Effects Of Exogenous Calcium And Abscisic Acid On Cucumber Seedling Growth And Physiological Characteristics Under Drought Stress

Cucumber?Cucumis sativus L.?is a worldwide vegetable.It's also one of the main vegetable cultivations in our country.Cucumber seedlings are easily affected by drought stress.Water shortage could seriously affect the growth of cucumber yield and quality.Drought is the recurrent factors affecting vegetable production,crop drought resistance mechanism research is increasingly attention.With exogenous substances to alleviate drought stress on crop damage research more and more,such as salicylic acid,betaine,oxalic acid and polyamine and so on.But there are few reports on effects of exogenous calcium which alleviated drought stress on the growth of cucumber seedlings and effects of exogenous calcium on ABA in induction of drought resistance of cucumber seedlings under drought stress response.Therefore this paper researched on these two aspects which has important theoretical and practical guidance for exogenous calcium and ABA in alleviating drought stress effect on the growth of cucumber seedlings.The main results were as follows:1.The experiment with different degrees of drought stress: normal nutrient solution respectively,moderate drought stress and severe drought stress,effects of spraying CaCl₂?10mmol/L?under different degrees of drought stress on the leaf on cucumber seedling growth,chlorophyll content,membrane lipid peroxidation,protein and proline accumulation and photosynthetic gas exchange parametersin in a nutrient solution adding PEG-6000?polyethylene glycol?simulated drought stress.The results showed that drought stress inhibited the growth of cucumber seedlings,while spraying CaCl₂?10mmol/L?on the leaf could promote the growth of cucumber seedlings under drought stress,improve the content of leaf chlorophyll,net photosynthetic rate,transpiration rate and use efficiency of water,reduce the level of membrane lipid peroxidation,reduce the accumulation of proline and soluble protein,which alleviated the negative impact of the drought on the cucumber seedlings to enhance the ability of plant to adapt to drought stress.2.In a nutrient solution adding PEG-6000?polyethylene glycol?simulated drought stress,spraying on the leaf of calcium and ABA to research photosynthesis and the activity of antioxidant enzymes in cucumber seedlings under drought stress,the cucumber was used as the experiment materials.There were five different treatments which were water application,ABA,CaCl₂+ABA,LaCl3?calcium channel inhibitor?+ABA and EGTA?calcium ion chelating agent?+ABA.The results showed that drought inhibited the growth of cucumber seedlings,and reduced the activities of antioxidant enzymes,nitrate reductase,net photosynthetic rate and fluorescence parameters of the leaves of cucumber seedlings.The application of ABA?1.0mg/L?reduced the inhibition of activities of SOD?POD?CAT and APX,photosynthesis?Pn?Gs?and the fluorescence parameters?Fv'/Fm'?qP and ETR?,and decreased part of the damage of drought stress on plant.Spraying CaCl₂+ABA could significantly promoted the positive effects of ABA,while EGTA+ABA and LaCl3 +ABA didn't showthe promoting effects.