The Non-hydraulic Root Sourced Signal And Osmotic Adjustment In Related To The Yield Performance In Soybean Under Drought Condition

Drought stress is a major constraint to the production and yield stability of soybean (Glycine max (L.) Merr.). Studying the drought adaptation mechanism in soybean can help us to breeding new cultivars with high drought tolerance, high yield and yield stability. We carried a pot experiment to investigate the effects of root signal and osmotic adjustment on the desiccation tolerance and the yield in soybean under drought. Four soybean cultivars breeding at different ear, zhonghuang30(ZH,2006s), jindou19(JD,2003s), huangsedadou (HD,1980s) and longxixiaohuangpi (LX,1980s) were used as experiment material. Zhonghuang30and jindou19were the new soybean cultivars; huangsedadou and longxixiaohuangpi were the old soybean cultivars.1、During the progressive soil drying, the ABA accumulate in the new soybean cultivars was more than the old soybean cultivars, the nHRS soil water threshold range in the new soybean cultivars was significant broader than the old soybean cultivars, the nHRS. soil water threshold range in the new cultivars had the high upper limit and low lower limit; the nHRS soil water threshold range in the new soybean cultivars were64.59-41.04%FWC (Field water capacity)(23.55%FWC),67.04-38.15%FWC (28.89%FWC) for zhonghuang30and jinfou19,respectively,and58.29-44.13%FWC (14.06%FWC),57.78-44.58%FWC (13.2%FWC) for the old soybean cultivars huangsedadou and longxixiaohuangpi,,respectively; non-hydraulic root signal and the hydraulic signal were triggered at the soybean branching stage (V4stage). With the time prolong and more soil water loss, the ABAcontent in the leaf was increased, the leaf ABA content in the new cultivars zhonghuang30and jindou19was significant higher than the old soybean cultivars huangsedadou and longxixiaohuangpi (P<0.05).2、The range of osmotic adjustment (OA) was0.27-0.42MPa and0.31-0.40MPa for the new soybean cultivars zhonghuang30and jindou19, the range of OA was0.15-0.25MPa�'�0.14-0.24MPa for the old soybean cultivars huangsedadou and longxixiaohuangpi. The OA in new soybean cultivars zhonghuang30and jindou19was significant higher than the old soybean cultivars huangsedadou and longxixiaohuangpi (P<0.05) but the range of the OA in the four soybean cultivars was the same; the lethal leaf water potential in the new soybean cultivars zhonghuang30(-3.95MPa) and jindou19(-4.28MPa) was significant lower than the old soybean cultivars huangsedadou (-2.45MPa) and longxixiaohuangpi (-2.33MPa)(P<0.05), indicated the leaf desiccation tolerance in the new soybean cultivars zhonghuang30and jindou19was better than the old soybean cultivars huangsedadou and longxixiaohuangpi.3、The dry matter partition in the new cultivars zhonghuang30and jindou19was very different form the old soybean cultivars huangsedadou and longxixiaohuangpi, the pod dry matter in the new cultivars zhonghuang30and jindou19was significant higher than the old soybean cultivars huangsedadou and longxixiaohuangpi but the leaf dry matter in the new soybean cultivars zhonghuang30and jindou19was significant lower than the old soybean cultivars huangsedadou and longxixiaohuangpi in three water treatments (P<0.05);the dry matter accumulation and the grain yield were significant decreased under drought stress(P<0.05).The grain yield, harvest index, hundred grain weight and water use efficiency for grain yield(WUEG) in the new soybean cultivars zhonghuang30and jindou19were significant higher than the old soybean cultivars huangsedadou and Longxixiaohuangpi in three water treatments(P<0.05).4、Using the correlation analysis, we found that the ABA content was significant negative correlation with the stomata conductance (r2=0.8391, P<0.0001).; the nHRS soil water threshold range was significant positive correlation with the grain yield (R2=0.31,P<0.001), OA(R2=0.77, P<0.001)and WUEG (R2=0.51,P<0.001) and significant negative correlation with the lethal leaf water potential (R2=0.91, P<0.001). The OA was significant positive correlation with the grain yield(R2=0.29,P<0.001) and WUEG (R2=0.49,P<0.001) but significant negative correlation with the lethal leaf water potential (R2=0.83,P<0.001).Overall, the leaf of new cultivars zhonghuang30and jindou19accumulated more ABA than the old cultivars huangsedadou and longxixiaohuangpi (P<0.05) under drought stress, so the new cultivars can trigger the nHRS and osmotic adjustment earlier and increase the leaf desiccation tolerance, these drought adaptation mechanism improved the drought tolerance and benefited for the yield and WUEG.