High Germination Temperatures Research Articles

THE SIGNIFICANCE OF CHLOROPHYLLS AND CAROTENOIDS IN ENHANCING SEED TOLERANCE TO ABIOTIC STRESS

the degradation of chlorophylls during seed ripening, residual levels are detectable in mature seeds, affecting their stress tolerance. Carotenoids, predominantly lutein and β-carotene, accumulate in seeds under accelerated aging conditions and high-temperature germination, influencing stress response. The ratio of carotenoid to chlorophyll content (Car/Chl) emerges as a potential indicator of seed stress tolerance, with higher ratios correlating with enhanced resilience to stressors. Objective: This study aims to elucidate the significance of chlorophylls and carotenoids in enhancing seed tolerance to abiotic stressors by investigating their roles and interactions within seeds under stress conditions. Methods: Physiologically mature seeds containing residual chlorophylls were subjected to stress treatments, and carotenoid levels were assessed during seed aging and germination experiments. The Car/Chl ratio was calculated to evaluate its relationship with seed stress tolerance. Results: Seeds with elevated Car/Chl ratios exhibited higher tolerance to stress treatments, suggesting a protective role of carotenoids against oxidative stress induced by chlorophylls under abiotic stress conditions. Carotenoid accumulation during aging and germination further underscored their role in stress response, influencing seed resilience. Conclusion: although residual in mature seeds, chlorophylls contribute to oxidative stress under abiotic stressors. Conversely, carotenoids act as antioxidants, mitigating stress-induced damage and enhancing seed tolerance. The Car/Chl ratio is valuable for assessing seed stress resilience, providing insights into seed physiology under adverse environmental conditions.

Linking ex situ germination to in situ direct seeding for landscape scale restoration efforts in the semiarid Mallee region of Victoria, Australia

Direct seeding has high potential for arid revegetation, but success is limited by decreased germination and seedling emergence. Direct seeding success may be improved through developing an understanding of the germination biology and requirements of species used for these projects. This study looked into the germination temperature and moisture requirements of four semiarid species from Victoria's Mallee ecosystems to understand how their germination biology may advise strategies for future plantings. Temperature's effect on germination was analyzed by incubating the seeds under three different regimes: 30/20, 25/15, and 17/7°C. Moisture requirements were determined by germinating seeds along a water potential gradient created using polyethylene glycol 8000 solutions. Results showed three different strategies employed by the study species: (1) Acacia ligulata has a generalist approach, germinating well in all temperatures with a reasonable tolerance to water stress; (2) Eucalyptus calycongona and Melaleuca lanceolata germinate rapidly under higher germination temperatures and have generally higher water stress tolerance; while (3) Callitris gracilis germinates poorly in hot or dry conditions restricting germination to cooler and wetter conditions. Based on our results, A. ligulata would be the most widely applicable species for direct seeding work based on generalist germination habits. Callitris gracilis appears to do well if planted in cool, wet conditions where the species prefers to germinate but would be intolerant to warm‐weather planting. The ideal planting time for a mixed species planting based on germination requirements would be mid‐autumn, as that is when temperature and moisture levels would be optimal for germination.

Identification of XTH Family Genes and Expression Analysis of Endosperm Weakening in Lettuce (Lactuca sativa L.)

Seed germination requires the relaxation of endosperm cap and radicle cell walls, with cell wall hydrolases playing a significant role in this process. Our study revealed that a type of cell wall hydrolase, xyloglucan endotransglucosylase, may significantly contribute to endosperm weakening during lettuce seed germination. Through bioinformatics analysis, the XTH gene family in lettuce was divided into five subfamilies localized on nine chromosomes. Notably, there were significant differences in gene structure among the members of the LsXTHs family containing 1–4 exons and 20 conserved motifs. Among these motifs, motif1, motif2, and motif3 encoded the XTH structural domain. The promoter regions of LsXTHs contained a large number of cis-acting elements responsive to various abiotic stresses, such as drought, anaerobiosis, low temperature, high temperature, and salt stress. Germination experiments showed that seeds imbibed in water and 5 μmol/L abscisic acid (ABA) were able to achieve typical germination with radicle protrusion from the endosperm cap, achieving germination of 100% and 36%, respectively. Conversely, in 0.3% sodium dichloroisocyanurate (SDIC), the swollen seeds were unable to germinate or complete atypical germination, resulting in a germination rate of 30%. Compared to the control, the mechanical strength of the endosperm cap of seeds imbibed in 0.3% SDIC for 8 h increased by 14%, indicating that SDIC may inhibit seed germination by enhancing the mechanical strength of the endosperm cap. Enzyme activity analysis revealed that during lettuce seed germination, XTH enzyme activity in the endosperm cap was significantly higher than in other tissues and increased gradually with imbibition. Transcriptome analysis of the endosperm cap detected the expression of 10 LsXTH genes. Among these, LsXTH43 exhibited the highest expression during germination and was significantly upregulated two-fold by high temperatures, suggesting a potential role in the high-temperature germination of lettuce seeds. Additionally, SDIC downregulated the expression of LsXTHs to varying degrees, with the expression of LsXTH15 reduced to only 6% of its original level. Low temperature, high temperature, drought, and salt stress all reduced the expression of most LsXTHs to different degrees; when seeds germinated under waterlogging and cadmium stress, LsXTH6, LsXTH7, LsXTH8, LsXTH32, and LsXTH33 were all upregulated to some extent.

Dispersal and Distribution of Thermophilic Endospores in Deep-Sea Ecosystems

The distance-decay relationship is a central concept in biogeography and spatial biodiversity, describing how two distinct entities decrease in similarity as the distance between them increases. The decay of community similarity with geographical distance is driven by multiple factors, such as gene drift, environmental selection, and the accumulation of mutations over time. While the distance-decay relationship has been recognized for several decades, there are certain circumstances where the biogeographical patterns of certain species and communities cannot be predicted by this relationship. The example addressed in this project is the case of thermophilic endospore-forming bacteria found in permanently cold deep ocean sediments. Thermophilic endospores (thermospores) are routinely found on the deep ocean floor, a permanently cold environment that does not support their metabolic activity (Hubert et al. 2009). Thermospores are metabolically dormant states developed by some thermophilic bacteria having optimal growth temperatures between 40°C and 70°C. There is evidence that these heat-loving bacteria originate from the deep subsurface and are transported upward to the deep ocean via geological features of the oceanic crust including geofluid fluxes in high-temperature axial systems and natural hydrocarbon seeps (Gittins et al. 2022). Due to the ability of endospores to stay viable for thousands of years and resist a wide range of physicochemical stressors, they can disperse over long distances while remaining unaffected by changing factors such as selection, drift, or mutation (Gittins et al. 2022; Fig. 1). Consequently, these thermospores have the potential to challenge the distance-decay relationship and exhibit unique biogeographical patterns. This work quantifies endospores in sediment cores at and around hydrocarbon seeps using cores from deep-sea Scotian Slope sediments. Given the challenge of quantifying specific groups of endospores (e.g., thermophiles but not mesophiles), high-temperature germination assays that allow tracking of an exponential increase in signal as spores in marine sediment samples germinate and grow can be used. Distinct exponential increases can be attributed to different populations of germinated thermospores in the post-germination growth phase and are being monitored through measurements of sulfate reduction rates (using radiolabelled 35SO4), strain-specific quantitative PCR (qPCR), and fluorescence in-situ hybridization (FISH) (Rezende et al. 2017). These measurements revealed growth dynamics enabling an estimation of the initial cell numbers using exponential functions. These approaches are being applied to samples obtained via push coring using a remotely operated vehicle at different distances from deep sea hydrocarbon seeps, to test for the presence of abundance gradients of different thermospores. Current results already show a difference in thermospore abundance between sites at different distances from the seep. Quantitative tracking of the dispersal of thermospores by oceanic currents in the deep sea provides an excellent opportunity to investigate their distribution and potential to colonize more remote habitats, improving the understanding of microbial biodiversity and biogeography on our planet. By investigating thermospores and their interactions with the geophysical features of the deep sea and deep subsurface, this study aims to challenge the canonical idea that speciation occurs with distance and presents new perspectives on the theme of microbial biogeography. The evidence supporting the subsurface origin of thermophilic endospores, along with the proposed model for their dispersal and distribution, will contribute toward improving an integrated understanding of ecology and geology and their intersection in the microbial realm.

Seed Priming Improves Enzymatic and Biochemical Performances of Rice During Seed Germination under Low and High Temperatures

As an abiotic stress, adverse germination temperatures cause serious disruptions in physiological and biochemical processes involved in seed germination. Using a factorial experiment, we examined the effects of different seed priming treatments on enzymatic and biochemical performances of rice seed germination under different temperatures. Each of the rice genotypes (Hashemi, Sadry-domsefid, IRON-70-7053-7 and NORIN-22) was primed with hydro-hardening, KCl, CaCl2 and ascorbic acid (AsA) and without a priming agent as a control at low (15 ºC), optimum (25 ºC) and high (35 ºC) germination temperatures. The results showed that the enzymatic and biochemical performances of all the rice genotypes were affected by the seed priming agents, especially under the low germination temperature. At 15 ºC, seed priming with AsA was found to be the best agent for the activities of amylase, α-amylase, catalase (CAT), peroxidase (POX), ascorbate peroxidase (APOX) and superoxide dismutase (SOD) as well as the content of soluble sugars in the NORIN-22 genotype, and for protease activity and soluble protein content in the IRON-70-7053-7 genotype. SOD at the low germination temperature and CAT, POX and protease at the optimum and high germination temperatures were the most important enzymes in occurrence of germination potential in terms of seedling length, vigor index, normal seedling rate and germination rate. Under the priming agents, the highest changes in normal seedling rate were observed at the low and optimum germination temperatures by AsA priming in the Hashemi and NORIN-22 genotypes, and at the high germination temperature under KCl priming in the Hashemi genotype.

The malting parameters: steeping, germination, withering, and kilning temperature and aeration rate as possibilities for styrene mitigation in wheat beer

Aiming at the mitigation of the toxicologically relevant styrene formed during wheat beer brewing, different malting parameters, such as steeping temperature, germination temperature, withering and kilning temperatures applied during kiln-drying, and aeration rate, were evaluated for their suitability to reduce the content of cinnamic acid, the precursor of styrene, in malts of barley and wheat, responsible for the input of the undesired precursor into the brewing process. According to the results of the present study, higher steeping temperatures, higher germination temperatures, lower aeration rates, and lower withering temperatures during malting are beneficial for the overall reduction of cinnamic acid in wort produced with barley and wheat malts. Thereby, the withering temperature showed the highest impact among the investigated parameters, able to reduce the soluble cinnamic acid content in wort by up to 72%, followed by the germination temperature in combination with the aeration rate and the steeping temperature with reduction capacities of 52 and 16%, respectively. Additionally, a kilning temperature of 200 °C led to the absence of enzyme activities in dark malts, which might also be the main reason for the low phenolic acid contents found in the corresponding wort, finally causing the low concentrations of styrene but also to a certain extent of desired vinyl aromatics in dark wheat beers.

Investigations into the Ability to Reduce Cinnamic Acid as Undesired Precursor of Toxicologically Relevant Styrene in Wort by Different Barley to Wheat Ratios (Grain Bill) during Mashing.

Styrene is a food-borne toxicant in wheat beer and due to its classification as possibly carcinogenic to humans by the International Agency for Research on Cancer in 2002, mitigation strategies had to be developed. Aiming at understanding the impact of the barley to wheat malt ratio (grain bill) during mashing on the contents of soluble and free (i) cinnamic, (ii) p-coumaric, and (iii) ferulic acid, precursors of (i) styrene and the desired vinyl aromatics (ii) 4-vinylphenol and (iii) 2-methoxy-4-vinylphenol in wheat beer, wort was prepared at four different barley to wheat malt ratios of 100:0, 25:75, 50:50, and 0:100 (w/w). Additionally, the malts were produced at different germination temperatures and aeration rates (12/32, 18/35, 18/25, 24/18, and 26/25 (°C; L/min)) to consider these two further parameters as well. Thereby, soluble and free phenolic acid contents in wort showed linear correlations to the percentage of wheat in the grain bill, highlighting the absence of synergistic effects when mixing barley and wheat malts. In contrast, the results described the phenolic acid contents as a function of the concentrations in the respective barley and wheat wort, multiplied by their percentage in the grain bill. However, a clear recommendation for favorable barley to wheat malt ratios leading to a decrease of soluble and free cinnamic acid in wort could not be made, as the contents in the present study proved to be highly dependent on the barley and wheat varieties used during mashing and the parameters applied during malting. This was not the case for p-coumaric acid for which a clear decrease of the soluble and free forms was found with increasing wheat malt contents. Differently, the soluble form of ferulic acid increased with an increasing percentage of wheat malt, while the free form decreased. The malting parameters clearly recommended high germination temperatures and low aeration rates when aiming at a reduction of undesired cinnamic acid in wort. Fortunately, soluble and free p-coumaric and ferulic acid contents were only slightly affected, indicating that the formation of the characteristic wheat beer aroma might not suffer when applying these favorable conditions for styrene reduction.

Dynamics of Germination Behaviour, Protein Secondary Structure, Technofunctional Properties, Antinutrients, Antioxidant Capacity and Mineral Elements in Germinated Dhaincha.

SUMMARYResearch backgroundDhaincha (Sesbania aculeata) is a forage legume primarily used for green manuring and animal feed. Good nutritional profile of dhaincha makes it a potential alternative legume in human nutrition. However, the presence of high amount of antinutrients poses a problem in its utilisation for food applications. The present investigation intends to germinate dhaincha seeds at different time-temperature regimes and to evaluate the process of germination to ascertain optimal conditions and improve its potential for utilisation.Experimental approachDhaincha seeds were germinated at 24, 28 and 32 °C for 24, 48 and 72 h. Germination characteristics and germination loss, spectral characteristics, technofunctionality, antinutrients, bioactive constituents, antioxidant capacity and mineral element content of germinated dhaincha were evaluated. Optimal balance of technobiofunctionality of germinated dhaincha seeds was validated by principal component analysis.Results and conclusionsSprout length and germination loss increased with the higher germination temperature and prolonged germination time. Seeds showed similar germination rate at 28 and 32 °C and it was markedly higher than at 24 °C. Germination for 24 h resulted in mild conformational changes in the secondary structure of proteins, whereas germination for 48 and 72 h exhibited major conformational changes in the β-sheets, resulting in the improvement in the hydration and foaming properties. Progression of germination (72 h) caused the decrease of tannin (24.47%), phytic acid (16.38%) and saponin (24.58%) mass fractions, and of trypsin inhibitor (40.33%) and lectin activity (62.50%). Slight decrease of DPPH˙ (3.7%) and ABTS˙+ (18.5%) values was also observed, whereas total flavonoid content (36.14%) and metal chelating activity (26.76%) increased. Total phenolics, FRAP, and reducing power decreased after 24 h, followed by a gradual increase. Zinc extractability increased drastically with germination. Germination at 28 °C for 72 h resulted in higher reduction of antinutrients with optimal retention of antioxidant activity and better functional characteristics, as validated by principal component analysis.Novelty and scientific contributionDhaincha is an unknown crop in Europe, and even in Asia it is predominantly used as green manure and animal feed. This research demonstrated that the intervention in germination can transform dhaincha into a promising crop for food industry. Germinated dhaincha exhibited enhanced technobiofunctionality for utilisation in various food formulations.

MAPK11 regulates seed germination and ABA signaling in tomato by phosphorylating SnRKs.

Seed germination is a critical stage in the plant life cycle and it plays an important role in the efficiency of agricultural production. However, our knowledge of the mechanisms that regulate seed germination remains limited. In this study, we identified a novel gene, MAPK11, that encodes mitogen-activated protein kinase 11; its expression was significantly higher in seeds of tomato varieties with a low optimum germination temperature than in those with a high optimum germination temperature. In tests at 25 °C, overexpression of MAPK11 in an accession with optimum germination at 25 °C resulted in a decrease in germination, whereas RNAi of MAPK11 in an accession with optimum germination at 15 °C resulted in increased germination. Furthermore, we found that lines overexpressing MAPK11 exhibited hypersensitivity to ABA during germination. These observations were at least partially explained by the fact that MAPK11 up-regulated both NCED1 expression and ABA biosynthesis, and that it also affected ABA signaling and negatively regulated germination by influencing the phosphorylation of SnRK2.2 in vivo. In addition, we found that MAPK11 interacts with and phosphorylates SnRK1 in vivo, thereby potentially inhibiting its activation. SnRK1 interacted with ABI5 and suppressed the transcription of ABI5, thereby affecting ABA signaling and the regulation of germination. Our results demonstrate that ABA signaling in tomato is affected by a mechanism that depends on MAPK11 phosphorylating SnRKs, and this ultimately influences seed germination.

Ґрунтова схожість насіння павловнії повстистої Paulownia Tomentosa (Thunb.) Steud. різного географічного походження

Досліджено ґрунтову схожість насіння павловнії повстистої, заготовленого у трьох регіонах України: Одеській, Закарпатській та Львівській областях. Встановлено, що насіння павловнії повстистої характеризується високою ґрунтовою схожістю незалежно від географічного походження материнських дерев в умовах України. Найвища ґрунтова схожість притаманна насінню походженням зі Львова. Оцінено вплив температурних умов на ґрунтову схожість насіння за двох змінних температурних режимів пророщування: +15 °С вночі і +20 °С вдень та +21 °С вночі і +25 °С вдень. Встановлено, що температура пророщування істотно впливає на ґрунтову схожість насіння. За температурного режиму пророщування +21…25 °С показники ґрунтової схожості значно вищі. Досліджено вплив стимуляторів схожості: попереднє намочування насіння у воді та розчинах стимовіту, корневіну, бурштинової кислоти, епіну, радіфарму на ґрунтову схожість насіння павловнії повстистої. Встановлено, що попереднє намочування насіння має найвищу стимуляційну дію на подальше проростання насіння в ґрунті серед досліджених стимуляторів схожості. Попереднє оброблення насіння препаратами стимовіт, корневін, бурштинова кислота, епін, радіфарм загалом дало позитивний ефект, підвищивши ґрунтову схожість насіння. Наведено дані з поширення плантацій представників роду Paulownia у країнах Європи.

Preliminary study in improving the malting properties of Dawa, local Sorghum (Sorghum vulgare) variety.

Improving the malting properties of local sorghum [Dawa] (sorghum vulgare) was investigated. Malting is the germination of cereal gain in moist air under controlled conditions, the primary objective being to promote the development of enzymes which are not present in the ingeminated grain. Steeping, germination and kilning temperatures and conditions were altered to affect the improvement of the malt to be produced. Aseptic conditions were employed to avoid contamination of the process. A steeping regime of 52 hours was adopted. The steeping cycle involves 22 hours water steep and 8 hours air rest. Germination was done for 5 days during which enzymes development took place. Kilning was done in an oven for 24 hours at 500C so as to arrest germination. After these, grain and malt analyses were carried out. During the analyses, the following results were obtained: Moisture content (5.4%), thousand corn weight (28.5g), Germinative energy (95.5%), Germinative capacity (90%), cold water extract (44.8%), hot water extract (23%) and malting loss (13%). The result obtained shows that the sorghum variety had high malting loss which was attributed to the high germination temperature used. Also from the result, a Germinative capacity of 90% was gotten. This makes the sorghum (Dawa) variety a good grain raw material for brewing.

Analyzing bean extracts using time-dependent SDS trapping to quantify the kinetic stability of phaseolin proteins

In common beans and lima bean, the storage protein phaseolin is difficult to degrade and SDS-resistant, a sign of kinetic stability. Kinetically stable proteins (KSPs) are characterized by having a high-energy barrier between the native and denatured states that results in very slow unfolding. Such proteins are resistant to proteolytic degradation and detergents, such as SDS. Here the method SDS-Trapping of Proteins (S-TraP) is applied directly on bean extracts to quantify the kinetic stability of phaseolin in lima bean and several common beans, including black bean, navy bean, and small red bean. The bean extracts were incubated in SDS at various temperatures (60–75 °C) for different time periods, followed by SDS-PAGE analysis at room temperature, and subsequent band quantification to determine the kinetics of phaseolin unfolding. Eyring plot analysis showed that the phaseolin from each bean has high kinetic stability, with an SDS-trapping (i.e. unfolding) half-life ranging from about 20–100 years at 24 °C and 2–7 years at 37 °C. The remarkably high kinetic stability of these phaseolin proteins is consistent with the low digestibility of common beans and lima bean, as well as their relatively high germination temperatures. From a practical perspective, this work exemplifies that S-TraP is a useful and cost-effective method for quantifying the kinetic stability of proteins in biological extracts or lysates. Depending on the protein to be studied and its abundance, S-TraP may be performed directly on the extract without need for protein purification.

Modelling seed germination response to temperature inEucalyptusL'Her. (Myrtaceae) species in the context of global warming

AbstractSeed germination is vital for persistence of many plant species, and is linked to local environmental conditions. Small increases in temperature during this critical life history transition may threaten species by altering germination timing and success. Such changes in turn may influence population dynamics, community composition and the geographic distributions of species. In this investigation, a bi-directional temperature gradient plate was used to profile thermal constraints for germination in 26 common, threatened and geographically restrictedEucalyptusspecies (Myrtaceae) from southern Western Australia. These observed data were used to populate models to predict optimum germination responses (mean time to germination, germination timing and success) under current (1950–2000 averages) and future (2070 high greenhouse gas emission climate scenario) mean monthly minimum and maximum temperatures. Many species demonstrated wide physiological tolerance for high germination temperatures and an ability to germinate outside current and forecast future autumn–winter wet season temperatures, suggesting that climatic distribution is a poor proxy for thermal tolerance forEucalyptusseed germination. Germination for some species is predicted to decline under forecast conditions, but the majority will maintain or improve germination particularly during the cooler winter months of the year. Although thermal tolerance may benefit persistence of manyEucalyptusspecies in southern Western Australia as warming becomes more severe, large rainfall declines are also forecast which may prove more detrimental to plant survival. Nonetheless, this framework has the potential to identify seed resilience to heat stress in an early life history phase and hence species vulnerability to one characteristic of forecast environmental change.

Can sensitivity to temperature during germination help predict global warming vulnerability?

AbstractSeed germination is vital for persistence in species that rely on seeds for post-disturbance regeneration. It is a high-risk phase and vulnerable to environmental parameters. Here, I assessed temperature sensitivity for germination in Banksia L.f. (Proteaceae) from south-western Australia, screening all 38 endemic obligate seeder species. A bi-directional temperature gradient plate with 49 temperature combinations (constant and fluctuating) between 5 and 40°C was used to profile germination temperature requirements and identify upper and lower temperature thresholds for germination. Using these data the impact of increasing temperatures on germination in these species was modelled under high and low greenhouse gas scenarios for 2050 and 2070. The results suggest that many Banksia species from the region have wide physiological tolerance for high germination temperatures, although a number of common, but geographically restricted species, such as B. praemorsa, B. oreophila and B. quercifolia, have more narrow temperature windows for germination than at least one of the rarer species (B. verticillata). Only B. dryandroides is expected to decline in germination in the future; however, the optimal germination timing for many species is predicted to occur later under climate warming. In conjunction with declining rainfall, this germination delay will place seedlings closer to the summer dry in this seasonal Mediterranean-climate ecosystem and thus they will be more vulnerable to desiccation. The framework developed here can be used to identify vulnerable species for monitoring of early population decline.

Genetic Variation for Thermotolerance in Lettuce Seed Germination Is Associated with Temperature-Sensitive Regulation of ETHYLENE RESPONSE FACTOR1 (ERF1).

Seeds of most lettuce (Lactuca sativa) cultivars are susceptible to thermoinhibition, or failure to germinate at temperatures above approximately 28°C, creating problems for crop establishment in the field. Identifying genes controlling thermoinhibition would enable the development of cultivars lacking this trait and, therefore, being less sensitive to high temperatures during planting. Seeds of a primitive accession (PI251246) of lettuce exhibited high-temperature germination capacity up to 33°C. Screening a recombinant inbred line population developed from PI215246 and cv Salinas identified a major quantitative trait locus (Htg9.1) from PI251246 associated with the high-temperature germination phenotype. Further genetic analyses discovered a tight linkage of the Htg9.1 phenotype with a specific DNA marker (NM4182) located on a single genomic sequence scaffold. Expression analyses of the 44 genes encoded in this genomic region revealed that only a homolog of Arabidopsis (Arabidopsis thaliana) ETHYLENE RESPONSE FACTOR1 (termed LsERF1) was differentially expressed between PI251246 and cv Salinas seeds imbibed at high temperature (30°C). LsERF1 belongs to a large family of transcription factors associated with the ethylene-signaling pathway. Physiological assays of ethylene synthesis, response, and action in parental and near-isogenic Htg9.1 genotypes strongly implicate LsERF1 as the gene responsible for the Htg9.1 phenotype, consistent with the established role for ethylene in germination thermotolerance of Compositae seeds. Expression analyses of genes associated with the abscisic acid and gibberellin biosynthetic pathways and results of biosynthetic inhibitor and hormone response experiments also support the hypothesis that differential regulation of LsERF1 expression in PI251246 seeds elevates their upper temperature limit for germination through interactions among pathways regulated by these hormones. Our results support a model in which LsERF1 acts through the promotion of gibberellin biosynthesis to counter the inhibitory effects of abscisic acid and, therefore, promote germination at high temperatures.

Multiple paths to similar germination behavior in Arabidopsis thaliana

Germination timing influences plant fitness, and its sensitivity to temperature may cause it to change as climate shifts. These changes are likely to be complex because temperatures that occur during seed maturation and temperatures that occur post-dispersal interact to define germination timing. We used the model organism Arabidopsis thaliana to determine how flowering time (which defines seed-maturation temperature) and post-dispersal temperature influence germination and the expression of genetic variation for germination. Germination responses to temperature (germination envelopes) changed as seeds aged, or after-ripened, and these germination trajectories depended on seed-maturation temperature and genotype. Different combinations of genotype, seed-maturation temperature, and after-ripening produced similar germination envelopes. Likewise, different genotypes and seed-maturation temperatures combined to produce similar germination trajectories. Differences between genotypes were most likely to be observed at high and low germination temperatures. The germination behavior of some genotypes responds weakly to maternal temperature but others are highly plastic. We hypothesize that weak dormancy induction could synchronize germination of seeds dispersed at different times. By contrast, we hypothesize that strongly responsive genotypes may spread offspring germination over several possible germination windows. Considering germination responses to temperature is important for predicting phenology expression and evolution in future climates.

Investigation of the Germination of Barley and Wheat Grains with a Design of Experiments for the Production of Hydrolases.

The production of hydrolases from cereals has been examined in order to investigate food-derived enzymes as an alternative source to microbial enzymes for the use in food processes. For that, the influence of temperature on the pretreatment, imbibition and germination of barley and wheat grains was determined by measuring the β-glucosidase, β-galactosidase and lipase activities using a design of experiments. The evaluation of the statistical model showed an increase of the β-glucosidase activity with low imbibition and low germination temperature for barley grains and low imbibition and high germination temperature for wheat grains. The maximum β-glucosidase activity in wheat extracts was (585±151) nkat per g of dry mass (dm), while in barley extracts it was (109±15) nkat per g of dm. The maximum β-galactosidase activities in barley and wheat extracts were (34±12) and (63±23) nkat per g of dm, respectively. The maximum lipase activities of (6.7±0.1) and (4.6±4.4) nkat per g of dm in barley and wheat extracts, respectively, were rather low compared to the glycosidase activities. The extracts were also tested for other hydrolase activities (e.g. peptidase and α-amylase activities). The insights obtained enable the basis for the potential use of cereal hydrolases in food processing, which might be attractive to consumers.

Association analysis of seed longevity in rice under conventional and high-temperature germination conditions

Seed longevity varies considerably in cultivated rice, but the underlying mechanism of longevity is not well understood. To measure seed longevity, we performed an aging treatment at 45 °C on seeds maintained at 14 % moisture content for 14 days. We measured the percentage germination of both treated and normal seeds at 25 °C as a control of seed longevity using four replications over 2 years. In total, 140 accessions from a core collection with diverse origins were genotyped using 204 SSR markers, which distributed into 12 chromosomes, to identify marker–trait associations with seed longevity. An analysis of the population structure revealed four subgroups. The r 2 values ranged from 0.0 to 0.8901 for all intrachromosomal loci pairs, with an average of 0.0773. Linkage disequilibrium (LD) between linked markers decreased with distance and displayed a substantial drop in LD decay values between 20 and 50 cM. Marker–trait associations were investigated using a mixed linear model approach, considering both population structure (Q) and kinship (K). Twelve marker–trait associations (P < 0.01) were common between the two germination treatments and over the 2-year study, explaining more than 10 % of the total variation. These ten different markers were distributed on five chromosomes. The significant associated SSR markers identified will be useful to seed-bank managers to ensure collections are maintained at high levels of viability to avoid loss of genotypes from the population and for marker-assisted selection.

Evaluation of global warming effects on the geographical distribution of weeds in paddy fields by characterizing germination time and morphological factors

Global warming, a consequence of climate change, alters rice-paddy ecosystems, especially through the changes of both growth rate of plants and the occurrences of pests, and affects both rice crop production and biodiversity. In this study, factors related to the germination temperatures of 80 weed species in paddy fields were analyzed to elucidate the effect of warming on morphological (leaf size), phenological (germination time), and population (distribution) responses. A self-organizing map (SOM) was used to classify the weed species on the basis of 5 factors related to germination temperature: the minimum, maximum, and optimum temperatures and the minimum and maximum optimal range. Climate data for the Korean Peninsula during 4 different decades (1990s, 2020s, 2050s, and 2080s) were obtained from a regional climate change model following the A1B emission scenario of the Intergovernmental Panel on Climate Change. Changes in the germination time and range of potential habitable areas for the weed species were estimated on the basis of the patterns of the SOM. The species associated with relatively lower germination temperatures tended to have smaller leaves, shorter stems, and earlier flowering and germination times than the species associated with higher germination temperature. The potential germination area increased progressively with rising temperature. The degree of potential increase in germination area was the greatest in the 2080s when the weeds could germinate in most of the southern Korean Peninsula. These results suggest that studying the patterns of germination temperature through SOM could provide necessary information for characterizing the germination of weeds on the basis of various characteristics (e.g., morphology, phenology, and distribution) and would be useful for maintaining agricultural productivity and agroecosystem biodiversity under global warming.

Seed dormancy in four Tibetan Plateau Vicia species and characterization of physiological changes in response of seeds to environmental factors

AbstractAlthough seed dormancy of temperate legumes is well understood, less is known about it in species that grow in subalpine/alpine areas. This study investigated dormancy and germination of four Vicia species from the Tibetan Plateau. Fresh seeds of V. sativa were permeable to water, whereas those of V. angustifolia, V. amoena and V. unijuga had physical dormancy (PY). One year of dry storage increased the proportion of impermeable seeds in V. angustifolia, but showed no effect on seed coat permeability in V. amoena or V. unijuga. Seeds of all four species also had non-deep physiological dormancy (PD), which was especially apparent in the two annuals at a high germination temperature (20°C). After 1 year of storage, PD had been lost. The hydrotime model showed that fresh seeds obtained a significantly higher median water potential [Ψb(50)] than stored seeds, implying that PD prevents germination in winter for seeds dispersed without PY when water availability is limited. After 6 months on the soil surface in the field, a high proportion of permeable seeds remained ungerminated, further suggesting that PD plays a key role in preventing germination after dispersal. Addition of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis, evened-out the differences in germination between fresh and stored seeds, which points to the key role of ABA biosynthesis in maintaining dormancy. Further, fresh seeds were more sensitive to exogenous ABA than stored seeds, indicating that storage decreased embryo sensitivity to ABA. On the other hand, the gibberellic acid GA3 increased germination rate, which implies that embryo sensitivity to GA is also involved in seed dormancy regulation. This study showed that PY, PD or their combination (PY+PD) plays a key role in timing germination after dispersal, and that different intensities of dormancy occur among these four Vicia species from the Tibetan Plateau.