In a large dam-regulated reservoir with regular hydrological pattern and strong flooding gradients across shore elevations, plants inhabiting in different shore elevations have to confront long-lasting flooding of differential intensities every year. Such persistent stress may lead to intraspecific differentiation of flooding tolerance in seeds. Echinochloa crusgalli var. zelayensis is a dominant annual plant in the shores of the Three Gorges Reservoir (TGR), which plays an important role in the shore vegetation. The objective of this study is to check whether intraspecific differentiation of seed flooding tolerance has occurred among E. crusgalli var. zelayensis populations in the TGR shores and whether such differentiation is associated with weak seed dispersal.
Both intact seed percentage and final seedling emergence rate after flooding significantly declined with increasing shore elevations where the seeds were collected, indicating that intraspecific differentiation in seed flooding tolerance has occurred among E. crusgalli var. zelayensis populations in the TGR shores after 7-year operation of the reservoir. The distance of seeds transported by rising water during reservoir impoundment was limited due to short-floating time of the seeds and relatively low speed of water level rise in the reservoir. This would be favourable to the development of intraspecific differentiation in seed flooding tolerance.
摘要：
大型水库消落带中西来稗种子耐淹性沿高程梯度的种内分化
在水文节律稳定、每年蓄水时间很长且水位涨落落差很大的水库中，生长在水库库岸消落带不同高程区域中的植物每年要面对长时间的不同强度的水淹，这种每年发生持续的水淹胁迫可能会导致水库库岸消落带中生长的植物的种子耐淹能力发生种内分化。西来稗(Echinochloa crusgalli var. zelayensis)是在三峡水库消落带中自然生长的优势一年生植物，在三峡水库消落带植被及消落带生态环境保护中发挥着重要作用。本研究的目的在于探究三峡水库消落带中生长的西来稗种子的耐淹能力是否已发生种内分化，以及此分化的发生是否与较弱的种子扩散能力有关。在本研究中，采集来自三峡水库消落带不同高程区域中生长的西来稗种子，在三峡水库即将蓄水时将所有采集的种子放置于三峡水库消落带中4个不同高程位置接受不同深度不同时长的水库蓄水水淹，同时把所有采集的种子也放置于不会被水库蓄水淹没的非消落带河岸上作为对照处理；测定种子在水中的漂浮持续时间和蓄水期间水库水位上涨速度以量化在水库蓄水水位上涨时种子的扩散能力，水库蓄水结束水退后检测放置于水库消落带和非消落带河岸上的种子的种子完好率、种子萌发能力和成苗率。研究结果发现，在经历三峡水库蓄水水淹后，西来稗种子的完好率和最终成苗率随种子母株在消落带中所处的高程的增加而显著降低，表明在三峡水库成库运行七年后，在三峡水库消落带中生长的西来稗的种子耐淹能力已发生了种内分化。三峡水库蓄水水位上涨时西来稗种子在水中较短的漂浮持续时间和水库蓄水时较慢的水位上升速度限制了西来稗种子的水媒传播和扩散距离，从而有利于西来稗种子的耐淹能力发生种内分化。
关键词:
种内分化,
种子耐淹能力,
水文情势,
种子扩散,
一年生植物,
三峡水库
