resume.
The components of the signal transduction pathway induced by salt stress were investigated in suspension cell cultures. The role of H2O2 and NO as signalling molecules in salt stress response was investigated in detail. In particular, the signature of H2O2 seemed to be important to determine the fate of the cells: acclimation in B versus programmed cell death in VN.
Moreover, to study Ca2+ signalling, transformed plants harboring Ca2+ sensors of both Italian rice varieties were obtained. These plants will be used as a tool to compare calcium signatures induced by salt stress in the sensitive and tolerant variety.<br>La tolleranza delle piante allo stress salino è un sistema complesso di tratti fisiologici, vie metaboliche, e reti molecolari e geniche (Gupta e Huang, 2014, Int J Genomics). Nelle piante, lo stress salino causa due tipi di stress: uno stress osmotico e uno stress ionico. Un’alta salinità provoca anche una eccessiva produzione di dannose specie reattive dell'ossigeno (Munns e Tester, 2008, Annu Rev impianto Biol). La percezione e il signalling dello stress sono necessari per l’attivazione di una risposta adeguata. I componenti chiave delle vie di signalling indotte da stress salino sono Ca2+ (Cavaliere et al., 1997, pianta J), NO e H2O2.
I cereali sono generalmente considerati sensibile al sale e, tra questi, il riso è il più sensibile.
Due varietà di riso italiano, Vialone Nano (VN) e Baldo (B), sono state selezionate per la loro contrastante sensibilità al sale: VN è risultato essere il più sensibile mentre B il più tollerante. Le analisi delle risposte allo stress salino in queste due varietà sono state effettuate sia in pianta che in colture cellulari generate a partire da semi.
A livello dell’intera pianta, analisi morfologiche, fisiologiche e molecolari hanno dimostrato che B è in grado di rispondere rapidamente allo stress, mettendo in atto un programma di adattamento che permette di riprendere la crescita.
I componenti della via di trasduzione del segnale indotto da stress sono stati studiati in colture cellulari in sospensione. Il ruolo di H2O2 e NO, come molecole segnale in risposta allo stress salino, è stato studiato in dettaglio. In particolare, un diverso andamento nella produzione di H2O2 sembra essere importante per determinare il destino delle cellule: acclimatazione in B contro morte cellulare programmata in VN.
Inoltre, sono state ottenute piante esprimenti sensori per il calcio per entrambe le varietà di riso italiano. Queste piante saranno uno strumento utile per studiare il signalling del calcio indotto da stress salino.
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Mattern, Heather R. "Laser peening for mitigation of stress corrosion cracking at welds in marine aluminum." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5710.
Full textAbstract:
Approved for public release; distribution is unlimited.<br>This work examines the use of laser peening (LP) for mitigation of stress corrosion cracking (SCC) in marine grade aluminum alloys (Al-Mg). These alloys can be sensitized during welding and will develop a tensile residual stress in the heat affected zone that may promote SCC in a salt water environment. Metal inert gas welded aluminum alloy 5083 (4.8wt% Mg) plate was laser peened using a variety of laser intensities to create compressive stresses. Mechanical tests were performed to investigate the SCC of the material including slow strain rate testing and potentiostatically driven, salt-water exposure. Microstructural and micromechanical tests were performed to characterize the effects of LP on the microstructure of the material. The slow strain rate testing showed a systematic decrease in ductility with increasing LP intensity. The fracture surfaces on all welded samples were indicative of ductile fracture but with a pre-crack length that scaled inversely with LP intensity. The hardness of the material increased with LP intensity. This work suggests that welded aluminum alloy 5083 does not readily stress corrosion crack. LP does affect the mechanical behavior of the material, but its full effect on stress corrosion behavior requires further study.