Combinational dormancy in seeds of Sicyos angulatus (Cucurbitaceae,tribe Sicyeae)

Seeds with a water‐impermeable seed coat and a physiologically dormant embryo are classified as having combinational dormancy. Seeds of Sicyos angulatus (burcucumber) have been clearly shown to have a water‐impermeable seed coat (physical dormancy [PY]). The primary aim of the present study was to confirm (or not) that physiological dormancy (PD) is also present in seeds of S. angulatus. The highest germination of scarified fresh (38%) and 3‐month dry‐stored (36%) seeds occurred at 35/20°C. The rate (speed) of germination was faster in scarified dry‐stored seeds than in scarified fresh seeds. Removal of the seed coat, but leaving the membrane surrounding the embryo intact, increased germination of both fresh and dry‐stored seeds to > 85% at 35/20°C. Germination (80–100%) of excised embryos (both seed coat and membrane removed) occurred at 15/6, 25/15 and 35/20°C and reached 95–100% after 4 days of incubation at 25/15 and 35/20°C. Dry storage (after‐ripening) caused an increase in the germination percentage of scarified and of decoated seeds at 25/15°C and in both germination percentage and rate of excised embryos at 15/6°C. Eight weeks of cold stratification resulted in a significant increase in the germination of scarified seeds at 25/15 and 35/20°C and of decoated seeds at 15/6 and 25/15°C. Based on the results of our study and on information reported in the literature, we conclude that seeds of S. angulatus not only have PY, but also non‐deep PD, that is, combinational dormancy (PY + PD).     

Advances in Understanding Seed Dormancy at the Whole-seed Level:An Ecological, Biogeographical and Phylogenetic Perspective

Following a brief account of the early foundations of seed germination ecology sensu lato, some historical and recent developments pertaining to the ecology, biogeography and phylogeny of seed dormancy are discussed.     

Advances in Understanding Seed Dormancy at the Whole-seed Level: An Ecological,Biogeographical and Phylogenetic Perspective

Following a brief account of the early foundations of seed germination ecology sensu lato , some historical and recent developments pertaining to the ecology, biogeography and phylogeny of seed dormancy are discussed .     

Immunogenic,cellular, and angiogenic drivers of tumor dormancy‐a melanoma view

In tumor cells, the ability to maintain viability over long time periods without proliferation is referred to as a state of dormancy. Maintenance of dormancy is controlled by numerous cellular and environmental factors, from immune surveillance and tumor–stroma interaction to intracellular signaling. Interference of dormancy (to an ‘awaken’ state) is associated with reduced response to therapy, resulting in relapse or in metastatic burst. Thus, maintaining a dormant state should prolong therapeutic responses and delay metastasis. Technical obstacles in studying tumor dormancy have limited our understanding of underlying mechanisms and hampered our ability to target dormant cells. In this review, we summarize the progress of research in the field of immunogenic, angiogenic, and cellular dormancy in diverse malignancies with particular attention to our current understanding in melanoma.     

种子休眠机理研究概述

种子休眠是植物本身适应环境和延续生存的一种特性,是种子植物进化的一种稳定对策。野生植物特别是原产温带的植物,其种子大多有深而长的休眠期。关于种子休眠的概念有多种,这些概念引出了许多学说、假说和模型。种壳障碍、胚形态发育不完全和生理后熟以及种子中含有化学抑制剂等,都可导致种子休眠。根据不同的分类标准可将种子分成不同类型,一般将种子分为强迫休眠和机体休眠;机体休眠又可分为外部休眠、内部休眠和综合休眠。植物种类不同休眠特性也不同;同种植物的种子来源于不同的居群和植株时,若采集时期不同,其休眠也可能不同;甚至在同一果实中的不同种子,休眠特性亦可能有差异。影响休眠性状表达的基因既有核基因,也有质基因,休眠通常表现为一种受多基因控制的数量性状。种子休眠具有重要的生态学意义,能有效地调节种子萌发的时空分布。研究种子的休眠特性和机理及其解除方法,有助于农业生产和植物多样性保护。     

A graphical method for identifying the six types of non‐deep physiological dormancy in seeds

We present a new seed dormancy classification scheme for the non‐deep level of the class physiological dormancy (PD), which contains six types. Non‐deep PD is divided into two sublevels: one for seeds that exhibit a dormancy continuum (types 1, 2 and 3) and the other for those that do not exhibit a dormancy continuum (types 4, 5 and 6). Analysis of previous studies showed that different types of non‐deep PD also can be identified using a graphical method. Seeds with a dormancy (D) ? conditional dormancy (CD) ? non‐dormancy (ND) cycle have a low germination percentage in the early stages of CD, and during dormancy loss the germination capacity increases. However, seeds with a CD/ND (i.e. D→CD?ND) cycle germinate to a high percentage at a narrow range of temperatures in the early stages of CD. Cardinal temperatures for seeds with either a D/ND or a CD/ND cycle change during dormancy loss: the ceiling temperature increases in seeds with Type 1, the base temperature decreases in seeds with Type 2 and the base and ceiling temperatures decrease and increase, respectively, in seeds with Type 3. Criteria for distinguishing the six types of non‐deep PD and models of the temperature functions of seeds with types 1, 2 and 3 with both types of dormancy cycles are presented. The relevancy of our results to modelling the timing of weed seedling emergence is briefly discussed.     

豆科植物种子物理性休眠解除机制的研究进展

物理性休眠普遍存在于豆科植物种子中,其休眠解除机制的研究对阐明自然条件下种群的繁殖更新、生态环境恢复及种质资源的保存等都具有重要意义.本文对国内外关于影响种子休眠解除的环境因素(温度与温度的波动、湿度或土壤含水量)和生物因素(动物捕食、微生物感染等),休眠解除的结构基础,以及各种因子作用于种子的方式和部位的研究进展进行综述,并简要评述了休眠解除机制的二阶段和四阶段假说,以期为豆科植物种子休眠的进一步研究提供参考.     

种子休眠与破眠机理研究进展

种子休眠机理主要围绕透性、抑制剂作用和光敏素转化等方面的研究而建立。种皮的阻碍作用可能是由于种皮的物理或化学特性引起．可导致对水、光、气体或溶质的透性改变。抑制剂作用机理是抑制物质可抵消促进细胞分裂和生长发育的激素的作用。光敏素转化机理来源于与休眠有关的生物活性化学物质的合成、活化或破坏受光诱导的观点,由于发现了光敏素蓝色蛋白的活化型（Pfr）和钝化型（Pr）而得到强有力的支持,种子光休眠取决于光敏素蓝色蛋白的活化型（Pfr）含量和Pfr／（Pr＋Pfr）比值。目前,打破休眠的方法一般有机械破皮法、激素处理法、分子生物学技术法、物理处理法（如激光、烟、热等处理技术）、CO2处理法等。激素的平衡由抑制剂占优势向促进物占优势的变化是打破休眠的决定因素。研究破眠机理的分子生物学技术有多种,包括ABA突变体的利用、分子标记、转基因技术、用反义RAN阻止基因的表达、cDNA克隆技术等。用激光照射种子,把适宜的光射入细胞,可增加细胞生物能,促进种子发育,从而可能打破休眠。热处理的机理是由于加热可以增加种皮的透气性。CO2之所以能提高某些物种的萌发率,在于其影响了种子内部乙烯的敏感性。     

Ecological and evolutionary significance of resting eggs in marine copepods: past, present, and future studies

The occurrence of a resting egg phase in the life cycle of marine and freshwater planktonic copepods is well documented and receiving increasing attention by investigators. The species generally occur in coastal marine waters, freshwater ponds and lakes in areas that undergo strong seasonal fluctuations, though examples have been reported for tropical and sub-tropical areas not subject to such extreme fluctuations. Typically such species disappear from the water column for portions of the year, but remain in the region as benthic resting eggs. Studies to date have focused on the conditions that promote the occurrence of resting eggs, the factors that affect their survival and hatching from sediments, the existence of egg banks in sediments, and the impact of resting eggs on plankton community structure. Benthic resting eggs of copepods include diapause eggs as well as subitaneous (non-diapause) eggs that are quiescent due to conditions in the sediments. As with other groups of organisms the resting egg phase is viewed as being critical for the perpetuation of species year after year, especially those that disappear from the water column for portions of the year. Some data indicate that eggs can survive for many years in sediments which would expand their influence to evolutionary time scales. This paper summarizes our understanding of embryonic dormancy in marine copepods.     

9种形态生理休眠的种子脱水对萌发和胚胎生长的影响

9种形态生理休眠的种子脱水对萌发和胚胎生长的影响 在具有形态生理种子休眠(MPD)的物种中，吸胀种子脱水对胚胎生长和萌发的影响鲜为人知。我们研究了9种不同MPD水平的种子对脱水的反应。对每个物种进行对照实验，使种子永久保持水化并暴露在最佳层积-培养顺序中以促进胚胎生长。同时也开展了室温条件下脱水中断种子层积处理1个月的实验。研究结果显示，具有非深度简单MPD的白藤铁线莲(Clematis vitalba)和高山茶藨子(Ribes alpinum)的胚生长 和种子活力均不受干燥影响，但干燥使高山茶藨子的萌发力下降了16%。具有深度简单上胚轴MPD的黄 水仙(Narcissus pseudonarcissus)种子在不同的胚生长阶段呈现脱水耐受性，但其萌发力略有下降。具有不同 MPD复杂水平的物种对脱水的反应更为多变：具有中度复杂MPD的Delphinium fissum亚种与具有深度复杂MPD的峨参(Anthriscus sylvestris)和熊根芹(Meum athamanticum)，具有脱水耐受性。与之相反，具有非深度复杂MPD的鹅莓(Ribes uva-crispa)、中度复杂MPD的Lonicera pyrenaica和深度复杂MPD的Chaerophyllum aureum，脱水后萌发力下降。虽然具有MPD简单水平的种子能够具备脱水耐受性，但一些具有复杂水平MPD的种子也具有很高的耐受性。因此，脱水不诱导胚生长后期的次生休眠。9种植物中大多数的吸胀种子的脱水耐受性可能表征其对地中海地区气候变化的适应性。     

极度濒危植物大果木莲种子的休眠与萌发

大果木莲种子具吸水性,胚未完全发育。新鲜种子25℃下的萌发率仅2％,在30／20℃和20／10℃的条件下30d内分别有27％和36％种子萌发。在20／10℃下,1000mg·L^-1浓度的GA3可以有效打破种子休眠。冷层积120d的种胚生长不显著,大果木莲种子具有条件休眠特性,属于浅度简单型形态生理休眠。种子经冷层积60d的萌发率最高,而后下降,提示其可能有休眠循环现象。     

Taxonomic complexity,population genetics,and plant conservation in Scotland

Summary

Groups of plants that are undergoing active diversification often do not fall into neat and tidy taxonomies. In such groups it can sometimes be very difficult to establish what does, and what does not, constitute a species. This presents problems for species-based conservation programmes that are based around prioritised species-lists (e.g. the UK Biodiversity Action Plans; BAPs), particularly as the inclusion or exclusion of taxa on these lists largely determines the allocation of conservation resources. This is an important issue as almost half of the BAP priority higher plant species for which Scotland has prime responsibility are taxonomically controversial.

Recent research using population genetic approaches to tackle some taxonomically complex plant groups has enhanced our understanding of their biology. Such approaches provide objective and independent assessments of whether a given entity is distinct or not. This information can then be used to contribute towards the decision making process of which taxa to prioritise for conservation, and address specific questions regarding BAP listed species. In the long term, however, a broader issue needs tackling. Actively evolving groups often contain a series of localised lineages, as well as complex populations that exhibit atypical levels of morphological diversity. These types of diversity do not fit well into a ‘standard’ species-based conservation system. In most cases protection will best be supplied by designated site protection or wider countryside habitat schemes. Where additional protection is need, a conservation policy is required that accepts the diversity in these actively evolving groups for what it is, rather than trying to squeeze it into conservation legislation derived for taxa whose delimitation is routine.     

药用植物种子休眠类型及休眠解除研究进展

种子休眠是植物在长期发育过程中形成的对不良环境条件主动适应的现象。介绍了常见药用植物种子休眠的原因,根据休眠原因对种子休眠与萌发的影响将种子休眠划分的几种类型,总结了对不同休眠类型的种子应分别采用的休眠解除方法,并评述了目前的研究进展。     

Interchangeable effects of gibberellic acid and temperature on embryo growth, seed germination and epicotyl emergence in Ribes multiflorum ssp. sandalioticum (Grossulariaceae)

Morphophysiological dormancy was investigated in seeds of Ribes multiflorum Kit ex Roem et Schult. ssp. sandalioticum Arrigoni, a rare mountain species endemic to Sardinia (Italy). There were no differences in imbibition rates between intact and scarified seeds, suggesting a lack of physical dormancy, while methylene blue solution (0.5%) highlighted a preferential pathway for solution entrance through the raphe. Embryos were small at seed dispersal, with an initial embryo:seed ratio (E:S) of ca. 0.2 (embryo length, ca. 0.5 mm), whereas the critical E:S ratio for germination was three times longer (ca. 0.6). Gibberellic acid (GA(3), 250 mg · l(-1)) and warm stratification (25 °C for 3 months) followed by low temperature (<15 °C) enhanced embryo growth rate (maximum of ca. 0.04 mm · day(-1) at 10 °C) and subsequent seed germination (radicle emergence; ca. 80% at 10 °C). Low germination occurred at warmer temperatures, and cold stratification (5 °C for 3 months) induced secondary dormancy. After radicle emergence, epicotyl emergence was delayed for ca. 2 months for seeds from three different populations. Mean time of epicotyl emergence was affected by GA(3) . Seeds of this species showed non-deep simple (root) - non-deep simple (epicotyl) morphophysiological dormancy, highlighting a high synchronisation with Mediterranean seasonality in all the investigated populations.     

The relationship between seed dormancy,seed size and weediness,in Crepis tectorum (Asteraceae)

Summary I examined the germination characteristics of weed and outcrop populations of Crepis tectorum to test the hypothesis that the presumably more ephemeral weed habitat favors the highest levels of seed dormancy. The winter annual habit characterizing most plants of this species was reflected in a rapid germination of seeds sown in late summer. A slightly higher fraction of surface-sown seeds of weed plants delayed germination. Buried seeds of weed plants also survived better than seeds produced by plants in most outcrop populations, supporting the idea that weediness favors seed dormancy and a persistent seed bank. However, the differences in seed dormancy between the two ecotypes were small and not entirely consistent. Furthermore, high levels of seed dormancy were induced during burial in the outcrop group, suggesting that there is a potential for a dormant seed population in this habitat as well. Demographic data from one of the outcrop populations verified the presence of a large between-year seed bank. Possible environmental factors favoring seed dormancy in outcrop populations are discussed. The unusually large seeds of weedy Crepis contrasts with the relatively small difference in seed dormancy between the two ecotypes.     

Germination requirements inCarex kobomugi (Sea Isle)

Laboratory and field germination experiments inCarex kobomugi seeds were pursued to clarify their germination requirements and availability of the requirements in the field. In the laboratory experiments, more than 50% of the seeds ofC. kobomugi germinated under 35/30C or 25/20C when they were scarified with 98% H₂SO₄ after removal of their utricles, and chilled in moist condition for 28 to 42 d. Seeds with utricles or those without scarified with H₂SO₄ did not germinate. Seeds sown at 10-cm depth at the Kado-ori coast on 11 February 1991 after soaked in H₂SO₄ showed 40% germination by 29 April 1991, whereas those without H₂SO₄ treatment did not germinate. These results suggest that seed-coat impermeability and embryo immaturity are possible causes of the dormant state in seeds ofC. kobomugi ripen in summer. In the field, the moist-chilling condition is available in winter and the seeds can germinate in the following spring if the seed-coat impermeability is relaxed before winter.     

海草种子休眠、萌发、幼苗生长及其影响因素的研究进展

海草床是沿岸海域重要的初级生产者,具有极其重要的生态价值和经济价值,是重要的浅海生态系统之一.本文综述了近年来国内外对海草种子休眠、萌发、幼苗生长及其影响因素的研究进展,总结了海草种子的休眠方式和休眠历期及其影响因素,探讨了盐度、温度、光、激素、溶解氧及种群等因素对海草种子萌发、幼苗存活和生长的影响,并对目前研究中存在的问题和今后的研究方向进行了展望.