Effect Of 5-Aminolevulinic Acid And Spermidine On Chilling Tolerance In Cucumber Seedlings

Effect of five components (Calcium chloride (CaCl2), Salicylic acid (SA), Abscisic acid(ABA), Spermidine(Spd)) on chilling tolerance in cucumber seedlings was studied. Components (ALA and Spd) which could obviously improve chilling tolerance of cucumber seedlings were selected. Their mechanisms were studied. The results were as follows:Cucumber seedlings with two true leaves were spread by different concentrations of five components (CaCl2, SA, ABA, Spd and ALA) under low temperature stress of 5℃for four days. Through analysis of leaf electrolytic leakage and chilling injury index of cucumber seedlings under four-day'low temperature stress, the results showed that pretreatment of ALA and Spd could obviously improve chilling tolerance of cucumber seedlings. Cucumber seedlings were spread by ALA at 0,0.05,0.5,1,5mg/l, and then they were stressed under low temperature of 5℃for four days. Effect of different concentrations of ALA on chilling tolerance in cucumber seedlings was studied. The results indicated that the cucumber seedlings treated by ALA at 0.5mg/l obtain lower chilling injury index, leaf electrolytic leakage and MDA content, higher activities of SOD and POD, higher content of ascorbic acid, proline and soluble sugar, and higher root activity under low temperature stress. This showed that 0.5mg/L ALA obviously improved chilling tolerance of cucumber seedlings.Cucumber seedlings with two true leaves which were spread by five different concentrations of Spd (0(CK), 0.01, 0.1, 0.5, 1mmol/L ) were used to study the effect of Spd on chilling tolerance of cucumber seedlings under 5℃for four days. The results showed that Spd at 0.5mmol·L-1 is more effective in improving chilling tolerance of cucumber seedlings. Pretreatment of Spd could obviously decrease chilling injury index, electrolytic leakage and MDA content, significantly increase activities of SOD , POD and CAT,content of ascorbic acid, proline and soluble sugar. Cucumber seedlings treated by Spd could maintain higher root activity.Cucumber seedlings with two true leaves were spread by 0.5mg/L ALA,0.5mmol/L Spd and stilled water .Then they were stressed under low temperature of 5℃for 5 days. The effect of ALA and Spd on chilling tolerance of cucumber seedlings was studied. The results showed that compared with Spd, pretreatment of ALA can obviously improve chilling tolerance of cucumber seedlings. Cucumber seedlings treated by ALA could obtain higher photosynthetic rate at 5d after four-day'low temperature stress, lower leaf and root electrolytic leakage under low temperature stress.