Effects of Low Temperature and Magnesium Stress on Growth and Physiological Characteristics of Cucumber Seedlings

In order to study the mechanism of magnesium nutrition in cucumber(Cucumis sativus L.),the effects of magnesium and low temperature stress on growth,carbon nitrogen metabolism and active oxygen scavenging enzymes system were explored in cucumber seedlings grown in artificial climate chamber.The experimental results indicated that the total leaves,leaf area,root length,total dry weight and health index of cucumber seedling were decreased,and root/shoot ratio was increased under low temperature and magnesium stress.The contents of soluble protein,reducing sugar and soluble total sugar,the activity of nitrate reductase were decreased,while root activity was increased under suitable temperature and magnesium stress.The activity of nitrate reductase,root activity and the content of soluble total sugar were decreased under low temperature,while the content of reducing sugar was increased.The content of soluble protein was decreased under excessive Mg stress or suitable Mg,and it was increased under deficient Mg.MDA,H2O2 contents and O2 concentration were increased under Mg stress,and the effects were more remarkable under deficient Mg stress than excessive Mg stress.Low temperature and Mg deficiency would bring the greatest harm to plant.This is mainly related to the increase of active oxygen.Under suitable temperature,Mg stress hoisted POD and SOD activities in plants,of which POD activity had the biggest rising extent,while CAT activity was decreased.And plant mainly resist Mg stress by increasing POD activity.