Effects Of Exogenous ABA On Drought Resistance Physiological Characteristics And Yield Of Soybean In The Grainy Stage Under Drought Stress

Drought-tolerance variety ‘Kangxian 9' and drought-sensitive variety ‘Suinong 26' that have great difference in drought resistance but similar growth period were employed in this study,were used as experimental materials with sand-cultivated method.During seed filling period,the test materials were treated with exogenous ABA under drought stress.We measured physiological and biochemical parameters of drought resistance and yield to study the effect of exogenous ABA on physiological characteristic and yields of soybean during seed filling period under drought stress.the results showed that:Drought caused significant decrease in leaf relative water content and bleeding sap weight,inhibited physiological parameters of photosynthesis including net photosynthetic rate,intercellular carbon dioxide concentration,stomatal conductance,transpiration rate,chlorophyll content,increased the content of osmoregulation substance including soluble sugar,soluble protein,free proline,increased the antioxidant enzyme activities(SOD,CAT,POD,APX)and antioxidants contents(ascorbic acid and glutathione),and increased relative leaf conductivities and MDA content.Exogenous ABA could alleviate the effects of drought stress on soybean physiological process during seed filling period,which increased leaf relative water content and bleeding sap weight,parameters of photosynthesis such as the net photosynthetic rate,the content of osmoregulation,antioxidant enzyme activities and antioxidants contents,alleviated the damage of drought to cell membrane.And the mitigative effect of exogenous ABA on drought-sensitive variety's physiological indexes of drought resistance(net photosynthetic rate,transpiration rate,soluble sugar,MDA,CAT,POD,APX)is more obvious than that of drought-tolerance variety.Drought during seed filling period had no effect on plant height,stem diameter,nod number,inefiective pod number,effective pod number,seeds per plant were not significantly influenced by drought,but significantly affected seed weight per plant and 100 seed weight,which lead to lower production.Exogenous ABA could alleviate the effects of drought stress on seed weight per plant and 100 seed weight,especially during the pre seed filling period(7th and 14 th Days after filling)the alleviating effect was significant,seed weight per plant of Kangxian 9 increased 18.78% and 21.22%,respectively,seed weight per plant of Suinong 26 increased 22.08% and 16.05%,respectively and increased soybean yield.