水分胁迫条件下草莓克隆分株间水分调控及其对光合功能的影响

以盆栽草莓(Fragaria×ananassa)为材料研究了水分胁迫下克隆植物草莓母株和子株间的水分调控机制及其与碳同化、光系统Ⅱ激发能分配的关系.实验材料分为匍匐茎连接和剪断两个大组,进行两步实验.第1步实验,对连接组和剪断组的所有母株控水,子株充分供水;4d后进入第2步实验,把连接组分为两小组,对其中一组充分供水子株开始控水,另一组保持不变.结果表明,土壤干旱引起母株叶片失水,并使其净光合速率和气孔导度显著降低.但是连接组中供水良好的子株能有效缓解缺水母株的水分胁迫.当供水良好的子株也开始受到干旱处理的时候,则会加剧与之相连母株的水分胁迫.受胁迫母株可以通过加强渗透调节能力和降低水势从相连子株获取水分.虽然土壤干旱会造成受胁迫母株叶片脱落酸(abscisic acid, ABA)含量的大幅度增加,但是与之相连子株的叶片ABA含量并没有增加;并且气孔导度与ABA变化趋势一致.(1)草莓母株和子株间的水分运输是由二者的水势差驱动的;(2)ABA不会通过匍匐茎在母株和子株间传递并影响相邻子株气孔导度;(3)在水分异质性较大情况下,生理整合可明显提高克隆系统的碳同化能力和光系统Ⅱ激发能利用效率.

The effects of water stress on water translocation and photosynthetic characteristics between clonal ramets in Strawberry

To further explore the water regulation mechanism of clonal plant and its effects on carbon assimilation and excitation energy distribution under water stress, the pair of strawberry (Fragaria×ananassa) ramets was utilized (the elder ramet was referred as mother and the other as daughter), in which the stolons between ramets was either cut (unconnected group) or left intact (connected group). At first, the daughter ramet in each pair was well watered and the mother ramet was exposed to soil water deficit. Four days later, the connected group was further subdivided into two groups, and part irrigated daughters were continually watered, and the other daughters began to suffer from soil water shortage gradually. Our results reveal that soil drying caused leaf dehydration in mother ramets and significantly decreased its photosynthetic rates and stomatal conductance. The well-watered daughter ramets in connected groups alleviated the water stress in mother ramets effectively. When the well-watered daughter ramets in the connected group began to dry gradually, the water stress of their connected mother ramets was significantly aggravated. Water uptake of stressed mother ramet was dependent on the decrease in water potential and enhancement of osmotic adjustment of its own. Though soil drying resulted in a substantial accumulation of ABA in water stressed ramets, but there was no ABA increasing in connected ones. And the stomatal conductance had the similar changing tendency with leaf ABA content. Accordingly, we concluded that: (1) Water translocation between the connected ramets may be determined by the gradients in water potential;(2) ABA produced in water-stressed ramet could not be delivered to the adjacent and connected ramet and affect its stomatal behavior;(3) Under heterogeneous wet conditions, water physiological integration between clonal ramets would significantly improve the carbon assimilation of entire clonal system and excited energy utilizing efficiency of PSⅡ.