水分胁迫对沙棘(Hippophae rhamnoides)和中间锦鸡儿(Caragana intermedia)蒸腾作用影响的比较

多年生灌木沙棘和中间锦鸡儿是黄土高原生态重建的重要物种，设计人工模拟水分胁迫实验，测量沙棘和中间锦鸡儿蒸腾作用的各种指标，研究其蒸腾特性对水分胁迫的适应方式。结果表明，同等水分处理条件下，中间锦鸡儿单叶水平上的蒸腾速率高于沙棘。沙棘和中间锦鸡儿的蒸腾速率日进程在晴天、阴雨天和生长发育的不同阶段明显不同。夜间蒸腾占全天蒸腾的比例相当大，夜间蒸腾在不同物种之间、不同供水量之间存在明显差异，而且越干旱的环境比例越大。两种植物气孔阻力的季节变化格局在不同水分处理间大体相似。沙棘的昼夜蒸腾节律在各种水分处理条件下都表现出明显的气孔振荡现象，而中间锦鸡儿没有。叶片温度、光合有效辐射和气孔阻力是各种水分条件下沙棘和中间锦鸡儿蒸腾作用的共同的限制因子，相对于沙棘，中间锦鸡儿还更多地受到空气相对湿度的影响。

The impact of water stress on transpiration indices in Hippophae rhamnoides and Caragana intermedia

Two perennial temperate shrubs, Hippophae rhamnoides Linn. and Caragana intermedia Kuang et H. C. Fu, are used extensively for ecological reconstruction in the Loess Plateau, China. In this study, a water gradient experiment was conducted to assess the ability of H. rhamnoides and C. intermedia to acclimate to water stress by measuring changes in various transpirational indices. Research results showed that transpiration rate per leaf area of C. intermedia was higher than that of H. rhamnoides under the same condition. Diurnal patterns in transpiration rate for both species differed between sunny, cloudy and rainy days, between day and night-time, and decreased in relation to drought stress. The proportion of transpiration quantity in the night-time to that in the whole day was considerable. It varied clearly with species and with water supply conditions, and furthermore, it increased with the drought degree. Seasonal patterns of stomatal resistance were similar for both species under varying degrees of drought stress. In H. rhamnoides, stomatal conductance showed a strong diurnal-nocturnal pattern and displayed oscillations. Leaf temperature, photosynthetically active radiation and stomatal resistance often limited transpiration in both species. The transpiration rate of C. intermedia was more sensitive to relative humidity than H. rhamnoides.