Intraspecific variations in seedling emergence and survival of Potentilla matsumurae (Rosaceae) between alpine fellfield and snowbed habitats

Potentilla matsumurae has a wide distribution from wind-blown fellfields to snowbeds in alpine regions of Japan. The environmental factors influencing seedling establishment differ between the fellfield and snowbed habitats; plants growing in each habitat may therefore have different germination strategies. Using a reciprocal sowing experiment, patterns of seedling emergence and survivorship were examined in both habitat types in the Taisetsu Mountains, Japan. Seeds derived from a fellfield population germinated earlier than did those derived from a snowbed population at both habitats, and the germination of fellfield seeds continued throughout the growing season. The timing of seedling emergence greatly affected subsequent survival at the fellfield. Seedlings that emerged in the first half of the growing season had low survivorship during the first year because of frost and drought damage, but the remaining seedlings had high survivorship during the winter; seedlings that emerged in the latter half of the growing season showed the opposite trend. At the snowbed, seedling survival was high throughout the growing season. Germination experiments in the laboratory highlighted a difference in the sensitivity of seeds from the fellfield and snowbed populations to fluctuating temperatures. These results indicate that intraspecific variation in emergence and survivorship may occur over a small scale in an alpine environment.     

Habitat‐related seed germination traits in alpine habitats

Understanding the key aspects of plant regeneration from seeds is crucial in assessing species assembly to their habitats. However, the regenerative traits of seed dormancy and germination are underrepresented in this context. In the alpine zone, the large species and microhabitat diversity provide an ideal context to assess habitat‐related regenerative strategies. To this end, seeds of 53 species growing in alpine siliceous and calcareous habitats (6230 and 6170 of EU Directive 92/43, respectively) were exposed to different temperature treatments under controlled laboratory conditions. Germination strategies in each habitat were identified by clustering with k‐means. Then, phylogenetic least squares correlations (PGLS) were fitted to assess germination and dormancy differences between species’ main habitat (calcareous and siliceous), microhabitat (grasslands, heaths, rocky, and species with no specific microhabitats), and chorology (arctic–alpine and continental). Calcareous and siliceous grasslands significantly differ in their germination behaviour with a slow, mostly overwinter germination and high germination under all conditions, respectively. Species with high overwinter germination occurs mostly in heaths and have an arctic–alpine distribution. Meanwhile, species with low or high germinability in general inhabit in grasslands or have no specific microhabitat (they belong to generalist), respectively. Alpine species use different germination strategies depending on habitat provenance, species’ main microhabitat, and chorotype. Such differences may reflect adaptations to local environmental conditions and highlight the functional role of germination and dormancy in community ecology.     

Climate warming could shift the timing of seed germination in alpine plants

Background and Aims

Despite the considerable number of studies on the impacts of climate change on alpine plants, there have been few attempts to investigate its effect on regeneration. Recruitment from seeds is a key event in the life-history of plants, affecting their spread and evolution and seasonal changes in climate will inevitably affect recruitment success. Here, an investigation was made of how climate change will affect the timing and the level of germination in eight alpine species of the glacier foreland.

Methods

Using a novel approach which considered the altitudinal variation of temperature as a surrogate for future climate scenarios, seeds were exposed to 12 different cycles of simulated seasonal temperatures in the laboratory, derived from measurements at the soil surface at the study site.

Key Results

Under present climatic conditions, germination occurred in spring, in all but one species, after seeds had experienced autumn and winter seasons. However, autumn warming resulted in a significant increase in germination in all but two species. In contrast, seed germination was less sensitive to changes in spring and/or winter temperatures, which affected only three species.

Conclusions

Climate warming will lead to a shift from spring to autumn emergence but the extent of this change across species will be driven by seed dormancy status. Ungerminated seeds at the end of autumn will be exposed to shorter winter seasons and lower spring temperatures in a future, warmer climate, but these changes will only have a minor impact on germination. The extent to which climate change will be detrimental to regeneration from seed is less likely to be due to a significant negative effect on germination per se, but rather to seedling emergence in seasons that the species are not adapted to experience. Emergence in autumn could have major implications for species currently adapted to emerge in spring.     

Some views on plants in polar and alpine regions

Many plants growing in polar and alpine regions clearly solve serious problems of life under extreme climatic conditions, as low temperatures, strong winds, unstable soils and in the North partly 24-h of light.     

Seed dormancy and germination in Dodonaea viscosa (Sapindaceae) from south-western Saudi Arabia

Dodonaea viscosa (Sapindaceae) is widespread in the mountainous highlands of the southwestern part of Kingdom of Saudi Arabia, where it is a medicinally important species for the people in Saudi Arabia. Seeds of this species were collected from Mount Atharb in Al-Baha region, at an altitude of 2100 m. The aims of this study were to determine if the seeds of D. viscosa have physical dormancy (i.e. a water-impermeable seed coat) and, if so, what treatments would break dormancy, and what conditions promote germination after dormancy has been broken. The dormancy-breaking treatments included: soaking of seeds in concentrated sulfuric acid (H₂SO₄) for 10 min, immersion in boiling water for 10 min and exposure to 50 °C for 1 min. After seeds had been pre-treated with H₂SO₄, to break dormancy, they were incubated at constant temperatures from 5 to 35 °C, under 12-h photoperiods or in continuous darkness, and germination recorded. Salinity tolerance was investigated by incubating acid-scarified seeds in different concentrations of mM NaCl in the light at 25 °C.Untreated seeds had low final germination 30%. Seeds that had been acid-scarified, immersed in boiling water or exposed to 50 °C all achieved 91% subsequently when incubated at 25 °C. Thus, seeds of this species in Saudi Arabia have physical dormancy, which can be broken by all three treatments designed to increase the permeability of the testa. After pre-treatment, there was a broad optimum constant temperature for germination that ranged between 5 and 25 °C but germination was inhibited by higher temperatures (30 and 35 °C). Light had little effect on this germination response. Scarified seeds were also sensitive to salinity, with the highest germination in distilled water and complete inhibition in 400 mM NaCl. Seeds that failed to germinate in saline treatments were mostly able to germinate on transfer to distilled water, suggesting osmotic inhibition.     

Differentiation in seed germination among populations of Capsicum annuum along a latitudinal gradient in Mexico

Toinvestigate variation in germination capability of wild Capsicumannuum seeds, the effects of light, fluctuating temperature,gibberellic acid (GA), soaking and sulfuric acid were analyzed in samples from14 populations from northwest Mexico. Germination was inhibited by darkness inall populations studied. Darkness inhibition of germination was overcome byfluctuating temperature and GA, factors which also increased germinationpercentage but not germination rate. Soaking treatments did not significantlyincrease germination of C. annuum seeds, while sulfuricacid treatments had negative effects on the process. Populations showed highvariation in germination response in all treatments, except for continuousdarkness. Principal component analysis differentiated some populations withhighgermination percentage and slow germination rate. Such differences did notcorrelate with climatic variables from collection sites. Given the variation ingermination patterns observed, some of these totally contrasting, we have to becautious when considering the results of studies based on a single wildpopulation.     

Effects of temperature, light, storage conditions, sowing time, and burial depth on the seed germination of Cardiocrinum cordatum var. glehnii (Liliaceae)

In this study, we conducted experiments to accumulate practical information on the propagation and establishment of a population of Cardiocrinum cordatum var. glehnii by seed sowing. C. cordatum var. glehnii seeds require approximately 19 months from seed dispersal to cotyledon emergence in the field. However, the period from seed dispersal to radicle emergence was shortened to approximately 7–8 months by the temperature transition of 25/15°C (60 days) → 15/5°C (30 days) → 0°C (120 days) → 15/5°C (i.e., 15/5°C represents alternating temperature treatment wherein the seeds were placed at 15°C for 12 h during the day and then at 5°C for 12 h during the night). More than 90% of the seeds, which were stored dry at 5°C for 12 months and sown in pots in the field, showed cotyledon emergence, whereas in seeds stored dry at 25°C, dry at room temperature, and non-dry at room temperature, cotyledon emergence was decreased by less than 1%. More than 88% of the seeds that were stored dry at 5°C and sown in the field in October 2002 immediately after collecting, November, and from April to July 2003 showed cotyledon emergence in spring 2004. However, seeds sown in August, September, and October 2003 showed cotyledon emergences of 57.6%, 0%, and 0% in spring 2004, respectively. Seeds collected in October 2002 and sown until July 2003 in the field received adequate high temperature in summer, moderate temperature in autumn, and cold temperature in winter; therefore, the percentage of cotyledon emergence was high in spring 2004. On the other hand, seeds sown in August 2003 or later could not receive enough high temperature; thus, cotyledons emerged from only a few seeds.     

Herb abundance and life-history traits in two contrasting alpine habitats in southern Norway

Colonisation is often a critical stage in the life history of plants, and recruitment success is expected to have a strong impact on plant frequencies especially among herbs. Several plant traits (seed size, plant height, leaf dry weight and specific leaf area) are suggested to be functionally important in early life stages, and the impact of such traits is expected to increase with habitat harshness. In this comparative study we examine the relative role of different plant traits for herb community patterns on both a local and regional scale in two contrasting alpine ecosystems in southern Norway: (1) a sub-continental region with more dry and productive, base-rich soils (Ho1, Hallingdal) and (2) an oceanic region, with humid acidic soils (Setesdal). Differences in species richness between regions were mainly due to higher herb richness in the base-rich region (n=55) than in the acidic region (n=13). Among traits, herb species seed weight was higher at the acidic site. The relative importance of traits for explaining herb local abundance and regional distribution tended to be stronger at the acidic site. No trait had a significant effect at the base-rich site, although seed weight and seed number were marginally non-significant. Plant clonality was positively related to local abundance and marginally to regional distribution at the acidic site. Plant frequency-trait correlations were generally higher in the acidic region then in the base-rich region. There was further a (marginal) increase of herbs with large seeds and with a dependence on sexual reproduction with increasing pH levels in Ho1. Soil pH was also the most important environmental variable for herb richness in Ho1, while no environmental variable was significantly related to herb richness in Setesdal. The study suggests that recruitment through seed is critical for the alpine herb community patterns especially in harsh habitats. Possible explanations for recruitment constraints include both soil acidity (low pH and Ca levels in addition to possible aluminium toxicity) and disturbance through grazing.     

Seed germination in temperate rain forest species of southern Chile: chilling and gap-dependency germination

Canopy gap and chilling requirements for seed germination were assessed in 61 and 44 species, respectively, in the temperate rain forest of southern Chile. Germination assays within canopy gap and understorey were carried out under natural conditions. Germination tests in cold stratified and non-stratified seeds were performed under laboratory conditions. Seeds were collected of common trees, shrubs, vines and perennial herbs of forests in southern Chile. Final percent germination was significantly enhanced under canopy gap conditions in 19 species, and significantly reduced in 11 species. Germination proved indifferent under gap vs. understorey conditions in half the species tested. Cold stratification affected germination in 11 species: significantly increasing final germination of four species, and significantly decreasing final percent germination of seven species. A Principal Components Analysis (PCA) was applied with the purpose of identifying groups of species with similar germination strategies. Four attributes were included in the PCA: final germination percentage in canopy gap, germination rate in the laboratory, and gap-and chilling-dependency indices (EGAP and STRAT, respectively). The first axis separated species mainly on EGAP variation while the second axis separated them mainly according to STRAT variation; the two axes together explaining 73% of the among-species variation. A small group of trees and vines germinating best in the understorey and neutral to chilling could clearly be distinguished from the remaining species analyzed. Multifactorial ANOVAs were used for evaluating the combined effect of successional status, seed mass, dispersal period, life form, phylogenetic categories, and dispersal syndrome on EGAP and STRAT variation. The EGAP value of secondary successional species proved significantly greater than that of primary successional species and species with endozoochorous seed dispersal were significantly less dependent on chilling (according to STRAT values) compared to species with mainly wind-dispersed seeds. The possible implications of these results for seedling establishment are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of light and temperature on the germination of lettuce seeds

A short period (15–30 min) at 30° C promotes germination of seeds of Lactuca sativa L. cv. Repolhuda in darkness. Far-red light reverses this stimulation, and the escape curves for phytochrome and high-temperature action are quite similar, indicating that the two factors act at a common point in the chain of events leading to germination. It is suggested that high temperature acts by decreasing the threshold of the active, far-red absorbing, form of phytochrome (Pfr) needed to promote germination.Abbreviations FR far-red light - Pfr far-red-absorbing form of phytochrome - R red light     

Determination of seed viability of eight wild Saudi Arabian species by germination and X-ray tests

Our purpose was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of eight wild species (Salvia spinosa, Salvia aegyptiaca, Ochradenus baccatus, Ochradenus arabicus, Suaeda aegyptiaca, Suaeda vermiculata, Prosopisfarcta and Panicumturgidum) from Saudi Arabia. Several days were required to determine viability of all eight species via germination tests, while immediate results on filled/viable seeds were obtained with the X-ray test. Seeds of all the species, except Sa.aegyptiaca, showed high viability in both the germination (98–70% at 25/15 °C, 93–66% at 35/25 °C) and X-ray (100–75%) test. Furthermore, there was general agreement between the germination (10% at 25/15 °C and 8% at 35/25 °C) and X-ray (5%) tests that seed viability of Sa.aegyptiaca was very low, and X-ray analysis revealed that this was due to poor embryo development. Seeds of P.farcta have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (98% at 25/15 °C and 93% at 35/25 °C) and X-ray (98%) test. Most of the nongerminated seeds of the eight species except those of Sa.aegyptiaca were alive as judged by the tetrazolium test (TZ). Thus, for the eight species examined, the X-ray test was a good and rapid predictor of seed viability.     

Seed viability of five wild Saudi Arabian species by germination and X-ray tests

Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (Moringa peregrina, Abrus precatorius, Arthrocnemum macrostachyum, Acacia ehrenbergiana and Acacia tortilis) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except Acacia ehrenbergiana and Acacia tortilis showed high viability in both germination (96–72% at 25/15 °C, 94–70% at 35/25 °C) and X-ray (100–80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of Acacia ehrenbergiana and Acacia tortilis was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of Abruspreca torius have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of Acacia ehrenbergiana and Acacia tortilis, were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.     

Effect of yak rumen content treatments on seed germination of 11 alpine meadow species on the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau is located in the ‘Third Pole’ of the world, characterized by a harsh environment. Despite this, the alpine meadow ecosystem have developed over a wide area but serious grassland degradation is threatening the ecological environment on the Plateau. Recruitment of new plants to the population, via germination and establishment, is vital to plant community survival. Previous work on the seeds in this area has mainly focused on community-wide germination strategies, seed germination characteristics and their correlations with seed size and seed mass. However, there have been no studies on the effects of soaking in rumen contents on the plant seed germination characteristics of alpine meadow species. The present study had two main objectives: (i) to determine the effect of fresh rumen content from yaks on seed germination characteristics and seedling growth of species common to the eastern Tibetan Plateau alpine meadow, and (ii) to develop an effective method to enhance seed germination. Seeds of 11 common species were collected together with fresh rumen content from three yaks that grazed there. Seed germination tests were conducted after they had been soaked in rumen content for one of six soaking periods (12, 24, 36, 48, 60 or 72 h). The seeds were incubated under natural light conditions of 8 h light at 25 °C and 16 h darkness at 15 °C, for the germination period of 34 days. The results showed that seed germination and seedling growth were affected by soaking time, seed coat completeness and seed type. After soaking in rumen content, the germination percentages of scarified (peeled or with the seed coat cut through) seeds of some species (true seeds Oxytropis ochrocephala and Medicago ruthenia var inschanica, nutlet Carex enervis, achenes Anemone rivularis and Polygonum sibiricum) and complete seeds of C. enervis, and A. rivularis were improved but the duration of soaking was also important. Seed germination of caryopsis Achnatherum inebrians (a toxic grass) was significantly inhibited by any exposure to rumen fluids. Scarified seeds generally had higher germination percentages than complete ones after treatment, but with the increase in soaking time, germination percentages declined and scarified seeds were more sensitive to the treatment than the complete seeds. After soaking in yak rumen content, the germination indices of scarified M. ruthenia at 12 h treatment, O. ochrocephala and achene Rumex acetosa at 12–24 h treatment, nutlet Kobresia humilis at 24 h treatment, P. sibiricum at 24–48 h treatment, C. enervis at 12–48 h treatment and A. rivularis at 12–60 h treatment were significantly higher than the control (P < 0.05), while the germination indices of complete C. enervis seeds at 12 h and 36 h treatment, and A. rivularis at 12–60 h treatment were significantly higher compared with the control. The germination indices of other species gradually decreased with the increase in soaking time. We concluded that yak rumen digestion could enhance, inhibit or not affect seed germination and seedling growth of the alpine meadow species, which might influence seedling recruitment, interspecific competition, and the plant community structure of the eastern Tibetan Plateau alpine meadow. Overall, yak digestion has a positive effect on alpine meadow seed germination and seed dispersal.     

温度对高山植物紫花针茅种子萌发特性的影响

温度是影响种子萌发的重要因子,在气候变暖和草地退化的背景下,认识温度变化对紫花针茅（Stipa purpurea） 种子萌发的影响有重要意义。作者系统研究了6个恒温条件（5、10、15、20、25、30℃）和3个变温条件（5/15、10/20、15/25℃）对不同居群紫花针茅种子萌发特性的影响。结果表明,紫花针茅种子适宜的萌发温度范围为15~25℃,低于10℃或高于30℃的温度都会抑制种子的萌发;与对应的恒温条件相比,变温条件不能起到促进紫花针茅种子萌发的作用;不同居群紫花针茅种子萌发对温度的响应既有相同点,也有不同点;海拔高度与种子萌发率存在极显著负相关关系,种子萌发季土壤温度与种子萌发存在显著负相关关系。本研究将为合理的保护和恢复紫花针茅草地提供一定科学依据。     

画眉草种子萌发对策及生态适应性

研究了画眉草种子在不同贮藏条件以及光照、温度和降雨等环境因素下的萌发对策.结果表明,画眉草新种子具有较强的内在休眠;4个月的干藏和冷藏处理对解除种子休眠作用不明显,但较长时间的贮藏（干藏1年）则能促进种子成熟.画眉草种子在光照和黑暗条件下都能萌发,但较强的光照更有利于种子萌发.种子萌发适宜温度是28 ℃,温度升高和降低都会导致画眉草种子萌发率下降;变温条件下（16～28 ℃）种子萌发率高于恒温28 ℃条件,但两个处理间的萌发率没有显著差异.种子萌发降雨阈值是10 mm,种子萌发率和萌发持续时间均随降雨量的增加而增加.画眉草种子具有迅速萌发和推迟萌发时间超过1年以上两种萌发对策.根据种子形态特征和萌发策略,推断画眉草具有持久土壤种子库.     

Light and nitrate interaction in phytochrome-controlled germination ofPaulownia tomentosa seeds

Pulsed light and nitrate exhibit an interactive effect on the germination ofPaulownia tomentosa Steud. seeds that require long periods of light irradiation. Two pulses of red light (R), separated by an adequately long dark interval, substitute for continuous prolonged irradiation. A far-red (FR) pulse given at the beginning of the dark interval inhibits germination, while it has no effect if given at the end. The requirement for certain ratios of the far-red-absorbing form of phytochrome/total phytochrome (P_fr/P_tot) differs when a FR+R-pulse is given as the first or second of two pulses (FR+R or R) separated by a dark interval. An equal decrease of the P_fr/P_tot ratio leads to a more pronounced decrease in germination when the pulse of the same FR+R ratio is given as the second pulse at the end of the dark interval. The length of dark interval between light pulses needed for maximal germination, differed in (i) seeds with a natural requirement for long periods of light irradiation from that in (ii) seeds with their long light requirement imposed by two weeks of imbibition in darkness or by (iii) imbibition in 40% heavy water. However, a single R pulse was sufficient to induce a high percentage of germination if the seeds were supplied with KNO₃ (10 mM) from the onset of imbibition up to the onset of light. This effect decreased with a delayed time of application, and was prevented if FR preceded the KNO₃ application. We dedicate this paper to Professor Hans Mohr on the occasion of his 60th birthday     

Habitat-specific responses in the flowering phenology and seed set of alpine plants to climate variation: implications for global-change impacts

The timing of the snowmelt is a crucial factor in determining the phenological schedule of alpine plants. A long-term monitoring of snowmelt regimes in a Japanese alpine area revealed that the onset of the snowmelt season has been accelerated during the last 17 years in early snowmelt sites but that such a trend has not been detected in late snowmelt sites. This indicates that the global warming effect on the snowmelt pattern may be site-specific. The flowering phenology of fellfield plants in an exposed wind-blown habitat was consistent between an unusually warm year (1998) and a normal year (2001). In contrast, the flowering occurrence of snowbed plants varied greatly between the years depending on the snowmelt time. There was a large number of flowering species in the fellfield community from mid- to late to late June and from mid- to late July. The flowering peak of an early-melt snowbed plant community was in the middle of the flowering season and that of a late-melt snowbed community was in the early flowering season. These habitat-specific phenological patterns were consistent between 1998 and 2001. The effects of the variation in flowering timing on seed-set success were evaluated for an entomophilous snowbed herb, Peucedanum multivittatum, along the snowmelt gradient during a 5-year period. When flowering occurred prior to early August, mean temperature during the flowering season positively influenced the seed set. When flowering occurred later than early August, however, the plants enjoyed high seed-set success irrespective of temperature conditions if frost damage was absent. These observations are probably explained based on the availability of pollinators, which depends not only on ambient temperature but also on seasonal progress. These results suggest that the effects of climate change on biological interaction may vary depending on the specific habitat in the alpine ecosystem in which diverse snowmelt patterns create complicated seasonality for plants within a very localized area.     

Interaction of light and temperature on seed germination of Rumex obtusifolius L.

Germination of Rumex obtusifolius L. seeds (nutlets) is low in darkness at 25° C. Germination is stimulated by exposure to 10 min red light (R) and also by a 10-min elevation of temperature to 35° C. A 10-min exposure to far-red light (FR) can reverse the effect of both R (indicating phytochrome control) and 35° C treatment. Fluence-response curves for this reversal of the effect of R and 35° C treatments are quantitatively identical. Treatment for 10 min with light of wavelenght 680, 700, 710 and 730 nm, after R and 35° C treatment, demonstrates that germination induced by 35° C treatment results from increased sensitivity to a pre-existing, active, far-red-absorbing form of phytochrome (Pfr) in the seeds.Abbreviations FR far-red light - P phytochrome - Pr red-absorbing form of P - Pfr far-red-absorbing form of P - R red light     

五蕊寄生种子萌发特性

采用室内与野外实验相结合的方法,对五蕊寄生（Dendrophthoe pentandra）种子萌发特性以及鸟类消化过程对其种子萌发的影响进行研究。结果表明：五蕊寄生种子对温度和光照较敏感,与黑暗条件相比,光照能显著提高种子的萌发率;20℃为种子萌发的最适温度,萌发率达53.8%,高温35℃及低温10℃均不利于种子萌发。研究发现纯色啄花鸟（Dicaeum concolor）是该植物的主要食果者,种子外的果肉不是限制种子萌发的关键因素,人为去除果肉并不能提高种子的萌发率,但可缩短种子萌发的时间,果实通过纯色啄花鸟类肠道消化后,随着粪便排出的种子萌发率显著提高（达69%）,暗示纯色啄花鸟在五蕊寄生的种子萌发过程中具有重要的作用。