The Study On Physiological Mechanism Of Brassinolide And Betaine In Inducing Drought Resistance In Tomato Seedlings

The injury which is caused by the drought stress to crops had already aroused many researchers' widespread interesting.Many researchers are seeking the different method to reduce the arid coercion to crops' injury.They have made a great progress at present.Some researchers have discovered that spraying brassinolide or betaine can enhance the energy of some crops effectively in the drought resistance.This experiment used brassinolide or betaine as drought resistance substances and studied their effects and physiological mechanism.The purpose is to provide some theoretic support to tomato seedling,production and breeding.This experiment treated the tomato seedlings using the brassinolide and betaine in five concentrations separately,in stage of 4～5 piece of leaves under the drought condition.The best concentrations of brassinolide and betaine were selected for further study on the physiological mechanism of these two substances in inducing drought resistance.The experimental results are as follows:1.Under drought stress condition,tomato seedlings which have sprayed brassinolide and betaine had the tendency of increased praline,reduced MDA,reduced relative conductivity,and increased the accumulation of dry matter in the seedlings.This indicates that spraying brassinolide and betaine can improve the drought resistance of tomato seedlings.The results showed that the treatment of 0.8mg·L^-1Brassinolide and 50mg·L^-1Betaine had the best effect.2.Spraying leaves with Brassinolide and Betaine both can enhance the photosynthesis of tomato seedlings under drought stress condition.In the study,Betaine seems improved of stomatal conductance and carbon dioxide concentration among cells which increased the net photosynthesis rate;as for the effect of Brassinolide,it is the stomata factors which work at initial stage of drought stress,while the non stomata factors do at later stage.3.Spraying leaves with both Brassinolide and Betaine seems had the effect on the activity of Antioxidas in a sort of same way.They both raise the activity of SOD,POD and CAT to some extent. While this effect is not obvious at initial stage of drought stress,but become clear as the drought stress getting more and more serious.The activity of Antioxidas is raised,and the biomembrane systems are protected from losing water.As a result,relative higher water content was kept in tomato seedlings and increase the drought resistance consequently.