中文摘要：

【目的】探明CO_2浓度倍增对干旱胁迫下白羊草光合特性及非结构性碳水化合物含量的影响,为未来大气CO_2浓度升高以及干旱、半干旱地区水分亏缺等逆境下白羊草的生长提供理论依据和技术参数。【方法】盆栽试验采用裂区设计,研究了黄土丘陵区典型草本植物白羊草光合特性和非结构性碳水化合物（NSC）及其组分（可溶性糖和淀粉）的含量对不同CO_2浓度（400μmol/mol和800μmol/mol）和不同水分处理[35%~40%FC（重度干旱胁迫）、55%~60%FC（轻度干旱胁迫）和75%~80%FC（对照）]的响应。【结果】CO_2浓度倍增和干旱胁迫对白羊草光合–光响应曲线参数和NSC及其组分含量有显著影响,但2个因素之间没有显著的交互作用。CO_2浓度倍增显著提高了白羊草叶片最大净光合速率（Pmax）、表观量子效率（AQY）、光饱和点（LSP）和光补偿点（LCP）（P〈0.01）,而干旱胁迫则显著降低了Pmax、AQY和LSP（P〈0.01）。CO_2浓度倍增和干旱胁迫均提高了白羊草地上部分可溶性糖含量。在正常CO_2浓度条件下,与对照相比,轻度干旱胁迫和重度干旱胁迫均显著降低了白羊草地上部分和根系部分淀粉含量。CO_2浓度倍增使对照、轻度干旱胁迫和重度干旱胁迫处理下白羊草地上部分淀粉含量分别提高了17.4%、44.2%和18.7%,根系部分淀粉含量分别提高了17.3%、88.4%和54.4%。轻度和重度干旱胁迫均显著降低了正常CO_2浓度条件下白羊草根系部分NSC含量。CO_2浓度倍增显著提高了对照处理和轻度干旱胁迫处理下白羊草地上部分以及轻度干旱胁迫处理和重度干旱胁迫处理下白羊草根系部分NSC含量。在正常CO_2浓度下,轻度和重度干旱胁迫导致白羊草地上部分和根系部分可溶性糖含量与总NSC含量比值的显著提高。在倍增CO_2浓度下,重度干旱胁迫显著提高了白羊草地上部分可溶性糖含量与总NSC含量的比值,?

英文摘要：

【Objectives】The objective of the study was to evaluate effects of doubled CO_2 concentration and drought stress on photosynthesis characteristics and non-structural carbohydrates（NSC） of Bothriochloa ischaemum, and provide scientific basis for the growth of B. ischaemum under future elevated CO_2 concentration in arid and semi-arid areas. 【Methods】 Using the split plot design, the effects of doubled CO_2 concentration and drought stress on the photosynthesis and NSC contents in B. ischaemum were investigated. The main plot was two CO_2 concentrations（ambient CO_2 concentration, 400 μmol/mol, and doubled CO_2 concentration, 800μmol/mol）, and the split-plot was three water treatments（severe drought stress, 35%–40% field capacity（FC）,moderate drought stress, 55%–60% FC, and control, 75%–80% FC）. 【Results】 The results showed that the parameters of photosynthesis-light response curves of B. ischaemum and the NSC contents were significantly influenced by the doubled atmospheric CO_2 concentration and drought stress, while there were no significant synergetic effects between them. The doubled CO_2 concentration significantly increased the maximum photosynthetic rate（Pmax）, apparent quantum yield（AQY）, light saturation point（LSP） and light compensation point（LCP）（P〈0.01）, while the drought stress significantly decreased Pmax, AQY and LSP（P〈0.01）. The doubled CO_2 concentration and drought stress increased the soluble sugar content in the aboveground part of B.ischaemum. Under ambient CO_2 concentration, the moderate drought stress and severe drought stress significantly decreased the starch contents in the aboveground and root parts of B. ischaemum. The doubled CO_2 concentration increased the starch contents in the aboveground part of B. ischaemum by 17.4%, 44.2%, and 18.7%, respectively under the control, moderate drought stress and severe drought stress, and in the root part by 17.3%, 88.4%, and54.4%, respectively. Under ambient CO_2 concentration, the mo