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

通过室内生长箱内盆栽实验,比较了苜蓿和沙打旺苗期的根冠生长和水分利用对5种土壤水分环境变化的响应和差异.结果表明,充分供水下苜蓿和沙打旺苗期生物量和蒸腾效率均最高，苜蓿均显著高于沙打旺.土壤水分减少后苜蓿苗期生物量和蒸腾效率下降幅度均大于沙打旺.从低水到阶段低水处理后土壤水分逐渐降低和降低后再复水到低水处理，苜蓿和沙打旺的生物量分别较持续低水处理显著减少47.8%和27.9%.旱后复水后苜蓿根冠比和单位根量耗水量较显著增加，蒸腾效率显著下降; 沙打旺根冠比显著下降，单位根量耗水量和蒸腾效率变化不显著.

Responses of Medicago sativa and Astragalus adsurgens seedlings growth and water use to soil moisture regime

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.