Abstract:

Populus euphratica Oliv., an established species in the Tarim Desert Area, was used to investigate variations in osmoregulatory substances and antioxidant enzyme activities of three typical heteromorphic leaves along the groundwater depth (GWD) gradient as well as differences in their adaptive strategies to drought stress. Results showed that: (1) with the increase in GWD, the relative water content, leaf water potential, soluble protein (SP) content, and peroxidase (POD) activity of the three heteromorphic leaves of P. euphratica showed a decreasing trend, while the water saturation deficit, free proline (Pro) content, soluble sugar (SS) content, and malondialdehyde (MDA) content showed an increasing trend, and superoxide dismutase (SOD) maintained high and stable activity. (2) The Pro and SS contents in lanceolate leaves showed a highly significant positive correlation with GWD, the SS and SP contents in oval leaves showed a significant positive correlation with GWD, and the SS content in serrated broad-oval leaves showed a highly significant positive correlation with GWD. (3) The lanceolate leaves maintained cellular osmotic potential through the synergistic action of Pro and SS to cope with water stress, oval leaves enhanced drought resistance through osmotic adjustment (SP, Pro, SS), and serrated broad-oval leaves maintained cellular expansion pressure with SS and Pro, while eliminating reactive oxygen species (ROS) through POD and SOD, which synergistically adapted to increasingly arid desert environments.

摘要：

以塔里木荒漠区建群种胡杨（Populus euphraticaOliv.）为实验材料，研究3种典型异形叶的渗透调节物质和抗氧化酶活性沿地下水埋深（GWD）梯度的变化规律及适应干旱胁迫的策略。结果显示：（1）随GWD的增加，3种异形叶的相对含水量、叶水势、可溶性蛋白质（SP）含量和过氧化物酶（POD）活性呈降低趋势，水分饱和亏缺、游离脯氨酸（Pro）含量、可溶性糖（SS）含量和丙二醛（MDA）含量呈增加趋势，而超氧化物歧化酶（SOD）始终保持较高活性且较稳定。（2）条形叶Pro、SS含量与GWD呈极显著正相关，卵形叶SS、SP含量与GWD呈显著正相关，锯齿阔卵形叶SS含量与GWD呈极显著正相关。（3）条形叶主要以Pro和SS协同维持细胞渗透势以应对水分胁迫，卵形叶以增强渗透调节能力（SP、Pro、SS）来提高其抗旱性，锯齿阔卵形叶则以SS、Pro维持细胞膨压，并通过POD、SOD清除活性氧（ROS）协同适应干旱的荒漠环境。