Добірка наукової літератури з теми "Rhizosphere process"
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Статті в журналах з теми "Rhizosphere process":
1
Ye, Fan, Miao Jiang, Peng Zhang, Lei Liu, Shengqun Liu, Chunsheng Zhao, and Xiangnan Li. "Exogenous Melatonin Reprograms the Rhizosphere Microbial Community to Modulate the Responses of Barley to Drought Stress." International Journal of Molecular Sciences 23, no. 17 (August 26, 2022): 9665. http://dx.doi.org/10.3390/ijms23179665.
Анотація:
The rhizospheric melatonin application-induced drought tolerance has been illuminated in various plant species, while the roles of the rhizosphere microbial community in this process are still unclear. Here, the diversity and functions of the rhizosphere microbial community and related physiological parameters were tested in barley under the rhizospheric melatonin application and drought. Exogenous melatonin improved plant performance under drought via increasing the activities of non-structural carbohydrate metabolism enzymes and activating the antioxidant enzyme systems in barley roots under drought. The 16S/ITS rRNA gene sequencing revealed that drought and melatonin altered the compositions of the microbiome. Exogenous melatonin increased the relative abundance of the bacterial community in carbohydrate and carboxylate degradation, while decreasing the relative abundance in the pathways of fatty acid and lipid degradation and inorganic nutrient metabolism under drought. These results suggest that the effects of melatonin on rhizosphere microbes and nutrient condition need to be considered in its application for crop drought-resistant cultivation.
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Ekyastuti, Wiwik, Dwi Astiani, Emi Roslinda, Hanna Artuti Ekamawanti, and Tri Widiastuti. "Population of Rhizosphere Bacteria on Several Species of Crops In The Tailings of Ex-Gold Mine." IOP Conference Series: Earth and Environmental Science 1153, no. 1 (May 1, 2023): 012024. http://dx.doi.org/10.1088/1755-1315/1153/1/012024.
Анотація:
Abstract Tailings of ex-gold mines leave several environmental damage problems. Environmental damage causes disruption of microorganisms including bacteria. The revegetation of ex-gold mine tailings in Menjalin sub-district, Landak district, West Kalimantan has begun by local communities using agricultural crops. Women as farmers have an important role in the tailing revegetation process using agricultural crops. Therefore, women can help improve the tailings ecosystem as well as the family economy. The objective of the study was to detect the presence and density of bacterial populations in the rhizosphere of the revegetation crops. The research was conducted by survey method. Soil samples were taken compositely from the rhizosphere of four species of agricultural crops cultivated in tailings, i.e: Capsicum frutescens L., Solanum melongena, Ipomoea batatas L., and Manihot utilissima. The results showed that soil bacteria found growing well in the rhizospheres of four species crops. Two genera of bacteria were found in the tailing rhizosphere of ex-gold mine in Menjalin sub-district, namely Azotobacter and Pseudomonas. The bacterial population density in the rhizosphere of M. utilissima was significantly the highest. Meanwhile, the bacterial population density in the rhizosphere of C. frutescens, I. batatas, and S. melongena did not differ in the medium category. Further investigation found that the bacterial population in the rhizosphere of M. utilissima was 126.8 – 217 times denser than the other three crop species.
3
Liu, Hong, Feifei Sun, Junwei Peng, Minchong Shen, Jiangang Li, and Yuanhua Dong. "Deterministic Process Dominated Belowground Community Assembly When Suffering Tomato Bacterial Wilt Disease." Agronomy 12, no. 5 (April 24, 2022): 1024. http://dx.doi.org/10.3390/agronomy12051024.
Анотація:
Soil microbial communities are closely associated with ecosystem functions. However, unravelling the complex nature of the microbial world and successfully utilizing all positive interactions for multipurpose environmental benefits is still a major challenge. Here, we describe the soil bacterial communities in different niches of healthy and diseased tomatoes under natural conditions. A higher abundance of the pathogen Ralstonia solanacearum and lower bacterial diversity were observed in the disease samples. The healthy tomato rhizosphere harbored more plant-beneficial microbes, including Bacillus and Streptomyces. Also, the co-occurrence network in the healthy rhizosphere samples was more complicated, so as to better adapt to the soil-borne pathogen invasion. Both the beta nearest-taxon-index (βNTI) and normalized stochasticity ratio (NST) analyses demonstrated that healthy rhizosphere communities were less phylogenetically clustered and mainly dominated by dispersal limitation, while homogeneous selection was the major assembly process driving the rhizosphere community of diseased samples. The results obtained with community assembly methods and co-occurrence network analysis revealed that healthy rhizosphere bacterial communities possessed potentially broader environmental stress (soil-borne pathogen stress) adaptability compared with diseased rhizosphere bacterial communities. In conclusion, this study contributed to widening our understanding of the potential mechanisms of soil bacterial community composition and assembly responding to soil-borne pathogen invasion.
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Nyonita Punjungsari, Tyas, Agung Setya Wibowo, Intan Fuji Arriani, and Palupi Puspitorini. "EKSPLORASI KONSORSIUM PBRM (PLANT BENEFICIAL RHIZOSPHERIC MICROORGANISM) DALAM NUE (NUTRIENT USE EFFICIENCY) PADA PERTUMBUHAN JAGUNG (Zea mays L)." VIABEL: Jurnal Ilmiah Ilmu-Ilmu Pertanian 13, no. 2 (November 14, 2019): 11–15. http://dx.doi.org/10.35457/viabel.v13i2.836.
Анотація:
PBRM (Plant Beneficial Rhizospheric Microorganism) is a microbe that is able to form colonies in plant roots (rhizosphere) that have the ability to fix nitrogen (N), and dissolve potassium (K), phosphorus (P), and zinc (Zn).
Increasing NUE can increase plant growth through various mechanisms. Population and dynamics of rhizosphere microorganisms are different from other soil microorganisms, this is caused by an increase. The purpose of this study was to determine the type of rhizosphere bacteria that can be as PBRM. The method used The research was conducted at the Microbiology Laboratory of the Faculty of Agriculture, Brawijaya University, Malang. The characterization process was carried out in UB's microbiology laboratory. 50 grams of soil for planting corn were put into an erlenmeyer containing 500 ml NB (for bacteria) and 500 ml liquid PDA (for mold) and then incubated with the secretary for about 24 hours and then diluted in series to a dilution rate of 10-3,10-4,10 -5. Then from the dilution factor of 10-3,10-4,10-5 0.1 ml is taken and inoculated in solid media by the pour plate method. The results showed that the antagonistic rhizosphere bacteria were P. fluorescens, B. subtillis, and Rhizobium sp.
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Elliott, Monica L., J. A. McInroy, K. Xiong, J. H. Kim, H. D. Skipper, and E. A. Guertal. "Taxonomic Diversity of Rhizosphere Bacteria in Golf Course Putting Greens at Representative Sites in the Southeastern United States." HortScience 43, no. 2 (April 2008): 514–18. http://dx.doi.org/10.21273/hortsci.43.2.514.
Анотація:
Taxonomic diversity of bacteria associated with golf course putting greens is a topic that has not been widely explored. The purpose of this project was to isolate and identify culturable bacteria from the rhizosphere of creeping bentgrass (Agrostris palustris Huds.) at two sites (Alabama and North Carolina) and hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] at two sites (Florida and South Carolina) for a minimum of 3 years with sampling initiated after the construction process. Randomly selected colonies were identified using gas chromatography for analysis of fatty acid methyl ester profiles. Over 9000 isolates were successfully analyzed. When a similarity index of 0.300 or higher was used, the average number of unidentifiable isolates was 38.6%. The two dominant genera in both bentgrass and bermudagrass rhizospheres were Bacillus and Pseudomonas with Bacillus dominant in bermudagrass and Pseudomonas dominant or equal to Bacillus in bentgrass. Other genera that comprised at least 1% of the isolates at all four sites were Clavibacter, Flavobacterium, and Microbacterium. Arthrobacter also comprised a significant portion of the bacterial isolates in the bentgrass rhizosphere, but not the bermudagrass rhizosphere. Overall, there were 40 genera common to all four sites. At the species level, there were five that comprised at least 1% of the isolates at each location: B. cereus, B. megaterium, C. michiganensis, F. johnsoniae, and P. putida. As has been reported for many grasses, we found considerable taxonomic diversity among the culturable bacterial populations from the rhizospheres of bentgrass and bermudagrass grown in sand-based putting greens.
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Liu, Zhixiang, Jizhe Ying, and Chengcheng Liu. "Changes in Rhizosphere Soil Microorganisms and Metabolites during the Cultivation of Fritillaria cirrhosa." Biology 13, no. 5 (May 11, 2024): 334. http://dx.doi.org/10.3390/biology13050334.
Анотація:
Fritillaria cirrhosa is an important cash crop, and its industrial development is being hampered by continuous cropping obstacles, but the composition and changes of rhizosphere soil microorganisms and metabolites in the cultivation process of Fritillaria cirrhosa have not been revealed. We used metagenomics sequencing to analyze the changes of the microbiome in rhizosphere soil during a three-year cultivation process, and combined it with LC-MS/MS to detect the changes of metabolites. Results indicate that during the cultivation of Fritillaria cirrhosa, the composition and structure of the rhizosphere soil microbial community changed significantly, especially regarding the relative abundance of some beneficial bacteria. The abundance of Bradyrhizobium decreased from 7.04% in the first year to about 5% in the second and third years; the relative abundance of Pseudomonas also decreased from 6.20% in the first year to 2.22% in the third year; and the relative abundance of Lysobacter decreased significantly from more than 4% in the first two years of cultivation to 1.01% in the third year of cultivation. However, the relative abundance of some harmful fungi has significantly increased, such as Botrytis, which increased significantly from less than 3% in the first two years to 7.93% in the third year, and Talaromyces fungi, which were almost non-existent in the first two years of cultivation, significantly increased to 3.43% in the third year of cultivation. The composition and structure of Fritillaria cirrhosa rhizosphere metabolites also changed significantly, the most important of which were carbohydrates represented by sucrose (48.00–9.36–10.07%) and some amino acid compounds related to continuous cropping obstacles. Co-occurrence analysis showed that there was a significant correlation between differential microorganisms and differential metabolites, but Procrustes analysis showed that the relationship between bacteria and metabolites was closer than that between fungi and metabolites. In general, in the process of Fritillaria cirrhosa cultivation, the beneficial bacteria in the rhizosphere decreased, the harmful bacteria increased, and the relative abundance of carbohydrate and amino acid compounds related to continuous cropping obstacles changed significantly. There is a significant correlation between microorganisms and metabolites, and the shaping of the Fritillaria cirrhosa rhizosphere’s microecology by bacteria is more relevant.
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Golestanifard, Alireza, Markus Puschenreiter, Amal Aryan, and Walter Wenzel. "Phosphorus depletion controls Cu and Zn biogeochemistry in canola and corn rhizosphere on a calcareous soil." Plant, Soil and Environment 67, No. 8 (August 12, 2021): 443–52. http://dx.doi.org/10.17221/122/2021-pse.
Анотація:
Phosphorus (P) deficiency may trigger rhizodeposition, including protons and organic compounds, with possible effects on metal solubility and speciation. To explore the relevance of this process, we investigated biogeochemical changes in the rhizosphere of P-deficient canola (Brassica napus L.) and corn (Zea mays L.) cultivars grown in a pot experiment on calcareous soil. Depletion of total soluble (0.005 mol/L Ca(NO3)2-extractable) P in the rhizosphere varied with crop species and cultivar but was generally strong and negatively correlated with dissolved organic carbon (DOC) in canola (R2 = 0.868) and corn (R2 = 0.844) rhizospheres, indicating rhizodeposition in response to limited P availability. DOC was correlated with dissolved Cu, explaining 86% of its variation in the rhizosphere and bulk soil solution of canola and corn cultivars, respectively, suggesting Cu mobilisation via the formation of Cu-organic complexes. In line with lower Zn-organic complex stabilities, the effect of rhizodeposition was less pronounced for Zn mobilisation. We show that the P nutritional status of plants and the related variation of rhizodeposition among crops and cultivars represents a major control of metal solubility in soil, with possible effects on micronutrient supply and toxicity. Hence, targeted P availability control should be considered in the management of polluted and micronutrient-deficient soils.
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Chowdhury, Saikat, Ramya Thangarajan, Nanthi Bolan, Julianne O'Reilly-Wapstra, Anitha Kunhikrishnan, and Ravi Naidu. "Nitrification potential in the rhizosphere of Australian native vegetation." Soil Research 55, no. 1 (2017): 58. http://dx.doi.org/10.1071/sr16116.
Анотація:
The rhizosphere influences nutrient dynamics in soil mainly by altering microbial activity. The objective of this study was to evaluate the rhizosphere effect on nitrogen transformation in Australian native vegetation in relation to nitrification potential (NP). Microbial activity, NP, and nitrifiers (ammonia-oxidising bacteria, AOB) were compared between rhizosphere and non-rhizosphere soils of several Australian native vegetation under field conditions. These parameters were also measured with increasing distance from the rhizosphere of selected plant species using plant growth experiments. To examine the persistence of nitrification inhibitory activity of rhizosphere soil on non-rhizosphere soil, the soils were mixed at various ratios and examined for NP and AOB populations. The rhizosphere soil from all native vegetation (29 species) had higher microbial activity than non-rhizosphere soil, whereas 13 species showed very low NP in the rhizosphere when compared with non-rhizosphere soil. Nitrification potential and AOB populations obtained in the soil mixture were lower than the predicted values, indicating the persistence of a nitrification inhibitory effect of the rhizosphere soils on non-rhizosphere soils. In plant growth experiments the microbial activity decreased with increasing distance from rhizosphere, whereas the opposite was observed for NP and AOB populations, indicating the selective inhibition of nitrification process in the rhizosphere of the Australian native plants Scaevola albida, Chrysocephalum semipapposum, and Enteropogon acicularis. Some Australian native plants inhibited nitrification in their rhizosphere. We propose future studies on these selected plant species by identifying and characterising the nitrification inhibiting compounds and also the potential of nitrification inhibition in reducing nitrogen losses through nitrate leaching and nitrous oxide emission.
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Huang, Ning, Xingmin Zhao, Xinxin Guo, Biao Sui, Jinhua Liu, Hongbin Wang, and Jialin Li. "Tillage Methods Change Nitrogen Distribution and Enzyme Activities in Maize Rhizosphere and Non-Rhizosphere Chernozem in Jilin Province of China." Processes 11, no. 11 (November 20, 2023): 3253. http://dx.doi.org/10.3390/pr11113253.
Анотація:
The tillage method in farming systems is essential to develop strategies to increase fertilizer uptake by plant roots and to avoid environmental pollution. The field study aimed to investigate the characteristics of nitrogen and enzyme activities in rhizosphere soil with different tillage methods. Four treatment plots applied with fertilizers were established: continuous rotary tillage (CR), plowing-rotary tillage (PR), continuous no-till (CN) and ploughing-no-till (PN). The total content of nitrogen in chernozem was high during early stages of plant growth, and then it decreased with the maize growth. In the rhizosphere soil, the total N accounted 1314.45, 1265.96, 1120.47, 1120.47, 1204.05 mg·kg−1 of CR, PR, CN, and PN, respectively, which were markedly greater than that of non-rhizosphere soil (1237.52, 1168.40, 984.51, 1106.49 mg·kg−1 of CR, PR, CN, and PN, respectively). At first growth stages, content of NH4+-N and NO3−-N in two soil regions was low, then increased gradually, which followed the order of CR < PR < PN < CN. The rhizosphere soil showed slightly higher concentration of NH4+-N and NO3−-N than non-rhizosphere. The soil enzymes were more active in the rhizosphere soil than that of non-rhizosphere during the whole maize growth stages. Due to minimal damage to the soil environment and optimal soil moisture and temperature, the urease and catalase activities were greatest in the rhizosphere for CN treatment. Therefore, CN was recommended to be used by farmers for the improvement of macronutrient availability and soil enzyme activities in the soil.
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Qin, Jianqiao, Huarong Zhao, Ming Dai, Peng Zhao, Xi Chen, Hao Liu, and Baizhou Lu. "Speciation Distribution and Influencing Factors of Heavy Metals in Rhizosphere Soil of Miscanthus Floridulus in the Tailing Reservoir Area of Dabaoshan Iron Polymetallic Mine in Northern Guangdong." Processes 10, no. 6 (June 18, 2022): 1217. http://dx.doi.org/10.3390/pr10061217.
Анотація:
Through field investigation and experimental analysis, the forms, contents and distribution of heavy metals (Zn, Pb, Cu, Cd, Ni, Cr) in rhizosphere and non-rhizosphere soils of Miscanthus floridulus growing everywhere in Tielongwei mine pond (sample plot 1), Caoduikeng tailings pond (sample plot 2), Donghua tailings pond (sample plot 3) and Small tailings pond (sample plot 4) in Dabaoshan, Guangdong Province were studied. The results showed that the main forms and distributions of heavy metals in rhizosphere and non-rhizosphere soils are basically the same, which shows that the mineral content accounts for most of the total amount of heavy metals, while the exchange content is low. Compared with non-rhizosphere soil, the proportion of exchangeable and organic heavy metals in rhizosphere soil increased significantly, in which the proportion of organic-bound Cu increased by 53.25%, the proportion of organic-bound Cd and Pb increased by more than 17%, and the proportion of Zn increased by 5.67%. At the same time, the contents of carbonate-bound and iron manganese oxide-bound decreased. Statistical analyses showed that the morphological distribution of Zn, Pb, Cu, Cd, Ni and Cr in rhizosphere soil was closely related to soil pH value, organic matter content, plant growth and other factors. The results of this study provided a basis for the restoration of heavy metal-contaminated sites by Miscanthus.
Дисертації з теми "Rhizosphere process":
1
Ndakidemi, Patrick Alois. "Nutritional characterisation of the rhizosphere of symbiotic cowpea and maize plants in different cropping system." Thesis, Cape Peninsula University of Technology, 2005. http://hdl.handle.net/20.500.11838/762.
Анотація:
Thesis (DTech (Chemistry))--Cape Peninsula University of Technology, 2005A 2-factorial experiment, involving 3 levels of phosphorus (0, 40, and 80 kg P.ha-I ) as main treatment and 4 cropping systems (mono crop, maize/cowpea inter-row, maize/cowpea intra-row, and maize/cowpea intra-hole cropping) as sub-treatment was conducted in the field for 2 consecutive years in 2003 and 2004 to assess i) the effects of exogenous P supply and cropping system on the concentrations of plant-available nutrients in the rhizosphere of cowpea and maize; ii) the effect of exogenous P supply on tissue concentrations of minerals in nodulated cowpea and maize in mixed plant cultures iii) the effects of exogenous P supply and cropping system on plant growth and N2 fixation, and iv) the effects of exogenous P supply and cropping system on phosphatase activity and microbial biomass in the rhizosphere of cowpea and maize. At harvest, it was found that applying 40 or 80 kg P.ha-I significantly increased cowpea grain yields by 59-65% in 2003 and 44-55% in 2004. With maize, the increases in grain yield were 2037% in 2003 and 48-55% in 2004 relative to zero-P control. In both cropping seasons, the number of pod-bearing peduncles per plant, the number of pods per plant, the number of seeds per pod, and seed yield per cowpea plant were significantly increased with the application of exogenous P. In contrast, these parameters were all significantly depressed by mixed culture relative to mono crop cowpea. Intercropping maize with cowpea produced higher total yields per unit land area than the sole crop counterpart.
2
Liu, Chang. "Phytostabilization of ion-adsorption rare earth element mine tailings using the fiber plant ramie (Boehmeria nivea L.)." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0341.
Анотація:
Les gisements à argiles ioniques sont l’une des principales sources mondiales de REEs lourdes (HREEs). Leur exploitation a engendré de vastes surfaces de stériles miniers, qui sont une menace sérieuse pour l'environnement et la santé des populations voisines. La restauration des écosystèmes nécessite des solutions efficaces et adaptées à de telles surfaces. La phytostabilisation repose sur l’installation de plantes avec ou sans amendement et, en général, utilise des plantes tolérantes. Mais des plantes à intérêt économique peuvent être envisagées. La ramie est une plante vivace qui produit des fibres de haute qualité. Elle est potentiellement utilisable en phytostabilisation car tolérante aux métaux lourds. Mais cette option n’a pas été encore testée avec des REEs et dans des milieux difficiles (e.g. pH). C’est pourquoi cette thèse a étudié : (i) la tolérance de la ramie à des concentrations élevées de REEs ; (ii) la réponse de la ramie en termes de croissance et de développement sur des résidus miniers de REEs ; (iii) la faisabilité de la phytostabilisation avec la ramie et l’apport d'amendements et les conséquences sur l’évolution des propriétés du sol. L’approche générale a reposé sur des essais culturaux en conditions contrôlées, hydroponiques et en rhizotrons, et sur des essais en vraie grandeur conduits sur un ancien site minier de REEs. Les cultures hydroponiques ont montré que la biomasse de ramie n’est pas affectée par des concentrations faibles de REEs (1,6 à 80 μmol/L), tandis que des concentrations supérieures (160–800 µmol/L) inhibent la croissance. Les concentrations de P et Mo dans les racines augmentent avec l'augmentation des concentrations de REEs. Les processus d'absorption conduisent à une anomalie positive en Ce et à un enrichissement en HREEs dans les feuilles. L’expérience en rhizotron a montré l’intérêt de l’amendement organique. Il augmente le pH et les concentrations en éléments nutritifs (Ca, Mg, N, P), et diminue les REEs et l'Al extractibles (90%) ; la croissance et le développement de ramie sont alors favorisés. Seules les racines fines se développent durant les premiers mois d’expérience, tandis que 75% de la biomasse racinaire est représentée par les grosses racines après cinq mois. Elles contiennent 7–15% des REEs et 31–35% de l’Al absorbés par la plante. Ramie ne modifie pas la concentration des REEs extractibles, mais diminue celle d'Al dans les horizons supérieurs du sol. Le suivi pendant deux ans d’une expérimentation in situ de phytostabilisation avec apport d’amendement organique confirme les changements observés des propriétés chimiques du sol en surface (pH, éléments nutritifs, REEs et Al extractibles). Les grosses racines stockent plus de 60% des REEs et de l’Al absorbé. En plus de l'amélioration des propriétés du sol par l’amendement organique, les racines de ramie contribuent à l'apport de C, l'activation des nutriments et la stabilisation des éléments toxiques. Au plan des propriétés physiques du sol, la phytostabilisation augmente la porosité du sol, et favorise la différentiation du profil en horizons distincts. Les concentrations de REEs et d’Al extractibles dans les horizons traités sont significativement inférieures à celle des témoins. Les grosses racines sont observées dans l’horizon amendé, tandis que les racines fines atteignent 50 cm. L’observation des lames minces de sol a révélé des associations racines-minéraux, matière organique-minéraux et minéraux-minéraux, qui contribuent à l’édification de la structure du sol. En conclusion, la thèse a permis de mieux comprendre les mécanismes de tolérance de la ramie aux REEs, de montrer les effets de la plante sur la dynamique des REEs et des éléments nutritifs, et de décrire les processus pédogénétiques précoces qui suivent l’implantation, notamment les processus de structuration du sol. Au plan pratique, le travail a montré que la phytostabilisation de sites miniers difficiles est possible avec une plante à fibre à usage [...]Ion-adsorption REE deposits are one of the world's main sources of heavy REEs (HREEs). Their exploitation has generated vast areas of mine tailings, which are a serious threat to the environment and the health of neighboring populations. The restoration of ecosystems requires effective solutions adapted to such large surfaces. Phytostabilization is based on the installation of plants with or without amendment and, in general, uses tolerant plants. But plants of economic interest can be considered. Ramie is a perennial plant that produces high quality fiber. It is potentially usable in phytostabilization because it is tolerant to heavy metals. But this option has not yet been tested with REEs and in difficult environments (e.g. pH). This is why this thesis studied: (i) the tolerance of ramie to high concentrations of REEs; (ii) the response of ramie in terms of growth and development on REE mine tailings; (iii) the feasibility of phytostabilization with ramie and the addition of amendments and the consequences on the evolution of soil properties. The general approach was based on cultivation trials under controlled, hydroponic and rhizotron conditions, and on full-scale trials conducted on a former REE mining site. Hydroponic cultures showed that ramie biomass is not affected by low concentrations of REEs (1.6–80 μmol/L), while higher concentrations (160–800 μmol/L) inhibit growth. P and Mo concentrations in the roots increased with increasing REE concentrations. The uptake processes lead to a positive Ce anomaly and an enrichment of HREEs in the leaves. The rhizotron experiment has shown the interest of organic amendment. It increases pH and nutrient concentrations (Ca, Mg, N, P), and decreases extractable REEs and Al (90%); the growth and development of ramie are then favored. Only the fine roots develop during the first months of the experiment, while 75% of the root biomass is represented by the large roots after five months. They contain 7–15% of the REEs and 31–35% of the Al taken up by the plant. Ramie does not modify the concentration of extractable REEs, but decreases that of Al in the upper soil horizons. The two-year follow-up of an in situ phytostabilization experiment with the addition of organic amendment confirms the changes observed in the chemical properties of the surface soil (pH, nutrients, REEs and extractable Al). Large roots store more than 60% of REEs and absorbed Al. In addition to improving soil properties through organic amendment, ramie roots contribute to the supply of C, the activation of nutrients and the stabilization of toxic elements. In terms of the soil physical properties, phytostabilization increases soil porosity, and favors the differentiation of the profile into distinct horizons. The concentrations of REEs and extractable Al in the treated horizons are significantly lower than those of the controls. Large roots are observed in the amended horizon, while fine roots reach 50 cm. Observation of the soil thin sections revealed root-mineral, organic matter-mineral and mineral-mineral associations, which contribute to building the soil structure. In conclusion, the thesis made it possible to better understand the mechanisms of tolerance of ramie to REEs, to show the effects of the plant on the dynamics of REEs and nutrients, and to describe the early pedogenetic processes that follow implantation, in particular the processes of soil structuration. Practically, the work has shown that phytostabilization of harsh mine sites is possible with a fiber plant for commercial use
3
Bach, Evelise. "Utilização de Burkholderia sp. 89 para o controle biológico de fungos fitopatogênicos e identificação de moléculas de seu metabolismo secundário envolvidas nesse processo." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/150647.
Анотація:
O uso de bactérias promotoras de crescimento vegetal ou agentes de biocontrole como inoculantes agrícolas é uma alternativa importante e ecologicamente correta, com grandes benefícios na agricultura para substituir, ou ao menos suplementar, a excessiva utilização de fertilizantes e pesticidas. Neste trabalho avaliamos a capacidade de biocontrole e de competência rizosférica de três bactérias com características de promoção de crescimento vegetal (Plant growth promoting - PGP): Bacillus mycoides B38V, Paenibacillus riograndensis SBR5 e Burkholderia sp. 89. As três bactérias avaliadas apresentaram grande versatilidade na utilização de substratos, o que poderia lhes garantir uma vantagem competitiva no ambiente rizosférico. Porém, inconsistências foram observadas nos ensaios em câmara de crescimento, ou seja, as características de PGP e de biocontrole observadas in vitro não se refletiram em benefícios para a planta. A linhagem 89 destacou-se pela produção de um metabólito estável com ampla atividade contra fungos fitopatogênicos. Através de abordagens genômicas e de análises multilocus, descrevemos Burkholderia sp. 89 como uma nova espécie membro do complexo Burkholderia cepacia, denominada de B. catarinensis 89T. O sequenciamento de seu genoma, seguido de uma análise pela ferramenta AntiSMASH, revelou a presença de um agrupamento gênico de peptídeo sintetases não ribossomais (NRPS) relacionadas com a biossíntese do sideróforo ornibactina e um agrupamento híbrido NRPS-policetídeo sintetase responsável pela biossíntese do glicolipopeptideo cíclico com atividade antifúngica burkholdina. Como estratégia de purificação de metabólitos secundários foi utilizada a metodologia da mineração de genoma combinada com fracionamento guiado por bioensaios seguida de análises em espectrômetro de massas. Desta forma, purificamos com sucesso duas variantes de ornibactina, D e F (761 e 789 Da, respectivamente), e detectamos a variante ornibactina B (m/z= 733) e as moléculas sinalizadoras homoserina lactonas C6-HSL, 3OH-C8-HSL e C8-HSL. Análises de espectrometria de massas demonstraram a presença de um grupo de metabólitos com massas de 1240, 1254, 1268, 1216, 1244 e 1272 Da, que, provavelmente, são novas variantes do antifúngico burkoldina. Sendo assim, B. catarinensis 89T possui potencial biotecnológico com possíveis aplicações farmacêuticas e agronômicas para o biocontrole de fungos fitopatogênicos.The use of plant growth promotion bacteria or biocontrol agents as agricultural inoculants is an important eco-friendly alternative to substitute, or at least supplement, the excessive use of fertilizers and pesticides. In this work, we evaluated the biocontrol potential and rhizosphere competence of three bacteria that had shown plant growth promotion (PGP) abilities: Bacillus mycoides B38V, Paenibacillus riograndensis SBR5 and Burkholderia sp. 89. All three bacteria presented great versatility in their substrate utilization, which could enable them to survive in a competitive rhizosphere environment. However, inconsistencies were observed in the greenhouse experiments, whereas their interesting abilities observed in vitro did not result in benefits to the plants. Strain 89 produces a stable metabolite with a wide range of antifungal activity. Genomic comparisons and multilocus sequence analysis revealed Burkholderia sp. 89 as a new species of the Burkholderia cepacia complex and we described it as B. catarinensis 89T. We sequenced its genome and analyzed it with the AntiSMASH tool. This in silico prediction revealed the presence of a nonribosomal peptide synthetase (NRPS) cluster, which is related to the production of the siderophore ornibactin. Moreover, a hybrid NRPS- polyketide synthetase cluster for the production of the antifungal cyclic glicolipopeptide burkholdin was also found. A genome mining combined with a bioassay-guided fractionation with further mass spectrometry analysis was applied for the purification of these compounds. This approach enabled us to purify and characterize two variants of the siderophore ornibactin, D and F (761 and 789 Da, respectively). Also, we could detect the variant ornibactin B (m/z= 733) and the quorum sensing molecules homoserine lactones C6-HSL, 3OH-C8-HSL and C8-HSL in the supernatant of B. catarinensis 89T. Mass spectrometry analysis showed the presence of a group of metabolites with the masses 1240, 1254, 1268, 1216, 1244 and 1272 Da, which are probably new variants of the antifungal metabolite burkoldin. Therefore, B. catarinensis 89T has a great biotechnological potential for the production of metabolites with pharmaceutical and agricultural applications for the biocontrol of phytopathogenic fungi.
4
LEMOS, Joice de Jesus. "Influ?ncia de diferentes fontes de nitrog?nio no processo de infec??o de plantas de feijoeiro por Fusarium oxysporum f. sp. phaseoli." Universidade Federal Rural do Rio de Janeiro, 2010. https://tede.ufrrj.br/jspui/handle/jspui/1693.
Анотація:
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CAPES
With the aims to study the efflux of H+ or OH- due nitrogen sources on the process of infection of Fusarium oxysporum f. sp. phaseoli in the rhizosphere of two beans cultivars Diamante Negro (susceptible) and Ouro Negro (more resistant), a series of experiments were done in greenhouse and growth chamber. Were applied to three different sources of nitrogen (N-N2 N-NO3- and N-NH4+) in three nitrogen concentrations (0, 30 and 120 kg ha-1), in plants grown in clay and sand soil. In addition, an experiment was conducted with different concentrations of inoculum of Fusarium (0, 10 ? and 106 conidia mL-1) in greenhouse in order to know the concentration that would affect the infection and when applied the fungi. Overall, the results suggested that nitrate decreased the infection process of Fusarium and ammonium increase. The association between nitrate with the cultivar more tolerant Ouro Negro, decreased the perceptual infection of fungi. The source of nitrogen influence of pH of rhizosphere occurred interaction with the type of soil. In all the experiments, found lower numbers of nodules. The concentration of inoculum or the times of inoculation not produce effect in the perceptual of infection.
Foram realizados estudos com duas cultivares de feijoeiro comum (Phaseolus vulgaris L.), a Diamante Negro, considerada suscet?vel ao Fusarium oxysporum f. sp. phaseoli e a Ouro Negro, mais resistente a esse fungo causador da murcha-de-fus?rio. Os experimentos foram instalados em c?mara crescimento ou em casa de vegeta??o. O objetivo deste trabalho foi o de analisar a influ?ncia da libera??o OH- ou H+ devido ao uso de fontes nitrogenadas na infec??o do fungo. Foram utilizadas tr?s fontes de nitrog?nio (N-N2, N-NO3 ? e N-NH4+) e diferentes doses de nitrog?nio (0, 30 e 120 kg ha-1) com plantas inoculadas com o referido fungo, crescidas no substrato areia ou em solos com diferentes teores de argila. Tamb?m foi realizado um experimento utilizando diferentes concentra??es de in?culo do Fusarium (0, 10? e 106 con?dios mL-1) com o objetivo de analisar qual concentra??o afetaria mais a infec??o na presen?a de fontes nitrogenadas. Foram analisados, o percentual de infec??o do Fusarium, o pH da rizosfera e n?o rizosf?rico, massas da parte a?rea e ra?zes secas, e o n?mero de n?dulos em diferentes ?pocas de amostragem. De modo geral foi observado que a fonte nitrato diminuiu o processo de infec??o do Fusarium e a fonte am?nio aumentou. Foi confirmado que a cultivar Ouro Negro ? mais tolerante ao fungo e que quando associada ? fonte de nitrog?nio nitrato aumentou ainda mais a resist?ncia. O pH da rizosfera e n?o rizosf?rico foram influenciados pela fonte de nitrog?nio: nitrato aumenta, e am?nio diminui. Os dados do trabalho sugeriram haver intera??o entre a fonte de nitrog?nio x dose x cultivar x solo. O n?mero de n?dulos encontrado nas condi??es experimentais foi baixo, especialmente nas amostragens na fase inicial do ciclo.
Книги з теми "Rhizosphere process":
1
Tinker, Peter B., and Peter Nye. Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.001.0001.
Анотація:
This is a completely revised edition of the previously titled Solute Movement in the Soil-Root System. It describes in detail how plant nutrients and other solutes move in the soil in response to plant uptake, and it provides a basis for understanding processes in the root zone so that they can be modeled realistically in order to predict the effects of variations in natural conditions or our own practices.
Частини книг з теми "Rhizosphere process":
1
Christensen, Søren, Peter Groffman, Arvin Mosier, and Donald R. Zak. "Rhizosphere Denitrification; A Minor Process but Indicator of Decomposition Activity." In Denitrification in Soil and Sediment, 199–211. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4757-9969-9_12.
2
Thiombiano, Benjamin, Kristýna Floková, Aimee Walmsley, and Harro J. Bouwmeester. "Striga Germination Stimulant Analysis." In Mutation Breeding and Efficiency Enhancing Technologies for Resistance to Striga in Cereals, 115–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 2023. http://dx.doi.org/10.1007/978-3-662-68181-7_8.
Анотація:
AbstractStriga is a flowering parasitic plant that can infect a broad range of crops including sorghum, maize and rice. The life cycle of Striga is intricately linked to its host, using host derived signals to initiate germination and attach to its host. Host susceptibility to Striga is thus directly correlated to the production and exudation of these signals. In this chapter we discuss the strigolactones, the most important class of Striga germination stimulants. We review the structural diversity of the strigolactones, their transport and biological relevance in plant and rhizosphere, and their importance for host specificity. In addition, we describe methods to analyse germination stimulant production by a Striga host: how to, reproducibly, collect the root exudate of a host, how to process these exudates, partially purify them and analyse them using analytical chemistry or a high-throughput image analysis-based germination bioassay.
3
Gobran, G. R., S. Clegg, and F. Courchesne. "Rhizospheric processes influencing the biogeochemistry of forest ecosystems." In Plant-induced soil changes: Processes and feedbacks, 107–20. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-2691-7_6.
4
Wang, Shengrui, and Zhihao Wu. "The Basic Theory of P-process at Sediment/Water Interface (SWI) in Lake." In DGT-based Measurement of Phosphorus in Sediment Microzones and Rhizospheres, 3–25. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-0721-7_1.
5
Welsh, David T., Peter Wellsbury, Sophie Bourguès, Rutger de Wit, and Rodney A. Herbert. "Relationship between porewater organic carbon content, sulphate reduction and nitrogen fixation (acetylene reduction) in the rhizosphere of Zostera noltii." In Coastal Lagoon Eutrophication and ANaerobic Processes (C.L.E.AN.), 175–83. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-1744-6_14.
6
Mallick, Rwitabrata. "Tea Rhizospheres and Their Functional Role in Tea Gardens." In Data Science for Agricultural Innovation and Productivity, 163–74. BENTHAM SCIENCE PUBLISHERS, 2024. http://dx.doi.org/10.2174/9789815196177124010011.
Анотація:
Darjeeling tea (Camellia sinensis) is famous worldwide for its excellent aroma and taste, and out of that, the best quality tea is produced in the Kurseong hill area. A year-long analysis of soil samples collected from different sites was done by applying the plate-count method in terms of colony-forming units for determining the presence of microbial population within soils cultivating tea on a monthly basis. Coordination in specific microbes might also be responsible for the impact. Fungi, bacteria, and actinomycetes – these three groups of microbes were tested during the process. Results showed that the neo tea plant, rhizosphere and rhizosphere of several other perpetual plants of various ages, flourishing in age-old tea gardens, seemed to expedite the growth of microbes. At present, the tea rhizosphere has been tested thoroughly, specifically in relation to plant-microbe response. Counter to the common outcomes, rhizosphere and soil ratios were found to be regularly less than 1 in samples collected from age-old tea gardens, showing an overall -ve rhizosphere impact. The finding of the 'negative rhizosphere effect' in old tea bushes is a significant and novel nature of the tea rhizosphere. The -ve impact on the rhizosphere of aged tea bushes does not seem to be a regular phenomenon that is related to the aging of plants generally but might be distinctive particular to tea plants. Other important and associated features include colonization of tea, rhizosphere, soil pH, etc. Supremacy of a certain population of microbes, an affinity towards a section of general opponents constitutes a good instance of reciprocated selection in the natural environment. These discoveries have unlocked newer paths for extended research in the field of 'rhizosphere microbiology'. The present study is an attempt to evaluate the transforming features coupled with the microbial activity and diversity in the tea rhizosphere and significant implications in the tea industry.
7
Tinker, Peter B., and Peter Nye. "Local Movement of Solutes in Soil." In Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.003.0008.
Анотація:
In the previous chapter, we dealt with the distribution of solutes between gas, liquid and solid phases in the soil at equilibrium; and with the rates of redistribution between these phases within soil pores. In this chapter, we consider movement of the order of 1 –1000 mm from one volume of soil to another. Such movements occur largely by diffusion and mass flow of the soil solution or soil air, and by mass movement of the body of the soil. Major movements that involve the balance and amount of solutes in the whole soil profile, including plant uptake and drainage losses, are treated in chapter 11. The process of diffusion results from the random thermal motion of ions, atoms or molecules. Consider a long column of unit cross-section orientated along the x axis, and containing a mixture of components in a single phase at constant temperature and external pressure. If the concentration of an uncharged component is greater at section A than at section B, then on average more of its molecules will move from A to B than from B to A. The net amount crossing a unit section in unit time, which is the flux, is given by the empirical relation known as Pick’s first law: . . . F = − D dC/dx (4.1) . . . where F is the flux, and dC/dx is the concentration gradient across the section. The minus sign arises because movement is from high to low concentration in the direction of increasing x. The diffusion coefficient, D, is thus defined by the equation as a coefficient between two quantities, F and dC/dx, which can be measured experimentally. It is not necessarily a constant. The diffusion coefficient of the molecules in a phase is directly proportional to their absolute mobility, u, which is the limiting velocity they attain under unit force. Terms D and u are related by the Nernst-Einstein equation: . . . D = ukT (4.2) . . . where k is the Boltzmann constant and T is the temperature on the Kelvin scale. The Nernst-Einstein equation is derived as follows (Atkins 1986, p. 675).
8
Tinker, Peter B., and Peter Nye. "The Uptake Properties of the Root System." In Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.003.0009.
Анотація:
The uptake of nutrient and other ions into the root from the surrounding soil is the main topic of this book. To understand it, we need to know how the nutrient uptake and demand of the plant is expressed at the root surface. The main interest is on how the demand at the root surface can be quantitatively defined in terms of its uptake characteristics. For this reason, our explanation of the ion uptake mechanism of the root itself is brief, and is intended mainly for readers who have not studied the subject deeply. The subject has become considerably more complex since 1977, but this detailed knowledge has not yet coalesced into a full model of how ions are absorbed, such as ultimately will allow root uptake properties to be predicted. There have been many good reviews in the recent past, and the following may be consulted: Clarkson & Hanson 1980; Glass 1983; Luttge 1983; Clarkson 1985; Sanders 1990; Clarkson & Luttge 1991; Marschner 1995. We will describe the structure of a single root only briefly here, since this information can be found in standard texts (Troughton 1957; Esau 1965; Cutter 1978; Fahn 1982). Figures 5.1-5.5 show the general structure, but here we stress points that have a special bearing on the process of ion uptake or root behaviour in soil. Byrne (1974) noted that the anatomy of soil-grown roots may differ somewhat from that of solution-grown roots. The architecture of whole root systems in soil is dealt with in chapter 9.The root tip is a highly important part of the root. The apical meristem (the ‘quiescent centre’) is a fraction of a millimetre behind the visible root tip; cells that form behind the centre of this develop into the root, whereas those in front of the centre form the root cap. These cells gradually reach the surface of the cap, and there are rubbed off and lost into the soil at a rate of several thousand per day in maize. Often, these cells are visible in the mucigel that forms from the base of the root cap and covers the young root (section 8.1.3), and can remain alive in the gel for a period.
9
Tinker, Peter B., and Peter Nye. "Solute Transport in the Soil near Root Surfaces." In Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.003.0010.
Анотація:
We discussed in chapter 4 the movement of solute between small volumes of soil, and in chapter 5 some properties of plant roots and associated hairs, particularly the relation between the rate of uptake at the root surface and the concentration of solute in the ambient solution. In the chapters to follow, we consider the plant root in contact with the soil, and deal with their association in increasingly complex situations; first, when the root acts merely as a sink and, second, when it modifies its relations with the surrounding soil by changing its pH, excreting ions, stimulating microorganisms, or developing mycorrhizas. In this chapter, we take the simplest situation that can be studied in detail, namely, a single intact root alone in a volume of soil so large that it can be considered infinite. The essential transport processes occurring near the root surface are illustrated in figure 6.1. We have examined in chapter 3 the rapid dynamic equilibrium between solutes in the soil pore solution and those sorbed on the immediately adjacent solid surfaces. These sorbed solutes tend to buffer the soil solution against changes in concentration induced by root uptake. At the root surface, solutes are absorbed at a rate related to their concentration in the soil solution at the boundary (section 5.3.2); and the root demand coefficient, αa, is defined by the equation . . . I = 2παaCLa (6.1) . . . where I = inflow (rate of uptake per unit length), a = root radius, CLa = concentration in solution at the root surface. To calculate the inflow, we have to know CLa, and the main topic of this chapter is the relation between CLa, and the soil pore solution concentration CL. The root also absorbs water at its surface due to transpiration (chapter 2) so that the soil solution flows through the soil pores, thus carrying solutes to the root surface by mass flow (convection). Barber et al. (1962) calculated whether the nutrients in maize could be acquired solely by this process, by multiplying the composition of the soil solution by the amount of water the maize had transpired.
10
Musheer, Nasreen, Mohd Gulfishan, Belal Ahmad, and Gaurav Kumar. "UNRAVELLING THE POTENTIAL: PLANT GROWTH-PROMOTING RHIZOBACTERIA IN SUSTAINABLE AGRICULTURE." In AGRICULTURE IN 21ST CENTURY. KAAV PUBLICATIONS, 2023. http://dx.doi.org/10.52458/9789388996815.2023.eb.ch-03.
Анотація:
Plant growth-promoting rhizobacteria (PGPR), often found in soil rhizosphere and capable of colonising plant roots, are a diverse group of free-living bacteria that are advantageous to plant development. The rhizosphere, a crucial component of soil ecology and plant health for interactions between plants and microbes, is connected to PGPR. Associative nitrogen fixers like Azospirillum, Enterobacter, Klebsiella, and Pseudomonas, as well as symbiotic nitrogen-fixing bacteria like Rhizobium, Bradyrhizobium, Azorhizobium, Allorhizobium, Sinorhizobium, and Mesorhizobium, have been demonstrated to attach to roots and effectively colonise root surfaces. The PGPR might support the promotion of sustainable plant development. Due to increased pesticide and fertiliser inputs, these microorganisms' importance in traditional agriculture is diminished, which results in the loss of biodiversity and its purpose. A shift from conventional intensive agriculture to sustainable agriculture is being brought about by greater awareness in many nations, including India. Sustainable agriculture refers to farming practises that limit the use of chemical pesticides and mineral fertilisers. This chapter has covered the function of PGPR in the process of promoting plant development, their methods, and significance of PGPR in crop production on a sustainable basis.
Тези доповідей конференцій з теми "Rhizosphere process":
1
Rawat, Monika. "Soil Respiration Variation under the Canopy of Dominant Tree Species across different seasons in Temperate Forest." In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0021.
Анотація:
Soil respiration is defined as the production of carbon dioxide when soil organisms are active. It is an important process in the ecosystem and has direct influence on climate change. Therefore understanding it under different vegetation types is an essential goal in soil science. The major sources which effect the soil respiration rate are plant roots, the rhizosphere, microbes and soil fauna and these sources are control by various factors like temperature, moisture, nutreint content and oxygen in the soil. Soil respiration rate is important for understanding soil biological activity, nutrient cycling, soil microbial biomass, soil organic matter and its decomposition.Therefore soil respiration was studied under the canopy of ten dominant tree species of temperate forest. Our study determined that highest soil respiration was under the canopy of Eunonymous pendulus (EP) i.e. 20.01 μmolm−2 s−1 and across season it was high during the rains.
2
Baquir, Mohammad, and Nadeem Khalil. "MUNICIPAL WASTEWATER TREATMENT IN SUBSURFACE VERTICAL FLOW CONSTRUCTED WETLANDS USING CONVENTIONAL MEDIA IN SETUP PHASE." In Computing for Sustainable Innovation: Shaping Tomorrow’s World. Innovative Research Publication, 2024. http://dx.doi.org/10.55524/csistw.2024.12.1.18.
Анотація:
Experimental investigation on municipal wastewater treatment through 6 pilot scale Subsurface Vertical Flow Constructed Wetlands (SSVF CWs) was studied utilizing two conventional materials as substrate used as 12 mm size gravel overlain by 2 mm size uniformly graded coarse sandat SWINGS site of Aligarh Muslim University, Aligarh, India. Among 6 CW beds first bed was kept unplanted and rest of the 5 beds were planted with Phragmites Karka, Canna Indica, Iris, Sagittaria and Phragmites Australis for conducting comparative study among macrophytes species used in context of contaminants removal. The primary emphasis of this study was the initial few months of the CWs running in setup phase. This phase encompasses improving phases in development of substrate permeability, microbial growth on substrate and rhizosphere, until the steady state for operation was achieved. The aims of this research paper are to assess duration requirement in setup phase for SSVF CWs through variations in removal efficiencies, and also to analyse the efficacy of conventional materials as substrate in the treatment of biological oxygen demand (BOD) and chemical oxygen demand (COD). The findings indicated that following a period of 174 days of running, the CWs had achieved a state of consistent permeability and commenced a stable removal process. The removal efficiencies for BOD and COD are found as Unplanted < Iris < Canna Indica < Sagittaria < Phragmites Karka < Phragmites Australis.
3
Asfha, Zekarias A., Nataliya E. Suzina, Yulia Kocharovskaya, Yanina Delegan, and Inna P. Solyanikova. "Isolation and Characterization of Plant Growth-Promoting Bacteria from the Rhizosphere of Chamaecytisus ruthenicus (Russian Broom) Growing in Chalky Soil." In International Electronic Conference on Processes. Basel Switzerland: MDPI, 2023. http://dx.doi.org/10.3390/ecp2023-14709.
Звіти організацій з теми "Rhizosphere process":
1
Crowley, David E., Dror Minz, and Yitzhak Hadar. Shaping Plant Beneficial Rhizosphere Communities. United States Department of Agriculture, July 2013. http://dx.doi.org/10.32747/2013.7594387.bard.
Анотація:
PGPR bacteria include taxonomically diverse bacterial species that function for improving plant mineral nutrition, stress tolerance, and disease suppression. A number of PGPR are being developed and commercialized as soil and seed inoculants, but to date, their interactions with resident bacterial populations are still poorly understood, and-almost nothing is known about the effects of soil management practices on their population size and activities. To this end, the original objectives of this research project were: 1) To examine microbial community interactions with plant-growth-promoting rhizobacteria (PGPR) and their plant hosts. 2) To explore the factors that affect PGPR population size and activity on plant root surfaces. In our original proposal, we initially prqposed the use oflow-resolution methods mainly involving the use of PCR-DGGE and PLFA profiles of community structure. However, early in the project we recognized that the methods for studying soil microbial communities were undergoing an exponential leap forward to much more high resolution methods using high-throughput sequencing. The application of these methods for studies on rhizosphere ecology thus became a central theme in these research project. Other related research by the US team focused on identifying PGPR bacterial strains and examining their effective population si~es that are required to enhance plant growth and on developing a simulation model that examines the process of root colonization. As summarized in the following report, we characterized the rhizosphere microbiome of four host plant species to determine the impact of the host (host signature effect) on resident versus active communities. Results of our studies showed a distinct plant host specific signature among wheat, maize, tomato and cucumber, based on the following three parameters: (I) each plant promoted the activity of a unique suite of soil bacterial populations; (2) significant variations were observed in the number and the degree of dominance of active populations; and (3)the level of contribution of active (rRNA-based) populations to the resident (DNA-based) community profiles. In the rhizoplane of all four plants a significant reduction of diversity was observed, relative to the bulk soil. Moreover, an increase in DNA-RNA correspondence indicated higher representation of active bacterial populations in the residing rhizoplane community. This research demonstrates that the host plant determines the bacterial community composition in its immediate vicinity, especially with respect to the active populations. Based on the studies from the US team, we suggest that the effective population size PGPR should be maintained at approximately 105 cells per gram of rhizosphere soil in the zone of elongation to obtain plant growth promotion effects, but emphasize that it is critical to also consider differences in the activity based on DNA-RNA correspondence. The results ofthis research provide fundamental new insight into the composition ofthe bacterial communities associated with plant roots, and the factors that affect their abundance and activity on root surfaces. Virtually all PGPR are multifunctional and may be expected to have diverse levels of activity with respect to production of plant growth hormones (regulation of root growth and architecture), suppression of stress ethylene (increased tolerance to drought and salinity), production of siderophores and antibiotics (disease suppression), and solubilization of phosphorus. The application of transcriptome methods pioneered in our research will ultimately lead to better understanding of how management practices such as use of compost and soil inoculants can be used to improve plant yields, stress tolerance, and disease resistance. As we look to the future, the use of metagenomic techniques combined with quantitative methods including microarrays, and quantitative peR methods that target specific genes should allow us to better classify, monitor, and manage the plant rhizosphere to improve crop yields in agricultural ecosystems. In addition, expression of several genes in rhizospheres of both cucumber and whet roots were identified, including mostly housekeeping genes. Denitrification, chemotaxis and motility genes were preferentially expressed in wheat while in cucumber roots bacterial genes involved in catalase, a large set of polysaccharide degradation and assimilatory sulfate reduction genes were preferentially expressed.
2
Minz, Dror, Stefan J. Green, Noa Sela, Yitzhak Hadar, Janet Jansson, and Steven Lindow. Soil and rhizosphere microbiome response to treated waste water irrigation. United States Department of Agriculture, January 2013. http://dx.doi.org/10.32747/2013.7598153.bard.
Анотація:
Research objectives : Identify genetic potential and community structure of soil and rhizosphere microbial community structure as affected by treated wastewater (TWW) irrigation. This objective was achieved through the examination soil and rhizosphere microbial communities of plants irrigated with fresh water (FW) and TWW. Genomic DNA extracted from soil and rhizosphere samples (Minz laboratory) was processed for DNA-based shotgun metagenome sequencing (Green laboratory). High-throughput bioinformatics was performed to compare both taxonomic and functional gene (and pathway) differences between sample types (treatment and location). Identify metabolic pathways induced or repressed by TWW irrigation. To accomplish this objective, shotgun metatranscriptome (RNA-based) sequencing was performed. Expressed genes and pathways were compared to identify significantly differentially expressed features between rhizosphere communities of plants irrigated with FW and TWW. Identify microbial gene functions and pathways affected by TWW irrigation*. To accomplish this objective, we will perform a metaproteome comparison between rhizosphere communities of plants irrigated with FW and TWW and selected soil microbial activities. Integration and evaluation of microbial community function in relation to its structure and genetic potential, and to infer the in situ physiology and function of microbial communities in soil and rhizospere under FW and TWW irrigation regimes. This objective is ongoing due to the need for extensive bioinformatics analysis. As a result of the capabilities of the new PI, we have also been characterizing the transcriptome of the plant roots as affected by the TWW irrigation and comparing the function of the plants to that of the microbiome. *This original objective was not achieved in the course of this study due to technical issues, especially the need to replace the American PIs during the project. However, the fact we were able to analyze more than one plant system as a result of the abilities of the new American PI strengthened the power of the conclusions derived from studies for the 1ˢᵗ and 2ⁿᵈ objectives. Background: As the world population grows, more urban waste is discharged to the environment, and fresh water sources are being polluted. Developing and industrial countries are increasing the use of wastewater and treated wastewater (TWW) for agriculture practice, thus turning the waste product into a valuable resource. Wastewater supplies a year- round reliable source of nutrient-rich water. Despite continuing enhancements in TWW quality, TWW irrigation can still result in unexplained and undesirable effects on crops. In part, these undesirable effects may be attributed to, among other factors, to the effects of TWW on the plant microbiome. Previous studies, including our own, have presented the TWW effect on soil microbial activity and community composition. To the best of our knowledge, however, no comprehensive study yet has been conducted on the microbial population associated BARD Report - Project 4662 Page 2 of 16 BARD Report - Project 4662 Page 3 of 16 with plant roots irrigated with TWW – a critical information gap. In this work, we characterize the effect of TWW irrigation on root-associated microbial community structure and function by using the most innovative tools available in analyzing bacterial community- a combination of microbial marker gene amplicon sequencing, microbial shotunmetagenomics (DNA-based total community and gene content characterization), microbial metatranscriptomics (RNA-based total community and gene content characterization), and plant host transcriptome response. At the core of this research, a mesocosm experiment was conducted to study and characterize the effect of TWW irrigation on tomato and lettuce plants. A focus of this study was on the plant roots, their associated microbial communities, and on the functional activities of plant root-associated microbial communities. We have found that TWW irrigation changes both the soil and root microbial community composition, and that the shift in the plant root microbiome associated with different irrigation was as significant as the changes caused by the plant host or soil type. The change in microbial community structure was accompanied by changes in the microbial community-wide functional potential (i.e., gene content of the entire microbial community, as determined through shotgun metagenome sequencing). The relative abundance of many genes was significantly different in TWW irrigated root microbiome relative to FW-irrigated root microbial communities. For example, the relative abundance of genes encoding for transporters increased in TWW-irrigated roots increased relative to FW-irrigated roots. Similarly, the relative abundance of genes linked to potassium efflux, respiratory systems and nitrogen metabolism were elevated in TWW irrigated roots when compared to FW-irrigated roots. The increased relative abundance of denitrifying genes in TWW systems relative FW systems, suggests that TWW-irrigated roots are more anaerobic compare to FW irrigated root. These gene functional data are consistent with geochemical measurements made from these systems. Specifically, the TWW irrigated soils had higher pH, total organic compound (TOC), sodium, potassium and electric conductivity values in comparison to FW soils. Thus, the root microbiome genetic functional potential can be correlated with pH, TOC and EC values and these factors must take part in the shaping the root microbiome. The expressed functions, as found by the metatranscriptome analysis, revealed many genes that increase in TWW-irrigated plant root microbial population relative to those in the FW-irrigated plants. The most substantial (and significant) were sodium-proton antiporters and Na(+)-translocatingNADH-quinoneoxidoreductase (NQR). The latter protein uses the cell respiratory machinery to harness redox force and convert the energy for efflux of sodium. As the roots and their microbiomes are exposed to the same environmental conditions, it was previously hypothesized that understanding the soil and rhizospheremicrobiome response will shed light on natural processes in these niches. This study demonstrate how newly available tools can better define complex processes and their downstream consequences, such as irrigation with water from different qualities, and to identify primary cues sensed by the plant host irrigated with TWW. From an agricultural perspective, many common practices are complicated processes with many ‘moving parts’, and are hard to characterize and predict. Multiple edaphic and microbial factors are involved, and these can react to many environmental cues. These complex systems are in turn affected by plant growth and exudation, and associated features such as irrigation, fertilization and use of pesticides. However, the combination of shotgun metagenomics, microbial shotgun metatranscriptomics, plant transcriptomics, and physical measurement of soil characteristics provides a mechanism for integrating data from highly complex agricultural systems to eventually provide for plant physiological response prediction and monitoring. BARD Report
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Lieth, J. Heiner, Michael Raviv, and David W. Burger. Effects of root zone temperature, oxygen concentration, and moisture content on actual vs. potential growth of greenhouse crops. United States Department of Agriculture, January 2006. http://dx.doi.org/10.32747/2006.7586547.bard.
Анотація:
Soilless crop production in protected cultivation requires optimization of many environmental and plant variables. Variables of the root zone (rhizosphere) have always been difficult to characterize but have been studied extensively. In soilless production the opportunity exists to optimize these variables in relation to crop production. The project objectives were to model the relationship between biomass production and the rhizosphere variables: temperature, dissolved oxygen concentration and water availability by characterizing potential growth and how this translates to actual growth. As part of this we sought to improve of our understanding of root growth and rhizosphere processes by generating data on the effect of rhizosphere water status, temperature and dissolved oxygen on root growth, modeling potential and actual growth and by developing and calibrating models for various physical and chemical properties in soilless production systems. In particular we sought to use calorimetry to identify potential growth of the plants in relation to these rhizosphere variables. While we did experimental work on various crops, our main model system for the mathematical modeling work was greenhouse cut-flower rose production in soil-less cultivation. In support of this, our objective was the development of a Rose crop model. Specific to this project we sought to create submodels for the rhizosphere processes, integrate these into the rose crop simulation model which we had begun developing prior to the start of this project. We also sought to verify and validate any such models and where feasible create tools that growers could be used for production management. We made significant progress with regard to the use of microcalorimetry. At both locations (Israel and US) we demonstrated that specific growth rate for root and flower stem biomass production were sensitive to dissolved oxygen. Our work also identified that it is possible to identify optimal potential growth scenarios and that for greenhouse-grown rose the optimal root zone temperature for potential growth is around 17 C (substantially lower than is common in commercial greenhouses) while flower production growth potential was indifferent to a range as wide as 17-26C in the root zone. We had several set-backs that highlighted to us the fact that work needs to be done to identify when microcalorimetric research relates to instantaneous plant responses to the environment and when it relates to plant acclimation. One outcome of this research has been our determination that irrigation technology in soilless production systems needs to explicitly include optimization of oxygen in the root zone. Simply structuring the root zone to be “well aerated” is not the most optimal approach, but rather a minimum level. Our future work will focus on implementing direct control over dissolved oxygen in the root zone of soilless production systems.
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Chen, Yona, Jeffrey Buyer, and Yitzhak Hadar. Microbial Activity in the Rhizosphere in Relation to the Iron Nutrition of Plants. United States Department of Agriculture, October 1993. http://dx.doi.org/10.32747/1993.7613020.bard.
Анотація:
Iron is the fourth most abundant element in the soil, but since it forms insoluble hydroxides at neutral and basic pH, it often falls short of meeting the basic requirements of plants and microorganisms. Most aerobic and facultative aerobic microorganisms possess a high-affinity Fe transport system in which siderophores are excreted and the consequent Fe complex is taken up via a cognate specific receptor and a transport pathway. The role of the siderophore in Fe uptake by plants and microorganisms was the focus of this study. In this research Rhizopus arrhizus was found to produce a novel siderophore named Rhizoferrin when grown under Fe deficiency. This compound was purified and its chemical structure was elucidated. Fe-Rhizoferrin was found to alleviate Fe deficiency when applied to several plants grown in nutrient solutions. It was concluded that Fe-Rhizoferrin is the most efficient Fe source for plants when compared with other among microbial siderophores known to date and its activity equals that of the most efficient synthetic commercial iron fertilizer-Fe EDDHA. Siderophores produced by several rhizosphere organisms including Rhizopus Pseudomonas were purified. Monoclonal antibodies were produced and used to develop a method for detection of the siderophores produced by plant-growth-promoting microorganisms in barley rhizosphere. The presence of an Fe-ferrichrome uptake in fluorescent Pseudomonas spp. was demonstrated, and its structural requirements were mapped in P. putida with the help of biomimetic ferrichrome analogs. Using competition experiments, it was shown that FOB, Cop B and FC share at least one common determinant in their uptake pathway. Since FC analogs did not affect FOB or Cop-mediated 55Fe uptake, it could be concluded that these siderophores make use of a different receptor(s) than FC. Therefore, recognition of Cop, FOB and FC proceeds through different receptors having different structural requirements. On the other hand, the phytosiderophores mugineic acid (MA and DMA), were utilized indirectly via ligand exchange by P. putida. Receptors from different biological systems seem to differ in their structural requirements for siderophore recognition and uptake. The design of genus- or species-specific drugs, probes or chemicals, along with an understanding of plant-microbe and microbe-microbe relationships as well as developing methods to detect siderophores using monoclonal antibodies are useful for manipulating the composition of the rhizosphere microbial population for better plant growth, Fe-nutrition and protection from diseases.
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Castellano, Mike J., Abraham G. Shaviv, Raphael Linker, and Matt Liebman. Improving nitrogen availability indicators by emphasizing correlations between gross nitrogen mineralization and the quality and quantity of labile soil organic matter fractions. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597926.bard.
Анотація:
A major goal in Israeli and U.S. agroecosystems is to maximize nitrogen availability to crops while minimizing nitrogen losses to air and water resources. This goal has presented a significant challenge to global agronomists and scientists because crops require large inputs of nitrogen (N) fertilizer to maximize yield, but N fertilizers are easily lost to surrounding ecosystems where they contribute to water pollution and greenhouse gas concentrations. Determination of the optimum N fertilizer input is complex because the amount of N produced from soil organic matter varies with time, space and management. Indicators of soil N availability may help to guide requirements for N fertilizer inputs and are increasingly viewed as indicators of soil health To address these challenges and improve N availability indicators, project 4550 “Improving nitrogen availability indicators by emphasizing correlations between gross nitrogen mineralization and the quality and quantity of labile organic matter fractions” addressed the following objectives: Link the quantity and quality of labile soil organic matter fractions to indicators of soil fertility and environmental quality including: i) laboratory potential net N mineralization ii) in situ gross N mineralization iii) in situ N accumulation on ion exchange resins iv) crop uptake of N from mineralized soil organic matter sources (non-fertilizer N), and v) soil nitrate pool size. Evaluate and compare the potential for hot water extractable organic matter (HWEOM) and particulate organic matter quantity and quality to characterize soil N dynamics in biophysically variable Israeli and U.S. agroecosystems that are managed with different N fertility sources. Ultimately, we sought to determine if nitrogen availability indicators are the same for i) gross vs. potential net N mineralization processes, ii) diverse agroecosystems (Israel vs. US) and, iii) management strategies (organic vs. inorganic N fertility sources). Nitrogen availability indicators significantly differed for gross vs. potential N mineralization processes. These results highlight that different mechanisms control each process. Although most research on N availability indicators focuses on potential net N mineralization, new research highlights that gross N mineralization may better reflect plant N availability. Results from this project identify the use of ion exchange resin (IERs) beads as a potential technical advance to improve N mineralization assays and predictors of N availability. The IERs mimic the rhizosphere by protecting mineralized N from loss and immobilization. As a result, the IERs may save time and money by providing a measurement of N mineralization that is more similar to the costly and time consuming measurement of gross N mineralization. In further search of more accurate and cost-effective predictors of N dynamics, Excitation- Emission Matrix (EEM) spectroscopy analysis of HWEOM solution has the potential to provide reliable indicators for changes in HWEOM over time. These results demonstrated that conventional methods of labile soil organic matter quantity (HWEOM) coupled with new analyses (EEM) may be used to obtain more detailed information about N dynamics. Across Israeli and US soils with organic and inorganic based N fertility sources, multiple linear regression models were developed to predict gross and potential N mineralization. The use of N availability indicators is increasing as they are incorporated into soil health assessments and agroecosystem models that guide N inputs. Results from this project suggest that some soil variables can universally predict these important ecosystem process across diverse soils, climate and agronomic management. BARD Report - Project4550 Page 2 of 249
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Minz, Dror, Eric Nelson, and Yitzhak Hadar. Ecology of seed-colonizing microbial communities: influence of soil and plant factors and implications for rhizosphere microbiology. United States Department of Agriculture, July 2008. http://dx.doi.org/10.32747/2008.7587728.bard.
Анотація:
Original objectives: Our initial project objectives were to 1) Determine and compare the composition of seed-colonizing microbial communities on seeds, 2) Determine the dynamics of development of microbial communities on seeds, and 3) Determine and compare the composition of seed-colonizing microbial communities with the composition of those in the soil and rhizosphere of the plants. Revisions to objectives: Our initial work on this project was hampered by the presence of native Pythium species in the soils we were using (in the US), preventing us from getting accurate assessments of spermosphere microbial communities. In our initial work, we tried to get around this problem by focusing on water potentials that might reduce damage from native Pythium species. This also prompted some initial investigation of the oomycete communities associated seedlings in this soil. However, for this work to proceed in a way that would allow us to examine seed-colonizing communities on healthy plants, we needed to either physically treat soils or amend soils with composts to suppress damage from Pythium. In the end, we followed the compost amendment line of investigation, which took us away from our initial objectives, but led to interesting work focusing on seed-associated microbial communities and their functional significance to seed-infecting pathogens. Work done in Israel was using suppressive compost amended potting mix throughout the study and did not have such problems. Our work focused on the following objectives: 1) to determine whether different plant species support a microbial induced suppression of Pythium damping-off, 2) to determine whether compost microbes that colonize seeds during early stages of seed germination can adequately explain levels of damping-off suppression observed, 3) to characterize cucumber seed-colonizing microbial communities that give rise to the disease suppressive properties, 4) assess carbon competition between seed-colonizing microbes and Pythium sporangia as a means of explaining Pythium damping-off suppression. Background: Earlier work demonstrated that seed-colonizing microbes might explain Pythium suppression. Yet these seed-colonizing microbial communities have never been characterized and their functional significance to Pythium damping-off suppression is not known. Our work set out to confirm the disease suppressive properties of seed-colonizing microbes, to characterize communities, and begin to determine the mechanisms by which Pythium suppression occurs. Major Conclusions: Compost-induced suppression of Pythium damping-off of cucumber and wheat can be explained by the bacterial consortia colonizing seeds within 8 h of sowing. Suppression on pea was highly variable. Fungi and archaea play no role in disease suppression. Potentially significant bacterial taxa are those with affinities to Firmicutes, Actinobacteria, and Bacteroidetes. Current sequencing efforts are trying to resolve these taxa. Seed colonizing bacteria suppress Pythium by carbon competition, allowing sporangium germination by preventing the development of germ tubes. Presence of Pythium had a strong effect on microbial community on the seed.
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Chefetz, Benny, Baoshan Xing, Leor Eshed-Williams, Tamara Polubesova, and Jason Unrine. DOM affected behavior of manufactured nanoparticles in soil-plant system. United States Department of Agriculture, January 2016. http://dx.doi.org/10.32747/2016.7604286.bard.
Анотація:
The overall goal of this project was to elucidate the role of dissolved organic matter (DOM) in soil retention, bioavailability and plant uptake of silver and cerium oxide NPs. The environmental risks of manufactured nanoparticles (NPs) are attracting increasing attention from both industrial and scientific communities. These NPs have shown to be taken-up, translocated and bio- accumulated in plant edible parts. However, very little is known about the behavior of NPs in soil-plant system as affected by dissolved organic matter (DOM). Thus DOM effect on NPs behavior is critical to assessing the environmental fate and risks related to NP exposure. Carbon-based nanomaterials embedded with metal NPs demonstrate a great potential to serve as catalyst and disinfectors. Hence, synthesis of novel carbon-based nanocomposites and testing them in the environmentally relevant conditions (particularly in the DOM presence) is important for their implementation in water purification. Sorption of DOM on Ag-Ag₂S NPs, CeO₂ NPs and synthesized Ag-Fe₃O₄-carbon nanotubebifunctional composite has been studied. High DOM concentration (50mg/L) decreased the adsorptive and catalytic efficiencies of all synthesized NPs. Recyclable Ag-Fe₃O₄-carbon nanotube composite exhibited excellent catalytic and anti-bacterial action, providing complete reduction of common pollutants and inactivating gram-negative and gram-positive bacteria at environmentally relevant DOM concentrations (5-10 mg/L). Our composite material may be suitable for water purification ranging from natural to the industrial waste effluents. We also examined the role of maize (Zeamays L.)-derived root exudates (a form of DOM) and their components on the aggregation and dissolution of CuONPs in the rhizosphere. Root exudates (RE) significantly inhibited the aggregation of CuONPs regardless of ionic strength and electrolyte type. With RE, the critical coagulation concentration of CuONPs in NaCl shifted from 30 to 125 mM and the value in CaCl₂ shifted from 4 to 20 mM. This inhibition was correlated with molecular weight (MW) of RE fractions. Higher MW fraction (> 10 kDa) reduced the aggregation most. RE also significantly promoted the dissolution of CuONPs and lower MW fraction (< 3 kDa) RE mainly contributed to this process. Also, Cu accumulation in plant root tissues was significantly enhanced by RE. This study provides useful insights into the interactions between RE and CuONPs, which is of significance for the safe use of CuONPs-based antimicrobial products in agricultural production. Wheat root exudates (RE) had high reducing ability to convert Ag+ to nAg under light exposure. Photo-induced reduction of Ag+ to nAg in pristine RE was mainly attributed to the 0-3 kDa fraction. Quantification of the silver species change over time suggested that Cl⁻ played an important role in photoconversion of Ag+ to nAg through the formation and redox cycling of photoreactiveAgCl. Potential electron donors for the photoreduction of Ag+ were identified to be reducing sugars and organic acids of low MW. Meanwhile, the stabilization of the formed particles was controlled by both low (0-3 kDa) and high (>3 kDa) MW molecules. This work provides new information for the formation mechanism of metal nanoparticles mediated by RE, which may further our understanding of the biogeochemical cycling and toxicity of heavy metal ions in agricultural and environmental systems. Copper sulfide nanoparticles (CuSNPs) at 1:1 and 1:4 ratios of Cu and S were synthesized, and their respective antifungal efficacy was evaluated against the pathogenic activity of Gibberellafujikuroi(Bakanae disease) in rice (Oryza sativa). In a 2-d in vitro study, CuS decreased G. fujikuroiColony- Forming Units (CFU) compared to controls. In a greenhouse study, treating with CuSNPs at 50 mg/L at the seed stage significantly decreased disease incidence on rice while the commercial Cu-based pesticide Kocide 3000 had no impact on disease. Foliar-applied CuONPs and CuS (1:1) NPs decreased disease incidence by 30.0 and 32.5%, respectively, which outperformed CuS (1:4) NPs (15%) and Kocide 3000 (12.5%). CuS (1:4) NPs also modulated the shoot salicylic acid (SA) and Jasmonic acid (JA) production to enhance the plant defense mechanisms against G. fujikuroiinfection. These results are useful for improving the delivery efficiency of agrichemicals via nano-enabled strategies while minimizing their environmental impact, and advance our understanding of the defense mechanisms triggered by the NPs presence in plants.
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Tuller, Markus, Asher Bar-Tal, Hadar Heller, and Michal Amichai. Optimization of advanced greenhouse substrates based on physicochemical characterization, numerical simulations, and tomato growth experiments. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7600009.bard.
Анотація:
Over the last decade there has been a dramatic shift in global agricultural practice. The increase in human population, especially in underdeveloped arid and semiarid regions of the world, poses unprecedented challenges to production of an adequate and economically feasible food supply to undernourished populations. Furthermore, the increased living standard in many industrial countries has created a strong demand for high-quality, out-of-season vegetables and fruits as well as for ornamentals such as cut and potted flowers and bedding plants. As a response to these imminent challenges and demands and because of a ban on methyl bromide fumigation of horticultural field soils, soilless greenhouse production systems are regaining increased worldwide attention. Though there is considerable recent empirical and theoretical research devoted to specific issues related to control and management of soilless culture production systems, a comprehensive approach that quantitatively considers all relevant physicochemical processes within the growth substrates is lacking. Moreover, it is common practice to treat soilless growth systems as static, ignoring dynamic changes of important physicochemical and hydraulic properties due to root and microbial growth that require adaptation of management practices throughout the growth period. To overcome these shortcomings, the objectives of this project were to apply thorough physicochemical characterization of commonly used greenhouse substrates in conjunction with state-of-the-art numerical modeling (HYDRUS-3D, PARSWMS) to not only optimize management practices (i.e., irrigation frequency and rates, fertigation, container size and geometry, etc.), but to also “engineer” optimal substrates by mixing organic (e.g., coconut coir) and inorganic (e.g., perlite, pumice, etc.) base substrates and modifying relevant parameters such as the particle (aggregate) size distribution. To evaluate the proposed approach under commercial production conditions, characterization and modeling efforts were accompanied by greenhouse experiments with tomatoes. The project not only yielded novel insights regarding favorable physicochemical properties of advanced greenhouse substrates, but also provided critically needed tools for control and management of containerized soilless production systems to provide a stress-free rhizosphere environment for optimal yields, while conserving valuable production resources. Numerical modeling results provided a more scientifically sound basis for the design of commercial greenhouse production trials and selection of adequate plant-specific substrates, thereby alleviating the risk of costly mistrials.
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Shani, Uri, Lynn Dudley, Alon Ben-Gal, Menachem Moshelion, and Yajun Wu. Root Conductance, Root-soil Interface Water Potential, Water and Ion Channel Function, and Tissue Expression Profile as Affected by Environmental Conditions. United States Department of Agriculture, October 2007. http://dx.doi.org/10.32747/2007.7592119.bard.
Анотація:
Constraints on water resources and the environment necessitate more efficient use of water. The key to efficient management is an understanding of the physical and physiological processes occurring in the soil-root hydraulic continuum.While both soil and plant leaf water potentials are well understood, modeled and measured, the root-soil interface where actual uptake processes occur has not been sufficiently studied. The water potential at the root-soil interface (yᵣₒₒₜ), determined by environmental conditions and by soil and plant hydraulic properties, serves as a boundary value in soil and plant uptake equations. In this work, we propose to 1) refine and implement a method for measuring yᵣₒₒₜ; 2) measure yᵣₒₒₜ, water uptake and root hydraulic conductivity for wild type tomato and Arabidopsis under varied q, K⁺, Na⁺ and Cl⁻ levels in the root zone; 3) verify the role of MIPs and ion channels response to q, K⁺ and Na⁺ levels in Arabidopsis and tomato; 4) study the relationships between yᵣₒₒₜ and root hydraulic conductivity for various crops representing important botanical and agricultural species, under conditions of varying soil types, water contents and salinity; and 5) integrate the above to water uptake term(s) to be implemented in models. We have made significant progress toward establishing the efficacy of the emittensiometer and on the molecular biology studies. We have added an additional method for measuring ψᵣₒₒₜ. High-frequency water application through the water source while the plant emerges and becomes established encourages roots to develop towards and into the water source itself. The yᵣₒₒₜ and yₛₒᵢₗ values reflected wetting and drying processes in the rhizosphere and in the bulk soil. Thus, yᵣₒₒₜ can be manipulated by changing irrigation level and frequency. An important and surprising finding resulting from the current research is the obtained yᵣₒₒₜ value. The yᵣₒₒₜ measured using the three different methods: emittensiometer, micro-tensiometer and MRI imaging in both sunflower, tomato and corn plants fell in the same range and were higher by one to three orders of magnitude from the values of -600 to -15,000 cm suggested in the literature. We have added additional information on the regulation of aquaporins and transporters at the transcript and protein levels, particularly under stress. Our preliminary results show that overexpression of one aquaporin gene in tomato dramatically increases its transpiration level (unpublished results). Based on this information, we started screening mutants for other aquaporin genes. During the feasibility testing year, we identified homozygous mutants for eight aquaporin genes, including six mutants for five of the PIP2 genes. Including the homozygous mutants directly available at the ABRC seed stock center, we now have mutants for 11 of the 19 aquaporin genes of interest. Currently, we are screening mutants for other aquaporin genes and ion transporter genes. Understanding plant water uptake under stress is essential for the further advancement of molecular plant stress tolerance work as well as for efficient use of water in agriculture. Virtually all of Israel’s agriculture and about 40% of US agriculture is made possible by irrigation. Both countries face increasing risk of water shortages as urban requirements grow. Both countries will have to find methods of protecting the soil resource while conserving water resources—goals that appear to be in direct conflict. The climate-plant-soil-water system is nonlinear with many feedback mechanisms. Conceptual plant uptake and growth models and mechanism-based computer-simulation models will be valuable tools in developing irrigation regimes and methods that maximize the efficiency of agricultural water. This proposal will contribute to the development of these models by providing critical information on water extraction by the plant that will result in improved predictions of both water requirements and crop yields. Plant water use and plant response to environmental conditions cannot possibly be understood by using the tools and language of a single scientific discipline. This proposal links the disciplines of soil physics and soil physical chemistry with plant physiology and molecular biology in order to correctly treat and understand the soil-plant interface in terms of integrated comprehension. Results from the project will contribute to a mechanistic understanding of the SPAC and will inspire continued multidisciplinary research.