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Germination Response (germination + response)
Selected AbstractsGermination responses of Spartidium saharae (Coss. & Dur.) Pomel (Fabaceae) to temperature and salinityAFRICAN JOURNAL OF ECOLOGY, Issue 1 2010Zammouri Jamila Abstract Spartidium saharae is an endemic species of the Saharo-Arabian region. It is a tall shrub widely distributed in many sandy habitats including desert dunes and sandy systems in south-western part of Tunisia, where water and salinity are serious constraints. Laboratory experiments were carried out to assess temperature and salinity effects on seed germination. The seed germination responses were determined in complete darkness over a wide range of temperatures and salinities. Germination was inhibited by either an increase or decrease in temperature from the optimal temperature range (15,20°C). Highest germination percentages were obtained under nonsaline conditions and an increase in NaCl concentrations progressively inhibited seed germination. An interaction between salinity and temperature yielded no germination at 200 mm NaCl. Résumé Spartidium saharae (Coss. & Dur.) Pomel est une légumineuse, exclusivement saharienne endémique de l'élément saharo-arabique. Cette espèce est un arbuste de haute taille, assez commune dans les habitats sableux et les dunes de sable au Sud-ouest de la Tunisie. Les effets de la température, de la salinité ainsi que leurs interactions sur la germination des semences ont étéévalués. La germination des semences a été retardée et réduite avec l'augmentation ou la diminution de la température par rapport à l'optimum thermique (15 à 20°C). Le maximum de germination a été obtenu dans des conditions non salines, l'augmentation du NaCl réduit d'une manière significative le pourcentage de germination. L'interaction de la température et du sel sur la germination entraine une inhibition totale de la germination à 200 mM de NaCl. Mots clés: Germination; Spartidium saharae, Température, Salinité. [source] Influence of temperature and salinity on the germination of Lotus creticus (L.) from the arid land of TunisiaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Mokhtar Rejili Abstract Effects of salinity, temperature and their interactions on the rate and final percentage of germination were evaluated for two populations (Msarref, Oued dkouk) of the invasive glycophyte Lotus creticus Linné, grown under arid environmental conditions of the Tunisia. Seeds that were not treated with NaCl germinated well in a wide range of temperatures. For both populations, maximum germination occurred in distilled water at 25°C and lowest germination for all salinities was at 35°C. Germination was substantially delayed and significantly reduced with an increase in NaCl to levels above 300 mm. Compared to the Oued dkouk population, final germination and germination rate of the Msarref population was completely inhibited at 300 mm NaCl. The interactive effect of temperature and NaCl concentration on final germination and germination rate was significant (P < 0.01), indicating that the germination response to salinity depended on temperature. The inhibition of Oued dkouk population seed germination at high salt concentration was mostly due to osmotic effects while ionic effects were noted at Msarref population. The germination behaviour of the Oued dkouk population would therefore imply adaptive mechanisms to saline environments, while in the Msarref population such mechanisms seem to be absent. Since seed germination is more sensitive to salinity stress than the growth of established plants, the greater tolerance to salinity of Oued dkouk population would be an adaptive feature of this population to saline environment. Résumé L'effet de l'interaction de la salinité et de la température sur la germination de deux populations (Msarref et Oued Dkouk) du lotier de crête (Lotus creticus L.), glycophyte poussant dans des conditions environnementales arides en Tunisie, est étudié. Chez les deux populations, le taux de germination le plus élevé est obtenu à 25°C et le plus faible à 35°C. A 300 mm de NaCl, la germination de la population d'Oued Dkouk est ralentie alors que celle de Msarref est complètement inhibée. L'effet de l'interaction de deux stress est hautement significatif (P < 0,01). Il semble, ainsi, que l'effet de chacun de deux stress est intensifié par l'autre. Cependant, les deux populations montrent un comportement halophytique différent. L'inhibition de la germination, par la salinité, chez Oued Dkouk est due à un effet osmotique alors que chez Mserref, il est ionique. Il en résulte que la population de oued Dkouk présente une capacité adaptative à l'aridité plus importante que celle observée chez la population Msarref. [source] Aerial seed bank dynamics and seedling emergence patterns in two annual Mediterranean AsteraceaeJOURNAL OF VEGETATION SCIENCE, Issue 3 2010F. Bastida Abstract Question: We explored the functional significance of seasonal aerial seed banks in two coexisting, heterocarpic annual Asteraceae with dormant (Chrysanthemum coronarium) and non-dormant (Anacyclus radiatus) achenes. We hypothesised that the plant achene pool is a significant component of total seed reserves, and that within-season seedling emergence timing is shaped by achene release patterns. Location: SW Spain. Methods: In an observational study, we established temporal achene release patterns. We also quantified the aerial and soil achene pools throughout the release season, and assessed seedling emergence timing. Sowing experiments were used to explore the influence of achene release dynamics on emergence timing, and to establish achene morph-specific patterns of between-year distribution of germination. Results: Achene release extended from late spring to late autumn (Chrysanthemum), or from early autumn to early winter (Anacyclus). Within species, achene morphs differed in release timing. Only in Chrysanthemum, a small achene fraction seemed to persist in the soil, and between-year germination distribution differed among morphs. In coexisting populations, the Anacyclus plant achene pool was an order of magnitude higher than the soil pool throughout the release season, whereas in Chrysanthemum both pools were of the same magnitude during autumn. Within-year seedling emergence was significantly staggered beneath parent plants compared with the pattern resulting solely from the germination response in soil, with the exception of Chrysanthemum in one of the two study years. Conclusions: Results suggest that seasonal aerial seed banks are effective within-season, risk-reducing traits in ruderal Mediterranean habitats characteristic of the study species. [source] Is seed conditioning essential for Orobanche germination?PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2009Dina Plakhine Abstract BACKGROUND: Parasitic Orobanchaceae germinate only after receiving a chemical stimulus from roots of potential host plants. A preparatory phase of several days that follows seed imbibition, termed conditioning, is known to be required; thereafter the seeds can respond to germination stimulants. The aim of this study was to examine whether conditioning is essential for stimulant receptivity. RESULTS: Non-conditioned seeds of both Orobanche cumana Wallr. and O. aegyptiaca Pers. [syn. Phelipanche aegyptiaca (Pers.) Pomel] were able to germinate in response to chemical stimulation by GR24 even without prior conditioning. Stimulated seeds reached maximal germination rates about 2 weeks after the onset of imbibition, no matter whether the seeds had or had not been conditioned before stimulation. Whereas the lag time between stimulation and germination response of non-conditioned seeds was longer than for conditioned seeds, the total time between imbibition and germination was shorter for the non-conditioned seeds. Unlike the above two species, O. crenata Forsk. was found to require conditioning prior to stimulation. CONCLUSIONS: Seeds of O. cumana and O. aegyptiaca are already receptive before conditioning. Thus, conditioning is not involved in stimulant receptivity. A hypothesis is put forward, suggesting that conditioning includes (a) a parasite-specific early phase that allows the imbibed seeds to overcome the stress caused by failing to receive an immediate germination stimulus, and (b) a non-specific later phase that is identical to the pregermination phase between seed imbibition and actual germination that is typical for all higher plants. Copyright © 2009 Society of Chemical Industry [source] Phytochromes differentially regulate seed germination responses to light quality and temperature cues during seed maturationPLANT CELL & ENVIRONMENT, Issue 10 2009JENNIFER M. DECHAINE ABSTRACT The ratio of red to far-red light (R : FR) experienced by seeds during maturation affects germination, but the genetic regulation of this effect is poorly understood. In Arabidopsis thaliana, responses to R : FR are governed by five phytochrome photoreceptors, PHYA,PHYE. PHYA, PHYB and PHYE mediate germination, but their roles in germination response to the seed maturation environment are largely unknown. Seeds of A. thaliana phytochrome mutants and natural accessions were matured in a factorial combination of cold (16 °C) and warm (24 °C) temperatures and high (R : FR = 1) and low (R : FR = 0.6) R : FR environments, resembling sunlight and foliar shade, respectively. Germination was observed in resulting seeds. All five phytochromes mediated germination responses to seed maturation temperature and/or R : FR environment. PHYA suppressed germination in seeds matured under cold temperature, and PHYB promoted germination under the same conditions. PHYD and PHYE promoted germination of seeds matured under warm temperature, but this effect diminished when seeds matured under reduced R : FR. The A. thaliana natural accessions exhibited interesting variation in germination responses to the experimental conditions. Our results suggest that the role of individual PHY loci in regulating plant responses to R : FR varies depending on temperature and provide novel insights into the genetic basis of maternal effects. [source] Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south-east AustraliaAUSTRAL ECOLOGY, Issue 6 2007PAUL B. THOMAS Abstract There is limited understanding of how fire-related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire-prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0,20 min) to 16 species that form soil seed banks in the Sydney region of south-eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential. [source] Bet-hedging and germination in the Australian arid zone shrub Acacia ligulataAUSTRAL ECOLOGY, Issue 4 2000MIKE LETNIC Abstract The diaspore of the Australian arid zone shrub Acacia ligulata is dispersed by birds and ants. To investigate the benefits of providing a dispersal structure attractive to both groups, we compared the germination response and viability of seeds eaten by birds, handled by ants or collected from trees to simulated precursors of germination: scarification, fire and rainfall were simulated. Seed germination and viability were related to the degree of preheating disturbance to the seed coat. Heating increased the germinability of seeds not scarified or eaten by birds. In the absence of heating, ingestion by birds increased germinability. Heating increased the mortality of seeds. Our results suggest that ingestion of seeds by birds may break seed dormancy and hence enable some seeds to germinate soon after dispersal. Alternatively, seeds not eaten by birds are likely to remain dormant until sufficiently scarified by soil or stimulated by fire. Consequently, in areas such as the Simpson Desert, A. ligulata may be able to use a range of seedling establishment ,windows' provided by monsoon rains, post-fire environments and unseasonal winter rains, and also spread the risk of unsuccessful seedling establishment by retaining dormant seeds in the seedbank. [source] Germination ecology of the clonal herb Knautia arvensis: Regeneration strategy and geographic variationJOURNAL OF VEGETATION SCIENCE, Issue 4 2003Vigdis Vandvik Lid & Lid (1994) Abstract. We investigated germination responses and seed recruitment in the clonal grassland herb Knautia arvensis (Dipsacaceae) throughout its distributional range in Norway. Four predicted relationships between germination responses and field regeneration behaviour were tested using phytotron experiments and experimental and observational field studies. Seedlings appeared in all experimental microsites in the field, corroborating phytotron predictions that gap- or depth-sensing strategies should be absent in the species. Seasonal timing patterns were predicted from a cold stratification response in the phytotron, but these were not supported in the field. The relationship between dormancy, germinability during storage, and seed carry-over in the field largely conformed to expectations. Seeds from four different geographical regions responded differently to temperature and cold stratification and storage. Dormancy and seed carry-over was higher in seeds from a coastal population, where winters are relatively mild and the probability of repeated freeze-thaw events is high, than in populations from mountain and inland areas, where winters are colder. This is discussed against two alternative hypotheses about the relationship between climate and dormancy in seasonal climates. [source] Phytochromes differentially regulate seed germination responses to light quality and temperature cues during seed maturationPLANT CELL & ENVIRONMENT, Issue 10 2009JENNIFER M. DECHAINE ABSTRACT The ratio of red to far-red light (R : FR) experienced by seeds during maturation affects germination, but the genetic regulation of this effect is poorly understood. In Arabidopsis thaliana, responses to R : FR are governed by five phytochrome photoreceptors, PHYA,PHYE. PHYA, PHYB and PHYE mediate germination, but their roles in germination response to the seed maturation environment are largely unknown. Seeds of A. thaliana phytochrome mutants and natural accessions were matured in a factorial combination of cold (16 °C) and warm (24 °C) temperatures and high (R : FR = 1) and low (R : FR = 0.6) R : FR environments, resembling sunlight and foliar shade, respectively. Germination was observed in resulting seeds. All five phytochromes mediated germination responses to seed maturation temperature and/or R : FR environment. PHYA suppressed germination in seeds matured under cold temperature, and PHYB promoted germination under the same conditions. PHYD and PHYE promoted germination of seeds matured under warm temperature, but this effect diminished when seeds matured under reduced R : FR. The A. thaliana natural accessions exhibited interesting variation in germination responses to the experimental conditions. Our results suggest that the role of individual PHY loci in regulating plant responses to R : FR varies depending on temperature and provide novel insights into the genetic basis of maternal effects. [source] Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south-east AustraliaAUSTRAL ECOLOGY, Issue 6 2007PAUL B. THOMAS Abstract There is limited understanding of how fire-related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire-prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0,20 min) to 16 species that form soil seed banks in the Sydney region of south-eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential. [source] | ||||||||||