Drought Stress Influence Soybean Yield Morphogenesis in Different Growth Stages

Seasonal drought is a main environmental factor limited soybean yield in northeast China.Our objective was to determine how drought stress imposed on soybean [Glycine max(L.) Merr.] at various growth stages affected plant characteristics.Twelve soybean cultivars were grown under greenhouse conditions and subjected to normal water supply(17%-18%soil-available water) and drought stress(8%-9%soil-available water) during seedling(V1-V5),flowering(R1-R4) and seed filling(R5-R8) stages.Root morphological traits including length,diameter,volume and surface area were all promoted by stress during seedling,while were inhibited by stress in other periods.Dry matter accumulation was decreased and root/shoot ratio was increased by stress in all tested periods.Drought stress at three periods all declined photosynthetic rate(Pn),and stress at flowering and seed-filling declined intercellular CO2 concentration(Ci),transpiration rate(Tr) and stomatal conductance(Cond).The decrease of seed yield caused by stress varied with varieties significantly.The performance of drought tolerance varied with growth periods,only a few cultivars showed resistant to drought stress at all growth stages.