干旱对梭梭水力性状及生理生化特性的影响

Effects of drought on hydraulic traits and physio-biochemical characteristics of Haloxylon ammodendron

以荒漠优势种梭梭(Haloxylon ammodendron)为对象,基于2017年在新疆古尔班通古特沙漠南缘布设的降水量变化(减少100%和对照)的野外原位实验,开展了连续3年干旱处理下梭梭茎的水力特性以及同化枝(叶片)生理生化特性的研究。结果表明:干旱处理对梭梭茎的水分传输效率(比导水率、叶比导水率)、栓塞程度以及枝叶性状并没有产生显著影响。干旱处理下,梭梭通过显著提高同化枝脯氨酸和可溶性蛋白含量来维持其渗透压,提高保水能力;同时,通过显著提高超氧化物歧化酶和过氧化氢酶活性使丙二醛含量维持在较低的水平。相关性分析结果表明,梭梭茎的比导水率与栓塞程度呈显著负相关,与比叶重呈显著正相关;木材横截面积与叶比导水率和栓塞程度呈显著正相关。由此可见,梭梭主要通过增加渗透调节能力和保护酶活性协同抵御干旱胁迫,以维持正常的生理活动,而较高的自然栓塞程度可能也是梭梭长期在荒漠区极端干旱生境中所形成的一种耐旱策略。

Haloxylon ammodendron is a dominant desert species. A three-year experiment of precipitation treatments(100% reduction and control) was conducted in the southern margin of the Gurbantunggut Desert, Xinjiang, to examine the changes of stem hydraulic traits and physio-biochemical characteristics of H. ammodendron. Our results showed that drought did not affect water transport efficiency(specific hydraulic conductivity, leaf-specific hydraulic conductivity), embolism degree, and branch and leaf traits of H. ammodendron. Under drought stress, H. ammodendron maintained osmotic pressure and improved water holding capacity by increasing the contents of proline and soluble protein. Meanwhile, the content of malondialdehyde was kept at a low level by significantly increasing the activities of superoxide dismutase and catalase. The results of correlation analysis showed that stem specific hydraulic conductivity of H. ammodendron was significantly negatively correlated with embolism degree and positively correlated with specific leaf weight, while wood cross-sectional area was significantly positively correlated with leaf-specific hydraulic conductivity and embolism degree. It is concluded that H. ammodendron could resist drought stress and maintain normal physiological activities by increasing osmotic regulation ability and protective enzyme activity. High degree of natural embolism could also be a drought tolerant strategy of H. ammodendron in extreme arid habitats of desert areas.