Of Calcium In Heat Shock Induced Resistance Of Cucumber Seedling Role In The Cold

The seeds were soaked with CaCl₂ solution and EGTA(Ca²⁺chelator)to study the effect of calcium on seedlings growth,antioxydization system,chlorophyll fluorescence kinetice and osmoregulation ability during heat-shock-induced chilling resistance in cucumber seedlings.The results showed that:(1)During chilling stress,Ca²⁺treatment could enhance the plant height,root length,leaf area,biomass,root/shoot ratio,root vigor and nitrate reductase activity of the heat-shock-induced cucmber seedings;But the EGTA treatment had the opposite effect.(2)During chilling stress,Ca²⁺treatment could delay the decrease of the activity of SOD,POD and CAT;And it could delay the decrease of the content of GSH,AsA and Car of the heat-shock-induced cucmber seedings.Therefore it enhanced the antioxydization ability,and reduced malon-diadehyde(product of membrane lipid peroxidation)and cytomembrane permeability of the heat-shock-induced cucmber seedings.But the EGTA treatment had the opposite effect.(3)During chilling stress,Ca²⁺treatment could delay the decrease of K⁺,Mg²⁺, soluable protein content and the increase of Ca²⁺content;And it could enhance the increase of soluable sugar,free amino acid,proline,heat stable protein and Na⁺ content of the heat-shock-induced cucmber seedings.Then it enhanced the osmoregulation ability and delayed the decrease of water potential of the heat-shock-induced cucmber seedings.But the EGTA treatment had the opposite effect.(4)During chilling stress,Ca²⁺treatment could delay the decrease of chlorophyll content and RuBPCase activity;And it could enhance Pn,Gs,Tr,the saturation point and dark respiratory speed of the heat-shock-induced cucmber seedings.So it reduced Ci.But the EGTA treatment had the opposite effect.(5)During chilling stress,Ca²⁺treatment could delay the decrease of Fm,Fv/Fo, Fv/Fm,Fv'/Fm',ΦPSⅡ,qP,ETR;And it could delay the increase of Fo and qN of the heat-shock-induced cucmber seedings.Then it delay the injury of PSⅡwhich caused by low temperature.But the EGTA treatment had the opposite effect.Based on the facts above,Ca²⁺treatment could enhance the antioxydization ability, the osmoregulation ability and the photosynthetic character of the heat-shock-induced cucmber seedings during chilling stress.Therefore it suggests that Ca²⁺probably plays an important regulation role in the heat-shock-induced chilling resistance of the cucumber seedlings.