Responses of Medicago sativa and Astragalus adsurgens seedlings growth and water use to soil moisture regime
苜蓿与沙打旺苗期生长和水分利用对土壤水分变化的反应

In the semi-arid area of Loess Plateau,seasonal drought often occurs during the vegetative stage of grass plants,leading to the subsequent serious reduction of their yield.Aimed to study the responses of the seedlings growth and water use of two perennial leguminous grasses Medicago sativa and Astragalus adsurgens to different soil moisture regimes,a pot experiment was installed with five treatments,i.e.,adequate water supply (HW),moderate water stress (LW),soil drying gradually from HW (DHW) and LW (DLW),and refilling water to LW after soil drying from LW (RWL).The results showed that under HW,the seedlings of both M.sativa and A.adsurgens had the highest biomass and transpiration water use efficiency (TWUE),and M.sativa had a significantly higher biomass than A.adsurgens (P<0.05).When the soil moisture content declined,M.sativa had a higher reduction rate in biomass and TWUE than A.adsurgens,and after the soil moisture regime changed from LW and DLW to RWL,the biomass of M.sativa and A.adsurgens was reduced by 47.8% and 27.9%,respectively,as compared to LW (P<0.05).At the same time,the root/shoot ratio (R/S) of M.sativa and its water consumption per unit root increased significantly,while the TWUE decreased significantly(P<0.05); but for A.adsurgens,its R/S decreased significantly (P<0.05),while the TWUE and the water consumption per unit root had no significant change.