水分胁迫及复水过程4种牧草形态及其生理特征表达

草地作为半干旱区的主要植被类型之一,开展牧草对土壤水分变化响应机制的研究,对于该地区水资源的可持续利用和生态环境的建设均有重要意义。本文以选取半干旱区4种典型牧草作为研究对象,在对其进行干旱及旱后复水处理模拟自然降水过程的基础上,分析牧草的形态、水分生理、光合生理等特征对土壤水分变化的响应,结果表明：① 水分胁迫下牧草地上形态指标（单叶面积、地上干重）呈显著的下降趋势,而地下形态指标（地下干重、根冠比）则反之;复水结束后,牧草形态特征指标有明显的恢复,披碱草(Elymus nutans Griseb.)和黑麦草(Lolium multiflorum Lam.)出现了超补偿效应。② 水分胁迫下牧草水分生理特征表现为明显的下降趋势,复水后逐渐恢复,复水14~21 d后基本恢复对照组水平。干旱条件下,2种豆科牧草能维持较高的水势,属于高水势延迟脱水型;而禾本科牧草属于低水势忍耐脱水型。③ 水分胁迫下,牧草光合生理特征也表现为明显的下降趋势,轻微水分胁迫能够暂时提高豆科牧草光合能力;豆科和禾本科牧草叶片光合特性对干旱的响应机制存在一定的差异,面对干旱胁迫,豆科牧草通过及时关闭气孔来减少水分散失,而禾本科牧草通过延缓气孔关闭牺牲叶片水分的方式维持正常生长。

Expressions of Morphological and Physiological Features of 4 Forage Species under Water Stress and Re-watering Process

Grasslandis one of the main vegetation types in semiaridarea. Research on theresponse and mechanism of forage to soil moisture content is of greatsignificance for the sustainable utilization of water resources and theconstruction of ecological environment inthis area. In this study, four grass species, response of forage morphology, waterphysiology, photosynthetic and physiological characteristics to water stressand water recovery process in the Loess Plateau were analyzed. The resultsshowed that:① Under water stress,the aboveground morphological indexes (i.e., the single leaf area and shoot dryweight) of the grass species were in a decrease trend, but the underground ones (i.e., the root dry weight and root-shootratio) were in an increase trend. After re-watering, the forage morphologicalcharacteristics were obviously recovered, and an over compensation of Elymusnutans Griseb. and Loliummultiflorum Lam. occurred;② Under water stress, the water physiological characteristics of forage weresignificantly decreased, but they were gradually recovered after re-wateringand resumed to the level of the control group after 2~3 weeks. These 2 speciesof leguminous forage could maintain a high water potential and had a strongwater conservation capability, which belonged to a delayed dehydration byincreasing water potential, and these 2 species of forages belonged to an enduringdehydration by developing low water potential under water stress; ③ Under water stress, the photosynthetic physiological characteristics of foragewere also in a significant decrease trend, and the short-term water stresscould temporarily improve the photosynthetic capacity of forage; thephotosynthetic characteristics of legumes and grasses were different insensitivity and adaptation mechanism to drought. Leguminous forage closed thestomata in time to avoid drought so as to reduce water loss, while grassessacrificed leaf water to keep stomata open to maintain normal plant growth.