Studies On Relationship Of ABA And PH And Ca～(2+)/CaM System Of Maize Under Drought Stress

The drought signal molelular and its relation with Ca2+/CaM system under drought stress were studied with exogenous ABA.pH and EGTA,verapamil,TFP in this paper.The results were as follows:1 The effects of drought stress on total ABA contents of different tissues,[ABAxyl] and pH of xylem sap,stomatal conductance and transpiration rate of maize seedlings showed that ABA was firstly synthesized by roots during drought stress.At the preliminary time of treatment, total ABA contents of the leaves were not changed ,but [ABAxyl]L increased. This were perhaps induced by increase of pH value of the xylem sap. As a result, the stomatal conductance and transpiration rate decreased.2 when maize seedlings were treated with both 100 mol/L exogenous ABA solution and drought stress.ABA bulk contents of maize seedlings did not increase, but [ABAxyl] and pH of the xylem sap were increased .stomatal conductance were decreased. The results showed that stomatal conductance was mainly controlled by ABA concentration of xylem sap.3 Both ABA contents of the leaves and [ABAxyl]L increased with the increase of exogenous pH buffer from 5 to 8, and pH value of xylem sap was raised when the maize were treated by pH buffer. At the same time , the stomatal conductance and transpiration rate decreased . The results verified the view that it is through modifying xylem sap ABA concentration that pH has effect on the stomatal conductance and transpiration rate. The studies of pH buffer and ABA suggested that ABA were accumulated easily in the alkaline circumstance.4 Hie total ABA contents of leaves decreased, but ABA concentration and pH of the xylem sap increased when the maize were treated by 2 mmol/L EGTA solution. Accordingly, the stomatal conductance decreased. The effects of 100 mol/L verapamil on maize seedlings were similar to that of EGTA. The results revealed that Ca2+participated in ABA synthesis process.5 ABA contents of the roots, pH of the xylem sap of leaves and roots ,and ABA concentration of the leaves xylem sap all increased when the maize were treated by 80 mol/L TFP solution. As a result, the stomatal conductance decreased . This showed that CaM may not participated in ABA synthesis and ABA signal transduction.