不同浇水量对毛乌素沙地沙柳幼苗气体交换过程及其光化学效率的影响

EFFECT OF DIFFERENT WATER SUPPLY ON GAS EXCHANGE PROCESSES AND PHOTOCHEMICAL EFFICIENCY IN SALIX PSAMMOPHILA SEEDLINGS IN THE MAOWUSU SANDLAND

利用毛乌素沙地优势灌木沙柳 (Salix psammophila)幼苗 ,研究气体交换及其 PS 的光化学效率对 4种浇水量响应。结果表明 :不同浇水量明显影响沙柳幼苗净光合速率、蒸腾速率、气孔导度、胞间 CO2 浓度和叶片温度日变化动态 ;除幼苗叶片温度随着浇水量的增加而降低外 ,其它以上因素均随浇水量的增加而增大。浇水量少时 ,幼苗净光合速率明显有“午睡”现象 ,而充足浇水能有效消除幼苗净光合速率的“午睡”现象 ;浇水量增加降低了沙柳幼苗光补偿点 ,提高了饱和光强和表观量子效率 ;浇水量显著影响幼苗的 PS 光化学效率 ,随着浇水量减少 ,幼苗的最大荧光、可变荧光、最大荧光比和最大光化学效率逐渐减小。相关分析反映了在不同施水量处理下 ,环境因子光合有效辐射、大气温度、大气饱和水汽压差及其生理变量气孔导度、叶片温度、胞间 CO2 浓度均显著影响幼苗净光合速率。

The effect of four different water supply levels on the gas exchange processes and photochemical efficiency in PSⅡ were investigated in seedlings of Salix psammophila , a dominant shrub in the Maowusu arid sandy region. Increasing water supply levels had a strong influence on diurnal changes in photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO 2 concentration (all increasing) and leaf temperature (decreasing) of the seedlings. The photosynthetic rate of seedlings showed a strong midday depression under low water supply but not under full water supply. Increasing water supply decreased the light compensation point and enhanced the saturation light and apparent quanta efficiency. Water supply significantly influenced photochemical efficiency in PSⅡ: maximal fluorescence, variable fluorescence, maximal fluorescence ratio and maximal photochemical efficiency all decreased with declining water supply. Correlation analysis showed that meteorological variables, such as photosynthetic active radiation, air temperature, air saturated water vapour pressure difference, and physiological variables, such as stomatal conductance, leaf temperature, intercellular CO 2 concentration, significantly affected the photosynthetic rates of the seedlings under varying water supply conditions.