Physiological effects of exogenous Ca~(2+),SA and ABA in alleviating low temperature stress of melon seedlings

Melon seedlings were sprayed with CaCl2,SA and ABA separately,and then plants were treated under 15 ℃/10 ℃ for 6 d to study the effects of exogenous Ca2+,SA and ABA on the physiological mechanism under low temperature stress.The results showed that pretreatments with certain concentrations of Ca2+,SA and ABA could alleviate cold damage.Soluble sugar and soluble protein contents in treatment seedlings changed insignificantly.Three substances pretreatments alleviated membrane lipid peroxidation especially salicylic acid best,and also activated rapidly the expression of SOD,CAT,POD,APX and the expression lasted longer time.Treatments of 5,10 mmol·L-1 CaCl2,3 mmol·L-1 SA and 20 mg·L-1 ABA kept SOD activity at higher levels which were respectively 1.94,2.30,2.10 and 3.42 times of those before stress.CAT acticity was enhanced by 1.36 times when sparyed with 3 mmol·L-1 SA.POD activity after treated with ABA was 1.48 times of that untreated;APX activities by the treatment of 1 mmol·L-1 SA and 40 mg·L-1 ABA were 1.53 and 2.12 times of those untreated.So the cold tolerance of melon seedling was enhanced with 5 and 10 mmol·L-1 CaCl2,1 and 3 mmol·L-1 SA and 20 mg·L-1 ABA treatment through alleviating low damages to physiology.