Study On Water-Consumption Characteristic And Drought-Resistance Mechanism Of Three Pastures

The pot expriment was carried out to study the characteristics of water consumption and drought-resistance physiology,water use efficiency,plant growth and biomass in Bromus inermis leyss., Onobrychis viciaefolia Scop and Coronilla varia L. under three different drought stress treatment,which are the suitable soil moisture,that is 70%-75% of maximum field capacity,the moderate soil moisture,that is 50%-55% of maximum field capacity and the severe soil moisture,that is 35%-40% of maximum field capacity.The comprehensive evaluation was conducted aimed at providing the theoretical foundation to the plant restoration in Loess plateau.1. Differences exist among three pastures in the characteristic of water comsumption.The water consumption of three pastures were significantly different among each treatment, in the order of CK>MD>SD.The water consumption of three pastures under the same treatment were different,too,in the order of Coronilla varia>Onobrychis viciaefolia>Bromus inermis under CK and MD,but the water consumption of Onobrychis viciaefolia was less than the other two pastures under SD.The daily water consumption of three pastures were almost consistent with each other,the distribution proportion of them were almost the same in ten-days period and monthly.The peaks of water consumption under each treatment were in the last ten days of June or the second ten days of July,which decreased gradually after then.There were differences among three pastures in water consumption diurnal courses,the Onobrychis viciaefolia and Coronilla varia was mono peak type while the Bromus inermis double peak type.2. Great changes had happened in the physiological indexes ralating to drought-resistence of three pastures under soil drought stress.The results showed that the relative water content decreased with the stress time,but the falling ranges were different,which was in the order of CK>MD>SD under each treatment.While the water saturation deficit increased with the stress time.There were differences among three pastures in leaf water conservation capacity,which of Bromus inermis is better than the other two pastures.A large quantity of osmoregulation substances were accumulated under soil drought stress,at the mean time,the MDA and superoxide anion free radical content of three pastures increased with the stress time,but significant differences among three pastures and each treatment in the value of superoxide anion free radical content.The trends of antioxidant enzyme activities in three pastures were similar,which increased with the stress time and the antioxidase activities under stress were higer than the control.The chlorophyll of three pastures under stress showed great fluctuation,carotenoid content increased with the stress time generally.The value of Chla/b increased at some time points as well as the value of Car/Chl increased with the stress time.In the end, by subordinate function analysis, the capacity of drought resistence of three pastures decrease in order of Bromus inermis> Onobrychis viciaefolia>Coronilla varia.3. The soil drought stress had significant influences on the growth of three pastures,which grew well under control,but the growth rate decreased under moderate drought stress and serious inhibited under severe drought stress.The soil drought stress depressed the plant height,root lengh,leaf area and biomass,but the root-shoot ratio inceased under stressed treatment in the order of SD>MD>CK.Differences existed amony three pastures in water use efficiency,the WUE in Bromus inermis decreased with the aggravation of drought stress,while the WUE in Onobrychis viciaefolia and Coronilla varia under MD with the highest.