Abstract

Aims

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.

Methods

We collected seeds of E. crusgalli var. zelayensis from different populations in the TGR shores, and then placed them at four elevations in the shores flooded by reservoir impoundment. Parameters reflecting seed flooding tolerance including post-flooding percentage of intact seeds, seed germinability and seedling emergence rate were investigated for the seeds from different populations and undergoing flooding of different intensities. Floating time of seeds and speed of water level rise during impoundment were examined, and used to quantify dispersal potential of seeds in the shores of the TGR when flooded.

Important Findings

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.

中文翻译：

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cru草种子浸种耐受性的种内分化。大型水库沿海拔的zelayensis种群

抽象的

目的

在一个大坝调节水库中，水文规律规律，并且整个岸上海拔都有很强的洪水坡度，居住在不同岸上海拔的植物每年都必须面对长期持续的不同强度的洪水。这种持续的压力可能导致种子内泛洪耐受性的种内分化。cru草（Echinochloa crusgalli var。）zelayensis是三峡水库（TGR）海岸的主要一年生植物，在海岸植被中起着重要的作用。这项研究的目的是检查是否间发生的洪水种子公差内分化稗草变种。泽莱族 TGR海岸的种群数量，以及这种分化是否与种子扩散较弱有关。

方法

我们收集了E. crusgalli var。的种子。zelayensis从TGR海岸不同人群，然后在岸边将它们放置在四个凸起淹没由水库蓄水。研究了来自不同种群和不同强度淹没的种子反映种子耐性的参数，包括完整种子的后淹水百分比，种子发芽率和幼苗出苗率。检查了种子的漂浮时间和蓄水期间水位上升的速度，并用于量化淹没时TGR海岸种子的扩散潜力。

重要发现

淹水后完整种子百分比和最终幼苗出苗率均随收集种子的岸上海拔的增加而显着下降，这表明在景天E. crusgalli var中已经发生了种子内水淹耐受性的种内分化。水库运行7年后，TGR海岸的斑马鱼种群数量增加。在水库蓄水期间，上升的水运走的种子的距离受到限制，这是由于种子的漂浮时间短和水库中水位上升速度较低的缘故。这将有利于种子内耐性的种内分化的发展。