不同地下水埋深下胡杨枝条水力导度及其季节变化

植物水力结构和功能的调整是植物适应环境水分变化的重要途径。通过观测新疆塔里木河沙雅河段垂向距离河道0.01 km、3 km和40 km处3个观测点不同地下水埋深,分析胡杨枝条水力导度及水势等相关水力结构参数的季节变化。结果表明:各观测点胡杨枝条平均导水率损失百分比数(PLC)均高于60%,各观测点之间无显著差异,表明受高蒸腾压力的区域环境影响,胡杨枝条木质部普遍存在较高程度的栓塞;低地下水埋深观测点胡杨比导率(Ks)、叶比导率(Kl)均显著增加,但枝条导水面积与叶面积之比(Hv)显著低于高地下水埋深观测点,表明胡杨主要通过提高Kl控制植物体内水势梯度,以适应深地下水条件,同时Kl增加主要受Ks增加影响,而非Hv;近河道浅地下水条件下,胡杨枝条导水功能受地下水季节波动影响明显,而远离河道深地下水条件下,主要受植物生长物候影响。

Hydraulic Conductivity and Its Seasonal Variation of Populus euphratica Shoot at the Sites with Varying Groundwater Depths

Adjustment of hydraulic structure and function plays a key role in plant acclimation to the variation of water regime.In this study, the seasonal variation of hydraulic conductivity and its related parameters of Populus euphratica shoot was observed at 3 sites along the Kayar reach in the upper reaches of the Tarim River.The sites were 0.01,3 and 40 km away from the watercourse, respectively, where the groundwater depth became deeper with the increase of distance away from the watercourse.The results showed that the averaged percentage loss of hydraulic conductivity (PLC) at all the sites was higher than 60％, and there was no significant difference between the sites,which revealed that there was a high cavitation in plant vessel under the high transpiration pressure in the study area.The xylem specific conductivity (Ks) and leaf specific conductivity (Kl) at the site with the deepest groundwater level were significantly increased, indicating an improved water use efficiency in leaves, on which the water potential gradient in plant could be lessened under water deficit.The ratio between sap area and leaf area (Hv) suggested that the Kl increase was driven by Ks rather than Hv.The seasonal variation of shoot hydraulic function was more subject to seasonal groundwater fluctuation at the site with shallow groundwater level,whereas to plant growth phenology at the site with deep groundwater level.