水分胁迫条件下白榆光合与蒸腾特性对光的响应

在不同水分胁迫条件下，即对照组（含水量90％）、轻度干旱胁迫（含水量70％）、中度干旱胁迫（含水量50％）和重度干旱胁迫（含水量40％），以1a生白榆（Ulmus pumila）为试验苗木，分1800、1000、500、200、50和0μmol·m^-2·s^-1 6个光照强度，利用LI-6400测定白榆幼苗的光合速率、蒸腾速率和水分利用率，探讨白榆的光合特性和蒸腾特性对光强的响应。试验结果表明：不同水分梯度下白榆的光合速率随光照强度的升高呈先上升然后逐渐趋向于平稳的趋势，蒸腾速率的变化曲线与光合速率变化曲线趋势大致相同，适度干旱胁迫下，水分利用效率有一定程度的提高，水分胁迫严重时，水分利用率开始下降。说明白榆具有抗旱能力，在比较干旱的条件下也能够很好的生长。

Responses of Photosynthesis Characteristics and Transpiration Characteristics of Ulmus pumila Species to the Light under the Water Stress Conditions

With 6 gradients of light intensity namely 1800, 1000, 500,200, 50 and 0 μmol·m^-2·s^-1 , LI - 6400 was used to measure the annum Ulmus pumila on the responses of photosynthetic characteristics, transpiration rate and water use efficiency under different water stress, which were the control group （90% moisture content）, mild drought stress （water content 70% ）, moderate drought stress （water content 50% ）, and severe drought stress （water content 40% ）. The purpose of this experiment was to discuss the photosynthetic characteristics and its response and adaptability of Ulmus pumila to the change of environment light intensity. The experiment results demonstrated that photosynthetic rate of Ulmus pumila went up and then kept stable as light intensity increased. The variation of transpiration rate and photosynthetic rate had a similar trend. Under appropriate drought stress, water use efficiency had a certain degree of improvement. But under severe water stress, water use efficiency began to decline. It was indicated that Ulmus pumila had drought resistant ability, which can grow well under arid condition.