Dissertations / Theses on the topic 'Germination'
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1
Tranbarger, Timothy John. "Isolation and regulation of genes expressed during Douglas-fir germination and post-germination." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ37366.pdf.
2
Zaman, S., S. Padmesh, and 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.
Abstract:
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.
3
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.
4
Elliott, Katherine Anne. "Barley germination and associated metabolism." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/713.
5
Liu, Bing. "Germination studies in terrestrial orchids." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303461.
6
Hampstead, Anthony. "Mathematical approaches to seed germination." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/13979/.
Abstract:
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.
7
Hayer, Kimran. "Germination of Aspergillus niger conidia." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14292/.
Abstract:
Aspergillus niger is a black-spored filamentous fungus that forms asexual spores called conidospores (‘conidia’). Germination of conidia, leading to the formation of hyphae, is initiated by conidial swelling and mobilisation of endogenous carbon and energy stores, followed by polarisation and emergence of a hyphal germ tube. These morphological and biochemical changes which define the model of germination have been studied with the aim of understanding how conidia sense and utilise different soluble carbon sources for germination. Microscopy and flow cytometry were used to track the morphological changes and results showed that the germination of A. niger conidia was quicker and more homogenous in rich media than in minimal media. The germination of conidia was also shown to be quicker in the presence of D-glucose than D-xylose. In the absence of a carbohydrate, no visual indicators of germination were evident. Added to this, the metabolism of internal storage compounds was shown to only occur in the presence of a suitable carbon source. Specific environmental carbon sources may therefore serve as triggers of germination, i.e. to initiate the catabolism of stores such as D-trehalose and the swelling of conidia. Studies carried out using D-glucose analogues identified the structural features of sugars that trigger or support conidial germination. These studies showed that the arrangement of atoms on carbons 3 and 4, on the pyranose ring structure of D-glucose, are essential to serve as a trigger of germination. The trigger step preceeds, and is separate from, the energy generation step that supports the continued outgrowth. Transcriptomic studies found that the most significant changes were associated with the breaking of dormancy. The data also revealed that fermentative metabolism present at the early stages of spore germination is rapidly replaced by respiratory metabolism.
8
Foster, S. J. "Biochemistry of Bacillus megaterium spore germination." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384466.
9
Araujo, Diego Kitahara. "Extratos de Ascophyllum nodosum no tratamento de sementes de milho e soja: avaliações fisiológicas e moleculares." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-07062016-155617/.
Abstract:
A obtenção de uma lavoura com população adequada de plantas depende da utilização de diferentes práticas agronômicas, estando o sucesso condicionado ao uso de sementes de boa qualidade. No entanto, a semeadura dificilmente é realizada em condições ideais o que resulta em problemas na emergência das plantas. Grande é a procura por alternativas que melhorem a germinação e o desenvolvimento inicial dos cultivos resultando em uniformidade de emergência, garantindo o estande e culminando em produção. O tratamento de sementes com agroquímicos fitossanitários é uma solução parcial no combate de agentes fitopatológicos e pragas, mas poucas são as soluções adotadas para melhorar o desenvolvimento vegetal inicial, que pode levar a desuniformidade e falhas no estande gerando prejuízos econômicos. Os extratos de algas já demonstraram em diversos estudos sua eficiência no desenvolvimento vegetal quando aplicados em plantas. Porém poucos são os estudos voltados para os efeitos dos extratos de algas na germinação e emergência. Assim, o intuito deste trabalho foi testar o extrato comercial de Ascophyllum nodosum, e diferentes fracionamentos do mesmo, no tratamento de sementes de soja e milho. Avaliou-se o efeito de diferentes doses no desenvolvimento das plântulas e as doses de melhor resposta foram utilizadas no tratamento de sementes de soja a fim de associar as respostas obtidas à expressão gênica de 9 genes relacionados ao processo germinativo em 24 e 48h de embebição. Sementes de soja tratadas com o extrato comercial resultaram em plântulas menos desenvolvidas o que pode estar relacionado ao alto teor de sais contidos no produto. O tratamento com as demais frações favoreceu o desenvolvimento das plântulas, principalmente o desenvolvimento radicular. Sementes de milho tratadas não apresentaram desenvolvimento tão satisfatório quanto as sementes de soja tratadas. A análise da expressão gênica relativa demonstrou que o tratamento com frações do extrato comercial é capaz de regular algumas vias do metabolismo hormonal, como a isopentenil transferase e a GA20 oxidase 2, e do catabolismo de reservas, como a acil-CoA oxidase. Em condições ótimas, o tratamento de sementes de soja com frações do extrato comercial de A. nodosum favoreceu o desenvolvimento inicial das plântulas de soja, no entanto não ocasionou grandes alterações no desenvolvimento de milho. Este estudo demonstrou a possibilidade de utilização de frações do extrato de A. nodosum no favorecimento do desenvolvimento inicial de plântulas de soja. Maiores estudos são necessários quanto às respostas em campo e na atenuação de estresses para viabilizar seu uso como um bioestimulante em sementes.To make a production field to achieve the suitable stand of plants someone depends on proper agronomic managements being the use of seeds of high quality one of the aspects to be taken into account. However, the sowing is rarely done under ideal conditions for the seeds germination, which leads to a considerable lack of uniformity of the stand. Researchers and farmers look for alternatives to improve the seeds germination as well as emergence and initial development of plants to achieve better stand uniformity, culminating in higher productivity. The seed treatment with fungicides and pesticides is a partial solution that control diseases and pests related to the seeds. However, very little attention is given to solutions to improve the initial development of plants that can result in poor stand and consequently lower economic yields. The A. nodosum extracts have shown through several studies their effectiveness in improving the plant development. However, those studies are not directed to the seeds germination and emergence of seedlings. Thus, this study was done to assess the A. nodosum extracts in different fractions on maize and soybean seeds treatment. Firstly, it was assessed the effect of different doses of A. nodosum extracts on the development of seedlings. The doses that showed better results were used for the soybean seed treatment aiming to associate the responses obtained to the expression of nine genes related to the germination process, at 24 and 48 hours of water uptake. Soybean seeds treated with the commercial extract of A. nodosum originated less developed seedlings. This effect can be due to the high content of salts present in the product. Treatments with the fractions of the product led to a better development of seedlings, mainly the radicular development. Maize seeds did not have the same performance as the soybean seeds. The relative gene expression analysis demonstrated that the treatment with fractions of commercial extract of A. nodosum is able to regulate some pathways of hormonal metabolism through enzymes as isopentenyl transferase and GA20 oxidase 2, and the storage catabolism, as acyl-CoA oxidase. Under ideal conditions, seed treatment with fractions of commercial extract of A. nodosum has improved the initial development of soybean seedlings, however, none or small changes were observed for the development of maize seedlings. This study shows the possibility of use of A. nodosum extract to favor the initial development of soybean crop. Additional studies are required to assess effects on fields and stresses attenuation to enable the use of the seaweed extract as a seed biostimulant.
10
Jayaraman, Padmavathy. "Analysis of Bacillus subtilis 1604 spore germination." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317752.
11
Ma, Liuyin. "THE ROLE OF POLYADENYLATION IN SEED GERMINATION." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/47.
Abstract:
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.
12
Mansfield, Stephen Gary. "Embryogenesis and germination in Arabidopsis thaliana L." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253657.
13
Homer, Karen Ann. "Anthranilate and conidial germination in colletotrichum musae." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315600.
14
Dobrenz, Albert, David Robinson, and Steve Smith. "Improving the Germination Salt Tolerance of Alfalfa." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/200482.
Abstract:
The development of alfalfa that can germinate at extremely high NaC1 levels will improve early emergence and establishment of this important forage crop in saline soils. We have identified plants in the eighth cycle of selection that germinated at -3.0 MPa (30,000 ppm). Seed from these plants displayed a 40% better germination at -2.1 MPa (21,000 ppm) than the previous cycle. Germination at higher salt concentrations were not different between the two germplasm sources.
15
McKimmie, Tim, and Albert Dobrenz. "Alfalfa Salt Tolerance from Germination to Establishment." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/200538.
16
Paul, Nancy Elizabeth 1960. "EFFECTS OF PARENT PLANT NUTRITION AND TIME OF HARVEST ON GERMINATION CHARACTERISTICS OF TWO GRASS SPECIES (GERMINATION RATE, FERTILITY)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276992.
17
Xia, Qiong. "Molecular aspects of temperature regulation of sunflower seed dormancy." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066629/document.
Abstract:
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
18
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.
19
Heeg, Daniela. "Spore formation and spore germination of Clostridium difficile." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594825.
Abstract:
Clostridium difficile is the major underlying cause of antibiotic-associated diarrhoea and poses a risk for healthcare systems worldwide. Endospores produced during sporulation are widely regarded to be the infectious agent of C. difficile associated diarrhoea. These spores are able to withstand a variety of antimicrobial agents and industrial cleaning products and are therefore able to reside on surfaces in healthcare settings for prolonged periods of lime. In order to cause disease in susceptible individuals, spores need to abjure dormancy and return to vegetative cell growth through germination. Sporulation and germination have been studied extensively in Bacillus spp. Knowledge about the sporulation and germination pathways in C. difficile, however, remains incomplete. Here, forward and reverse genetics methods were employed to analyse sporulation and germination phenotypes of C. dfficile. Using forward genetics, 19 mutants with potential sporulation and/or germination phenotypes were isolated, three of which were completely deficient for sporulation. In an attempt to explore the use of transposon suicide vectors, a protocol for the successful transformation of C. difficile was developed. A reverse genetic mutant in the germination specific lytic transglycosylase Slee created by ClosTron mutagenesis was used to study spore germination in vivo. This study is the first report of the use of a germination mutant in vivo. The sporulation characteristics of 52 clinical C. difficile isolates have been analysed indicating that a variation in the rate of sporulation is not associated with molecular type. The germination characteristics of 37 clinical C. difficile isolates were examined, indicating that different isolates exhibit varying germination characteristics in response to bile salts.
20
Johnson, Christian Lloyd. "Proteins involved in the germination of bacillus spores." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425623.
21
Siegel, Richard S., and John H. Brock. "Germination Requirements of Key Southwestern Woody Riparian Species." University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/609112.
Abstract:
Germination requirements of selected Southwestern woody riparian species were studied in the laboratory. Four common tree species selected for study were Fremont Cottonwood (Populus fremontii), Goodding Willow (Salix gooddingii), Arizona Sycamore (Platanus wrightii) and Velvet Mesquite (Prosopis velutina). Seeds were collected from two major riparian habitats in the southwest. The species tested required a temperature range of 16° C to 27° C for germination. Fremont Cottonwood, Goodding Willow and Velvet Mesquite showed good germination at moisture stress levels of -4 bars or less, whereas Arizona Sycamore only germinated well at 0 bars. For all species tested, germination was better at salinity levels lower than 50 meq /liter NaCl. All species displayed successful germination responses between pH 5 to 7. Velvet Mesquite germinated at all pH levels (5 -10). Longevity of seeds of riparian species is reported to be of short duration. This was confirmed in these studies with southwestern woody riparian species.
22
Sumugat, Mae Rose S. "Glutathione Dynamics in Arabidopsis Seed Development and Germination." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/36420.
Abstract:
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
23
Leonard, Jenny. "Germination success and drought response in Erica coccinea." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15559.
Abstract:
Resprouters and seeders are two common phenotypes found in fire-prone ecosystems. Although the distribution of the two forms is usually attributed to fire frequency, it has been proposed that the distribution of resprouter and seeder Erica in the Cape Floristic Region (CFR) of South Africa is determined more by water availability. Erica seeders are predicted to withstand the mild droughts of the southwest CFR better than Erica resprouters, which would account for the abundance of seeders in this region. This thesis tested the assumptions that 1) seeders germinate more quickly and successfully than resprouters and 2) seeders survive mild drought better than resprouters. A germination experiment (Chapter 2) and a drought experiment (Chapter 3) were conducted using Erica coccinea, a common Erica species in the CFR, which contains both a resprouter and a seeder form. Germination success was also tested for a third form of E. coccinea found only in fire refugia. I predicted that this form would not require smoke as a cue for germination. Results indicated that (1) resprouters germinated faster than seeders in the presence of smoke, (2) seeders had better germination success than resprouters in the absence of smoke, (3) the "pyrofuge" form did not require smoke to germinate and (4) seeders had lower survival than resprouters during drought. Overall, these results refuted the proposition that E. coccinea seeders have improved germination and drought tolerance. However, variation between populations within the seeder form indicated that more populations should be tested to verify that these results represent the species as a whole. Due to the lack of variation between populations of the "pyrofuges", it is clear that this form has adapted to its' fire-free environment by allowing for germination in the absence of fire.
24
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.
Abstract:
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.
25
Muthui, Wangechi. "Changes in muskmelon perisperm envelope tissue during germination." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06302009-040400/.
26
St, Hilaire Rolston. "Seed Coat Treatments Influence Germination of Taxodium mucronatum." University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/554341.
Abstract:
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.
27
McKimmie, T., and A. K. Dobrenz. "Developing Salt Tolerant Alfalfa Beyond the Germination Stage." College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200494.
28
Kobriger, J., N. Oebker, N. Simons, and D. Wager. "Germination of Several Pepper Cultivars at High Temperatures." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/214129.
29
Kobriger, J., N. Oebker, N. Simons, and D. Wager. "Germination of Several Tomato Cultivars at High Temperatures." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/214130.
30
Ralowicz, A. E., C. F. Mancino, and D. M. Kopec. "Variation in Flowering and Germination in Hilaria belangeri." College of Agriculture, University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/215831.
31
TUDELA, ISANTA MARIA. "A comparative germination study among different alpine habitats." Doctoral thesis, Università degli studi di Pavia, 2017. http://hdl.handle.net/11571/1214891.
Abstract:
If species inhabit in a specific habitat two conditions should be befallen: first seeds must be present through dispersal or in the soil seed bank and secondly, conditions for germination must occurred. If suitable germination niche is not met, germination will not occur and, consequently, species will not be present. In an alpine context, the large species and microhabitats pool found have resulted in a variety of germination and dormancy patterns, which make it difficult to define a common alpine germination niche or behaviour. Therefore, to better understand germination ecology in alpine environment and their functional role in filtering the regional species pools into local communities a habitat-related germination study is needed. A habitat-related approach will contribute to a better comprehension of which are the key factors affecting germination in alpine habitats and define the different alpine germination niches. To this end, a germination study of species inhabiting in two Sites of Community Interest (SCI) “Passo dello Stelvio (46° 32’N, 10° 25’E)” and “Val Viola, Dosde (46º 24’N, 10º12E)”, located in the Alps of Lombardy (Sondrio, Northern Italy) was done. These SCI belong to two habitats types defined by the European Habitat Directive Natura 2000 classification: Habitat #6230- Nardus-rich species grasslands” or “siliceous habitat”; and Habitat #6170- Alpine calcareous grasslands’ or “calcareous habitat”. Firstly, I described and compare the type and level of seed dormancy and assessed species’ germination strategies of 53 alpine species growing in two different habitats. Results showed that calcareous and siliceous species showed different germination strategies, with a slow, mostly overwinter germination on calcareous species’, and with fast and undifferentiated timing germination for siliceous ones. Moreover, specialized regenerative strategies were observed among microhabitats with species mostly occurring in heats showing high overwinter germination. In conclusion, alpine species use different germination strategies depending on habitat provenance, species’ main microhabitat and chorotype. Subsequently I defined the germination and vegetative traits of seven pairs of closely related species inhabiting in these habitats. Results showed some germination traits dissimilarities according to habitat provenience. Conversely, other germination traits and vegetative traits were similar in both habitats. The high vegetative traits convergence hints at small differentiations in adult plants between habitats. However, the separate habitat clusters when using germination traits suggest that species occurrence in the two habitats may be limited at the earliest stages of plant development, particularly by germination. Finally, I predict species germination timing in the field using thermalmodels. Results showed species were dormant when dispersal and different germination timings were predicted for each specie. The different dormancy types detected here indicate that dormancy may play a significant role in controlling germination, always awarding risk-averse strategies to escape winter. The different germination timing detected reduce probability to overlap species’ germination niche, thus having different timings species do not compete for the same resources. In conclusion, this thesis describes germination ecology on alpine habitats and identify the main factors affecting species’ specific germination behavior. Special attention was putted on the possible functional role of germination and dormancy on driving species distribution and community assembly. Finally, all outputs reached here and future outputs that new research will bring hint at important implication in developing good practices for restoration and conservation activities in alpine habitats and contribute to a better understanding of the response of alpine plants in the regeneration from seeds due to global warming.If species inhabit in a specific habitat two conditions should be befallen: first seeds must be present through dispersal or in the soil seed bank and secondly, conditions for germination must occurred. If suitable germination niche is not met, germination will not occur and, consequently, species will not be present. In an alpine context, the large species and microhabitats pool found have resulted in a variety of germination and dormancy patterns, which make it difficult to define a common alpine germination niche or behaviour. Therefore, to better understand germination ecology in alpine environment and their functional role in filtering the regional species pools into local communities a habitat-related germination study is needed. A habitat-related approach will contribute to a better comprehension of which are the key factors affecting germination in alpine habitats and define the different alpine germination niches. To this end, a germination study of species inhabiting in two Sites of Community Interest (SCI) “Passo dello Stelvio (46° 32’N, 10° 25’E)” and “Val Viola, Dosde (46º 24’N, 10º12E)”, located in the Alps of Lombardy (Sondrio, Northern Italy) was done. These SCI belong to two habitats types defined by the European Habitat Directive Natura 2000 classification: Habitat #6230- Nardus-rich species grasslands” or “siliceous habitat”; and Habitat #6170- Alpine calcareous grasslands’ or “calcareous habitat”. Firstly, I described and compare the type and level of seed dormancy and assessed species’ germination strategies of 53 alpine species growing in two different habitats. Results showed that calcareous and siliceous species showed different germination strategies, with a slow, mostly overwinter germination on calcareous species’, and with fast and undifferentiated timing germination for siliceous ones. Moreover, specialized regenerative strategies were observed among microhabitats with species mostly occurring in heats showing high overwinter germination. In conclusion, alpine species use different germination strategies depending on habitat provenance, species’ main microhabitat and chorotype. Subsequently I defined the germination and vegetative traits of seven pairs of closely related species inhabiting in these habitats. Results showed some germination traits dissimilarities according to habitat provenience. Conversely, other germination traits and vegetative traits were similar in both habitats. The high vegetative traits convergence hints at small differentiations in adult plants between habitats. However, the separate habitat clusters when using germination traits suggest that species occurrence in the two habitats may be limited at the earliest stages of plant development, particularly by germination. Finally, I predict species germination timing in the field using thermalmodels. Results showed species were dormant when dispersal and different germination timings were predicted for each specie. The different dormancy types detected here indicate that dormancy may play a significant role in controlling germination, always awarding risk-averse strategies to escape winter. The different germination timing detected reduce probability to overlap species’ germination niche, thus having different timings species do not compete for the same resources. In conclusion, this thesis describes germination ecology on alpine habitats and identify the main factors affecting species’ specific germination behavior. Special attention was putted on the possible functional role of germination and dormancy on driving species distribution and community assembly. Finally, all outputs reached here and future outputs that new research will bring hint at important implication in developing good practices for restoration and conservation activities in alpine habitats and contribute to a better understanding of the response of alpine plants in the regeneration from seeds due to global warming.
32
Gaudreault, Mélanie. "Amorçage et séparation des graines d'épinette noire (Picea mariana (Mill.) B.S.P.) : amélioration de la germination des lots de semences forestières /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
33
Bond, Alison Marguerite. "Germination ecology of Carex (Cyperaceae) : effects of light, stratification, and soil moisture." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21514.
Abstract:
Congeneric species occupying different habitats might be expected to have different seed dormancy strategies and germination requirements while those growing in the same habitats may be more similar. I tested this hypothesis with a broad survey of the germination of 51 Carex species from mesic deciduous forests, wet deciduous forests, and wetland or seasonally flooded areas in response to different controlled environmental conditions. A canonical discriminant analysis based on the responses of 29 species to various treatments showed clear differences among seeds from each habitat with respect to germination behaviour. Germination of seeds from mesic deciduous forest species was generally faster after moist stratification than after either submersion or dry storage. In seeds from most wet areas of deciduous forest, wetland, or seasonally flooded habitats, germination was similar or greater after submerged as compared to moist stratification. Total germination was significantly increased by light in all species except Carex pedunculata , an ant-dispersed species. Germination was not significantly different on a poorly drained peat soil than on a well-drained sandy loam. Seeds of most species were at least physiologically dormant at maturity and germination of fresh seeds was generally low. Spring germination was similar among species from all habitats and generally began in late May or early June, at fairly high temperatures (min 7°C, max 17°C), which is unusual for forest species but consistent among Carex species.
34
Burnett, Edward Charles. "Development of a non-targeted transposon mutagenesis system in Nicotiana plumbaginifolia." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339676.
35
Seyedhosseini, S. H. "Ion implantation of seeds." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358378.
36
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.
Abstract:
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).
37
Wills, Sarah L. "Regulation of storage reserve mobilisation in Arabidopsis." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274482.
38
Willmott, Ruth Louise. "#alpha#-amylase genes of Avena fatua." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238827.
39
Stone, Marlon C. "Understanding the role of gibberellin in the developmental physiology of wheat using a transgenic approach." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274613.
40
Pierre, Johann. "Combinaison d’approches transcriptomique et écophysiologique pour l’analyse de la croissance hétérotrophe de Medicago truncatula à basse température." Rennes, Agrocampus Ouest, 2012. http://www.theses.fr/2012NSARI065.
Abstract:
Le froid est un facteur environnemental majeur affectant les processus de germination et de croissance hétérotrophe. Nous avons étudié la croissance hétérotrophe de l’hypocotyle de la plantule de Medicago truncatula, organe portant la plantule hors de terre, et dont la croissance est fortement impactée par des basses températures. Une analyse transcriptomique combinée à une analyse des bases cellulaires de la croissance de l’hypocotyle a été menée, pour deux génotypes aux croissances contrastées, à l’obscurité à 20°C et à 10°C. L’analyse des variations du transcriptome menée sans a priori révèle plusieurs centaines de gènes dont l’expression est modifiée au cours de la cinétique de croissance, entre températures et entre génotypes. La majorité d’entre eux sont communs à deux ou aux trois effets étudiés. On note une proportion importante de régulation du transcriptome dépendant du génotype en interaction avec la température. Pour obtenir un cadre plus ciblé des gènes mis en évidence, nous avons étudié les bases cellulaires de la croissance de l’hypocotyle. Celle-ci s’avère liée à l’allongement des cellules de l’épiderme, sans augmentation de leur nombre. La très forte augmentation de ploïdie observée juste après la germination est corrélée au fort accroissement de la longueur de l’hypocotyle à ce même moment. Les fortes valeurs de ploïdie sont aussi corrélées à l’augmentation de surface radiale des cellules du cortex et de l’épiderme à basse température, et diffèrent entre génotypes. La mobilisation des sucres de réserve est très importante au moment de l’élévation de ploïdie, elle est aussi plus importante au froid mais en interaction avec le génotype. Enfin, le nombre de cellules de l’épiderme de l’hypocotyle, qui est donc mis en place dans l’embryon, diffère entre les génotypes. Nous avons poursuivi l’analyse des différences de transcriptome entre températures en utilisant ces informations et en examinant les gènes présentant des profils d’expression différentielle entre températures communs aux deux génotypes. De nombreux gènes impliqués dans l’élongation cellulaire sont plus exprimés à température optimale. La littérature sur la fonction de ces gènes et de leur co-expression suggère que le froid pourrait modifier la biosynthèse des gibbéréllines et des brassinostéroides, le transport polaire de l’auxine et la signalisation par l’éthylène et que plusieurs enzymes de modification (et non de synthèse) de la paroi, certaines protéines impliquées dans les flux d’eau et composant le cytosquelette et dans la synthèse de la cuticule cireuse participeraient aux différences d’allongement d’hypocotyle entre températures. D’autres gènes sont plus exprimés au froid. Il s’agit gènes de la catégorie « Lipide », associés à la composition et au degré de saturation des lipides membranaires, pouvant jouer un rôle important dans la fluidité membranaire. Les autres gènes plus exprimés au froid suggèrent une augmentation du taux de transcription et de traduction, et donc un plus fort métabolisme en conditions froides, parallèlement à une augmentation des transcrits des enzymes clés de la néoglucogenèse. Les différences de longueur entre génotypes étant largement dues au nombre de cellules initial dans l’embryon, l’interaction entre croissance du génotype et température portaient sur des modifications de largeur d’hypocotyle, en relation avec des modifications de niveau de ploidie et de mobilisation des sucres. Ces résultats ont aussi amené à refondre l’analyse des gènes répertoriés sous les QTL de croissance de l’hypocotyle, identifiés dans une étude précédente, dans le but d’identifier des gènes pouvant être impliqués dans les variations le de tolérance au froid modifiant les possibilités d’allongement de l’hypocotyle entre génotypes. Ce travail apporte d’une part la première analyse transcriptomique de la croissance hétérotrophe de la plantule de Medicago truncatula sous l’effet d’un stress abiotique, les basses températures. D’autre part l’analyse à l’échelle cellulaire met en avant l’importance de la phase de formation de la graine dans les potentialités la croissance hétérotrophe de l’hypocotyle. Cet ensemble des résultats ouvre différentes pistes pour mieux analyser d’un point de vue physiologique et cellulaire les bases de l’adaptation de la croissance au froid au cours de la phase hétérotrophe et pour analyser les sources potentielles de différences entre génotypesCold is a major environmental factor affecting the process of germination and heterotrophic growth. We studied the heterotrophic growth of the hypocotyl of the seedling of Medicago truncatula whose growth is heavily impacted by low temperatures. A transcriptomic analysis combined with an analysis of the cellular bases of growth of the hypocotyl was conducted for two genotypes with contrasting growth, in the dark at 20 ° C (optimal) and 10 ° C (cold conditions). The without a priori analysis of changes in the transcriptome revealed several hundred genes whose expression is modified during the growth kinetics between temperatures and between genotypes. Most of them are common to two or three studied effects. A significant proportion of the regulation of transcriptome depends on genotype in interaction with temperature. For a more targeted identification of genes, we studied the cellular basis of hypocotyl growth. This one appeared to depend on the extension of epidermal cells with no increase in their number. The sharp increase in ploidy observed just after germination was correlated with the strong increase in the length of the hypocotyl at the same time. High ploidy values weare also correlated to the increase in cell radial surfaces of the cortex and epidermis at low temperature, and this differed between genotypes. The mobilization of reserve sugars was very important at the time of the ploidy increase, it was also more important in the cold but in interaction with genotype. Finally, the epidermis cell number of the hypocotyl, which is established in the embryo differs between genotypes. We continued the analysis of transcriptome differences between temperatures using this information and examining the genes with differential expression profiles common to both genotypes. Many genes involved in cell elongation were more expressed at optimal temperature. The literature on the function of these genes and their co-expression suggested that cold affected the biosynthesis of gibberellins and brassinosteroids, polar transport of auxin and ethylene signaling. Several enzymes modifying cell wall, some proteins involved in water flow control, in building the cytoskeleton and in the synthesis of the waxy cuticle could be also involved in hypocotyl elongation differences between temperatures. Other genes were more expressed in cold. Genes in the category "Lipid" associated with the composition and degree of saturation of membrane lipids, may play an important role in membrane fluidity. Other genes more expressed in cold suggested an increased rate of transcription and translation, and therefore a higher metabolism in cold conditions, along with an increase of transcripts of key enzymes of gluconeogenesis. The hypocotyl length differences between genotypes was mainly due to the initial number of cells in the embryo, and the interactions between genotype and growth temperature were for changes in hypocotyl width in relation to changes in ploidy level and mobilization of sugars. These results led to recast the analysis of genes identified in the QTL for hypocotyl growth, highlighted in a previous study in order to identify the determinism of genotypic differences in cold tolerance changing opportunities elongation of the hypocotyl. On the one hand, this work brings the first transcriptome analysis of the heterotrophic growth of Medicago truncatula seedlings under the influence of abiotic stress, low temperatures. On the other hand, the analysis at the cellular level highlights the importance of the embryo developmental stages in the heterotrophic growth potential of the hypocotyl. This set of results opens up different ways to better analyze the adaptation of heterotrophic growth to cold temperatures and the potential sources of differences between genotypes,from a physiological point of view and also on cellular bases
41
Sheikh, Saghir Ahmad. "Effects of temperature and waterlogging on cotton seedlings roots." Thesis, Bangor University, 1994. https://research.bangor.ac.uk/portal/en/theses/effects-of-temperature-and-waterlogging-on-cotton-seedlings-roots(b6b7873d-5a4e-4cbb-8c2d-9218101544a9).html.
Abstract:
Experiments were carried out to study changes in the physiological and biochemical properties of cotton seedling roots with respect to high temperature and waterlogging treatments. It to clear from these, studies that both high temperature and waterlogging significantly damaged the seedling roots and affected their physiological and biochemical activities. Cultivars showed no effect an their root growth for heat stresses up to 30'C but were adversely affected when stressed above this temperature. Cultivar MIN-93 performed well up to about 38'C, while Qalandari showed an inhibition at temperatures of 35 *C and above. At a temperature of 45 C, roots of both cultivars were Irreparably damaged. When careful statistical analysis of the data was carried out. however. no significant differences were found between the cultivars studied. Fresh weight and dry weight values were only determined for MR-93, but they confirmed the findings of the root growth measurements for that cultivar. Stress temperatures above 40*C caused a loss of phospholipids. The results of (MO_14 C) choline incorporation studies revealed that each of four cultivare showed different rates of incorporation into PC under normal germinating conditions at 25'C. Longer roots incorporated more (Me- 14C) choline than shorter roots. At temperatures of 40*C and above, (Me_14 C) choline incorporation decreased with increasing temperature. At 50 C, more than 802 of the activity was lost in all the four cultivars studied. in general, no significant differences were found between the cultivars studied. The results of fatty acid analyses suggested that greater unsaturation occurred with increasing germination time. High temperature had a marked effect on fatty acid composition and caused significant changes especially in neutral lipid and glycolipid fatty acids. Small changes were also observed in phospholipid fatty acids. A large increase of free fatty acids was found in MM-93 but not In S-12 at the end of recovery following heat shock. In this respect, the cultivar 5-12 appeared to be a relatively better cultivar than MNH-93, since free fatty acids are known to be damaging to cells. Waterlogging had significant effects on root growth in all the four cultivars studied. Increasing waterlogging time caused greater damage to the root system and waterlogging for 24 hours stopped further root growth completely. In terms of both root growth and visible damage, S-12 was clearly a more tolerant cultivar than KKK-93, Rehmani or Qalandari. Aerated waterlogging caused smaller reductions in root growth in two cultivars studied (Qalandari and S-12). In this treatmwnt, no visible damage to the roots was seen. Waterlogging also caused large reductions in respiratory activities. During recovery following waterlogging treatments, Qalandarj recovered its r*spiratory activity such faster than the cultivar S-12, however. in this respect, Qalandari appeared to be a more tolerant cultivar than S-12. Patty acid analyses following waterlogging showed changes in both their levels and their relative composition. This treatmmt caused a marked Increase in the amount of esterified fatty acids. Waterlogging also enhanced the synthesis of a set of low molecular weight compounds and suppressed the synthesis of all the "normal" fatty acids. A significant increase in free fatty acids was observed in MNH-93 but not in 3-12. This particular met of results suggests that 5-12 was & rolatively better cultivar than the "NU-93. When taken altogether, the results suggested that there in very little genetic variability between the cultivars of cotton commonly grown in Pakistan with respect to beat tolerance and waterlogging tolerance.
42
Gelormini, Christophe. "Optimisation des propriétés germinatives des graines de colza par initialisation : aspects méthodologiques et fondamentaux." Rennes 1, 1995. http://www.theses.fr/1995REN10101.
Abstract:
Une etude est realisee sur plusieurs lots de graines de differentes varietes commerciales de colza (brassica napus l. ) dans le but d'ameliorer par differents traitements leur vigueur germinative. Les tests de germination realises en conditions standards ne permettent pas de reveler cette vigueur. Differentes epreuves penalisantes appliquees avant ou pendant la germination des graines donnent acces a leurs reelles qualites germinatives. La germination realisee a temperature infra-optimale ou le vieillissement accelere des graines permettent de discriminer entre les differents lots, que ceux-ci soient pellicules ou non. Le pelliculage lui-meme affecte negativement les qualites germinatives et l'elimination du revetement correspondant peut restituer une partie des proprietes perdues. La diminution de la valeur germinative au cours de la conservation est imputee pour une part a la nature meme de certains constituants du pelliculage tel l'oftanol et d'autre part au passe des graines. La teneur des graines en proline libre est representative du niveau d'imbibition de la graine. Comme celle des galactosides elle augmente lorsque les proprietes germinatives sont remises en cause. Les teneurs de ces composes pourraient donc etre utilisees comme des indicateurs de la valeur germinative des graines de colza. La vigueur germinative peut etre amelioree par osmoconditionnement avec d'autant plus d'efficacite que la vigueur initiale est faible. Les osmoconditionnements en boite de petri ou en colonne aeree se revelent efficaces pour des traitements n'excedant pas une semaine effectues a l'aide d'une solution de peg 6000 de potentiel -15 bars. Les solutions de glycerol, de mannitol et les solutions salines de meme potentiel se revelent inutilisables pour initialiser osmotiquement les graines de colza. L'initialisation en matrice solide est aussi efficace que l'osmoconditionnement quant a l'acceleration de la vitesse de la germination et a l'augmentation de la faculte germinative. Le benefice de l'initialisation osmotique est conserve pendant les 10 mois qui suivent le traitement. Des essais preliminaires realises au champ a l'aide de graines osmoconditionnees suggerent qu'elles ont une emergence acceleree conduisant a un taux final d'implantation accru. Des effets favorisants sur le rendement sont egalement perceptibles. Il reste a les confirmer par des experiences complementaires. Sur le plan physiologique les traitements d'initialisation realises ne semblent pas provoquer des effets relevant de processus pregerminatifs. Ils ont pour consequence l'acceleration de la prise d'eau par les graines lors de l'imbibition, l'augmentation de la teneur en proline libre et l'hydrolyse d'une partie des facteurs antinutritionnels constitues par la sinapine et les glucosinolates. Le raffinose et le stachyose sont metabolises au cours de l'initialisation osmotique alors que le saccharose n'est pas consomme. Il parait desormais envisageable de valoriser sur le plan industriel la technique d'osmoconditionnement et celle d'initialisation en matrice solide humectee testees au laboratoire
43
Nadeem, Muhammad. "Remobilization of seed phosphorus reserves and exogenous phosphorus uptake during germination and early growth stages of maize (Zea mays L.)." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14439/document.
Abstract:
Le phosphore (P) est un élément indispensable pour la croissance des plantes. De nombreux travaux montrent des réponses très précoces à une limitation de la disponibilité en P. Pendant la germination et la croissance juvénile, la demande en P des plantules peut être satisfaite par la remobilisation des réserves en P des graines et le prélèvement racinaire. Les objectifs de la thèse sont d’étudier la contribution respective de la remobilisation des réserves en P des graines et du prélèvement racinaire de P à l’alimentation en P des plantules de maïs, et les interactions entre ces deux processus. Différentes expériences ont été conduites pour i) étudier les cinétiques de la remobilisation des réserves en P des graines, ii) identifier précisément le début du prélèvement de P exogène par les racines, iii) quantifier la contribution relative de ces flux à l’alimentation en P de la plantule, iv) comprendre les interactions entre ces flux. Des graines riches et des graines pauvres en P on été cultivées à différents niveaux de disponibilités P exogènes pendant quatre semaines. Le traçage isotopique du P exogène (32P) a été utilisé pour quantifier le flux de prélèvement et calculer le flux de remobilisation du P des graines. Initialement, 86% du P sous forme phytate et 13% du C de la graine est localisé dans le scutellum indépendamment du niveau de richesse en P de la graine. 4 jours après le semis, 98% des phytates des graines sont hydrolysés. La cinétique d’hydrolyse des phytates est indépendante de la richesse en P des graines et de la disponibilité en P dans le milieu. Le P issu de l’hydrolyse des phytates est stocké temporairement dans la graine avant d’être transporté vers les organes en croissance de la plantule. Le prélèvement de P exogène commence dès l’émergence de la radicule (4ième jour) et dépend de la disponibilité en P dans le milieu. L’initiation du prélèvement et son intensité ne dépend pas du flux de remobilisation des réserves en P de la graine. Le P issu de la remobilisation et du prélèvement est distribué dans les mêmes proportions entre les parties ariennes et racinaires. Un bilan de P à l’échelle de la plantule entière et de la graine a permis de mettre en évidence un efflux de P depuis la graine vers l’extérieur pendant la phase d’hydrolyse des phytates. La modélisation des flux de P pendant la germination et la croissance précoce permet de rendre compte des observations sous l’hypothèse d’absence d’interaction entre les flux de remobilisation et de prélèvement de P bien que ces deux processus se chevauchent dans le temps. Nos résultats démontrent l’importance de la disponibilité locale en P dans le milieu pendant les stades précoces indépendamment du niveau de richesse en P des grainesPhosphorus (P) is an essential element for plant growth. Many studies have shown a very early seedling response to the limitation on the availability of P. During germination and early growth, the seedling P demand may be satisfied by the remobilization of seed P reserves and exogenous P uptake by developing roots. The objective of the thesis was to study the relative contribution of remobilization of seed P reserves, the exogenous P uptake by seedling roots and the interaction between these two processes. Various experiments were conducted to i) study the kinetics of the remobilization of seed P reserves, ii) identify precisely the beginning of exogenous P uptake by seedling roots, iii) quantify the relative contribution P fluxes in developing seedlings and iv) the interaction between these two P fluxes. Seeds with low and high P reserves were cultivated at different levels of exogenous P availability for the growth period of four weeks. The exogenous P was labelled with radioactive P (32P) to identify and quantify the P flux in young seedlings coming from exogenous P uptake and seed P reserves remobilization. Initially, 86% of P in the form of phytate and 13% C of seed reserves is localised in scutellum regardless of P initial seed P reserves. Four days after germination, 98% of seed phytate reserves are hydrolyzed. The kinetics of seed phytate hydrolysis was independent of seed P reserves and exogenous P availability. The hydrolyzed forms of phytate were temporarily stored in the seed before being translocated towards newly growing seedling compartments. The exogenous P uptake started soon after the radicle emergence (4th day) and depend mainly on the availability of exogenous P in the growth medium. The beginning of exogenous P uptake and its intensity was not influenced by the seed P reserves remobilization. The proportion of distribution of remobilized seed P reserves and the exogenous P uptake was similar among seedling shoot and roots. The whole seed and seedling P budget showed the significant P losses from germinating seeds by P efflux with the beginning of phytate hydrolysis in seeds. We proposed a model for the seed P remobilization and exogenous P uptake during germination and early growth. Assuming no interaction between seed P reserves remobilization and exogenous P uptake, the simulations were found to be in close agreement with experimental data. Our results showed the importance of exogenous P availability in growth medium during early growth stages regardless of seed P reserves
44
Nanguy, Sidje Paule Marina. "Influence de l'état physiologique sur la germination de spores appartenant aux genres Aspergillus et Penicillium." Thesis, Dijon, 2011. http://www.theses.fr/2011DIJOS016.
Abstract:
Les spores ou les conidies fongiques sont responsables de la dissémination des champignons filamenteux dans l'environnement (air, eau, sol,…). Ensuite les spores fongiques peuvent se déposer sur les équipements dans les ateliers de fabrication, sur les matières premières agricoles et sur les aliments. Au laboratoire, les spores sont obtenues en cultivant les champignons filamenteux en conditions optimales en termes de température, activité de l'eau, nutriments, de manière à obtenir le matériel biologique le plus rapidement possible. Or naturellement, lors de la sporulation, les champignons sont soumis à différents stress, notamment hydrique, ce qui entraîne des différences notables dans l'état physiologique de la spore. Ainsi notre objectif durant cette thèse est d’évaluer l’état physiologique des spores lorsqu’elles sont soumises à certaines conditions. Une première partie de la thèse vise à établir un nouveau modèle pour une meilleure détermination du temps de germination. L’étape suivante présente l’évaluation de l’influence du stress hydrique de la sporogénèse à la germination des spores. Les deux dernières parties présentent enfin l’évaluation des conditions de stockage sur la germination des spores. L’état physiologique est un facteur clé dans le processus de germination, il serait opportun de l’intégrer dans les modèles prédictifs de la germinationFungal spores or conidia are responsible for filamentous fungi spread in environment (air, water, soil…). Then, they can be found on several environments including foods. In laboratory spores are obtained under favorable conditions. However, these conditions are not real, spores are subject to various stress including water stress after their formation. These conditions can make some interactions with their physiological state. Thus, our aim consists in evaluating spores physiological state after their exposition to various conditions of storage. First part of this thesis is about definition of a new model of germination for improving germination time determination. Next step concerns evaluation of water stress during spore’s germination process. The last two parts are finally dedicated to evaluation of storage condtions on spore’s germination time. Physiological state is a key factor in the germination process. It would be appropriate to include this factor in predictive models
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Nolan, Daryl Guy. "Seed germination characteristics of Centaurea diffusa and C. Maculosa." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27605.
Abstract:
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
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Bloomberg, Mark. "Modelling germination and early seedling growth of radiata pine." Lincoln University, 2008. http://hdl.handle.net/10182/681.
Abstract:
Background: This study seeks to model aspects of the regeneration of radiata pine (Pinus radiata D.Don) seedlings under a range of environmental conditions. This study investigated whether “hybrid” mechanistic models, which predict plant growth and development using empirical representations of plant physiological responses to the environment, could provide a realistic alternative to conventional empirical regeneration models. Objectives: The objectives of this study were to 1) identify the functional relationships between the environmental conditions controlling germination, establishment and growth of radiata pine seedlings, under a range of those environmental conditions as specified by temperature and available light and soil water; and 2) specify those functional relationships in hybrid mechanistic (“hybrid”) models. Methods: Radiata pine seedling germination and growth were measured under controlled environmental conditions (incubators for seed germination, growth cabinets for seedlings), and results used to adapt, parameterise and test two published hybrid models; one for germination (the hydrothermal time model); and one for seedling growth in the first six months after germination, based on plant radiation use efficiency (RUE). The hydrothermal model was tested by incubating commercial radiata pine seeds under factorial combinations of temperature and water potentials where germination was likely to occur (12.5 ºC to 32.5 ºC and 0 MPa to –1.2 MPa.). 100 seeds were germinated for each factorial combination. The hydrothermal germination model was fitted to the germination data using non-linear regression modles, will allowed simultaneous estimation of all modle parameters. Seedlings were grown in controlled growth cabinets, and their RUE was calculated as the ratio of net primary production (NPP, specified in terms of an increase in oven dry biomass), to PAR intercepted or absorbed by a seedling. Estimation of seedling RUE required development of novel techniques for non-destructive estimation of seedling oven dry weight, and measurement of PAR interception by seedlings. The effect of varying PAR flux density on RUE was tested by measuring RUE of seedlings grown at 125, 250 and 500 µmol m⁻² s⁻¹. In a second experiment, the effect of deficits in available soil water on RUE was tested by measuring RUE of seedlings grown under 250 µmol m⁻² s⁻¹ PAR flux, and at different levels of available soil water. Available soil water was specified by a soil moisture modifier factor (ƒθ) which ranges between 1 for moist soils and 0 for soils where there is insufficient water for seedling growth. This soil moisture modifier had not previously been applied in studies of tree seedling growth. Temperatures for both seedling experiments were a constant 17.5 ºC (day) and 12.5 ºC (night). Results: Hydrothermal time models accurately described radiata pine seed germination. Model predictions were closely correlated with actual seed germination over the full range of temperature and water potentials where germination was likely to occur (12.5 ºC to 32.5 ºC and 0 MPa to –1.2 MPa. The minimum temperature for germination (base temperature) was 9.0 ºC. Optimum temperatures for germination ranged from ~20ºC for slow-germinating seeds to ~27 ºC for the fastest germinating seeds. The minimum water potential for seed germination varied within the seed population, with an approximately normal distribution (base water potential = –1.38 MPa, standard deviation of 0.48 MPa). In the process of developing the model, a novel explanation for the decline in germination rates at supra-optimal temperatures was developed (Section 3.4.6), based on earlier models proposed by Alvarado & Bradford (2002) and Rowse & Finch-Savage (2003). This explanation was that the decline in germination rate was not driven just by temperature, but by accumulated hydrothermal time above the base temperature for germination (T₀). This in turn raised the base soil water potential (Ψb) towards 0, so that the reduction in germination rate arose from a reduced accumulation of hydro-time, rather than from thermal denaturation of enzymes facilitating germination – the conventional explanation for non-linear accumulation of thermal time at supra-optimal temperatures for plant development. Upwards adjustment (towards 0 MPa) of base water potentials of germinating seeds occurred also at very cold temperatures in combination with high water potentials. In both cases (very cold or else supra-optimal temperatures) this upwards adjustment in base water potentials prevented germination of part of the seed population, and is proposed as a mechanism which enables seed populations to “hedge their bets” when germinating under less than ideal germination conditions. RUE of young germinated radiata pine seedlings growing in a controlled growth cabinet was not significantly different over a range of constant PAR flux densities. Mean RUE’s were 3.22, 2.82 and 2.58 g MJ⁻¹ at 125, 250 and 500 µmol m⁻² s⁻¹ respectively. In the second experiment, the novel use of a soil moisture modifier (ƒθ) to predict RUE of seedlings subjected to water stress proved successful within a limited range of soil water stress conditions. Measured seedling transpiration and stomatal conductance were closely correlated but seedling photosynthesis was less correlated with available soil water. This result suggests that photosynthesis was not coupled with stomatal conductance when PAR flux was 250 µmol m⁻² s⁻¹, which is well below saturating irradiance for C₃ plants. Conclusions: The use of hybrid, quasi-mechanistic models to describe tree seedling growth has been seldom explored, which necessitated the development of novel experimental and analytical techniques for this study. These included a predictive model of germination decline at sub- and supra-optimal temperatures; a method for accurately estimating seedling dry weights under a range of PAR flux densities; and a novel method for estimating light interception by small seedlings. The work reported in this thesis showed that existing hybrid models (the hydrothermal time germination model and the RUE model) can be adapted to model germination and growth of radiata pine seedlings under controlled environmental conditions. Nonetheless, further research is needed before the models can be confidently used as an alternative to conventional empirical models to model regeneration in “real-world” forests. Research priorities are the performance of hydrothermal germination models under variable field conditions, and the use of the soil moisture modifier for seedlings growing on a range of soil textures and under a range of PAR fluxes.
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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.
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Roig, Yann. "Microfluidique supercritique : réactivité chimique et germination - croissance de nanocristaux." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00758340.
Abstract:
Les propriétés spécifiques des milieux fluides supercritiques sont exploitées depuis denombreuses années dans les domaines de la séparation, de la chimie et des matériaux.Aujourd'hui, les activités de recherche se focalisent vers une meilleure compréhension et unmeilleur contrôle des processus thermodynamiques, physiques et chimiques mis en jeu, ce quinous a naturellement amené à développer la microfluidique supercritique. C'est dans cecontexte que s'inscrivent ces travaux de thèse ayant pour objet le développement et l'utilisationde l'outil microfluidique pour l'étude de la réactivité chimique et de la germination-croissance enmilieux fluides supercritiques.Notre premier objectif a concerné le développement de l'outil microfluidique supercritique etde microsystèmes résistants aux conditions de température et de pression. Quelquescaractéristiques physiques associées à ces dispositifs sont proposées de manière à observerclairement les avantages attendus du couplage de la microfluidique et des fluides supercritiques.Nous avons ensuite validé l'apport de la microfluidique supercritique sur la réactivité chimiqueet la chimie des matériaux via, d'une part, l'étude de l'oxydation hydrothermale du méthanol et,d'autre part, l'élaboration de nanocristaux de ZnO. Les propriétés de photoluminescence de cesnanocristaux de ZnO ont été caractérisées; nous avons montré que l'outil microfluidiquesupercritique permet de synthétiser des nanocristaux de ZnO avec une luminescenceexcitonique.
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Cutting, S. M. "Genetics and properties of germination mutants of Bacillus subtilis." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375228.
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Burns, David Alexander. "Analysis of the spore germination mechanisms of Clostridium difficile." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11852/.
Abstract:
Clostridium difficile is the leading cause of hospital acquired diarrhoea and a major burden to healthcare services worldwide. Endospore production plays a pivotal role in infection and disease transmission, but in order to cause disease these spores must germinate and return to vegetative cell growth. Therefore, knowledge of spore germination is important and may have direct applications in future disease prevention. Germination has been well studied in Bacillus and in some clostridia, but the mechanisms of C. difficile spore germination remain unclear. Apparent homologues of genes important for germination in other spore formers have been identified in the C. difficile genome and ClosTron technology was used to inactivate homologues of sleC, cspA, cspB and cspC (Clostridium perfringens) and cwlJ, sleB and cwlD (Bacillus subtilis) in both C. difficile 630Δerm and a BI/NAP1/027 isolate (a ‘hypervirulent’ type associated with outbreaks of increased disease severity). Using a combination of several different assays to study these mutants in detail, a number of the identified target genes appear to be essential for germination and outgrowth of C. difficile spores. This is the first report of using reverse genetics to study the germination of C. difficile spores and the first gene characterisation by mutagenesis in a BI/NAP1/027 isolate of C. difficile. Furthermore, this study uncovered evidence of significant variation in the sporulation and germination characteristics of different C. difficile strains, but this variation did not appear to be type-associated.