旱生芦苇对地下水位变化的生态响应及适应机制

地下水作为干旱半干旱地区可利用水的主要存在形式,是影响植被生存的主要生态因子。通过人工模拟地下水位,探讨了旱生芦苇对不同地下水位的生态响应及适应机制。结果表明:(1)随地下水位的降低,旱生芦苇净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)和胞间CO_2浓度(C_i)均呈先增后减的变化趋势,其生长季均呈单峰曲线,以7—8月为峰值;(2)旱生芦苇叶绿素(Chl)含量随地下水位的降低呈先增后减的动态变化;(3)旱生芦苇脯氨酸(Pro)、可溶性糖(SS)和可溶性蛋白质(SP)含量随地下水位及其生长季的变化规律不一致,但三者在抑制干旱胁迫过程中存在相互补偿的关系;(4)随地下水位的降低,丙二醛(MDA)含量呈先增后减的变化趋势,且随生长季变化增加显著;超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性增加显著,且SOD比CAT对干旱胁迫反应更敏感,是适应干旱胁迫的主要抗氧化酶;(5)旱生芦苇生理因子对P_n的重要性大小顺序为G_sSPChlT_rC_iSS。

Ecological response and adaptation mechanism of Phragmites australis to changes in groundwater level

Groundwater, as the main form of available water in arid and semi-arid areas, is the primary ecological factor affecting the survival of vegetation. In this paper, the ecological response and adaptive mechanism of Phragmites australis under different groundwater levels were discussed using artificial simulation of groundwater levels. The results showed that with a decrease in groundwater level:(1) Net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), and intercellular CO₂ concentration (C_i) tended to increase first and then decrease, and the growth season exhibited a single peaked curve, which peaked from July to August; (2) Chlorophyll (Chl) content increased first and then decreased; (3) The change in proline (Pro), soluble sugar (SS), and soluble protein (SP) content, the osmolytes of cells in P. australis, was inconsistent with the variation in groundwater levels and the growing season, but there was a mutual compensation relationship among them in the process of inhibiting drought stress; (4) Malon dialdehyde (MDA) content exhibited a trend of first increasing and then decreasing, and the growth season was significantly increased; superoxide (SOD) and catalase (CAT) activity increased significantly; and SOD was more sensitive than CAT to drought stress, which is the main antioxidant enzyme that adapts to drought stress; (5) For P. australis, the order of importance of its physiology factors to P_n was G_s > SP > Chl > T_r > C_i > SS.