Sánchez-Vilas J, Retuerto R
Department of Ecology, Faculty of Biology, University of Santiago de Compostela, Santiago de Compostela, Spain.
Plant Biol (Stuttg). 2009 Mar;11(2):243-54. doi: 10.1111/j.1438-8677.2008.00105.x.
The gender of dimorphic plant species is often affected by ecophysiological variables. Differences have been interpreted as a response of the sexes to meet specific resource demands associated with reproduction. This study investigated whether sex-specific variations in ecophysiological traits in response to water availability determine the performance of each sex in different habitats, and therefore promote extreme spatial segregation of the sexes in the subdioecious plant, Honckenya peploides. Twenty-seven plants of each sex were individually potted in dune sand and assigned randomly to one of three water treatments. Well-watered plants were watered daily to field capacity, whereas plants in the moderate and high-water stress treatments received 40% and 20%, respectively, of the water given to well-watered plants. Photochemical efficiency, leaf spectral properties and components of relative growth rate (leaf area ratio and net assimilation rate) were measured. Photochemical efficiencies integrated over time were higher in male than in female plants. Water deficit decreased maximum quantum yield in female plants more rapidly than in male plants, but female plants (unlike male plants) had recovered to initial values by the end of the experiment. Maximum quantum yield in male plants was more affected by water stress than in female plants, indicating that male plants were more susceptible to photoinhibition. The two sexes did not differ in growth rate, but male plants invested a higher proportion of their biomass in leaves, had a higher leaf area per unit biomass and lower net assimilation rate relative to female plants. Female plants had a higher water content and succulence than male plants. Differences in stomatal density between the sexes depended on water availability. The results suggest that the two sexes of H. peploides have different strategies for coping with water stress. The study also provides evidence of sex differences in allocation traits. We conclude that between-sex differences in ecophysiological and allocation traits may contribute to explain habitat-related between-sex differences in performance and, therefore, the spatial segregation of the sexes.
两性植物物种的性别常受生态生理变量的影响。这些差异被解释为两性为满足与繁殖相关的特定资源需求而做出的反应。本研究调查了响应水分可利用性时生态生理特征的性别特异性变化是否决定了不同生境中两性各自的表现，进而促进了半雌雄异株植物海滨碱蓬中两性的极端空间隔离。每种性别的27株植物分别种植在沙丘沙中，并随机分配到三种水分处理之一。充分浇水的植物每天浇水至田间持水量，而中度和高度水分胁迫处理的植物分别接受充分浇水植物所浇水量的40%和20%。测量了光化学效率、叶片光谱特性和相对生长率的组成部分（叶面积比和净同化率）。随时间积分的光化学效率在雄株中高于雌株。水分亏缺使雌株的最大量子产量比雄株更快下降，但雌株（与雄株不同）在实验结束时已恢复到初始值。雄株的最大量子产量比雌株受水分胁迫的影响更大，表明雄株更容易受到光抑制。两性在生长速率上没有差异，但相对于雌株，雄株将更高比例的生物量投入到叶片中，单位生物量的叶面积更高，净同化率更低。雌株的含水量和肉质比雄株更高。两性之间气孔密度的差异取决于水分可利用性。结果表明，海滨碱蓬的两性应对水分胁迫有不同的策略。该研究还提供了分配性状存在性别差异的证据。我们得出结论，生态生理和分配性状的两性差异可能有助于解释与栖息地相关的两性表现差异，进而解释两性的空间隔离。
