Germination Strategies Research Articles

植冠与土壤种子库储存种子的萌发特性及策略

PDF HTML阅读 XML下载 导出引用 引用提醒 植冠与土壤种子库储存种子的萌发特性及策略 DOI: 10.5846/stxb201608061617 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41371280，41501290）；黄土高原土壤侵蚀与旱地农业国家重点实验室开放基金（A314021402-1512）；辽宁省博士启动基金（201601368）；辽宁工程技术大学第五批生产技术问题创新研究基金（20160046T） Seed germination characteristics and strategies of seeds stored in canopy and soil seed banks Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度，选择研究区7种具有种子库的主要物种为研究对象，以刚成熟和室内储存种子为对照，比较植冠宿存（5个宿存期）和土壤埋藏（5a埋藏期）对植物种子萌发特性的影响，探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明：7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异，黄刺玫（Rosa xanthina）和水栒子（Cotoneaster multiflorus）种子萌发力表现为植冠宿存不变型、土壤储存增强型，土壤储存明显提高水栒子种子萌发速率；达乌里胡枝子（Lespedeza davurica）和狼牙刺（Sophora davidii）种子萌发力表现为植冠宿存增强型、土壤储存减弱型，种子萌发历时表现为植冠宿存延长型，土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时；茭蒿（Artemisia giralaii）和铁杆蒿（Artemisia gmelinii），种子萌发率随植冠宿存时间先升高后降低，随土壤储存时间先降低后升高，土壤储存可推迟其萌发，铁杆蒿种子萌发速率在植冠与土壤储存后均加快；紫丁香（Syringa oblata）种子萌发率随植冠宿存先升高后降低，土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区，植物种子经过植冠或土壤种子库储存，或增加、加快、提早萌发充分利用有利条件提高占据性，或减少、减缓、推迟萌发分摊不利条件的风险；而且该区植物植冠与土壤储存后种子萌发特性间的关系，体现各自适应环境与应对干扰的分工与协作策略，主要表现为：单一主导型和相辅相成型。 Abstract:To determine how seeds improve their individual fitness by regulating their germination characteristics, we selected seven species with obvious canopy and soil seed banks in the hill-gully Loess Plateau. Effects of the duration of canopy storage (five storage periods) and soil storage (burial periods of five years) on seed germination were analyzed, which were compared with seeds of just matured or stored in laboratory as control. And the germination strategies of seeds after storage in canopy seed bank and soil seed bank were discussed. Our results indicated that the seed germination characteristics of the seven species were obviously different after storage. For Rosa xanthina and Cotoneaster multiflorus, storage improved the seed germination ability of the soil seed bank but had no effect on that of the canopy seed bank, and the seed germination rates of the soil seed bank of the C. multiflorus was considerably increased. For Lespedeza davurica and Sophora davidii, storage improved the seed germination ability of the canopy seed bank but weakened that of the soil seed bank. Meanwhile, the seed germination lasting times of the canopy seed bank were prolonged after storage, whereas the seed germination rate and seed germination lasting times of the soil seed bank were accelerated and shortened for L. davurica, respectively. For Artemisia giralaii and A. gmelinii, seed germination percentages initially increased but then declined as the duration of canopy storage increased, whereas the seed germination rate initially declined and then increased. Storage of the soil seed bank also delayed the seed germination for both species, whereas storage of both the canopy and soil seed banks increased the seed germination rates of A. gmelinii. For Syringa oblate, seed germination percentages initially increased but then declined as the duration of canopy storage increased, and storage of the soil seed bank both increased the germination rates and promoted seed germination. In conclusion, seeds from the hill-gully Loess Plateau either (1) took full advantage of favorable conditions to finish regeneration in right time quickly by increasing germination percentage, speeding up seed germination rate and germinating at high concentration during the early stages of storage or (2) shared the risk of unfavorable conditions by reducing germination percentage, slowing down seed germination rate and deferring seed germination through seed storage in the canopy or soil seed bank. In addition, the relationship between seed germination characteristics of the canopy storage and that of soil seed bank storage indicated that plant use the division and cooperation storages of canopy and soil seed bank to adapt environments and to respond disturbance, which strategies mainly presented as single-dominant and tow-complementary patterns. 参考文献 相似文献 引证文献

Field Sandbur (Cenchrus pauciflorus) Seeds in the Same Bur Respond Differently to Temperature and Water Potential in Relation to Germination in a Semi-Arid Environment, China.

The success of a biological invasion relies on the environment and is closely linked to factors such as water and temperature. Invasive plant species display different seed characteristics, including shape. Field sandbur (Cenchrus pauciflorus) is a globally widespread invasive species capable of adapting to broad environmental conditions. However, its germination response to water and temperature still remains unclear. C. pauciflorus contains two seeds in the same bur that differ in size: big seeds (M) and small seeds (P). Separate greenhouse experiments were conducted under different temperature regimes (0/10°C, 5/15°C, 10/20°C, 15/25°C, 18/28°C, 20/30°C and 25/35°C) and water potentials (-1.50Mpa, -1.00Mpa, -0.75Mpa, -0.50Mpa, -0.25Mpa and 0Mpa) for M and P seeds. The results support the hypothesis that germination of C. pauciflorus is significantly influenced by seed type, temperature and water potential. M and P seeds responded differently to varied alternative temperatures and water potentials. However, M and P seeds were more sensitive to water potential than to temperature. Optimal conditions for M and P seed germination were measured at 25/35°C (night temperature/day temperature) and 20/30°C, respectively. In contrast, the highest germination rate was observed for the 0Mpa of the water potential treatment. Additionally, base temperature (Tbase) and base water potential (Wbase) were lower for M (7.7°C, -1.11Mpa at 10/20°C, and -1.07Mpa at 20/30°C) than for P (9.4°C, -0.92Mpa at 10/20°C, and -0.52Mpa at 20/30°C). These different germination strategies of M and P seeds with respect to temperature and water potential increased overall plant propagation. These results indicate that tropical and subtropical regions water potentials beyond -0.50Mpa (10/20°C) or -1.00Mpa (20/30°C) face a potential risk of C. pauciflorus invasion.

Phylogeny, Seed Trait, and Ecological Correlates of Seed Germination at the Community Level in a Degraded Sandy Grassland.

Seed germination strongly affects plant population growth and persistence, and it can be dramatically influenced by phylogeny, seed traits, and ecological factors. In this study, we examined the relationships among seed mass, seed shape, and germination percentage (GP), and assessed the extent to which phylogeny, seed traits (seed mass, shape, and color) and ecological factors (ecotype, life form, adult longevity, dispersal type, and onset of flowering) influence GP at the community level. All analyses were conducted on the log-transformed values of seed mass and arcsine square root-transformed values of GP. We found that seed mass and GP were significantly negatively correlated, whereas seed shape and GP were significantly positively correlated. The three major factors contributing to differences in GP were phylogeny, dispersal type, and seed shape (explained 5.8, 4.9, and 3.1% of the interspecific variations independently, respectively), but GP also influenced by seed mass and onset of flowering. Thus, GP was constrained not only by phylogeny but also by seed traits and ecological factors. These results indicated that GP is shaped by short-term selective pressures, and long-term phylogenetic constrains. We suggest that correlates of phylogeny, seed traits, and ecology should be taken into account in comparative studies on seed germination strategies.

Germination Strategies of Seeds of Cassia auriculata, a Perennial Weed Species of Arid and Semiarid Regions

The timing of seed germination is one of the critical events that determines the success of seedling establishment in wild species in their natural habitat. This is particularly so in species growing in arid and semiarid regions characterized by seasonal rainfall, which is irregular, often with long dry spells. Germination strategies of seeds of Cassia auriculata (Fabaceae, Caesalpinoideae), a perennial weed species of arid and semi-arid regions, were investigated both in petri plate cultures and under field conditions. The results show that seed dormancy is controlled by both physical (impermeable seed coat) and physiological (presence of germination inhibitors) mechanisms. The seeds are capable of withstanding repeated hydration and desiccation cycles during germination. The seeds sown in cultures as well as in the soil do not germinate simultaneously but show staggered germination over a period of several months. Many of the seedlings dry up during intermittent dry periods but many survive in the field during the ensuing summer months until the next rainy season. Staggered germination and ability to withstand repeated hydration and desiccation cycles are important ecological adaptations to maximize seedling establishment under arid and semi-arid environments.

Spatiotemporal heterogeneity in precipitation patterns explain population-level germination strategies in an edaphic specialist.

Many locally endemic species in biodiversity hotspots are restricted to edaphic conditions that are fixed in the landscape, limiting their potential to track climate change through dispersal. Instead, such species experience strong selection for germination strategies that can track suitable conditions through time. Germination strategies were compared among populations across the geographic range of a California vernal pool annual, Lasthenia fremontii Local germination strategies were tested to determine the associations with geographic variation in precipitation patterns. This study evaluated patterns of seed germination, dormancy and mortality in response to simulated variation in the timing, amount and duration of the first autumn precipitation event using seeds from six populations that span a geographic gradient in precipitation. Next, it was tested whether the germination strategies of different populations can be predicted by historical precipitation patterns that characterize each site. A significant positive relationship was observed between the historical variability in autumn precipitation and the extent of dormancy in a population. Marginal populations, with histories of the most extreme but constant autumn precipitation levels, expressed the lowest dormancy levels. Populations from sites with historically higher levels of autumn precipitation tended to germinate faster, but this tendency was not statistically significant. Germination in L. fremontii is cued by the onset of the first rains that characterize the beginning of winter in California's Great Central Valley. However, populations differ in how fast they germinate and the fraction of seeds that remain dormant when germination cues occur. The results suggest that seed dormancy may be a key trait for populations to track increasingly drier climates predicted by climate change models. However, the low dormancy and high mortality levels observed among seeds of the southernmost, driest populations make them most vulnerable to local extinction.

Host influence on germination and reproduction of the facultative hemi‐parasitic weed Rhamphicarpa fistulosa

AbstractRice Vampireweed, Rhamphicarpa fistulosa, was a minor parasitic weed until recently when rice cultivation in sub‐Saharan Africa was expanded into marginal wetlands, that are the parasite's natural habitat. Unlike most of the parasitic weeds, R. fistulosa is facultative, meaning that the parasite is able to complete its life cycle without a host. However, when not connected to a host plant, its biomass and seed production is lower. Because very little is known regarding the germination ecology of the parasite, the main objective of our study was to identify the cues that favour germination. We hypothesised that, first, being a wetland species, germination of R. fistulosa is stimulated by light and high soil moisture. Second, we hypothesised that if host plant presence increases its reproductive output then a germination stimulatory effect from host presence is likely to have developed. A Petri‐dish and pot experiment showed that light and completely saturated soils were a requirement for germination, demonstrating that germination requirements of R. fistulosa are typical of species that grow in environments with fluctuating water levels. A pot experiment in which five infestation levels of R. fistulosa were installed in the absence and presence of a rice plant, showed that host plant presence resulted in a 3.7 times higher seed production rate and a 15% larger average seed size. Despite this reproductive advantage, a pot experiment with three rice cultivars, selected because of their difference in strigolactone production, showed that host plant presence, regardless of the development stage, did not influence the emergence rate of R. fistulosa. In a follow‐up study, the germination stimulation effect of root exudates collected from the same three rice cultivars and a treatment consisting of an artificial germination stimulant (GR24) was compared with a treatment consisting of plain water. In these treatments, seeds of R. fistulosa were compared with seeds of the obligate parasite Striga hermonthica. Germination of S. hermonthica was strongly advanced by the presence of root exudates and GR24 but was completely absent in water, whereas germination of R. fistulosa in all treatments was similar to that in plain water. The absence of a host recognition mechanism at the germination stage suggests that the regulation of germination through light and soil moisture is near optimal. Our finding might also indicate that for this facultative parasitic plant species, a more opportunistic germination strategy is superior. Implications of the findings for management of R. fistulosa in rice cultivation are discussed.

Seed Collection and Germination Strategies for Common Wetland and Coastal Sage Scrub Species in Southern California

Abstract There is a need for a consolidated source of information on native vegetation seed collection and germination strategies in southern California. Published literature on these methods is often experimental, species-specific, and widely scattered throughout online and print media. Planting and restoration strategies may need to be site-specific; however, similar methodological approaches are often utilized allowing for the development of general strategies for seed collection, storage, and germination methods. A better understanding of species-specific seed attributes and growth processes will help restoration ecologists collect high-quality, viable seed, thereby increasing the potential success of the restored vegetation community by reducing plant mortality, project costs, and effort. This paper synthesizes seed collection and germination strategies for native vegetation common to southern California estuarine wetland, coastal dune, and coastal sage scrub systems.

Maternal habitat affects germination requirements of Anabasis setifera, a succulent shrub of the Arabian deserts

The effects of maternal habitat on light and temperature requirements during germination were assessed for the succulent desert shrub Anabasis setifera. Seeds were collected from the Mediterranean habitats of Egypt and the hyper-arid subtropical habitats of the United Arab Emirates (UAE). Seeds from the two populations were germinated in three temperature treatments in both a light/dark regime and continuous darkness. Seeds from the Egyptian population germinated significantly greater and faster than those of UAE. Seeds stored for four months at room temperatures have little dormancy and germinate at wide range of temperatures and light conditions, but seeds stored four months in the natural habitat lost their ability to germinate and rotted 10 days after incubation. The germination response to temperature depended on the habitat type. Seeds of the Egyptian population attained a significantly greater germination at lower temperatures, compared with seeds from the UAE population, but there was no difference in germination between the two populations at higher temperatures. Germination of A. setifera was very fast; most seeds germinated within four days. These results reflect the adaptive strategy of germination in both populations, and may help explain the wide distribution of this species in different climatic regions.

Comparative seed germination traits in bog and fen mire wetlands

Mires are continental wetlands of high scientific and conservation interest. Knowing the seed germination traits of mire species is essential for understanding their regeneration ecology and conducting active restoration policies. Here, a comparative study of seed germination traits was performed with 34 plant species from bog and fen communities, including many European indicators of these habitats. Freshly collected seeds were exposed to a laboratory germination experiment designed to characterize their response to (1) cold stratification and (2) simulated field temperatures. Germination strategy groups were interpreted according to these responses, and the relation between these groups and different mire types was discussed. Seeds of all tested species had physiological dormancy. Most of them showed conditional type 2 non-deep physiological dormancy: fresh seeds could germinate only at warm temperature, but attained the ability to germinate at colder temperature as they lost dormancy. Most mire species from bogs, poor fens and base-rich fens followed a warm germination strategy analogous to that of other wetland species. Species from this warm group responded to very warm temperatures which rarely occur in the field, and this was interpreted as a gap-detecting mechanism. In contrast, species from calcareous springs and flushes had a cold germination strategy, which would fit with the cold and stable soils where they occur. Finally, a group of species associated with the pioneer Rhynchosporion vegetation of bare peat areas had very low germination, suggesting an intermediate or deep seed dormancy and a long term seed bank.

干旱胁迫下白刺花种子大小与萌发对策

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱胁迫下白刺花种子大小与萌发对策 DOI: 10.5846/stxb201312032878 作者: 作者单位: 仲恺农业工程学院,贵州省草业研究所,仲恺农业工程学院,贵州省现代农业发展研究所,贵州省草业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31260572, 71263012);贵州省农业攻关项目(黔科合NY字[2010]3045号) Seed size and germination strategy of Sophora davidii under drought stress Author: Affiliation: Zhongkai Unversity of agriculture and Engineering,Guizhou Institute of Prataculture,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:种子大小与种子萌发及其与环境因子的关系是植物种子萌发对策研究中的重要科学问题之一。采用PEG模拟干旱法研究不同干旱胁迫强度(0,5%,10%,15%,20%)下,白刺花(Sophora davidii)种子萌发进程、种子大小与种子萌发及种子命运的关系。结果表明:不同干旱胁迫下,白刺花种子具有相似的萌发进程,但中度干旱处理(10% PEG)萌发率显著高于零干旱(0% PEG)和重度干旱处理(P < 0.05),重度干旱处理(20% PEG)种子萌发开始时间晚于零干旱和中度干旱处理;种子大小与种子萌发开始时间的关系表现为零干旱处理下呈极显著负线性关系,中度干旱处理(5% PEG,10% PEG)下无相关关系,重度干旱处理(15% PEG,20% PEG)下呈负二次曲线关系;种子大小对种子命运的影响表现为零干旱处理有利于大、小种子萌发和小种子休眠,中度干旱处理(10% PEG)增加中等种子萌发、大种子休眠和小种子死亡风险,重度干旱处理(15% PEG,20% PEG)增加大种子死亡风险、中等种子和小种子休眠。综合分析表明,白刺花种子大小与萌发行为及种子命运的关系具有较强的环境依赖性,即种子萌发行为表现为顺境下种子越大萌发越快,逆境下小种子和大种子较中等种子萌发更快;种子命运表现为顺境增加种子死亡的风险,中度干扰有利于种子萌发,逆境则有利于种子休眠。 Abstract:Sophora davidii is an important leguminous shrub that is widely used for revegetating areas experiencing karst rocky desertification in southwest China. Karst is a fragile environment that is very sensitive to environmental and climate change, and is often under considerable drought stress. Seed size is a prominent life history trait of plants. Experiments were conducted in the laboratory to evaluate the effect of osmotic potential and seed size on germination, dormancy and mortality. The effect of drought stress on seed germination was examined by using different concentrations of polyethylene glycol treatments(0, 5%, 10%, 15%, and 20%) to provide designated osmotic potentials. The results showed that S. davidii seeds had a similar germination process under different degrees of drought stress. Seed germination percentage under moderate drought stress(10% PEG) was significantly higher than under non-stress and severe stress treatment(P < 0.05). The initiation of seed germination under severe drought stress(20% PEG) was slower than under non-stress and moderate stress. Seed size had a significant negative linear correlation with the initiation time for seed germination under non-stress treatment and a negative curve correlation for treatments under severe stress treatments(15% PEG, 20% PEG), while there was no correlation for moderate drought stress(5% PEG, 10% PEG). The relationship between seed size and seed fate of S. davidii showed that non-stress conditions may beneficial to germination for large or small seeds and dormancy for small seeds; moderate drought stress can drive medium seed germination, large seed dormancy and small seed mortality, and severe drought stress(15% PEG, 20% PEG) can lead to large seed mortality, and medium and small seed dormancy. Seed size, germination behavior and seed fate were heavily dependent on environmental factors. The germination strategy had a diverse pattern, that is, the larger seed size, the earlier seeds germination; in non-stress conditions, but larger and smaller seeds germinate earlier than medium seeds in adversity. The seed fate of S. davidii showed that seed mortality increased in non-stress conditions, seed germination was facilitated under moderate stress, and that seed dormancy was expedited in adversity. The information in this study may help land managers develop effective and sustainable revegetation management strategies. 参考文献 相似文献 引证文献

Bet-hedging strategies of native and exotic annuals promote coexistence in semiarid Chile

Scientists are increasingly interested in the evolutionary responses of organisms to unpredictable, variable, and extreme climate changes. In semiarid environments, inter-annual variability in the frequency and amount of rainfall affects both the growth and recruitment of plant species, especially annuals. In these inherently variable environments, individual selection should favor demographic responses that spread the risk of mortality over time and enhance long-term reproductive success (i.e., bet-hedging strategies). However, the same processes that allow the persistence and recruitment of native species could facilitate the introduction and establishment of exotics. We assessed whether native and exotic annuals in semiarid Chile displayed similar or contrasting bet-hedging traits, and discuss mechanisms of coexistence of both types of species and their demographic variation under interannual rainfall variability driven by El Niño Southern Oscillation (ENSO). We analyzed a proxy of long-term fitness, i.e., the variability of seed density over 17 years, for the two most common native and two exotic annual plant species present in the study area. We experimentally tested whether the quality of the maternal environment (soil water supply in a given year) had an extended effect (e.g. the next year) on the proportion of seed germination or on the mean and/or variability of seed size and seed dormancy. Results showed that native and exotic species in this annual plant assemblage displayed contrasting bet-hedging strategies as evolutionary responses to variable rainfall. Although rainfall variability promotes the evolution of bet-hedging strategies, the nature of these strategies varies across species, presumably to minimize competitive exclusion. In semiarid Chile, the success of two exotic ephemerals that are components of a diverse community of native annual species seems to reflect bet-hedging germination strategies that complement rather than compete with those expressed in dominant natives.

Effects of salinity and sulphide on seed germination of three coastal plants

The sensitivity of coastal plants to salinity and sulphide influences their performances in salt marshes. The combined effects of salinity and sulphide on the germination characteristics of three coastal plant species (Suaeda salsa, Phragmites australis and Spartina alterniflora) were studied under controlled conditions in the laboratory. Treatments included three salinity levels (0, 250 and 500mM) and five sulphide levels (0, 3, 6, 9 and 12mM) using a complete randomized block design. The germination percentage, germination speed and shoot length of all plants decreased in response to increasing salinity. S. salsa and S. alterniflora in the high salinity treatments showed significantly higher recovery percentages in comparison to low salinity treatments. Germination speed of S. salsa and P. australis increased with elevated sulphide level in freshwater, reaching maximum values in the 6 and 9mM sulphide treatments, respectively. Sulphide did not increase shoot length of S. salsa and P. australis, but stimulated S. alterniflora to elongate rapidly under freshwater and low salinity conditions. These results showed that these three coastal plant species have different germination strategies. For S. salsa and P. australis, sulphide increased the number of germinated seeds or accelerated the speed of germination under freshwater and low salinity conditions, which benefits for their establishments by increasing the number of seedlings. Nevertheless, S. alterniflora would enhance shoot elongation to increase its competitive advantages under moderate sulphide conditions.

Effect of the harvest year and cultivation temperature on the germination of Hirschfeldia incana (Brassicaceae): inferences on its invasiveness in Chile

The hoary mustard (Hirschfeldia incana (L.) Lagr.-Foss.) is a recently alien weed in Chile, recording a rapid increase in local abundance and spread. This species is distributed mainly on urban ecosystems, and field observations suggest that seed germination may have a key role to understanding its population persistence. In this line, it has been suggested that a successful germination strategy for weeds is to have both persistent seeds in the soil as rapidly germinable seeds, extending the ability to germinate over time. We evaluated germination of seeds of H. incana according to different harvest years (2010, 2011, and 2012), searching to understand how harvest time affects seed germination. For this proposal, seeds were cultivated at different temperatures (eight levels between 5 and 40 °C), covering a wide thermal gradient. Our results showed a lower germination percentage (43 %) in seed harvested in 2012 compared to the harvested in 2010 and 2011 (both cases >60 %), supporting that Hirschfeldia delay seed germination but keeping a seed stock able to germinate the same year in which were produced. The maximum germination percentage (>80 %) occurred with temperatures between 20 and 35 °C, and germination did not occur at 5 °C. These results suggest that temperature is not limiting the geographical spread of H. incana in Chile, as temperatures <5 °C are unusual. Thus, we expect that H. incana may increase its local abundance and latitudinal spread, if appropriate measures are not taken in Chile.

Seed germination strategies: an evolutionary trajectory independent of vegetative functional traits.

Seed germination strategies vary dramatically among species but relatively little is known about how germination traits correlate with other elements of plant strategy systems. Understanding drivers of germination strategy is critical to our understanding of the evolutionary biology of plant reproduction.We present a novel assessment of seed germination strategies focussing on Australian alpine species as a case study. We describe the distribution of germination strategies and ask whether these are correlated with, or form an independent axis to, other plant functional traits. Our approach to describing germination strategy mimicked realistic temperatures that seeds experience in situ following dispersal. Strategies were subsequently assigned using an objective clustering approach. We hypothesized that two main strategies would emerge, involving dormant or non-dormant seeds, and that while these strategies would be correlated with seed traits (e.g., mass or endospermy) they would be largely independent of vegetative traits when analysed in a phylogenetically structured manner.Across all species, three germination strategies emerged. The majority of species postponed germination until after a period of cold, winter-like temperatures indicating physiological and/or morphological dormancy mechanisms. Other species exhibited immediate germination at temperatures representative of those at dispersal. Interestingly, seeds of an additional 13 species “staggered” germination over time. Germination strategies were generally conserved within families. Across a broad range of ecological traits only seed mass and endospermy showed any correlation with germination strategy when phylogenetic relatedness was accounted for; vegetative traits showed no significant correlations with germination strategy. The results indicate that germination traits correlate with other aspects of seed ecology but form an independent axis relative to vegetative traits.

Hydrothermal Germination Models: Comparison of Two Data‐Fitting Approaches with Probit Optimization

ABSTRACTProbit models for estimating hydrothermal germination rate yield model parameters that have been associated with specific physiological processes. The desirability of linking germination response to seed physiology must be weighed against expectations of model fit and the relative accuracy of predicted germination response. Computationally efficient empirical models have been proposed that do not require a priori assumptions about model shape parameters, but the accuracy of these models has not been compared to the more common probit‐optimization procedure. Thirteen seedlots, representing six native perennial rangeland grasses and an invasive annual weed, were germinated over the constant temperature range of 3 to 36°C and water potential range of 0 to ‐2.5 MPa. Hydrothermal germination models were generated using probit optimization, optimized regression, and statistical gridding. These models were evaluated for the pattern and magnitude of residual model error and the relative magnitude of predictive errors under field‐simulated temperature and moisture conditions. Residual model errors in predictions of germination rate were greatest for the probit optimization procedure. Statistical gridding and optimized regression produced lower predictive model error, but the latter procedure could not resolve germination response for slower‐germinating seed populations. The more computationally efficient and accurate regression and statistical‐gridding procedures may be desirable for identifying germination strategies and syndromes that are based on predicted response to simulated conditions of field temperature and moisture.

Flowering time and seed dormancy control use external coincidence to generate life history strategy.

Climate change is accelerating plant developmental transitions coordinated with the seasons in temperate environments. To understand the importance of these timing advances for a stable life history strategy, we constructed a full life cycle model of Arabidopsis thaliana. Modelling and field data reveal that a cryptic function of flowering time control is to limit seed set of winter annuals to an ambient temperature window which coincides with a temperature-sensitive switch in seed dormancy state. This coincidence is predicted to be conserved independent of climate at the expense of flowering date, suggesting that temperature control of flowering time has evolved to constrain seed set environment and therefore frequency of dormant and non-dormant seed states. We show that late flowering can disrupt this bet-hedging germination strategy. Our analysis shows that life history modelling can reveal hidden fitness constraints and identify non-obvious selection pressures as emergent features.

Diversity of germination strategies and seed dormancy in herbaceous species of campo rupestre grasslands

AbstractThe effects of fire on the vegetation vary across continents. However, in Neotropical fire‐prone grasslands, the relationship between fire and seed germination is still poorly understood, while their regeneration, especially after strong anthropogenic disturbance, is challenging for their conservation. In the present study, we assessed diversity of germination strategies in 15 dominant herbaceous species from Neotropical altitudinal grasslands (locally known as campos rupestres). We exposed seeds to several fire‐related treatments. We also compared germination between regularly and post‐fire fruiting species. Finally, we investigated the diversity of dormancy classes aiming at better understanding the biogeography and phylogeny of seed dormancy. Germination strategies varied among families. Velloziaceae and Xyridaceae produced non‐dormant, fast‐germinating seeds. Cyperaceae and Poaceae showed an extremely low or null germination due to a high proportion of unviable or embryo‐less seeds. The seeds of campo rupestre grasslands are fire resistant, but there is no evidence that fire triggers germination in this fire‐prone ecosystem. Although heat and charred wood did not promote germination, smoke enhanced germination in one grass species and decreased the mean germination time and improved synchrony in Xyridaceae and Velloziaceae. Fire had a positive effect on post‐fire regeneration by stimulating fruit set in some Cyperaceae and Poaceae species. These species produced faster germinating seeds with higher germination percentage and synchrony compared to regularly fruiting Cyperaceae and Poaceae species. This strategy of dispersion and regeneration seems to be an alternative to the production of seeds with germination triggered by fire. Physiological dormancy is reported for the first time in several clades of Neotropical plants. Our data help advance the knowledge on the role of fire in the regeneration of Neotropical grasslands.

Aridity level, rainfall pattern and soil features as key factors in germination strategies in salt-affected plant communities

In arid environments, particularly in halophytic habitats, germination ecophysiology is strongly affected by environmental factors, primarily water availability, which is influenced by quantity and seasonal distribution of precipitation and soil properties.The aim of this paper was to demonstrate that water availability is essential for the control of germination and the response of seedlings growing in saline areas. With this approach, we compared the germination strategies in two Halocnemum populations with contrasting rainfall regimes and soil aridity. The germination behavior and radicle growth under various temperature regimes, light conditions and salinity levels were evaluated.Differences were found for all parameters between the populations. Seeds from the drier Mediterranean population exhibited common opportunistic behavior and germinated in a wide range of conditions, whereas germination in the Temperate population preferred conditions with light and was restricted to alternating temperatures, adaptations to temporary waterlogged environments. This restriction was eliminated when seeds were previously exposed to high salt concentrations, which confirmed an osmopriming effect.Based on our results, the development of global conservation plans for species with large distributions is not recommended. Successful management plans for threatened habitats should consider single populations and the reproductive strategies that developed in response to local environmental conditions.

Germination sensitivities to water potential among co-existing C3 and C4 grasses of cool semi-arid prairie grasslands.

An untested theory states that C4 grass seeds could germinate under lower water potentials (Ψ) than C3 grass seeds. We used hydrotime modelling to study seed water relations of C4 and C3 Canadian prairie grasses to address Ψ divergent sensitivities and germination strategies along a risk-spreading continuum of responses to limited water. C4 grasses were Bouteloua gracilis, Calamovilfa longifolia and Schizachyrium scoparium; C3 grasses were Bromus carinatus, Elymus trachycaulus, Festuca hallii and Koeleria macrantha. Hydrotime parameters were obtained after incubation of non-dormant seeds under different Ψ PEG 6000 solutions. A t-test between C3 and C4 grasses did not find statistical differences in population mean base Ψ (Ψb (50)). We found idiosyncratic responses of C4 grasses along the risk-spreading continuum. B.gracilis showed a risk-taker strategy of a species able to quickly germinate in a dry soil due to its low Ψb (50) and hydrotime (θH ). The high Ψb (50) of S.scoparium indicates it follows the risk-averse strategy so it can only germinate in wet soils. C.longifolia showed an intermediate strategy: the lowest Ψb (50) yet the highest θH . K.macrantha, a C3 grass which thrives in dry habitats, had the highest Ψb (50), suggesting a risk-averse strategy for a C3 species. Other C3 species showed intermediate germination patterns in response to Ψ relative to C4 species. Our results indicate that grasses display germination sensitivities to Ψ across the risk-spreading continuum of responses. Thus seed water relations may be poor predictors to explain differential recruitment and distribution of C3 and C4 grasses in the Canadian prairies.

Effect of Different Techniques on Germination Efficacy and Antioxidant Capacity of Indigenous Legumes of Pakistan

The present study investigated five different strategies for germination, utilizing distinctive substrata like jute bag, separating funnel, muslin cloth, filter paper and aluminum foil followed by evaluation of percent germination, radicle size, weight gain, total phenols and antioxidant activity of eleven indigenous legumes. The results revealed that jute bag displayed the most elevated percent germination in all legumes (84-96) % with the exception of kabuli chick pea, desi chick pea, garbanzo bean and cow pea which demonstrated improved percent germination when filter paper was utilized as substrata. The longest root length (3.1cm) was seen in cow pea when filter paper was used as substrata. It was additionally observed that jute bag demonstrated the highest increment in total phenolic compounds after germination in soy bean i.e. 6.3 mg gallic acid/gram. Among all germinated legumes, cowpea demonstrated the most elevated amount of total antioxidant activity (98.1%) when either filter paper or separating funnel was utilized. The results revealed that every bean requires optimum sprouting technique/conditions inorder to enhance its antioxidant capacity to maximum extent.