水分对胡杨幼苗光合及生长特性的影响

采用盆栽控制实验方法对不同水分条件下胡杨幼苗的光合日变化以及生长特性进行分析研究.结果显示:(1)不同水分条件下胡杨幼苗的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)日变化曲线均呈单峰型,峰值时间均在12:00;当土壤含水量为21.6%～24.0%时,幼苗的水分利用效率(WUE)日变化曲线呈不明显的双峰型,峰值时间分别在8:00和18:00,其他处理均为单峰型,但峰值时段有差异;随着土壤含水量的减小,胡杨幼苗的Pn、Gs、Ci和Tr日均值逐渐降低,当土壤含水量为12.0%～19.2%时,幼苗的WUE日均值显著高于其他处理.(2)幼苗的株高、基径、各器官的生物量及总生物量均随土壤含水量的减小而降低,当土壤含水量为12.0%～19.2%时,幼苗地下生物量的降低程度大于地上生物量,且幼苗的根冠比也增大.研究表明,土壤含水量对胡杨幼苗的光合特性及其生长具有显著影响,当土壤含水量大于12.0%时,幼苗能够通过增大水分利用效率,改变根冠比提高抗旱性;当土壤含水量小于9.6%时,幼苗自我调节能力减弱,生长受到抑制.

Photosynthetic Characteristics and Growth of Populus euphratica Seedlings with Water Stress

The effects of water stress on the photosynthesis and growth characteristics of Populus euphratica seedlings were studied by pot experiment in Aksu Water Balance Station,CAS.The results indicated that the daily curve of the net photosynthetic rate (Pn),stomatal conductance (Gs) ,intercellular CO2 concentration (Ci) and transpiration rate(Tr) were hardly influenced by water stress.All of the daily change curve of Pn,Gs,Ci and Tr showed single-peak,and the peak time of Pn,Gs,Ci and Tr of the daily curve were at 12:00.As soil water content was in the range of 21.6%～24.0%,the water use efficiency (WUE) of seedlings was not obvious double-peak curve,the peak time of WUE of the daily change curve was at 8:00 and 18:00,respectively.Others showed single-peak type,while the peak times were different.The daily average value of Pn,Gs,Ci and Tr of seedlings decreased with the soil water content decreasing.As soil water content was in the range of 12.0%～19.2%,the daily average value of the WUE was the highest.The height,stem diameter,biomass accumulations of different organs and the total biomass of seedlings reduced significantly with the decreasing of soil water content.As soil water content was in the range of 12.0%～19.2%,the decreased degree of aboveground biomass of seedlings was higher than the underground biomass,and the root-shoot ratio (R/T) was increased obviously.The photosynthetic and growth were effected obviously by different water treatments.When the soil water content was higher than 12.0%,the seedling drought tolerance was increased with the increasing of WUE and the changing of root-shoot ratio.In the condition of the soil water content lower than 9.6%,the regulating ability of seedlings was decreased,therefore the growth of seedlings was inhibited.