极干旱胁迫对雀麦、多年生黑麦草生长和体内水分的影响

The Effects of Extreme Drought Stress on Growth and Water Content in Pasture Brome and Perennial Ryegrass

为研究极端干旱对牧草生长的影响,选择多年生黑麦草(Lolium perenne,Lp)和雀麦(Bromus valdivianus,Bv)给予80%~85%植物有效水(Plant available water,PAW)和20%~25%PAW 2种水分处理,分析两种牧草生长及体内水分状况对干旱胁迫的响应。研究表明:80%~85%PAW充足水分下,两种牧草生物量积累、水势(Water potential,WP)、相对含水量(Relative water content,RWC)和净光合速率(Net photosynthetic rate,Pn)无明显种间差异。Bv叶片宽而重,蒸腾速率(Transpiration rate,Tr)、CO_(2)总导度(Total conductance to CO_(2),CndCO_(2))和气孔导度(Conductance to H 2O,Gs)显著高于Lp。而Lp分蘗多、叶多汁,瞬时水分利用效率是Bv的1.63倍。20%~25%PAW对两种牧草生长影响不完全一致,叶饱和重、干重和叶面积有相反变化趋势,但与充足水分相比差异不显著;Pn,Tr,CndCO_(2),Gs和RWC则极显著降低,WP极显著降低了1.60 MPa,致使枯叶占比和叶温差显著升高。总之,雀麦和多年生黑麦草生长相近,水分利用模式不同;遭受极端干旱,不同种的两种牧草耐旱机制具有一定的共性,通过增强叶片持水力、降低水分循环、减少蒸腾失水以提高牧草抗旱性。

In order to study the effects of extreme drought on growth of forage grasses,perennial ryegrass(Lolium perenne,Lp)and pasture brome(Bromus valdivianus,Bv)were used as materials in pot experiment.80%-85%plant available water(PAW)(well watered)and 20%-25%PAW(extreme drought)were applied to analyze adaptive changes of growth and responses to water status in forage grasses to drought stress.The results indicated that:1)Under 80%-85%PAW,there were no dramatic differences between Bv and Lp in biomass accumulation,water potential(WP),relative water content(RWC)and net photosynthesis rate(Pn).However,Bv had larger and heavier blade than Lp and its transpiration rate(Tr),total conductance to CO_(2)(CndCO_(2))and conductance to H 2O(Gs)were markedly higher than those in Lp.While Lp had slender,juicy blades and more tillers,instantaneous water use efficiency(iWUE)of Lp was 1.63 times of Bv.2)Under 20%-25%PAW extreme drought,the growth of two forage grasses were not completely consistent,leaf turgid weight,dry weight and blade area showed opposite trend,but were not significant difference compared to that of the well watered condition.Pn,Tr,CndCO_(2),Gs and RWC in Bv and Lp observably decreased,especially WP reduced by 1.60 MPa,which resulted in dead blade ratio and blade temperature difference increasing.In conclusion,Bv and Lp had similar growth characteristic in biomass accumulation and different water use models.When suffering extreme drought,two forage grasses from different species,their drought tolerance mechanism having some commonalities,improved their drought resistance by enhancing blade water retention,reducing water recycle and cutting down transpiration water loss.