Role of Na~+ in Plant Cells

众所周知，Na^+不是大多数植物的必需元素。除耐盐性研究外，有关植物细胞Na^+代谢、Na^+转运的研究几乎没有。最近，我们发现Na^+在植物生命中也可能起着重要的作用。本文主要研究Na^+在植物细胞功能中的作用。本论文主要研究了Na^+的膜转运系统、Na^+在细胞内的分布以及植物细胞对Na^+环境的识别，发现缺磷条件下轮藻细胞诱导Na^+驱动的质膜Pi吸收系统，并对其生理转运机制进行了分析。此外，我们还发现Na^+/Pi共转运系统的启动需要细胞外Na^+的存在。第二，在缺K^+条件下，Na^+通过积累在液泡中对植物的生长起着重要的作用。最后，我们发现红树林细胞在盐胁迫下液泡体积迅速增加。在这一现象中，Na^+的运输部分是通过囊泡运输进入液泡来实现的。

It is well known that Na^+ is not an essential element for most plants. Except for the salt tolerance, therewas almost no work on Na^+ metabolism, Na^+ transport in plant cells. Recently, we have found that Na^+ may play some important roles in plant life, too. In the present study, we focused roles of Na^+ in plant cell functions. We mainly investigated about Na^+ membrane transport systems, intracellular distribution of Na^+ and recognition of Na^+ environment by plant cells.We have found that under Pi deficiency, Chara cells induced Na^+ driven Pi uptake system in the plasma membrane and its physiological transport mechanism was analyzed. Furthermore, we found that the induction of Na^+/Pi cotransport system absolutely needs the presence of extracellular Na^+. Second, under K^+ deficiency, we found that Na^+ is playing an important role for plant growth by being accumulated in the vacuole. Lastly, we found the vacuolar volume quickly increased when mangrove cells are exposed to the salt stress. In this phenomenon, Na^+ transport was partly mediated with the vesicle transport into the vacuole.