Abstract:

To investigate the influencing mechanism of CO₂ concentration on the drought resistance and water use efficiency of tall fescue, the physiological characteristics, water use efficiency and main contribution factor of tall fescue were analyzed by controlling soil moisture conditions and atmospheric CO₂ concentration in the experiment. The major influencing factor of transpiration rate and net photosynthetic rate were also analyzed in the study. The results showed that high atmospheric CO₂ concentration had compensation effect on the negative effects of drought stress and improved the drought resistance of tall fescue. In the meantime, it was found that atmospheric CO₂ concentration was the main environmental factor of affecting the water use efficiency of tall fescue under the interaction of high atmospheric CO₂ concentration and drought stress. Both the net photosynthetic rate and transpiration rate of tall fescue were mainly affected by stomatal restrictive factors. There was linear relationship between stomatal conductance and transpiration rate when high atmospheric CO₂ concentration interacted with drought stress, and R² exceeded 0.97. In addition to the influence of stomatal conductance, chlorophyll content and intercellular CO₂ concentration were also significantly related with net photosynthetic rate. So the net photosynthetic rate is the result of combined effects of a few factors.

Key words: Tall fescue, CO₂ concentration, Drought stress, Drought resistance, Water use efficiency

摘要：

为探明CO₂浓度对高羊茅(Festuca arundinacea)抗旱性及水分利用效率的影响机制,通过控制土壤水分及大气CO₂浓度条件获得不同生境中高羊茅的生理光合参数,利用对比和统计分析的方法研究高羊茅的生理特征变化,并对影响高羊茅水分利用效率、蒸腾速率、净光合速率变动的主要环境因子进行了甄别与分析。结果表明:高大气CO₂浓度对干旱胁迫给高羊茅带来的负效应具有补偿作用,可提高高羊茅的抗旱性;在高大气CO₂浓度和干旱胁迫的交互作用下,影响高羊茅水分利用效率的主要环境因子是大气CO₂浓度,而该效应产生的主要原因是蒸腾作用的减弱;高羊茅的净光合速率及蒸腾速率主要受气孔导度等限制因素的影响。在高大气CO₂浓度和干旱胁迫交互作用时,蒸腾速率与气孔导度成线性关系,且R²超过0.97;而净光合速率除受气孔导度影响外,还与叶绿素含量及胞间CO₂浓度关系显著,是多种因素综合作用的结果。

关键词: 高羊茅, CO₂浓度, 干旱胁迫, 抗旱性, 水分利用效率