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The aim of this study was to investigate the effects of appendages on the maintenance of viability and germination of the diaspores of the three shrubs Calligonum junceum (Fisch. et Mey.) Litv., Atraphaxis pungens (Bieb.) Jaub. et Spach. and Reaumuria soongarica (Pall.) Maxim. that have high potential for restoration of degraded temperate arid regions. It has been hypothesized that appendages on diaspores of A. pungens, C. junceum, and R. soongarica help maintain seed viability during dry storage at room temperatures and during moist storage in soil outdoors, but they inhibit seed germination. Fresh diaspores of each species were tested for germination; and diaspores with and without appendages were stored in moist soil outdoors in Xinjiang Province of northwest China; and dry diaspores at room condition for 4 months. Viability and percentage of diaspores with and without appendages that germinated during burial were determined. After burial or dry storage, diaspores with and without appendages were tested for germination. Regardless of storage condition, appendages had no effect on diaspore viability of C. junceum and A. pungens but significantly reduced mortality of R. soongarica diaspores by 50%. During burial outdoors, appendages inhibited germination of C. junceum diaspores but not of A. pungens; no diaspores of R. soongarica germinated. After burial, appendages inhibited germination of A. pungens diaspores but had no effect on C. junceum. Appendages had no effect on germination of R. soongarica diaspores after storage in both locations. To use these three species for revegetation, it is recommended that appendages should be removed from diaspores of C. junceum and A. pungens before storage and sowing, but appendages should be retained on seeds of R. soongarica. [ABSTRACT FROM AUTHOR]

Direct seeding is a more cost-effective method for plant community restoration than transplanting pot-grown plants, but this method is not applicable to all plant species and all regions. To evaluate the effectiveness of direct seeding to restore mined cold desert vegetation without irrigation, Atraphaxis frutescens (L.) Ewersm., Calligonum junceum (Fisch. et Mey.) Litv., Peganum harmala L., and Seriphydium gracilescens (Krasch. et Iljin) Poljak. were directly sown in the bottom of dry furrows and on a flat site in the mined wasteland before the second snowfall in late autumn. Seedling emergence, survival, and growth were monitored for 3 years. For the four species, cumulative seed germination in the furrows ranged from 6.4 to 23.6% and the highest germination was 23.0 and 23.6% for A. frutescens and C. junceum, respectively. Survival at the end of 3 years was 7.0–56.1% for the four species. In the flat area, cumulative seedling emergence for C. junceum, A. frutescens, P. harmala, and S. gracilescens was 0, 0, 0.7, and 1.4%, respectively, and all seedlings died with the onset of drought. Thus, under natural precipitation conditions, the success of direct seeding depends on the microsite and species. We conclude that direct seeding can be an effective method for establishing the shrubs A. frutescens and C. junceum in mined wasteland if seeds are sown in furrows that have been created across the landscape. [ABSTRACT FROM AUTHOR]

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Gynomonoecy, the occurrence of both pistillate (female) and perfect (hermaphroditic) flowers on the same plant, has received little attention compared to gynodioecy and other plant sexual systems. Eremurus anisopterus is a perennial ephemeral in the cold desert of northwest China with a hermaphrodite–gynomonoecious sexual system in the same population. The primary aim of this study was to compare the early life history traits and inbreeding depression between progeny from pistillate and hermaphrodite flowers in hermaphrodites and gynomonoecious individuals. All of the traits of progeny from outcrossed pistillate flowers on gynomonoecious plants were significantly greater than for other pollination types. Selfing (vs. outcrossing) resulted in a decrease in all traits, indicating inbreeding depression (ID) during early life history stages of gynomonoecious and hermaphroditic plants. ID for seed mass, seed germination and seedling survivorship under water stress for pistillate flowers on gynomonoecious plants was significantly higher than it was for hermaphrodite flowers on both gynomonoecious and hermaphrodite plants. The advantage of the offspring of pistillate (vs. hermaphrodite) flowers may contribute to the maintenance of gynomonoecy in E. anisopterus in its cold desert sand dune habitat. [ABSTRACT FROM AUTHOR]

Caragana shrublands are the main type of vegetation in some cold desert ecosystems in Xinjiang in northwest China, and information on seed dormancy and germination of Caragana species is needed to help restore disturbed areas. Freshly matured seeds of Caragana aurantiaca, C. dasyphylla C. polourensis, C. roborovskyi, C. soongorica, C. spinosa and C. tekesiensis, collected from three natural ecosystems were tested for germination in light at 15/5, 20/10, 25/15 and 30/15 °C after dry storage at room temperature for 1 week and 9 months. Depending on the species, 1–84% of the seeds had physical dormancy (i.e., water-impermeable seeds). At 15/5, 20/10, 25/15 and 30/15 °C, fresh seeds of C. aurantiaca, C. spinosa and C. dasyphylla germinated from 74% to 100%, those of C. soongorica 15% to 52% and those of C. roborovskyi and C. polourensis 13–73%. After 9 months of storage, germination percentages increased significantly over wide range of temperatures for seeds of C. soongorica, C. tekesinsis C. roborovskyi and C. polourensis but decreased significantly for C. spinosa and C. dasyphylla. Most fresh seeds of the floodplain species and desert species are water-permeable and can germinate over a wide range of temperatures; consequently, they could be planted in the field at any time during the growing season. Dry storage of seeds of C. roborovski and C. tekesiensis increased the percentage of water-permeable seeds. Seeds of these species germinate best at high temperatures and should be planted in summer. If C. polourensis is used for restoration, the seeds need to be scarified before planting. [ABSTRACT FROM AUTHOR]

Many studies have been done on the relationship between variation in morphology, dispersal ability and degree of dormancy of heterocarpic species with dimorphic diaspores. However, there are far fewer such studies on species that produce trimorphic diaspores. Our aim was to compare dormancy and germination of achenes from peripheral, intermediate and central positions in the capitulum of the diaspore-trimorphic cold desert annual Asteraceae species Heteracia szovitsii , an important component of plant communities in the cold deserts of NW China. Dormancy breaking/germination responses of the three achene morphs and of seeds isolated from the pericarp were tested in the laboratory using standard procedures, and seedling emergence phenology of the achene morphs was monitored under natural cold desert temperature conditions in an experimental garden with and without supplemental watering. Depth of dormancy of the three achene morphs was peripheral > intermediate > central. Seedlings from the three morphs emerged in spring and in autumn. Cumulative seedling emergence percentage from achenes during 47 months of burial was central > intermediate > peripheral. Central achene morphs emerged over a period of ~12 months after sowing, while intermediate and peripheral achene morphs did so for ~40 and 47 months, respectively. Thus, H. szovitsii exhibits a temporal dispersal strategy. No viable central or intermediate achene morphs were present after 16 and 40 months, respectively, but ~60 % of the non-emerged peripheral achenes morphs were viable after 47 months. Based on our results on diaspore dormancy and those of a previous study of diaspore spatial dispersal of H. szovitsii , we conclude that this species has a high–intermediate–low risk diaspore dispersal/dormancy strategy that likely increases the chances for population persistence over time and space. [ABSTRACT FROM AUTHOR]

Our aim was to identify temperature and moisture modifications needed for improvement of seed germination, growth and establishment of the protein-rich forage legume Vicia unijuga A.Br. so that it could become large enough and store sufficient root reserves to survive in subalpine conditions. Germination tolerance of scarified V. unijuga seeds to various temperatures and water potentials was tested in the laboratory, and a 3-year field experiment was conducted in the subalpine region of China to evaluate the effects of modified soil temperature and moisture conditions generated by mulching with plastic film and barley straw on seedling emergence, growth, root nutrient reserves and subsequent overwinter performance. The highest germination percentage and rate occurred at the optimum temperature of 15–20°C, which improved these germination traits at low water potentials between –0.6 and –1.0 MPa. Higher soil temperature and water content were recorded in the plastic mulch treatment than in the control and straw mulch treatments. This enhanced establishment and accumulation of biomass and root reserve pools in the plastic mulch treatment, with nearly 100% of the plants surviving overwinter. The relative contribution of soil temperature was greater than of soil-water content to the variation in biomass and root nutrient reserves. Root starch content explained the most variation in overwinter survival. In conclusion, scarified V. unijuga seeds can germinate over a wide range of conditions, including those in the subalpine zone in spring. The plastic mulch treatment provided adequate soil temperature and water resources to improve growth and root starch reserves in first-year plants of V. unijuga , thereby improving overwinter survival in the subalpine environment. Scarified Vicia unijuga seeds can germinate over a wide range of conditions, including those in the harsh subalpine zone in spring. Mulching with plastic film increased root nitrogen and starch reserves in first-year plants of V. unijuga , thereby improving overwinter survival and perenniality of this forage legume in the subalpine environment. Applying plastic mulching could reduce the need for re-seeding with further direct and indirect costs and labour for farmers, and enhance productivity in the second year. [ABSTRACT FROM AUTHOR]

Soil salinisation and overgrazing are two important factors limiting plant growth in the Songnen Grassland, Northeast China. Leymus chinensis , a dominant rhizomatous grass, resists grazing and tolerates saline–alkali stress. However, its adaptive mechanisms to the dual effects of grazing and saline–alkali stress remain largely unknown. A two-factorial field experiment was conducted in two consecutive years in the natural L. chinensis community, combining the addition of mixed saline–alkali solution (NaCl : NaHCO3 : Na2CO3 1 : 1 : 1, amount 559.13 g m–2 year–1) with clipping (removal of 60% of aboveground biomass, AGB). Saline–alkali addition significantly increased AGB and total biomass in the no clipping but not in the clipping treatment. Irrespective of clipping, ramet density was significantly decreased, and individual ramet biomass was significantly increased under salt stress. The significant increase in AGB was due to a high K+ : Na+ ratio, high water-use efficiency, and an increase in leaf area index and net photosynthesis rate of individual ramets under salt–alkali stress. Clipping significantly decreased AGB and total biomass regardless of saline–alkali addition, possibly because of decreased sugar content of rhizomes. Saline–alkali and clipping had an interactive effect on AGB and total biomass of L. chinensis. The significant reduction in AGB and total biomass were mainly caused by reduced proline and water-soluble carbohydrate content under dual stress. A modified and simplified graphic model of the limiting resource model was proposed based on our results. Leymus chinensis can grow well under saline–alkali stress via ramet biomass compensation, in which the significant decrease in ramet density is compensated by the significant increase in individual ramet biomass. Ramet compensation and clonal integration were identified to be main mechanisms of herbivory and saline–alkali tolerance. Soil salinisation and overgrazing are two important factors limiting plant growth in the Songnen Grassland, China; how the dominant species Leymus chinensis resists the dual effect of these stresses remains largely unknown. Our results highlight the importance of rhizome soluble sugar during clipping and saline–alkali tolerance. This study provides a theoretical basis for promoting the restoration of L. chinensis grassland under the combined clipping and saline–alkali stresses. [ABSTRACT FROM AUTHOR]

Litter accumulation resulting from land use change (enclosure) is one of the key variables influencing seedling recruitment and consequently the regeneration of plant populations and seed persistence in the soil seed bank. A better understanding of the effects of litter on seed germination and seedling emergence is crucial for developing a new set of indicators for grassland ecosystem health and for grassland management policy. We investigated the effects of seed position in litter and amount of litter covering the seed on seedling emergence and seed persistence of three common species on the Loess Plateau in northwestern China. Seed position beneath the litter layer provided a suitable environment for seedling emergence of the three species. A moderate amount of litter (160 g/m²) was beneficial for seedling emergence of the small-seeded species Stipa bungeana and Lespedeza davurica from seeds from beneath the litter layer. The largeseeded species Setaria glauca was more tolerant of a high amount of litter (240 g/m²) than the two small-seeded species. Seed persistence in the soil differed among the three species and also was affected by seed position in litter and amount of litter cover. The proportion of viable seeds of Stipa bungeana and Setaria glauca on top of the litter layer increased with an increase in amount of litter. Seedling emergence and seed persistence varied significantly among species, amount of litter and seed position in litter. A moderate amount of litter and seeds positioned beneath the litter layer were better for seedling recruitment than for those on top of the litter layer. A high amount of litter was more favorable for persistence of seeds positioned on top of the litter than for those beneath the litter. Our study showed that maintaining litter amount between 80 and 160 g/m² is optimal for S. bungeana dominated grassland on the Loess Plateau. We suggest that litter amount can serve as a guide for monitoring and managing grassland ecosystems, as it is an indicator of ecosystem processes that are essential for biodiversity conservation and restoration. [ABSTRACT FROM AUTHOR]

Several studies have compared seed banks of the different morphs of heteromorphic species, but none of them was on an amphi-basicarpic species. Our primary aim was to compare the relative ability of aerial and basal diaspores of an amphi-basicarpic species to form a seed bank. We compared the seed-bank dynamics of basal and aerial diaspores of three populations of the cold-desert annual Ceratocarpus arenarius growing in the Junggar Desert in north-western China. A 2.5-year experimental garden study compared germination phenology and retention of viability in basal (a) and aerial (c and f) morphs. Aerial morphs formed a modified Thompson and Grime type III seed bank (small proportion of seeds carried over to next year) and the basal morph a modified type IV seed bank (large proportion of seeds carried over to next year). Seeds germinated only in spring, and cumulative germination percentages were f>c>a (year 1), f = c>a (year 2) and f = c = a (year 3). The relationship between length of germination period, retention of viability during burial and relative ability to form a persistent seed bank was basal morph > aerial morphs. The results of this seed-bank study on C. arenarius are in full agreement with those published previously on seed dispersal and dormancy in this species. Thus, strong additional support is provided for a high risk–low risk germination strategy in this cold-desert annual. [ABSTRACT FROM AUTHOR]

Background: Induction of apoptosis by endoplasmic reticulum (ER) stress is implicated as the major factor in the development of multiple diseases. ER stress also appears to be a potentially useful major response to many chemotherapeutic drugs and environmental chemical compounds. A previous study has indicated that one major apoptotic regulator, p53, is significantly increased in response to ER stress, and participates in ER stress-induced apoptosis. However, the regulators of p53 expression during ER stress are still not fully understood. Principal Findings: In this report, we demonstrate that induction of p53 expression is mediated through NF-κB signaling pathways during ER stress in MCF-7 cells. Tunicamycin or brefeldin A, two ER stress inducers, increased p53 expression in MCF-7 and Hela cells. We found p53 nuclear localization, activity, and phosphorylation at serine 15 on p53 increased during ER stress. Nuclear translocation of NF-κB and activity of NF-κB were also observed during ER stress. ER stress-induced p53 expression was significantly inhibited by coincubation with the NF-κB inhibitor, Bay 11-7082 and downregulation of NF-κB p65 expression. The role of p53 in mediating Brefeldin A-induced apoptosis was also investigated. Induction of p53 expression by Brefeldin A was correlated to Brefeldin A-induced apoptosis. Furthermore, downregulation of p53 expression by p53 siRNA significantly reduced Brefeldin A-induced apoptosis in MCF-7 cells. Significance: Taken together, NF-κB activation and induction of p53 expression is essential for ER stress-induced cell death which is important for therapeutic effects of clinical cancer drugs. Our results may provide insight into the mechanism of cancer chemotherapy efficacy that is associated with induction of ER stress. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity can play an important role in colonization and survival of plants in an environmentally fluctuating habitat. The primary aim of this study was to determine the influence of level of abiotic (soil moisture and nutrient availability) and biotic (density and herbivory) factors on phenotypic plasticity in the number and proportional mass allocation to the heteromorphic dehiscent upper (high dispersal, low dormancy) and indehiscent lower (low dispersal, high dormancy) siliques of individuals of the cold desert winter annual/spring ephemeral Diptychocarpus strictus derived from different seed morphs. Plants produced from seeds sown in an experimental garden were subjected to different levels of soil moisture, nutrient supply, density and simulated herbivory. Mass allocated to vegetative and reproductive components was measured and number of upper and lower siliques counted. Except for number ratio of upper: lower siliques under nutrient supply, levels of the four treatments resulted in significant variation in total plant mass, reproductive mass, number of siliques (upper and lower), number and mass of each silique morph, individual seed mass, upper/lower silique ratio and mass allocation to each organ in an individual. In favorable environments, the upper/lower silique ratio was relatively high, while in unfavorable environments it was relatively low. The relative allocation to upper and lower siliques was significantly negatively correlated, suggesting that allocation to upper siliques in good growth conditions occurred at the expense of allocation to lower siliques. This appears to be the first report on the effect of herbivory on diaspore morph ratio in heterocarpic plants and one of only a very few on the effect of density on morph ratio in this group. In D. strictus, stressful vs nonstressful growth conditions caused a shift in the ratio of heteromorphic diaspores, which themselves are assumed to be bet-hedging. [ABSTRACT FROM AUTHOR]

• Premise of the study: Little is known about the effect of environmental conditions on seed dormancy break at the community level or how it could be affected by climate change. This study tested the effects of storage conditions on germination of 489 species from high-elevation natural grasslands on the Tibet Plateau. • Methods: We stored seeds in dry cold, dry warm, and wet cold environments to test the effect of these conditions on germination. Germination responses were classified with the use of cluster analysis. The effect of phylogeny on germination response to storage conditions was determined. • Key results: Compared with results of wet cold conditions, storing seeds at dry warm or dry cold conditions decreased the mean community germination percentage by 17.93% and 16.07%, respectively. Storing seeds at dry warm vs. dry cold conditions decreased the community mean germination percentage by 4.61%. The germination response to moisture conditions during storage showed significant phylogenetic patterns, whereas the germination response to storage temperature did not. On the basis of the germinability of seeds of the same species stored under different conditions, germination may increase, decrease, or stay the same. • Conclusions: Within the high-elevation Tibetan grassland community, the different responses in dormancy breaking and germination behavior to the same storage conditions may have implications for understanding how this community might respond to climate change, in particular, some species may increase in the community, whereas others may decrease or remain the same. However, the potential for such change can be detected only by studying the responses of many species. [ABSTRACT FROM AUTHOR]

Background and Aims: Diptychocarpus strictus is an annual ephemeral in the cold desert of northwest China that produces heteromorphic fruits and seeds. The primary aims of this study were to characterize the morphology and anatomy of fruits and seeds of this species and compare the role of fruit and seed hetermorphism in dispersal and germination. [ABSTRACT FROM PUBLISHER]

Effects of cold-dry storage on dormancy break and viability were determined for seeds of the five sub-alpine woody species Philadelphus incanus, Berberis vernae, Berberis dubia, Betula utilis, and Picea purpurea collected along an altitudinal gradient on the eastern part of the Qinghai-Tibet Plateau in China. Germination tests were conducted at 20/5°C for seeds stored dry at ambient room temperature for 4 weeks and then at 3–4°C for 0, 6, 12, and 24 weeks. Dormancy break during dry storage, i.e., afterripening, was indicated by an increase in germination percentages and rates. Duration of cold-dry storage and altitude of seed collection had significant effects on germination. With an increase in duration of storage, germination percentages and rates of P. incanus and B. vernae increased with a decrease in altitude of seed collection, while they increased with an increase in altitude for seeds of B. utilis and P. purpurea. Seeds of B. dubia did not exhibit changes in germination percentages and rates with altitude because a high number of seeds remained dormant during storage. Seed viability after 24 weeks of storage ranged from high (88, 93.3, 92.7%) for B. utilis to low (15% for high altitude) for P. incanus. The potential for dormancy break to occur during cold-dry storage should be considered when studies on basic seed dormancy are conducted or when seeds from various locations are stored prior to propagating plants from them. [ABSTRACT FROM AUTHOR]

Simple Summary: The broad objective of our study was to evaluate the life history flexibility of the annual Erodium oxyrhinchum in relation to the predicted changes in precipitation in the cold desert due to climate change. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring- and autumn-germinated seeds of the cold desert annual E. oxyrhinchum from 2016–2020. Also, the future climate for the region was modeled. Our results found that given the flexibility in the life history of E. oxyrhinchum, it seems unlikely that future climate change will have much of an impact on the life history and dominant position of this species in the herbaceous plant community in the unpredictable-rainfall environment of the cold desert. Our study challenges the commonly-held perception that desert organisms may be negatively affected by climate change. Interannual seasonal variability in precipitation may strongly affect the life history and growth of desert annual plants. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring (SG)- and autumn (AG)-germinated seeds of the cold desert annual Erodium oxyrhinchum. Vegetative and reproductive growth and F2 seed dormancy and germination were monitored from September 2016 to November 2020 in the sandy Gurbantunggut Desert in NW China in Central Asia. Dry autumns decreased the density of AG plants, and dry springs decreased the density of SG plants and growth of SG and AG plants. In dry springs, SG plants were more sensitive to precipitation than AG plants, while in wet springs SG and AG plants had similar responses to precipitation. During growth in both dry and wet springs, most morphological characters of SG and AG plants initially increased rapidly in size/number and then plateaued or decreased, except for SG plants in dry springs. In dry springs, most morphological characters of AG plants were larger or more numerous than those of SG plants, and they were larger/more numerous for SG plants in wet than in dry springs. The percentage biomass allocated to reproduction in SG plants was slightly higher in a wet than in a dry spring. A much higher proportion of dormant seeds was produced by AG plants in a wet spring than in a dry spring. Projected changes in precipitation due to climate change in NW China are not likely to have much of an effect on the biology of this common desert annual plant. [ABSTRACT FROM AUTHOR]

Background and Aims: Seed heteromorphism is a plant strategy that an individual plant produces two or more distinct types of diaspores, which have diverse morphology, dispersal ability, ecological functions and different effects on plant life history traits. The aim of this study was to test the effects of seasonal soil salinity and burial depth on the dynamics of dormancy/germination and persistence/depletion of buried trimorphic diaspores of a desert annual halophyte Atriplex centralasiatica., Methods: We investigated the effects of salinity and seasonal fluctuations of temperature on germination, recovery of germination and mortality of types A, B, C diaspores of A. centralasiatica in the laboratory and buried diaspores in situ at four soil salinities and three depths. Diaspores were collected monthly from the seedbank from December 2016 to November 2018, and the number of viable diaspores remaining (not depleted) and their germinability were determined., Results: Non-dormant type A diaspores were depleted in the low salinity "window" in the first year. Dormant diaspore types B and C germinated to high percentages at 0.3 and 0.1 mol L -1 soil salinity, respectively. High salinity and shallow burial delayed depletion of diaspore types B and C. High salinity delayed depletion time of the three diaspore types and delayed dormancy release of types B and C diaspores from autumn to spring. Soil salinity modified the response of diaspores in the seedbank by delaying seed dormancy release in autum and winter and by providing a low-salt concentration window for germination of non-dormant diaspores in spring and early summer., Conclusions: Buried trimorphic diaspores of annual desert halophyte A. centralasiatica exhibited diverse dormancy/germination behavior in respond to seasonal soil salinity fluctuation. Prolonging persistence of the seedbank and delaying depletion of diaspores under salt stress in situ primarily is due to inhibition of dormancy-break. The differences in dormancy/germination and seed persistence in the soil seedbank may be a bet-hadging strategy adapted to stressful temporal and spatial heterogeneity, and allows A. centralasiatica to persist in the unpredictable cold desert enevironment., (© 2024. The Author(s).)

Main Conclusion: Individuals of the annual halophyte Atriplex centralasiatica produce three kinds of diaspores that differ in dispersal, dormancy/germination response and type of seed bank formed, which likely is a bet-hedging strategy in the rainfall-unpredictable environment on the semi-arid, saline Ordos Plateau in Inner Mongolia, China. Seasonal fluctuations in environmental conditions provide germination cues for the establishment of seedlings at the right time and place to ensure plant survival and population regeneration. Diaspore heteromorphism is a phenomenon in which diaspores with stark qualitative differences in morphology and ecology are produced by the same maternal plant. Germination responses and dispersal times of the annual halophyte Atriplex centralasiatica were examined to determine the role of diaspore heteromorphism in its adaptation to salt desert conditions. A. centralasiatica is a tumbleweed that produces three types of diaspores that differ in morphology and ecophysiology. The relative potential dispersal ability and intensity of dormancy of the three diaspore types was type A (fan-shaped diaspores with yellow fruits) < type B (fan-shaped diaspores with black fruits) < type C (globular diaspores with black fruits). In the field, type A retained high germinability, but all of them were depleted from the (transient) soil seedbank in the first growing season. Types B and C cycled between dormancy and nondormancy, and 0 and > 90.0% remained in the soil seedbank 2 years after dispersal, respectively. The dormancy, dispersal and salt tolerance of type B diaspores were intermediate between those of A and C. Type A exhibited low dispersal-nondormancy, type B exhibited intermediate dispersal-intermediate dormancy and type C exhibited high dispersal ability-high dormancy. In the unpredictable salt desert habitat, the functional differences in germination and dispersal of the three diaspores act as a bet-hedging mechanism and ensure population establishment in different years by spreading germination over time and space.

Sand burial plays important role in the life history of species in sandy areas of arid and semi-arid temperate regions, by affecting seed germination, seedling growth and survival and plant community. However, few studies have focused on the effects of sand burial on the dynamics of seed dormancy in such areas. In this study, seed germination characteristics of Allium tenuissimum, a dominant perennial herb in the dune ecosystem in Ordos Plateau in northern China, was investigated. Dormancy dynamics were monitored for seeds buried at sand depths of 0, 2 and 5 cm in the natural habitats for 13 months. Freshly matured seeds of A. tenuissimum were conditionally dormant and germinated to high percentages at high but not low temperatures. Germination percentages were increased by incubation at summer temperature (15/25 °C) and dry storage, but GA 3 and cold stratification had no significant effects. These results suggested that seeds of A. tenuissimum were conditionally dormant, and incubation under warm, wet (but not cold, wet) conditions and dry after-ripening resulted in complete dormancy releasing. Seeds buried at 2 and 5 cm in the field for 13 months exhibited seasonal changes in germination, with an increase in spring and summer followed by decrease in autumn and winter. However, seeds on the soil surface (0 cm) gradually came out of dormancy beginning in January, and germinated percentage was highest in July, after which remained high. The peak of nondormancy for seeds buried in the field was in the summer, which corresponds to the period of highest annual precipitation. Sand burial helped mediate seeds dormancy dynamics of A. tenuissimum via seasonal dormancy cycling. Our finding contributes to a better understanding of how timing of seedling establishment is controlled in a semiarid dune ecosystem in temperate climate., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Seed dormancy profiles are available for the major vegetation regions/types on earth. These were constructed using a composite of data from locations within each region. Furthermore, the proportion of species with nondormant (ND) seeds and the five classes of dormancy is available for each life form in each region. Using these data, we asked: will the results be the same if many species from a specific area as opposed to data compiled from many locationsare considered? Germination was tested for fresh seeds of 358 species in 95 families from the Xishuangbanna seasonal tropical rainforest (XSTRF): 177 trees, 66 shrubs, 57 vines and 58 herbs. Seeds of 12.3% of the species were ND, and 0.3, 14.8, 60.6, 12.0 and 0% of the species had morphological (MD), morphophysiological (MPD), physiological (PD), physical (PY), and combinational (PY + PD) dormancy, respectively. PD was more important than ND in all life forms, PY was highest in shrubs, MD was not important in any life form and MPD was most common for herb and vines. The seed dormancy profile for XSTRF differs considerably from the composite profile for this vegetation type worldwide, most obviously in ND being much lower and PD much higher in XSTRF.

Seed predation by insects is common in seeds of Fabaceae (legume) species with physical dormancy (PY). However, the consequences of insect seed predation on the life history of legumes with PY have been little studied. In the largest genus of seed plants, Astragalus (Fabaceae), only one study has tested the effects of insect predation on germination, and none has tested it directly on seedling survival. Thus, we tested the effects of insect predation on seed germination and seedling growth and survival of Astragalus lehmannianus, a central Asian sand-desert endemic. Under laboratory conditions, seeds lightly predated in the natural habitat of this perennial legume germinated to a much higher percentage than intact seeds, and seedlings from predated and nonpredated seeds survived and grew about equally well. Further, in contrast to our prediction seedlings from predated seeds that germinated "out-of-season" under near-natural conditions in NW China survived over winter. The implication of our results is that individual plants from predated seeds that germinate early (in our case autumn) potentially have a fitness advantage over those from nonpredated seeds, which delay germination until spring of a subsequent year.

Premise of the Study: Temperature and water potential for germination based on the thermal and hydrotime models have been successfully applied in predicting germination requirements of physiologically dormant seeds as well as nondormant seeds. However, comparative studies of the germination requirements of physically dormant seeds from different ecosystems have not been done., Methods: Germination of scarified seeds of four legume species collected from the Qing-Tibetan Plateau and of four collected in the Alax Desert in China was compared over a range of temperatures and water potentials based on thermal time and hydrotime models., Key Results: Seeds of species from the Qing-Tibetan Plateau had a lower base temperature (T b) and optimal temperature (T o) for germination than those from the Alax Desert. Seeds of the four species from the Qing-Tibetan Plateau germinated to high percentages at 5°C, whereas none of the four desert species did so. Seeds of species from the Alax Desert germinated to a high percentage at 35°C or 40°C, while no seeds of species from the Qing-Tibetan Plateau germinated at 35°C or 40°C. The base median water potential [Ψ b(50)] differed among species but not between the two habitats., Conclusions: The thermal time and hydrotime models accurately predicted the germination time course of scarified seeds of most of the eight species in response to temperature and water potential; thus, they can be useful tools in comparative studies on germination of seeds with physical dormancy. Habitat temperatures but not rainfall is closely related to germination requirements of these species., (© 2015 Botanical Society of America, Inc.)

Background and Aims: Diaspores of heteromorphic species may germinate at different times due to distinct dormancy-breaking and germination requirements, and this difference can influence life history traits. The primary aim of this study was to determine the effect of germination time of the two seed morphs of Suaeda corniculata subsp. mongolica on life history traits of the offspring., Methods: Germinated brown and black seeds were sown on the 20th of each month from April to September in a simulated but near-natural habitat of the species. Phenological and vegetative traits of the maternal plants, and number, size and germination percentage of the offspring were determined., Key Results: Germinated seeds sown late in the year produced smaller plants that had a higher proportion of non-dormant brown than dormant black seeds, and these brown seeds were larger than those produced by germinated seeds sown early in the year. The length of the seedling stage for brown seeds was shorter than that for black seeds, and the root/shoot ratio and reproductive allocation of plants from brown seeds were more variable than they were for plants from black seeds. Late-germinating brown seeds produced larger plants than late-germinating black seeds., Conclusions: Altering the proportion of the two seed types in response to germination timing can help alleviate the adverse effects of delayed germination. The flexible strategy of a species, such as S. corniculata, that produces different proportions of dimorphic seeds in response to variation in germination timing may favour the maintenance and regeneration of the population in its unpredictable environment., (© The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after mechanical removal of palea and lemma (hulls), chemical scarification and dry storage. Fresh and one-year-stored seeds were sown in the field, and seedling emergence was monitored weekly for 8 weeks. Furthermore, seeds were buried at different soil depths, and then retrieved every 1 or 2 months to determine seed dormancy and seed viability in the laboratory. Fresh seeds (caryopses enclosed by palea and lemma) had non-deep physiological dormancy. Removal of palea and lemma, chemical scarification, dry storage (afterripening), gibberellin (GA3) and potassium nitrate (KNO3) significantly improved germination. Dormancy was completely released by removal of the hulls, but seeds on which hulls were put back to their original position germinated to only 46%. Pretreatment of seeds with a 30% NaOH solution for 60 min increased germination from 25% to 82%. Speed of seedling emergence from fresh seeds was significantly lower than that of seeds stored for 1 year. However, final percentage of seedling emergence did not differ significantly for seeds sown at depths of 0 and 1 cm. Most fresh seeds of S. bungeana buried in the field in early July either had germinated or lost viability by September. All seeds buried at a depth of 5 cm had lost viability after 5 months, whereas 12% and 4% seeds of those sown on the soil surface were viable after 5 and 12 months, respectively.

Premise of the Study: Differences in seed germination responses of trees in tropical forests to temperature and light quality may contribute to their coexistence. We investigated the effects of temperature and red:far-red light (R:FR ratio) on seed germination of two gap-demanding species (Ficus hispida and F. racemosa) and two shade-tolerant species (F. altissima and F. auriculata) in a tropical seasonal rainforest in southwest China., Methods: A R:FR ratio gradient was created by filtering fluorescent light through polyester filters. Four temperature treatments were used to test the effect of temperature on seed germination of the four Ficus tree species across the R:FR gradient., Key Results: Seeds of the four Ficus species were positively photoblastic. Seed germination of F. hispida and F. racemosa was not affected across the R:FR ratio gradient (0.25-1.19) at 25/35°C, but it was inhibited under low R:FR at 22/23°C. By contrast, germination percentages of F. altissima and F. auriculata were not inhibited along the entire light gradient in all temperature treatments., Conclusions: Differences in germination responses of Ficus species might contribute to differences in their habitat preferences. The inhibitory effect of understory temperatures in the forest might be a new mechanism that prevents positively photoblastic seeds of the gap-demanding species such as F. hispida and F. racemosa from germinating in the understory and in small canopy gaps.

Populus euphratica is a dominant tree in riparian ecosystems in arid areas of northwest China, but it fails to regenerate in these systems. This study evaluates causes for the failure of sexual and asexual regeneration of this species in the wild. P. euphratica disperses as many as 85743 seeds/m(2) during summer, and the seeds germinate to 92.0% in distilled water and to 60.8% on silt. However, very few seeds (3.6%) can germinate on unflooded soil. The seed-rain season is prolonged by temporal variability in seed dispersal among individuals, which ensures that seedling emergence can occur during favorable conditions (i.e., floods and rainfall). As a result of water shortage and river channeling due to water usage and altered river flows, there are no safe sites on river banks for seed germination, which has led to the failure of P. euphratica to regenerate from seed. Root suckers of P. euphratica were present in 86% of the forest gaps investigated. However, extensive grazing has destroyed many of them and thus has reduced this form of regeneration. This research suggests that human activities are resulting in the failure of P. euphratica to regenerate. Changes in land management such as reduced use of concrete canals in Populus forests and/or reduced sheep grazing in these areas may promote their regeneration.

Background and Aims: Most studies on seed position-dependent effects have focused on germination characteristics. Our aim was to determine the effects of seed position in the spikelet on differences in timing of germination and on the ecological life history of the grass Eremopyrum distans in its cold desert habitat., Methods: For seeds in three spikelet positions, morphology, mass and dormancy/germination characteristics were determined in the laboratory, and seeds planted in field plots with and without watering were followed to reproduction to investigate seedling emergence and survival, plant size and seed production., Key Results: After maturation, of the seeds within the spikelet, basal ones (group 1) are the largest and have the highest proportion with physiological dormancy, while distal ones (group 3) are the smallest and have the highest proportion of non-dormant seeds. A higher percentage of seeds after-ripened in groups 2 and 3 than in group 1. Seeds sown in the field in early summer and watered at short, regular intervals germinated primarily in autumn, while those under natural soil moisture conditions germinated only in spring. Both cohorts completed their life cycle in early summer. Seeds in group 1 had lower percentages of seedling emergence and higher percentages of seedling survival than those in groups 2 and 3. Also, plants from group 1 seeds were larger and produced more seeds per plant than those from groups 2 and 3., Conclusions: Seed position-dependent mass was associated with quantitative differences in several life history traits of E. distans. The environmentally enforced (low soil moisture) delay of germination from autumn to spring results in a reduction in fitness via reduction in number of seeds produced per plant.