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1
Hampstead, Anthony. "Mathematical approaches to seed germination". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/13979/.
Testo completoAbstract (sommario):
Plant seeds progress through specific stages during germination, from quiescence in the dry state through water uptake, testa rupture and finally endosperm rupture. The stages of seed germination are fairly well classified but the underlying biochemical and mechanical processes are unknown. The ability to control a seeds progression through the stages of germination has implications on farming efficiency and so the following thesis explores Arabidopsis thaliana and Lepidium sativum seeds during the germination process. A systematic approach to analysing the shape of cells within the radicle (embryonic root tissue) is developed, using confocal imaging, in order to characterise the shape of cells in the different tissues of the radicle. The cell shape approximations are not refined enough to characterise the different cell tissues. With more data, this approach would hope to find the region in which cells alter through the germination process. Change in the activity of cell wall modifying enzymes within the endosperm, that surrounds the emerging embryo, is a key part of the germination process and temporally and spatially defined high resolution transcriptomics data-sets are available to inform models. Through the course of this thesis, biochemical networks are developed, with ordinary and partial differential equation models being constructed and analysed. The models highlight elements for further investigation as well as differences between the two species considered. The mathematical models, along with data from biomechanical experiments on the endosperm, inform discussion on how the cell wall biochemistry of a cell wall alters the cell wall properties. These discussions focus on cell wall permeability, extensibility and the final cell separation event associated with germination. From the considered proteins, polygalacturonase and pectin lyase arise as the only viable candidates to cause the cell separation event with the model framework.
2
Ma, Liuyin. "THE ROLE OF POLYADENYLATION IN SEED GERMINATION". UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/47.
Testo completoAbstract (sommario):
Seed germination has many impacts on the uses of seeds, and is an important subject for study. Seed germination is regulated at both transcriptional and post-transcriptional levels. Therefore, it is important to study how polyadenylation regulates gene expression during seed germination. To this end, a modified Illumina GAIIx sequencing protocol (described in Chapter Two) was developed that allows deep coverage of poly(A) site position and distribution.
Alternative polyadenylation (APA) regulates gene expression by choosing one potential poly(A) site on a precursor RNA consequentially shortening/lengthening the mRNA relative to other possible sites. To further explore this phenomenon, genes affected by APA during seed germination and other developmental stages were identified (Chapter Three). These genes were categorized based on the location of poly(A) sites. Several genes were chosen to demonstrate how APA, especially that occurring in the coding regions and 5’ untranslated regions, might down regulate gene expression by generating truncated transcripts.
In animal oocytes, maternally-derived mRNAs are stored with short poly(A) tails and reactivated by the cytoplasmic polyadenylation complex. It has been reported that seeds also contain stored mRNAs. Moreover, germination and its completion are less sensitive to de novo transcription inhibitors than to poly(A) polymerase inhibitors. Together, these considerations suggest that stored RNA without or with a short poly(A) tail (stored, unadenylated RNA) may be present in dry seed and function in seed germination upon reactivation by cytoplasmic polyadenylation. To further explore this, in Chapter Four, mRNA polyadenylation was studied through the course of germination using a combination of transcriptional inhibitors and the modified sequencing protocol described in Chapter Two. 273 putative stored, unadenylated RNAs were identified. Gene ontology analysis revealed that genes whose products are involved in translation are overrepresented; these genes encode 21 60S- and 10 40S-ribosomal proteins. These results indicate that transcripts whose products are involved in translation might be a major component of the stored, unadenylated RNA pool and, more importantly, translation might be the first cellular process to be activated during seed germination.
3
Mirdad, Zohair M. "The evaluation and improvement of seed quality and storage potential in cauliflower and cabbage seeds". Thesis, University of Aberdeen, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288381.
Testo completoAbstract (sommario):
This study aimed to improve seed quality in cauliflower and cabbage, firstly though the development of rapid methods for the evaluation of germination and seed storage potential using measurements of seed leachates conductivity and secondly, through the application of seed treatments both as pre-storage treatments and to improve germination under stress conditions. Significant negative correlations between germination and the conductivity of seed leachate were observed both when seed had high germinations after ageing and when a range of germinations resulted from either combinations of dead plus living seeds, or ageing. This suggested that conductivity measurements could be applied to predict seed germination. Seed quality declined during storage at two moisture contents (12% and 6.5%) and two temperatures (25oC and 35o C) as reflected by the increase in seed leachate conductivity and decline in germination and vigour. Differences in seed storage potential were best predicted by the controlled deterioration (CD) test and by CD followed by measurements of leachate conductivity. Other pre-storage assessments (laboratory germination, Ki, conductivity) were less consistent in prediction of storage potential. The second approach used to improve seed quality was to apply pre-storage seed treatments to improve seed storage potential. The most striking improvements in seed storage potential occurred after pre-storage hydration treatments, aerated hydration (AH) for 12h or 18h and water soaking for 3h or 6h, with smaller improvements after antioxidant treatments (0.1% a-tocopherol and 0.1% ascorbic acid). Halogenation (I2) treatment had no effects on storage potential. Improved seed quality was also revealed after AH treatment by both the increased ability of seed to germinate at high temperature (35oC) and more rapid germination at reduced water potential and under salinity stress. AH treatment also increased the ability of seeds to recover from exposure to higher temperature (40oC) and reduced water potential (-1.90 MPa).
4
Soltani, Ali. "Improvement of seed germination of Fagus orientalis Lipsky /". Umeå : Dept. of Silviculture, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s275.pdf.
Testo completo
5
Kandolo, Sadiki Delphin. "Effect of fungicide seed treatments on germination and vigour of maize seed". Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/29544.
Testo completoAbstract (sommario):
Fungicides have been developed to protect plants against diseases and pests, which cause serious problems such as the loss of germination and vigour. The aim of this study was to test the germination and vigour of maize (Zea mays L.) seeds treated with several fungicides Apron® Star 42 WS (difenoconazole, thiamethoxam, and metalaxyl-m), Apron® XL (mefenoxam), Celest® XL (fludioxonil, mefenoxam) and thiram in the laboratory. In the greenhouse, the efficacy of fungicide treatment was evaluated in soil inoculated with Fusarium graminearum. The control consisted of untreated seeds. Germination and vigour were evaluated according to the International Seed Testing Association (1ST A) rules. The results from the standard gennination tests showed that all the fungicide treated seeds did not differ to the untreated control. The conductivity of solute leakage was read following slow and fast imbibition. Maize seeds treated with Apron® Star 42 WS, Celest® XL, Apron® XL and thiram improved or maintain vigour, which was indicated by a reduced or equivalent solute leakage following fast imbibition when compared with the untreated control. The good performance of fungicide treated seed expressed during conductivity test after fast imbibition correlated with the tetrazolium. All the fungicide treated seeds maintained the same viability as the untreated control following fast imbibition. After 6 h after fast imbibition, Apron® Star 42 WS, Celest® XL and Apron® XL treated seeds maintained similar germination percentages when compared to the untreated control with the exception of thiram treated seeds that exhibited a decline in seed viability. There was reduction in vigour in all the fungicide treated seeds fo llowing 24 and 40 h fast imbibition as illustrated by the reduction in germination percentage below the acceptable level (70%) when compared with the untreated control. The greenhouse study showed that all the fungicide treated seeds maintained the same emergence percentage in both inoculated and uninoculated soil with the exception of thiram treated seeds, where emergence improved in inoculated soil when compared to the untreated control. Apron® Star 42 WS and Celest® XL reduced the disease caused by F. graminearum in the inoculated soil. This study also revealed that the application of Apron® Star 42 WS, Celest® XL and thiram to seeds improved both the shoot and root dry mass of plants in the inoculated soil.Dissertation (MInstAgrar)--University of Pretoria, 2011.
Microbiology and Plant Pathology
unrestricted
6
Zaman, S., S. Padmesh e H. Tawfiq. "Effect of Pre-germination Treatments on Seed Germination of Helianthemum lippii (L.) Dum.Cours". University of Arizona (Tucson, AZ), 2009. http://hdl.handle.net/10150/556666.
Testo completoAbstract (sommario):
Helianthemum lippii (L.) Dum. Cours. is a perennial shrubby plant 10-45 cm tall that belongs to the family Cistaceae. The effects of pretreatments on germination of Helianthemum lippii provide information regarding germination requirements of this species, which could be used for conservation studies. Five different pretreatment were applied to enhance seed germination. Scarification followed by germination at 6 different constant temperatures (10, 15, 20, 25, 30 and 35°C) with continuous light or dark, Scarification followed by GA3 soaking (100, 250,500,750 and 1000 ppm), Heat and moist stratification (only intact seeds), KNO₃ and H₃BO₃ soaking (only intact seeds). The results obtained from this study indicate that germination in H. lippii was promoted by scarification. Scarification of seeds resulted in high germination while increasing germination temperature (35°C) decreased the germination of scarified seeds. Exposure to light and dark had no effect on germination. Heat stratification, cold stratification, KNO₃ and H₃BO₃ treatments were ineffective in increasing germination of H.lippii seeds. Scarification yielded maximum germination without soaking in GA₃ It increased the germination of Helianthemum lippii seeds from 1 to 99%. Increase in GA₃ concentration decreased the germination of this species. Scarification succeeded in breaking dormancy of H.lippii seeds suggesting that this species exhibits seed coat dormancy and in nature it may happen due to the abrasion of seed coat by sand particles or other biotic and abiotic factors.
7
Omami, Elizabeth Nabwile. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants /". [S.l. : s.n.], 1993. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030603.091907/index.html.
Testo completo
8
Sumugat, Mae Rose S. "Glutathione Dynamics in Arabidopsis Seed Development and Germination". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/36420.
Testo completoAbstract (sommario):
Seed desiccation and germination have great potential for oxidative stress. Glutathione, one of the most abundant antioxidants in plant cells, is a crucial to the plant's defense mechanisms. To better understand glutathione's responses during these two stages, we examined its dynamics in wildtype Arabidopsis seeds and in a transgenic line containing an antisense glutathione reductase2 (anGR2) cDNA insert. Seeds from the two genotypes were compared morphologically. Glutathione levels in maturing and germinating seeds were measured by HPLC, and GR activity by native PAGE. Cytosolic glutathione was measured in situ by confocal laser scanning microscopy. Stress in the form of natural and accelerated ageing, and germination at high and low temperature and at low water potential was applied to both WT and anGR2 seeds to test vigor. Results show similar glutathione levels and GR activity (except during late imbibition) in WT and anGR2. In both genotypes, GSH/GSSG ratio increased and GR activity decreased during seed maturation. During imbibition, the glutathione pool becomes very reduced (<1% GSSG) and in WT seeds, GSH levels increase mostly by GSSG recycling. Cytosolic GSH in embryonic epidermal cells was estimated to be 1.1-1.6 mM. AnGR2 seeds aged faster, and were less tolerant of heat and drought stress than WT. Accumulation of glutathione during maturation indicated that glutathione is a major antioxidant in the seed during storage. Changes in GSH levels during imbibition coincided with ROS production during radicle protrusion. Under stress conditions, anGR2 seeds showed lower vigor, indicating perturbations in the ROS scavenging systems particularly GR2.Master of Science
9
Kyereh, Boateng. "Seed phenology and germination of Ghanaian forest trees". Thesis, University of Aberdeen, 1994. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU068828.
Testo completoAbstract (sommario):
Seed production and germination of some timber tree species were studied in Ghana for possible prediction of seed yield and natural regeneration. Seed phenology in 13 species was monitored for two years, using permanent seed traps in two forest sites. Seed germination tests were conducted in neutral, green shade and dark in shade houses for 20 species. In the forest, germination was tested in forest gaps receiving different irradiances. Fruiting frequency ranged from twice in each year to supra-annual fruiting. Fruiting periods for species were consistent between years. Fruiting synchrony was higher among individuals of a population than between sites for the same species. Fecundity differed between years for the majority of species and between sites for species common to both sites. Premature fruit abscission was quite common. Maximum seed weight and percentage germination occurred during peak fall of mature seeds. Seeds of the majority of species germinated equally in light and dark and also in neutral and low red: far red ratio. These included some species previously classified as pioneers. In the forest germination was depressed in a large clearing for the majority of species. The use of photoblastic germination alone to define pioneers leads to a smaller group of pioneer species than is presently recognised. Large gaps due to logging may discourage natural regeneration.
10
St, Hilaire Rolston. "Seed Coat Treatments Influence Germination of Taxodium mucronatum". University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/554341.
Testo completoAbstract (sommario):
The range of Taxodium mucronatum Ten. (Mexican bald cypress) is declining rapidly, yet relatively little is known about the propagation of this valuable ornamental tree. The objective of this study was to determine whether seed coat treatments could enhance the germination of Mexican bald cypress. Seeds of Mexican bald cypress were collected from Las Cruces and the Gila National Forest, New Mexico. In one experiment, seed coats were knicked or left intact, then germinated on moist filter paper or flooded with water. In another experiment, seed coats from the Las Cruces provenance were treated with sulfuric acid, knicked, left intact, or removed (excised embryos) and germinated on moist filter paper. Knicked and moist seeds had a greater mean cumulative germination percentage (13.5 %) than intact and flooded seeds (4.2 %). Final germination percentage of the Las Cruces source was similar among knicked seeds, intact seeds, and excised embryos, but intact seeds took a longer time (15 days) to reach 50% of final germination percentage than did excised embryos (10 days) and knicked seeds (8 days). Seeds treated with sulfuric did not germinate. Results indicate seed coat pretreatments are needed to release physical dormancy and promote efficient germination of Mexican bald cypress.
11
Haigh, Anthony Mark. "Why do tomato seeds prime?: physiological investigations into the control of tomato seed germination and priming". Australia : Macquarie University, 1988. http://hdl.handle.net/1959.14/35668.
Testo completoAbstract (sommario):
Thesis (PhD) -- Macquarie University, School of Biological Sciences, 1988.Bibliography: leaves 112-121.
General introduction to seed priming -- Water relations of tomato seed germination -- Water relations to tomato seeds during priming -- Water relations of germinating primed tomato seeds -- Histological study of tomato seed germination and priming -- Endosperm weakening during germination and priming of tomato seeds -- General discussion -- References.
It is the aim of this thesis to examine hypotheses regarding the prevention of radicle emergence during priming and of the enhancement of germination following priming. This work should identify the control sites in the processes of radicle emergence and their modification during priming. -- For the most part these hypotheses are underlain by an analysis of germination as a special case of plant cell expansion. A study of cell expansion requires an understanding of the water relations of the tissues involved. Therefore, the sequence of events during the germination of tomato seeds was first examined through a water relations study then the changes caused by priming were examined. -- The study of the water relations of germinating tomato seeds revealed that the seeds came into Ψ equilibrium with the imbibitional solution, whereas, the embryo was measured at much lower Ψ. There was no evidence of a lowering of embryo Ψπ nor of an increase in embryo Ψp prior to radicle emergence. The embryo Ψ measurements need to be interpreted with caution for they are ex situ measurements and thus do not directly measure these properties in the seed. It is unlikely that a large ΔΨ could be maintained within the seed during imbibition. Thus the existence of a large seed to embryo Ψp can be inferred from these measurements. The moisture release isotherm of the excised embryo confirmed this inference. The endosperm tissue enclosing the embryo was found to restrict the hydration level of the embryo prior to its emergence. As the embryo was capable of expansive growth prior to radicle emergence, it was concluded that the weakening of the endosperm controlled radicle emergence in tomato seeds. -- During priming the tomato seeds were in Ψ equilibrium with the priming solution, but the embryo was not. As the embryo was capable of growth after 2 days of the 6 day priming treatment, it was concluded that radicle emergence was prevented by the maintenance of the endosperm restraint. Germinating primed seeds did not display a marked plateau during imbibition. Both seed and embryo water contents were higher than those of non-primed seeds. However, embryo Ψ and Ψπ were lower than those of embryos from non-primed seeds, eventhough embryo Ψπ measurements during priming had not revealed significant lowering. The relative growth rate of seedlings from primed seeds was higher than that of non-primed seeds for the first 12 h after radicle emergence.
The endosperm of tomato seeds consisted of two distinct cell types found in separate locations within the seed. At the micropylar end of the seed the endosperm cells had thin walls, whereas those in the rest of the seed had thickened walls. The outer walls of outermost endosperm cells in the rest of the seed had massively thickened walls whereas these were lacking from the outer cells of the micropylar region. -- All cells, except those of the root cap, contained protein bodies. The protein bodies of the micropylar region endosperm cells were seen to breakdown to form vacuoles prior to radicle emergence. The protein bodies in other cells did not appear to change prior to this time. During priming protein body breakdown was more extensive in the micropylar region endosperm cells and vacuole formation also occurred in the radicle. After radicle emergence the cells of the radicles from primed seeds were found to be about 50% larger than those of the radicles from non-primed seeds. -- Endosperm weakening preceded radicle emergence in tomato seeds. Slower germinating seeds within the population had higher values for endosperm resistance. Endosperm weakening during priming resulted in values for endosperm resistance which were lower than those measured from a population of germinating non-primed seeds. Germinating primed seeds had resistances which were similar to those of priming seeds. It was concluded that a final rapid endosperm weakening step may be necessary for radicle emergence to occur. -- These studies have shown that tomato seeds prime because the endosperm does not weaken sufficiently to permit expansion of the radicle. The mechanism by which some endosperm weakening was permitted, but the final weakening for radicle emergence was prevented was not identifiable. Priming advanced the timing of radicle emergence by improving the rate of water uptake by the seeds; by eliminating the time necessary for the loosening of embryo cell walls and by permitting the completion of the first step of the endosperm weakening process. Enbryos from primed seeds had improved cell wall extensibilities which permitted higher relative growth rates during the first 12 h after radicle emergence.
Mode of access: World Wide Web.
x, 121 leaves, 4 leaves of plates ill
12
Khalif, Ahmed Sheikh Hassan. "GERMINATION RESPONSES OF SORGHUM VARIETIES (SORGHUM BICOLOR L. MOENCH) TO FUNGICIDE SEED TREATMENTS". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275262.
Testo completo
13
Xia, Qiong. "Molecular aspects of temperature regulation of sunflower seed dormancy". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066629/document.
Testo completoAbstract (sommario):
La graine est le produit de la reproduction sexuée chez les Angiospermes. Elle assure la survie et la dispersion de l'espèce. La germination des graines est la première étape de la croissance des plantes. La transition entre l'état de dormance des graines et leur germination est une étape clef dans le cycle de vie des plantes qui a des conséquences écologique et commerciale. Depuis plusieurs décennies, de nombreux facteurs de l'environnement ont été étudiés pour leurs implications et leurs conséquences dans le processus de dormance et de germination des graines. Les études sur la réponse des semences aux changements de température en liens avec le réchauffement climatique ont un intérêt primordial. Le but de ce travail a été d'étudier la régulation de la dormance et de la germination des graines de tournesol par la température. Une analyse protéomique et un profilage enzymatique ont été réalisés afin de mieux comprendre la régulation du métabolisme pendant la levée de dormance par la température. L'utilisation d'approches moléculaires et cytologiques, nous ont permis d'appréhender l'interaction entre la température et les phytohormones impliquées dans ce processus. Nos résultats ont révélé le rôle joué par la température comme facteur externe affectant la dormance et la germination des graines en agissant d'une part sur le métabolisme et d'autre part sur la quantité et la localisation cellulaire des principales hormones endogènesA seed is the product of sexual reproduction and the means by which the new individual is dispersed by angiosperms. Seed germination being the first step of plant establishment, the ultimate role of the transition between seed dormancy and germination during plant lifecycle is an important ecological and commercial trait. Last several decades, several environment factors have been reviewed to strongly effect the process of seed dormancy and germination. However, studies about seed response to temperature change are acute with the global warming. The aim of this work was to investigate temperature regulation of dormancy and germination in sunflower seeds. Proteomic analysis and enzyme profiling have been used to study metabolism regulation during seed dormancy release by temperature. Moreover, using molecular and cytological approaches, we investigate the interaction between temperature and phytohormones involved in this process. Our results revealed that temperature as an external factor to effect seed dormancy and germination by affecting, in one hand, the metabolism, and in the other hand the level and localization of major endogenous hormones
14
Zhou, Dongfang. "Seed Germination Performance and Seed Coat Mucilage Production of Sweet Basil (Ocimum basilicum L.)". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/49553.
Testo completoAbstract (sommario):
Sweet basil (Ocimum basilicum L.) is a warm season herb usually propagated from seeds. Establishment of basil is difficult as seed germination may be limited, particularly during field seeding at cold soil temperatures. The germination of six cultivars (\'Italian Large Leaf\', \'Italian Large Leaf\' 35X, \'Nufar\', \'Genovese\', \'Genovese Compact Improved\' and \'Aroma 2\') of sweet basil seeds were tested on a one dimensional thermo-gradient table over temperatures ranging from 0 to 50"C. At temperatures below 20"C, germination among cultivars was more variable and the mean time to germination (MTG) increased to greater than 25 days for some cultivars. Germination declined sharply and had a sudden termination at high temperatures above 40"C for all six cultivars. There were statistical differences among the cultivar base temperatures, which ranged between 10.1 and 13.3"C. The optimal and ceiling temperatures for germination were similar and did not differ statistically among the cultivars compared in this study. The average optimal temperature for all cultivars was 35 ± 0"C, while the average ceiling temperature was 43 ± 1.3"C. Stored seeds (> 5 years) had lower seed vigor and lower germination percentage, also lower ceiling temperature compared with the fresh seeds of the same cultivar (\'Italian Large Leaf\'), but the base temperatures were the same for both new and old seeds.
Sweet basil (Ocimum basilicum L.) seeds produce a thick layer of mucilage around the pericarp within minutes after hydration. Mucilage is most prevalent among plant species adapted to surviving in arid sandy soils, though its significance in determining ecological fitness is unclear. The mucilage produced by seeds is reported to be composed of cell-wall polysaccharides that are deposited in testa pericarp cells during development. In this study, sweet basil seeds were examined using light and environmental scanning electron microscopy. The mucilage of basil seeds is held together by columnar structures that unfolded from the pericarp and helped hold and stabilize the mucilage to the outer surface. The mucilage was removed using diluted hydrochloric acid to compare performance of seeds with and without mucilage. Mucilage removal did not inhibit seed germination under ideal laboratory conditions but decreased the water content of seeds significantly. The water content of intact seeds was almost 4 times greater than seeds without mucilage. Mucilage enabled seeds cling to an incline board set to a steeper angle than seeds without mucilage. The fully hydrated seeds approached zero water potential, so the mucilage did not prevent seeds from fully hydrating. Soil (media) germination testing showed the seeds with mucilage had higher germination percentage than the seed without mucilage on several different types of media. Seeds with mucilage also had higher survival percentages after 10 days on different types of media. Basil seeds mucilage acts as a reservoir to hold loosely bound water at high water potential so it is available for seed germination and early seedling development.Master of Science
15
Nolan, Daryl Guy. "Seed germination characteristics of Centaurea diffusa and C. Maculosa". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27605.
Testo completoAbstract (sommario):
The problematic reinfestation of chemically-treated sites by diffuse and spotted knapweed {Centaurea diffusa and C. maculosa) is thought to occur from dormant seeds in the soil. This study confirmed that reserves of dormant seeds are present in the soil of infested sites, although greater numbers of seeds were recovered from senesced plants. Knapweed plants produce both non-dormant and dormant seeds (germination polymorphism), the relative proportions of which vary between individual plants within a site, as well as between bulk samples collected from different sites. Two types of dormant seeds were identified. Dormancy of some seeds was broken by exposure to red light ('light-sensitive seeds'). Light-sensitivity was evident at 10, 15, 20, 25, and 30°C. Germination in light-sensitive seeds was shown to be mediated by phytochrome. A lesser number of dormant seeds failed to respond to red light ('light-insensitive seeds').
Dry after-ripening released dormancy in both light-sensitive and light-insensitive seeds. However, no apparent loss of dormancy from after-ripening occurred when the relative humidity was too low or too high. At the highest relative humidity level tested (90.7%), dormancy was induced in some seeds while other seeds died. Dormancy was also induced when imbibed seeds were incubated in darkness at 25, 30, 35, and 40°C for 5 days. Dormancy induction was greatly enhanced by incubating submerged seeds in de-oxygenated water (anaerobiosis). However, some seeds died when incubated anaerobically for 5 days. Dormancy was broken in a small percentage of dormant seeds by incubation in a 10 mM solution of potassium nitrate or potassium nitrite; 100 mM potassium nitrite killed most seeds. Gibberellic acid was a much stronger germination stimulant. Some dormant seeds germinated at 25 °C if they were previously chilled at 3°C.
To compare laboratory findings with field germination behaviour, seeds from two samples of each species were buried to a depth of about 3 cm in mesh packets during November, April and August near Salmon Arm, B.C. Seeds exhibiting higher levels of germination in darkness in vitro also germinated to higher levels in situ when burial occurred in November. However, burial in April and August led to lower germination levels in situ. Light sensitivity was still prominent following 17 months of burial. Most of the decline in viable seed numbers during burial were attributable to in situ germination. Theoretical discussions of the source of germination polymorphism in knapweed seeds, the importance of light to field germination and seedling mortality, and a potential strategy for controlling these weeds are presented.Land and Food Systems, Faculty of
Graduate
16
Jorge, Marcal Henrique Amici. "GERMINATION AND CHARACTERIZATION OF GUAYULE (Parthenium argentatum GRAY) SEED". Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1247%5F1%5Fm.pdf&type=application/pdf.
Testo completo
17
Levesque-Tremblay, Gabriel. "Pectin methyl esterification functions in seed development and germination". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46351.
Testo completo
18
Dzomeku, Israel K. "Modelling seed dormancy, germination and emergence of Striga hermonthica". Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252261.
Testo completo
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Barros, Galvão Thiago. "Regulation of seed dormancy and germination in Arabidopsis thaliana". Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15593/.
Testo completoAbstract (sommario):
Seed germination is one of the most important developmental steps in the life cycle of a higher plant. Because of this, seed producing plants have evolved mechanisms, such as dormancy, that time germination based on environmental cues. The present study uses Arabidopsis thaliana as a model to address questions about seed dormancy and germination. Three different lines of investigation were followed. The first involved an investigation of how light quality regulates phytohormones in order to control germination. This identified a light-dependent mechanism that differentially regulates expression of the ALLENE OXIDE SYNTHASE and OXOPHYTODIENOATE-REDUCTASE 3 genes resulting in accumulation of cis-12-oxo-phytodienoic acid (cis-OPDA) and repression of seed germination under FR conditions. The second line of investigation involved a re- examination of the role of the ABSCISIC ACID INSENSITIVE (ABI) 5 and ABI4 transcription factors in regulating seed germination and oil mobilization respectively. The study found that abscisic acid (ABA) is able to block testa rupture in nicked seeds and this involves the ABI5, but not the ABI4, transcription factor. Furthermore, it was found that ABI4 is involved in the repression of ABA and cis-OPDA biosynthesis in a light- dependent manner, but has only a minor role in regulating oil mobilization in seeds. The third line of investigation focused on the regulation of dormancy during after-ripening and found that changes in phytohormone levels over an extended period can account for changes in dormancy state.
20
Brits, Gert Johannes. "Ecophysiology of Leucospermum R. Br. seed germination in fynbos". Thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/26071.
Testo completo
21
Bond, Laureanne Marie Wright Amy Noelle Guertal Elizabeth A. "Seed germination and growth requirements of selected wildflower species". Auburn, Ala., 2010. http://hdl.handle.net/10415/2042.
Testo completo
22
Dobrenz, Albert K., Jeffrey C. Silvertooth e Jill Martin. "Germination and Respiration of Cotton Seed Produced in Arizona". College of Agriculture, University of Arizona (Tucson, AZ), 1993. http://hdl.handle.net/10150/209585.
Testo completoAbstract (sommario):
The germination percentage and seedling respiration were evaluated on 11 cultivars of Cotton produced in Arizona. Respiration rates of 5-day old seedlings ranged from 6.0 to 16.9 mg /g⁻¹ hr⁻¹ for DP -5690 and KC-311, respectively. Germination percentage ranged from 31 to 87% for KC-311 and DP-51, respectively. A significant negative correlation (r = -.90) between respiration rates and the germination percentage indicates that seed quality is closely associated with early seedling metabolic rates.
23
Palzkill, D. A., L. DePaul e C. Sivilli. "Seed Germination Response of Penstemon spp. To Gibberellic Acid". College of Agriculture, University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/215861.
Testo completoAbstract (sommario):
Treatment of seed with gibberellic acid (GA) resulted in significant increases in germination percent for Penstemon ambiguous, P. barbatus, P. eatoni, P. palmeri, P. parryi. P. pseudospectabilis, P. secundiflorus, and P. strictus in one or both of two experiments which were conducted. Germination of several other species increased with GA treatment, but differences were not significant.
24
Harding, Kourtney T. "Sclerocactus wetlandicus: Habitat Characterization, Seed Germination and Mycorrhizal Analysis". DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6497.
Testo completoAbstract (sommario):
The Uinta Basin hookless cactus (Sclerocactus wetlandicus) is a threatened species native to Eastern Utah. The cactus is found in a landscape highly disturbed by non-renewable energy production. To understand the environmental conditions that support natural growth of this cactus, we asked whether plant communities differed in the undisturbed areas where the cactus is and is not found. We then compared undisturbed communities to those found on disturbed areas such as reclaimed well pads. Plant community characterization was accomplished with the line-point intercept method, and data were analyzed using Non-Metric Multidimensional Scaling. There was no significant difference in occupied and unoccupied undisturbed plant communities; S. wetlandicus associates with the common vegetation found in the study area. In contract, plant communities on the well pads were significantly different from those present in undisturbed locations. The disturbed areas were dominated by non-native weedy species and bare soil, thus differing from undisturbed habitats that contained higher relative vegetation cover and a mix of species from all functional groups both native and non-native.
To help restore this threatened cactus in disturbed habitats as well as prevent future extinction, we developed and tested a protocol for cactus seed germination in the greenhouse and successfully produced seedlings with a ~75% germination rate. Additionally, an important factor contributing to the successful growth of this threatened cactus is the presence of arbuscular mycorrhizal fungi (AMF). By extracting the DNA from root samples of wild cacti we were able to identify the presence of AMF from the families Glomeraceae and Claroideoglomeraceae representing three genera: Rhizophagus, Glomus, and Claroideoglomus. Sequences closest to Rhizophagus irregularis were identified from multiple root samples. Cactus seedlings may be inoculated with the fungi to promote their growth and ultimately their survival in the wild. Our study indicates that because S. wetlandicus is part of the common plant community of the study area and the well pads are vastly different from the common plant community, disturbed areas should be reclaimed in a way that better resembles undisturbed habitats to increase the likelihood that the newly planted cacti can thrive.
25
Guerin, Jennifer Ross. "Endopeptidases in barley seed and their action during germination". Thesis, Adelaide Thesis (Ph.D.)--University of Adelaide, Department of Plant Science, 1993. http://hdl.handle.net/2440/21658.
Testo completo
26
Guerin, Jennifer Ross. "Endopeptidases in barley seed and their action during germination". Adelaide Thesis (Ph.D.)--University of Adelaide, Department of Plant Science, 1993. http://hdl.handle.net/2440/21658.
Testo completo
27
Tasaki, Hiromi. "Light Effect on Seed Chlorophyll Content and Germination Performance of Tomato and Muskmelon Seeds". Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/43868.
Testo completoAbstract (sommario):
The stage of maturity of seeds at harvest is an important factor that determines seed vigor. Separating seeds from a seed lot composed of many different stages of development can be difficult especially after maximum dry mass is attained. Separating seeds based on their physiological maturity is more challenging than sorting seeds based on their physical properties. Seeds may be non-destructively sorted using chlorophyll fluorescence (CF) as a marker of seed maturity. This study was conducted to test whether CF could be used to remove low vigor immature seeds from muskmelon (Cucumis melo L.'Top Mark') and tomato (Lycopersicum esculentum) seed lots. Light treatments were applied to determine whether the light environment during seed harvesting and processing could affect chlorophyll content and seed vigor. Seeds from nine stages of development were collected from 'TopMark'. Seeds from three stages of fruit development (red ripe, breaker, and mature green) were harvested from tomato cultivar Money Maker and two phytochrome mutants: phytochrome A mutant, fri-1 and phytochrome B mutant, tri-1. The SeedMaster Analyzer (Satake USA Inc., Houston Texas) was used to measure CF and to sort individual seeds according to CF levels. Immature tomato seeds and muskmelon, harvested from green fruits, had the highest CF (p>0.001). Contrary to the results obtained with the other tomato genotypes, the vigor of tri-1 did not change inversely with changing CF levels, rather, seeds with low CF had the same vigor as seeds with high CF. This result may suggest that the presence of phytochrome B exerts an inhibitory influence on vigor in tomato seeds, and that the persistent presence of chlorophyll during seed development does not affect vigor. The light treatments had no consistent effect on seed chlorophyll content or on vigor in either tomato or muskmelon.Master of Science
28
Wood, Christopher. "Oxidative stress and seed survival". Thesis, Abertay University, 1998. https://rke.abertay.ac.uk/en/studentTheses/79d28b74-9210-4ebd-a3b8-66a610bd8c87.
Testo completoAbstract (sommario):
Free radical and aldehydic breakdown product content were determined, by EPR and UV / visible spectroscopy, primarily in intermediate (desiccation tolerant) seeds of Carica papaya L. (Papaya) and recalcitrant (desiccation intolerant) seeds of Aesculus hippocastanum L. (Horse chestnut), but also in other species covering a range of desiccation tolerances, with a view to determining the role of oxidative stress as a diagnostic marker for desiccation tolerance. Axes of non-senescent highly viable recalcitrant seeds of horse chestnut were metabolically active, contained products of lipid peroxidation, displayed low levels of enzymatic protection against activated oxygen and peroxides, and a two-peak free radical EPR signal. During fully hydrated storage at 16 °C for up to 18 months, seeds exhibited, sequentially, an increase in germination rate, a transient increase in intensities of both the low field and high field EPR peaks, a significant increase in membrane leakage and decrease in seed viability, germination rate, and SOD and peroxidase activities. Drying 'unstored' seeds below and embryonic axis moisture content of 40 to 50 % initiated viability loss. At < 25 % moisture content all axes were inviable and displayed a 2- to 4-fold increase in solute leakage, lipid peroxidation products and the low field EPR signal. Seed desiccation sensitivity increased with hydrated storage. The accumulation of lipid peroxidation products and free radicals on drying generally occurred to a greater extent, or at a higher moisture content, than observed with unstored seeds. The results indicate a mediating role for oxidative stress in recalcitrant seed viability loss which is differentially expressed during hydrated, 'natural' ageing and desiccation. Similar trends were seen in other recalcitrant species with the increase in lipid peroxidation products occurring around the point of viability loss. However the study of a more orthodox species (papaya) revealed no such trends.
29
Metcalf, Daniel James. "Seed size, litter and regeneration in tropical rain forest trees". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336743.
Testo completo
30
Redfearn, Melanie. "Nucleic acid integrity and synthesis in relation to seed vigour in sugar beet". Thesis, Open University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321321.
Testo completo
31
Legesse, Nigussu. "Genotypic comparisons of imbibition in chickpea (Cicer arietinum L.) and cowpea (Vigna unguiculata (L.) Walp.)". Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU546773.
Testo completoAbstract (sommario):
Examination of the imbibition characteristics of eighty chickpea genetic lines (53 Desi and 27 Kabuli types) and eleven cowpea cultivars revealed that in both species seeds with unpigmented testae imbibed more rapidly than the pigmented seeds. Rapid imbibition was associated with high solute leakage, indicative of possible imbibition damage. Further evidence of imbibition damage was revealed in cowpea where the rapidly imbibing unpigmented seeds had poor vital staining with tetrazolium chloride after 24h imbibition. In chickpea, all the genetic lines of white Kabuli seeds had similar rapid rates of imbibition. In contrast, the pigmented Desi genetic lines revealed a range of rates of water uptake although many imbibed more slowly than the Kabuli lines. The incidence of delayed imbibers, that is, seeds which failed to imbibe until after 8h in water, was the main reason for reduced rates of imbibition in Desi lines. The restriction to water uptake by the pigmented seeds was mainly influenced by the properties of the seed coat. In cowpea seeds, the permeability of the seed coat was the most important factor limiting water uptake whereas in chickpea the permeability of the seed coat as a whole and of the micropyle as well as the degree of adherence of the seed coat to the cotyledons were important in regulating the movement of water into the seed. Investigation of the rate of imbibition during the maturation of dwarf French bean, cowpea and chickpea seeds revealed that development of slow water uptake by coloured cultivars was clearly associated with the appearance of pigmentation. In chickpea, this also coincided with the development of the adherence of the seed coat to the cotyledons. In contrast, seeds from unpigmented cultivars imbibed rapidly at all stages of maturation. Examination of the seed coat anatomy of chickpea and cowpea indicated that the pigmented seeds tended to have shorter and narrower palisade cells and also shorter tracheid bars than the unpigmented seeds. Differences in water uptake by Kabuli and Desi seeds were not evident when seeds were stored at 100% relative humidity and 40oC for days. All seeds deteriorated at a similar rate. However, the importance of initial seed quality in influencing deterioration during storage was emphasised by the rapid loss of germination of the Kabuli seeds in which germination and vital staining revealed poor initial quality.
32
Daws, Matthew. "Mechanisms of plant species coexistence in a semi-deciduous tropical forest in Panama". Thesis, University of Aberdeen, 2002. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU160354.
Testo completoAbstract (sommario):
Niche-differentiation has been proposed to explain the coexistence of large numbers of tree species in tropical forests. Previous studies on established individuals have found little evidence for this. However, niche-differentiation may be apparent at the seed and seedling stages. This study investigated the effects of environmental variation in germination and seedling establishment for a range of Central Panamanian species. Firstly, topography has a large impact on soil water availability; slopes are wetter than nearby plateaux. The potential impact on seedling emergence and survival was studied by monitoring seedling emergence and survival over 15 months. This revealed that small-seeded species are unlikely to establish on plateaux, presumably because of the rider conditions. Secondly, the germination of four pioneer species in response to four environmental variables, related to canopy gap size, was investigated. Species exhibited consistent patterns of response suggesting adaptation for germination in particular gap sizes; Piper marginatum responded to nitrate, had a low base potential for germination and tolerated large temperature fluctuations, suggesting adaptation for germination in comparatively large gaps. Conversely, Pipe peltatum exhibited responses, which suggested adaptations for germination in small gaps. Finally, germination and seedling mortality for four pioneer species in two sizes of canopy gap was predicted using computer modelling. This indicated that large-seeded pioneers can germinate and establish in large gaps. Conversely, percentage germination and survival of small-seeded species was low in large gaps. However, small-seeded species produce greater quantities of seed than large-seeded species. Consequently they may "win by default" in large gaps, because of the absence of seeds of larger species. These results indicate that there are a number of axes of environmental variation along with nice-differentiation can occur. Furthermore, the response is variable between species. Thus niche-differentiation is important for fostering species coexistence, although density-dependent mortality and dispersal-limitation also contribute.
33
Liebenberg, Louis Christian Cronje. "Studies on the seed-setting and on the germination of the seed of indigenous grasses with particular reference to methods for overcoming delayed germination". Pretoria : [s.n.], 1990. http://upetd.up.ac.za/thesis/available/etd-06042007-134353.
Testo completo
34
McElhannon, Laura Michelle Waters Luther. "Enhancement of seed germination and seedling growth of Lenten rose". Auburn, Ala., 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Horticulture/Thesis/Moore_Laura_47.pdf.
Testo completo
35
Ali, Abdou-Djalilou. "Prediction of tomato seed germination from images with deep learning". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24666/.
Testo completoAbstract (sommario):
Assessment of seed germination is an essential task for seed researchers to measure the quality and performance of seeds not only to achieve high productivity but also for economic growth. In fact, knowing in advance the germination rate of the seeds can give farmers a better idea of how much their fields will produce. The seeds assessment can be done before or after the experiment. In the after-experiment assessment, trained analysts evaluate the seed germination by counting the seeds which present radicles or leaves emanating from them. However, the counting process done by analysts is cumbersome, error-prone, and time-consuming. Hence, machine learning-based methods have been proposed for the situation in which the assessment of seeds is done after experiment, to determine whether a seed germinated or not. Assessment of the seeds done before or after the experiment via model-based approach present many advantages: it is fast, more repeatable, and more accurate. In this thesis, we will consider the situation where the assessment of seeds is performed instead before the start of the experiment. That is, the proposed model will try to predict the seeds that are going to germinate and those that are not going to germinate before they will be placed in a chamber under proper growing condition for seven days. Prediction before the experiment holds the potential to further reduce the time required to select the seeds that are going to germinate and to let only valid seeds proceed to use the germination equipment. Therefore, in this thesis, we study the performance of a model-based approach that uses modern convolutional neural networks to predict the germination of tomato seeds, that is, whether a seed will germinate or not after it will have spent some period in the controlled environment for growing purposes.
36
Allison, Edwin. "Effects of seed adjuvants on germination and development of onions". Thesis, Cape Technikon, 2001. http://hdl.handle.net/20.500.11838/2000.
Testo completoAbstract (sommario):
Thesis (MTech (Agriculture))--Cape Technikon, 2001.Onion seeds (cultivar Caledon Globe), and soil into which the seedlings were planted, were treated with various adjuvants including fungicides, a seed disinfectant and a soil sterilant, as well as soil-applied growth stimulants to determine the effect of these on germination of seed, the growth of plants and the storage life of onions obtained. Three sets of germination trials were undertaken in petri dishes, and sets of seed was also sown in deep seed trays. A trial planting was made and the crop graded and stored. Seed was also sown in pots in soil obtained from a commercial undertaking where poor germination had been obtained. A portion of this soil was pasteurised and a portion inoculated with Fusarium spp. Growth of these seedlings was then followed by re-sowing in the same pots using seed of additional cultivars.
37
Gallagher, Robert Sean. "Ecophysiological aspects of phytochrome-mediated germination in soil seed banks /". The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933648650464.
Testo completo
38
Burgess, Tyler Lynne. "Seed Germination Studies of Southern Seaoats (Uniola paniculata)". NCSU, 2002. http://www.lib.ncsu.edu/etd/public/etd-138080102270/etd.pdf.
Testo completo
39
Morgan, Michael John. "Increasing seed germination and quantifying drought tolerance of Bursera graveolens". [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041327.
Testo completo
40
Kendall, Sarah. "Temperature regulation of seed dormancy and germination in Arabidopsis thaliana". Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3109/.
Testo completoAbstract (sommario):
The environmental regulation of seed dormancy and germination by temperature is an important process which allows the environmental conditions experienced by plants in the following generation to be controlled. Coping with temperature effects during seed maturation is essential for the consistent production of high quality seeds, but currently temperature signalling pathways in seeds are poorly understood. Previous work has shown that temperature during seed maturation regulates the levels of dormancy which are induced in the seed, although a mechanism for this pathway is currently unknown. Low temperature during imbibition promotes germination and although this is known to involve alterations to GA metabolism, again a mechanism is missing. Therefore, the aim of this study was to identify components of the mechanisms which regulate the temperature control of dormancy and germination in the model plant Arabidopsis thaliana. Cool and warm seed maturation temperatures induce high and low levels of dormancy respectively in Arabidopsis. These changes to dormancy levels are coupled with altered ABA and GA levels and gene expression controlling hormone synthesis and breakdown. Changes in maturation temperature do not appear to be linked to altered seed coat morphology or embryo development. During testing of cold-response mutants for dormancy phenotypes the expression of CBFs, a group of transcription factors which were characterised through the study of cold acclimation, was found to be necessary for dormancy. CBF RNAi and mutant seeds display reduced dormancy when matured at low temperature. However, the expression of CBFs is not promoted by exposure to low temperature in seeds, suggesting that this is not an important mechanism for the temperature control of dormancy. More strikingly, the E3 ligase HOS1 is absolutely required for high dormancy levels in response to low maturation temperature. hos1 mutants show a complete loss of dormancy when matured at any temperature and this phenotype is maternally inherited. The germination of hos1 seeds in the presence of PAC or ABA does not differ from wild-type, thus suggesting that sensitivity to GA and ABA is not altered in these seeds. However, levels of GA are increased in hos1 mutant seeds, which could be important for the reduced dormancy phenotype. The expression of TT genes, which are responsible for the accumulation of anthocyanidins in the seed coat, is downregulated in hos1 mutants and so could be involved in the regulation of dormancy by HOS1. Therefore; HOS1 defines a novel essential maternal pathway that regulates dormancy levels which involves the regulation of GA metabolism. A forward genetic screen identified a number of cold stratification insensitive (cosi) mutants. A thorough characterisation of these mutants revealed interesting phenotypes, but phenotypic variation and a lack of robust segregation data meant that the cosi mutants were not mapped.
41
Just, Michael. "Seed morphology, dormancy and germination of South-West Australian Ericaceae". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2051.
Testo completoAbstract (sommario):
The Ericaceae in South West Australia contains species with difficult to germinate seeds, including many species with deep intractable dormancy. A better understanding of seed biology and species specific dormancy, and germination mechanisms is required to overcome these difficulties. Land clearing, salinity and disease has resulted in over 125 species within 15 genera being listed as rare, highly restricted, threatened and endangered (Western Australian Herbarium 1998–). The present study examined the seed biology of eight species of Ericaceae native to Western Australia, exploring fruit and seed morphology, dormancy and germination. Cold and warm stratification was used in combination with gibberellic acid to classify dormancy. Among the two distinct fruit types that occur within the Ericaceae separate patterns of dormancy were found. Seeds held within a dehiscent capsule were found to possess non-deep and intermediate physiological dormancy whilst those within an indehiscent drupe possessed physiological and morphophysiological dormancy. Oxygen and nitric oxide enriched atmospheres, removal of seeds from endocarps and propagation from cuttings provided potential avenues for the propagation of study species.
42
PETROLLINI, Elisa. "Medicago marina (L.) seed: unravelling mechanisms controlling germination and dormancy". Doctoral thesis, Università degli studi del Molise, 2012. http://hdl.handle.net/11695/66384.
Testo completoAbstract (sommario):
L’obiettivo generale di questo lavoro di tesi è studiare i complessi e poco conosciuti meccanismi che regolano la dormienza e la germinazione del seme di Medicago marina (L.), una specie mediterranea presente sulle coste dell’intera penisola italiana e che si è adattata a vivere in habitat specializzati come le dune.
I semi di questa specie sono caratterizzati da una forte dormienza che ne impedisce la germinazione e i risultati ottenuti durante il primo periodo del corso di dottorato, sono stati recentemente pubblicati (Scippa et al., 2011). I meccanismi che regolano dormienza/germinazione e la risposta agli stress dei semi di questa specie, sono stati studiati attraverso analisi fisiologiche e di proteomica. Fra i pretrattamenti utilizzati (scarificazione meccanica, congelamento a -20°C e riscaldamento a 100°C per un’ora), la scarificazione e il congelamento sono stati più efficaci nella rimozione della condizione di dormienza. Il ruolo dell’acido abscissico (ABA) è stato studiato attraverso un dosaggio immunoenzimatico (ELISA) che ha permesso di determinarne la concentrazione nei semi trattati, germinati e non germinati (semi maturi utilizzati come controllo). Fra tutti, la maggiore concentrazione di ABA è stata riscontrata nei semi sottoposti a riscaldamento, mentre il confronto fra la concentrazione di ABA raggiunta nei campioni germinati, di controllo e trattati ha fatto supporre che, nel seme, si attivino diverse vie di segnalazione in grado di regolare da un lato l’omeostasi dell’ABA in risposta a diverse condizioni di stress e dall’altro la germinazione. L’analisi del proteoma ha rivelato la presenza di 46 proteine espresse in maniera differenziale fra i campioni trattati e il controllo, di cui 14 sono state sequenziale e identificate attraverso spettrometria di massa. Diverse, fra le proteine identificate, sono importanti fattori di risposta a situazioni di stress, essendo coinvolte nel metabolismo dei lipidi, nel folding proteico e nella protezione della cromatina. L’analisi del fosfoproteoma ha dimostrato che la funzione di molte proteine, soprattutto nei semi sottoposti a riscaldamento, è modulata attraverso modificazioni post-traduzionali. Questi risultati lasciano presupporre che i semi di M. marina adottano una strategia di dormienza basata sulla presenza di robusti tegumenti (hardseededness) in grado di prevenire l’assorbimento di acqua e la germinazione; inoltre la dormienza può essere regolata da altri complessi meccanismi fisiologici, quali la termoinibizione.
Da questi primi risultati, si è portato avanti lo studio volto a definire il ruolo di controllo della dormienza e della germinazione da parte dell’endosperma micropilare. A questo scopo, utilizzando la tecnica del puncture force, è stato misurato il weakening dell’endosperma micropilare nei semi sottoposti a scarificazione meccanica e a trattamento con ABA durante un time course di circa 22 ore. L’effetto dell’ABA è stato valutato anche sulla velocità e sul tasso di germinabilità finale dei semi sottoposti a tale trattamento. I risultati ottenuti hanno dimostrato che l’ABA è in grado di provocare un ritardo sia del weakening dell’endosperma sia della velocità di germinazione, che si traduce a sua volta in una considerevole diminuzione della percentuale di germinazione finale. In seguito, attraverso l’analisi del proteoma e l’analisi statistica multivariata sono state individuate 95 proteine che potrebbero rappresentare markers specifici dei diversi stati fisiologici, quando, superata la fase di dormienza il seme si prepara per la germinazione. Risultati preliminari suggeriscono che l’endosperma micropilare può contribuire all’instaurarsi della condizione di dormienza fisica che, ancora una volta, può essere rimossa efficacemente attraverso la scarificazione meccanica; inoltre l’ABA può svolgere un ruolo predominante nella regolazione temporale della geminazione, agendo sul weakening dell’endosperma micropilare.The general aim of this thesis is to understand the complex and unknown mechanisms underlying dormancy and germination of Medicago marina (L.), a Mediterranean species distributed along the whole coasts of Italian peninsula and adapted to living in a specialized life habitats, like the dunes. Seeds of this species show strong dormancy that prevents germination. Results obtained during the first period of PhD program are published in a paper by Scippa et al., (2011). An integrated approach of physiological analyses and proteomics was used to investigate the mechanisms that control M. marina dormancy/germination and that underlie stress tolerance. First, was evaluated the effects on dormancy breaking of the following treatments: mechanical scarification, freezing at -20 °C, storage for 4 months and heating at 100 °C for 1 h. Mechanical scarification and freezing were the most effective treatments in overcoming dormancy. The role of abscisic acid (ABA) in M. marina dormancy was studied by ELISA immuno-enzymatic assay, determining the ABA content of germinated and non germinated mature (control) and treated seeds. The level of ABA was higher in treated seeds than in control seeds; the most significant increase occurred in the heated seeds. A comparison of the ABA level in the germinated, control and treated seeds suggests that different mechanisms modulate ABA content in response to different stresses, and that a specific ABA-signaling pathway regulates germination. Proteomic analysis revealed 46 proteins differentially expressed between treated and untreated seeds; 14 of these proteins were subsequently identified by mass spectrometry. Several of the proteins identified are important factors in the stress response, and are involved in such diverse functions as lipid metabolism, protein folding and chromatin protection. Lastly, an analysis of the phosphoproteome maps showed that the function of many proteins in seeds subjected to temperature treatment is modulated through post-translational modifications. Taken together, the data obtained showed that M. marina seeds adopt a dormancy strategy based on a hard seed coats, known as hardseededness, which prevent water uptake and germination; also, dormancy it can be regulated by other complex mechanisms beside seed coats, such as thermoinhibition, a delaying mechanisms of germination adopted by different species during late summer or early autumn. Starting from these first results, the PhD project proceeded in further investigations of mechanisms involved in the control of germination timing and dormancy establishment, due to the mechanical constraints of the micropylar endosperm, besides the seed coat. In order to accomplish this aim, the weakening of the endosperm was analyzed trough the puncture force measurements in seeds subjected to mechanical scarification and ABA treatment, along a 22 hours time course of imbibition. In addition to that, the effect of ABA and gibberellic acid treatments on germination rate and speed, were analyzed by performing germination test. Results obtained from the puncture force and germination tests for scarified seeds treated or not with ABA, revealed that the endosperm weakening, occurring in M. marina seeds before the germination, is delayed by ABA, which deferred also the germination of treated seeds. Then, the using of 2D analysis coupled whit the multivariate statistical analysis allowed the individuation of 95 spots that represent specific markers of different physiological states and might be expressed in seeds when dormancy is overcome in order to complete germination. First results suggest that the micropylar endosperm can contribute to the establishment of M. marina physical dormancy, that once again, it can be removed by mechanical scarification. Moreover, abscisic acid seems to be strongly involved in regulation of germination timing, by its action on micropylar endosperm weakening.
43
Saeidi, Ghodratollah. "The effect of seed colour and linolenic acid concentration on germination, seed vigour, seed quality and agronomic characteristics of flax". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27429.pdf.
Testo completo
44
Jones, Stephen Keith. "Sitka spruce (Picea sitchensis [Bong.] Carr.) seed germination in relation to seed development, dormancy and storage". Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283746.
Testo completo
45
Stutchbury, P. A. "The regulation of seed dormancy in the genus Acer". Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379534.
Testo completo
46
Lindgren, Ove. "Carotenoid biosynthesis in seed of Arabidopsis thaliana /". Uppsala : Dept. of Plant Biology and Forest Genetics, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a431.pdf.
Testo completo
47
Dutt, Manjul. "USING SEQUENTIAL IMAGERY TO EVALUATE ASPECTS OF SEED VIGOR AND GERMINATION". UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_theses/410.
Testo completoAbstract (sommario):
A sequential imaging system using a flat bed scanner interfaced to a personal computer was developed to study seed germination and vigor. The utility of the system was demonstrated in studies relating aspects of seed vigor in impatiens seed lots and for dormancy release in two woody perennials. Impatiens seed lots were kept in storage for 6 months to obtain a range in vigor levels. The ability to see differences at the individual seed level was possible because of the development of the sequential imaging system. It was observed that seeds deteriorated both under optimum 4OC as well as 25OC storage conditions. It was determined that both germination rate and seedling growth rate were appropriate measures of seed vigor. As untreated and primed seed lots were aged, germination percentage was negatively correlated with germination rate and positively correlated with seedling growth. However, there was a lack of correlation between germination rate and seedling growth on an individual seed basis. The data suggests that germination rate and seedling growth rate appear to be measuring different aspects of vigor. Sequential imagery also showed subtle changes in seed and seedling growth as seeds came out of dormancy that would not be detectable otherwise. This technique revealed changes in seed morphology that were previously not documented for seeds with physical dormancy. The current study furthered the utility of the imaging system by the development of sequential imaging that allows for samples to be collected hourly without technician input. This permitted very accurate determinations of germination rate and seedling growth on a single seed basis.
48
Naim, Elissa. "The oxidative modifications in the macromolecules of sunflower seed during germination". Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS536.pdf.
Testo completoAbstract (sommario):
Nos travaux ont porté sur la caractérisation des propriétés de la paroi cellulaire et de l’état d’oxydation des protéines, ainsi que sur leur relation avec la levée de dormance et le processus de germination. Ainsi, nous avons étudié le changement de résistance de la paroi cellulaire en utilisant différents traitements de levée de dormance: la post-maturation au sec, les espèces réactives de l’oxygène (reactive oxygen species, ROS) et une hormone (l’éthylène). L’étude du changement de résistance de la paroi cellulaire a montré une diminution de rigidité chez les graines traitées, capables de germer, par rapport à celles dormantes. La quantification des monosaccharides de la paroi n’a pas mis en évidence de différence significative, ce qui suggère l’absence de phénomènes associés au métabolisme des polysaccharides à ce stade de la germination sensu stricto. Seules les graines dormantes traitées avec les ROS ont présenté une diminution significative de l’activité de la pectine méthylestérase, une enzyme de la paroi connue pour son rôle dans l’élongation et la croissance. Une analyse immunocytologique a permis de décrire une paroi cellulaire plus estérifiée chez les graines dormantes. Ainsi, les ROS pourraient avoir une action non-enzymatique alors que l'éthylène pourrait agir en synergie avec les ROS afin d'obtenir le relâchement nécessaire de la paroi cellulaire pour la croissance. En outre, une analyse protéomique combinant la technique chromatographie à une analyse LC-MS / MS a été utilisée sur des graines de tournesol dormantes et non dormantes à différents temps d'imbibition afin d’identifier des protéines contenant des méthionines sulfoxydées, une oxydation protéique réversible. Des analyses préliminaires suggèrent un niveau d'oxydation des protéines au niveau de la méthionine plus important dans les graines non dormantes. De façon intéressante, de nombreuses protéines cibles de l’oxydation de la méthionine sont liées à de différents processus biologiques (traduction, métabolisme des protéines, énergie et le métabolisme, processus d’oxydo-réduction) connus pour être des acteurs impliqués dans la germination, suggérant ainsi l’importance de l’oxydation de la méthionine dans la régulation de différentes voies cellulaires impliquées dans la levée de dormance et la germinationOur work focused on the relationship of cell wall properties and protein oxidation state on dormancy alleviation and germination process. Different dormancy alleviation treatments have been used: afterripening, reactive oxygen species (ROS) and hormone (ethylene). Thus, the study of the change in resistance of the cell wall has shown a decrease in rigidity in treated seeds, able to germinate, compared to dormant ones. Quantification of the identified cell wall monosaccharides did not show any significant difference suggesting the absence of phenomena related to the metabolism of polysaccharides at this stage of germination sensu stricto. Only dormant seeds treated with ROS showed a significant decrease in pectin methylesterase activity, a cell wall enzyme known for its role in elongation and growth. An immunocytological analysis has described a more esterified cell wall in dormant seeds. Thus, the ROS could have a non-enzymatic action while ethylene could act in synergy with the ROS to fulfil the needed relaxation of the cell wall for growth. In addition, a proteomic analysis combining the diagonal chromatography technique with an LC-MS / MS analysis was used on dormant and non-dormant sunflower seeds at different imbibition times in order to identify proteins containing methionine sulfoxyde, a type of reversible protein oxidation. Preliminary analyzes suggest a higher level of protein oxidation in non-dormant seeds. Interestingly, many proteins affected by the oxidation of methionine are related to different biological processes (translation, protein metabolism, energy and metabolism, oxidation-reduction processes) known to be involved in germination, thereby suggesting the importance of methionine oxidation in the regulation of different cellular pathways involved in dormancy emergence and germination
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Ghita, Melania Georgeta. "Molecular biomechanics of seed germination in Arabidopsis thaliana and Lepidium sativum". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14480/.
Testo completoAbstract (sommario):
Seed germination is a key process in world agriculture. For this reason, the capacity of a seed to germinate with minimum input from farmers is highly desirable, keeping the production costs as low as possible. The physiological mechanism of germination is well known, involving the rupture of the endosperm and testa envelope by the expanding embryo, but the molecular and biomechanical changes underlying this process are poorly understood. In order to answer the question of how the plant developmentally regulates changes in cell wall stiffness associated with germination, an innovative molecular biomechanics approach was developed. It combines biophysical, engineering and molecular biology approaches. A comparative approach was taken using the related species Arabidopsis thaliana and Lepidium sativum, the former due to the wealth of genomic resources, and the latter due to larger size and ease of use in biomechanics experiments. Environmental scanning electron microscopy imaging revealed that the endosperm structure is intact after protrusion of the radicle, confirming the fact that rupture occurs between individual cells. Germination is a process that requires targeted cell separation or/ and cell wall remodeling. For this reason, following the predictions of the gene network SeedNet, containing the endosperm-specific sub-network cluster 19 (Bassel et al., 2011), endosperm specific genes were studied. In order to localize their expression, promoter::GUS constructs were used for the genes DELTA-VPE, SCPL51 and DOF2.1, and different mutant alleles of four transcription factors from cluster 19 (athb23, bhlh-115, bee2 and dof2.1) were screened to identify changes in germination behaviour. DELTA-VPE and SCPL51 were proven to be endosperm specific and ABA insensitive. DELTA-VPE was GA insensitive and SCPL51 expression required GA. Also, DELTA-VPE expression could be observed after 15 minutes of imbibition in the whole endosperm, while SCPL51 showed a temporal expression requiring 18 hours of imbibition before being observed in all endosperm cells. The analysed T-DNA lines showed an epistatic relationship between ATHB23 and DOF 2.1 and a decreased sensitivity to stress factors like osmotic and salt stresses, than the wild type. Using nanoindentation, a differentiation between different regions of endosperm was attempted, but the methodology was not sensitive enough. However, different elastic modulus values for imbibed and dry Lepidium seeds were registered. To image the internal changes in seed structure during germination, micro-CT was used, estimating values for endosperm thickness from dry state to germinated one. This work enforces the knowledge of the molecular biology and biomechanical properties of the endosperm.
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Kasumu, Exildah Chibengele Chisha. "Improving exploitation of Pterocarpus angolensis : seed germination, micropropagation and genetic diversity". Thesis, University of Aberdeen, 2005. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU207620.
Testo completoAbstract (sommario):
Studies of seed dormancy breakage, micropropagation and genetic diversity were conducted on seed from Zambia and Zimbabwe. In seed dormancy breakage, nicking part of the seed coat and gibberellic acid treatments GA3 and GA4/7 were investigated. In Study 1) nicking had significantly higher germination, with a rate of 99% within five days of sowing, whereas GA3 treatment and the control had 65 and 69% germination respectively after four weeks. In study 2) 36, 36, 55 and > 91% germination were obtained with GA4/7, GA3, the control and nicking respectively after six weeks. In micropropagation experiments designed to investigate the optimum conditions for plantlet production, 6-benzylaminopurine (BAP), isopentenyl-adenine (2-iP) and thidiazuron (TDZ) were tested for shoot induction of cuttings from four weeks old P. angolensis seedlings. BAP at 5 mg.l-1 had significantly higher shoot multiplication compared to 0 - 2 mg.l-1 BAP concentrations. Sprouted axillary buds in 0.1 to 2 mg.l-1 TDZ treated cuttings did not elongate to usable sizes compared with BAP treated shoots. 2-iP at 0.5 - 5 mg.l-1 produced roots instead of shoots. Indole-3-butyric acid (IBA), indole-3-acetic acid (IAA) and the control were tested for ability to root cuttings. IAA at 1 mg.l-1 and IBA at 1- 4 mg.1-1 had a significantly higher number of roots. The control was efficient in root production. Using RAPD markers, within population genetic variation was revealed. Moderately high population differentiation of PHIst = 0.165 and 0.192 were found in two studies. This revealed significant gene flow between populations. These studies can be used to guide sustainable management, utilisation and domestication of P. angolensis in the future.