水分胁迫下雌雄异株植物葎草繁殖策略的可塑性调节

研究雌雄异株草本植物应对环境胁迫的繁殖策略及生殖分配可塑性，对发展雌雄异株植物的生活史进化理论和该类植物资源保护利用具有重要意义。实验以葎草为材料，通过设置轻度(LS)、中度(MS)、重度(RS)水分胁迫梯度，研究雌、雄单株的花芽分化、生物量分配、花穗性状、花药(或子房)数、花粉数及活力等与生殖生长相关的可塑性。结果表明:1)葎草通过提前花芽分化应对水分胁迫，雄株先于雌株进入生殖生长(P＜0.01)。2)雄株增加生殖分配应对LS胁迫，雌株减少花穗生物量应对水分胁迫;在RS胁迫时雄株的生殖分配为雌株的近3倍。3)葎草通过减少花穗数应对胁迫，雄株显著增加单个花穗的小花数来应对轻中度缺水(P＜0.05)，雌株则减少开花频次降低水分胁迫下生殖能量消耗。4)轻中度水分胁迫对雌株子房宽度无显著影响;中重度胁迫虽使雄株显著缩短了花药长度、减少了单个花药的花粉数(P＜0.05)，但花粉大小、花粉活性受影响较小。5)雄株花穗的POD和SOD活性显著高于雌株，雄株对水分胁迫更加敏感。在水分胁迫下，葎草在生存和防御功能稳定的基础上，可以通过协调分配有限资源，实现有性繁殖来完成草本植物较为短暂的生活史。

Plasticity of reproductive strategy of dioecious Humulus scandens in response to variation in water deficit stress

In order to investigate the reproductive strategy and plasticity of reproductive allocation of the climbing, dioecious herb Humulus scandens under environmental stress, we established plants of one variety under a gradient of 3 water stress levels (light, moderate and severe), and explored its plasticity of reproductive growth. Measurements were performed for both female and male H. scandens, and included among others:flower bud differentiation, biomass allocation, spike traits, quantity and activity of pollen and anthers, and ovary characteristics. The results showed: 1) H. scandens responded to water deficit stress by earlier differentiation of flower buds, and the timing of floral initiation in male plants was earlier than that of female plants (P<0.01). 2) Male plant responded to light water deficit stress by increasing reproductive allocation, but female plants adapted to water shortage by decreasing flower biomass. Reproductive allocation of male plants was significantly larger than that of female plants (P<0.05), with a nearly threefold difference under severe stress. 3) Both female and male H. scandens responded to water deficit stress by decreasing the number of spikes. Under light and moderate water deficit stress, male plants significantly increased floret number per spike when adapting to environmental stress (P<0.05), while female plants decreased flower number and hence would have a lower energy cost of reproduction. 4) Under light and moderate water deficit stress, there was no significant difference in thickness of the female plant ovary. Under moderate and severe water stress, male plants had significantly shortened anther length and reduced pollen grain numbers per anther (P<0.05), but the pollen size and pollen activity was unaffected. 5) Floral POD and SOD activity was significantly higher in male plants than that female plants, possibly indicating that male plants are more sensitive to water stress. In summary, H. scandens, exhibits a response to water deficit stress involving earlier flowering and differences between male and female plants in investment in reproductive effort.