中文摘要：

以多枝柽柳幼苗为研究对象,设置4个不同地下水位（U1、U2、U3和U4,分别距离地面为1、2、3、4m）,研究不同地下水位处理对多枝柽柳幼苗光合作用和抗逆性的影响.结果表明：随着地下水位的下降,多枝柽柳幼苗的表观量子效率、暗呼吸速率、羧化效率、光呼吸速率、最大净光合速率均下降,且对有效光合辐射和CO2浓度的利用范围减小,U1最大净光合速率为25.24（±4.95） μmol/m2·s,U4最大净光合速率下降了88.99％,下降到2.78（±0.11）μmol/m2·s;地下水位下降导致幼苗气孔导度下降,水分利用效率提高;CO2加富降低了幼苗气孔导度,但显著提高了水分利用效率;随着地下水位的下降,幼苗叶绿素含量显著下降、MDA积累,U2、U3、U4的叶绿素含量分别比U1下降4.6％、14.14％、30.85％,MDA升高165％、256％、225％,干旱胁迫逐渐加剧,而多枝柽柳幼苗通过提高脯氨酸、可溶性糖含量以及超氧化物歧化酶（SOD）、过氧化物酶（POD）活性等调控物质来适应干旱胁迫所带来的影响.

英文摘要：

Saplings of Tamarix ramosissima were planted in pots with simulated water tables （U1, U2, U3 and U4） of depth 1, 2, 3, 4 m, respectively, to study the impacts of water tables on the photosynthetic characteristics and stress tolerance of T. ramosissima. The results showed that the apparent quantum yield, dark respiration rate, carboxylation efficiency, photorespiration rate and maximum net photosynthetic rate decreased, in addition, the using range of effective photosynthetic radiation and CO2 concentration reduced with water table lowering. The maximum net photosynthetic rate of U1 was 25.24 （±4.95） p.mol/m2·s, and the maximum net photosynthetic rate of U4 reduced by 88.99%, down to 2.78 （±0.11） μmol/m2·s. Also, stomatal conductance of saplings declined and water use efficiency increased with water table lowering; CO2 enrichment reduced stomatal conductance of saplings, but significantly improved water use efficiency. With water table lowering, chlorophyll content of saplings significantly decreased and MDA accumulated. Compared to U1, the chlorophyll contents of U2, U3 and U4 decreased by 4.6%, 14.14% and 30.85%, MDA increased by 165%, 256% and 225%. Drought stress increased gradually, however, T. ramosissima adapted to the effects of drought stress by improving regulating materials like proline, soluble sugar content and SOD, POD activity etc.