水分胁迫对黄河三角洲河口湿地芦苇光合参数的影响

Effects of water stress on photosynthetic parameters of Phragmites australis in estuarine wetland of Yellow River Delta

通过盆栽试验,分析了多梯度土壤水分条件对黄河三角洲河口湿地淡水沼泽芦苇快速生长期叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)、水分利用效率(WUE)和光能利用效率(LUE)等光合参数的影响,探讨淡水沼泽芦苇正常生长发育适宜的土壤水分条件.结果表明:淡水沼泽芦苇的Pn、Tr、WUE及LUE对土壤水分的变化有明显的响应阈值.渍水状态不是淡水沼泽芦苇生理状态最好的水分条件.维持淡水沼泽芦苇快速生长期正常生长,适宜的土壤体积含水率(Wv)应大于25.7%(即相对含水率Wr>66.6%),最佳Wv为36.9%(Wr为95.6%),正常生长所允许的最低土壤含水率Wv为21.5%(Wr为55.7%).气孔限制是淡水沼泽芦苇对水分胁迫的主要响应机制.干旱胁迫下,淡水沼泽芦苇的最大净光合速率(Pnmax)和表观量子效率(AQY)均显著下降,其暗呼吸速率(Rd)降低,减少呼吸作用对光合产物的消耗,提高WUE,以维持较高的光合速率.

A pot experiment was conducted to study the effects of soil water content on the net photosynthetic rate （Pn） , transpiration rate （Tr ） , stomatal conductance （Gs） , intercellular CO2 concentration （Ci）, water use efficiency （ WUE）, and light use efficiency （LUE） of fresh water swamp Phragmites australis from estuarine wetland of Yellow River Delta, with the appropriate soil water condition approached. The results showed that the Pn, LUE, Tr, and WUE of fresh water swamp P. australis had obvious response thresholds on the alteration of soil water content. Waterlogged status was not the optimal water condition for fresh water swamp P. australis. To maintain the normal growth of fresh water swamp P. australis during its fast growth period, soil volumetric water content （ Wv ） should be above 25.7% （ i. e. , relative water content Wr 〉 66. 6% ）, optimal Wv should be 36.9% （i. e. , Wr=95.6% ）, and the most deficient degree of Wv should be about 21.5% （i. e. , Wr = 55.7% ）. Stomatal limitation was the main tolerance mechanism of fresh water swamp P. australis under water deficit. Under drought condition, the maximum net photosynthetic rate （Pn max ） and apparent quantum yield （AQY） of fresh water swamp P. australis declined obviously. In the meanwhile, fresh water swamp P. australis could reduce its dark respiration （Rd ） to decrease the consumption of photosynthetic products, and improve its water use efficiency （WUE） to keep high photosynthetic rate.