Xinjiang Key Laboratory of Grassland Resources and Ecology, College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urümqi 830052, China.
Ann Bot. 2013 Dec;112(9):1815-27. doi: 10.1093/aob/mct240. Epub 2013 Nov 5.
Several studies have demonstrated trade-offs between depth of seed dormancy and dispersal ability for diaspore-dimorphic species. However, relatively little is known about trade-offs between these two life history traits for a species that produces more than two diaspore morphs. The aim of this study was to investigate the relationship between seed dormancy and dispersal in Ceratocarpus arenarius, an amphi-basicarpic cold desert annual that produces a continuum of dispersal unit morphs.
A comparison was made of dispersal and dormancy breaking/germination responses of dispersal units from ground level (a), the middle of the plant canopy (c) and the top of the plant canopy (f). Various features of the morphology and mass of dispersal units and fruits (utricles) were measured. The role of bracteoles in diaspore dispersal by wind, settlement onto the soil surface and dormancy/germination was determined by comparing responses of intact dispersal units and fruits. Movement of dispersal units by wind and animals, seed after-ripening, germination phenology and the presence of water-soluble germination inhibitors in bracteoles were tested using standard procedures.
Dispersal units a, c and f differed in morphology and mass; in the majority of cases, extremes were exhibited by a and f, with c being intermediate. Overall, relative dispersal ability was f > c > a, whereas relative intensity of dormancy was a > c > f. Bracteoles increased dispersal distance by wind, enhanced settlement of diaspores onto the soil surface and mechanically inhibited germination.
The results provide evidence for a model in which there is a continuous inverse-linear relationship between diaspore dispersal ability and depth of dormancy. Thus, dispersal unit heteromorphism of C. arenarius results in a continuum, from no dispersal ability/high dormancy (dispersal unit a) to high dispersal ability/low dormancy (unit f), which may be a bet-hedging strategy in the cold desert environment.
已有多项研究表明，在具有异型种子的物种中，种子休眠深度与扩散能力之间存在权衡关系。然而，对于产生两种以上异型种子的物种，人们对这两个生活史特征之间的权衡关系知之甚少。本研究的目的是调查具有异型种子的滨藜属植物（Ceratocarpus arenarius）中种子休眠与扩散之间的关系，该物种为具有连续分布的扩散单位形态的两栖基生一年生植物。
比较了地面水平（a）、植物冠层中部（c）和植物冠层顶部（f）产生的扩散单位的扩散和休眠打破/萌发响应。测量了扩散单位和果实（胞果）的形态和质量的各种特征。通过比较完整的扩散单位和果实的响应，确定了苞片在风传播、沉降到土壤表面和休眠/萌发中的作用。使用标准程序测试了扩散单位的风传播和动物传播、种子后熟、萌发物候和苞片中水溶性萌发抑制剂的存在。
形态和质量方面，a、c 和 f 型扩散单位存在差异；在大多数情况下，a 和 f 型的极端情况较多，而 c 型则处于中间位置。总体而言，相对扩散能力为 f>c>a，而相对休眠强度为 a>c>f。苞片增加了风的扩散距离，促进了种子在土壤表面的沉降，并通过机械作用抑制了萌发。
研究结果为以下模型提供了证据，即种子扩散能力与休眠深度之间存在连续的负线性关系。因此，滨藜属植物的扩散单位异形性导致从无扩散能力/高休眠（扩散单位 a）到高扩散能力/低休眠（单位 f）的连续变化，这可能是在寒冷沙漠环境中的一种风险分散策略。
