三种牧草对干旱胁迫的生理响应及抗旱性评价

摘要

为了解不同牧草对干旱胁迫的响应，筛选抗旱性强的牧草种类，试验选用扁穗牛鞭草、高丹草和拉巴豆为材料，盆栽研究了水分胁迫对牧草生长的影响及其生理反应。结果表明，牧草对干旱的响应因牧草种类和生理指标不同而异。随着旱情加剧，3种牧草的生物量持续降低，最大降幅可比对照降低18．29％（牛鞭草）、31．21％（高丹草）和33．55％（拉巴豆）。但是，轻、中度干旱对牛鞭草和高丹草的根系生长影响较小，根冠比增加。牧草地上部生物量减少有益于降低水分消耗，根冠比增加使相对更多的根系参与水分和养分吸收。干旱导致细胞膜破坏，丙二醛含量提高，胞内物质外渗，电导率增加，叶绿素和根系活力降低，进而抑制牧草生长。在干旱条件下，牧草体内的脯氨酸是对照的1．3～8．1倍，可溶性糖和蛋白质含量显著提高，产生渗透调节。干旱还能诱导激活牧草体内的超氧化物歧化酶、过氧化物酶和过氧化氢酶，促进消除游离氧自由基，减轻干旱危害。采用隶属函数法综合评价牧草的抗旱性表明，扁穗牛鞭草的抗旱性最强，拉巴豆次之，高丹草最差。%The aim of this study was to evaluate the drought stress responses of various forages and to select forage cultivars with high drought resistance.A pot experiment was carried out to study the effects of drought stress on the growth and physiology of Hemarthria compressa ,Sudangrass (a Sorghum hybrid),and Dolichos lab lab .The drought responses,as measured using various physiological indices,differed among the three for-ages.The biomass of the three forages continuously decreased as the duration of the drought treatment extend-ed.The maximum decrease in biomass under drought,as compared with their respective controls,was 18.29% for H .compressa,31.21% for Sudangrass,and 33.55% for D .lab lab .Light and medium drought treatments had little effect on the root growth of H .compressa and Sudangrass,but increased their root:shoot ratios.The decrease in shoot biomass under drought reduced water consumption,and the increased root:shoot ratios increased the water and nutrition absorption capacity of the plants.The drought treatments damaged cell membranes and increased the malondialdehyde content,resulting in leakage of intracellular materials,increased relative electric conductivity,reduced chlorophyll content,and lower root activity,all of which inhibited growth of the three forages.Under drought stress,the proline content in tissues of the three forages was 1.3-8.1 times that in their respective controls,and there were significant increases in soluble sugar content and sol-uble protein content,which aided osmotic adjustment.The drought treatments also promoted the activity of antioxidant enzymes (superoxide dismutase,peroxidase,and catalase)in the three forages.The increased an-tioxidant enzyme activities helped to eliminate free oxygen radicals to mitigate drought damage.A comprehen-sive evaluation of the drought resistance of the three forages using the membership function method ranked their drought resistance,from strongest to weakest,as follows:H .compressa>D .lab lab >Sudangrass.