| The banana (Musa AAA Group cv. Dazhong Gaoba) is an originally tropical fruit, and low temperature is unfavorable to its growth.If the temperature is close to chill temperature, the chilling-injury will happen.In China, the main producing area is in South China area, and Guangdong is a primary area, too.Chilling-injury is one of the important nature frosts for the banana.Therefore, the study on the chilling-injury of banana seedlings had important meanings both in theory and production. Basing on the theory of free radical, this paper studied the effects of low temperature and light, cold acculimation on some physiological and biochemical indexes in banana seedlings, and inquired into the function of some exogenous substances ,such as CaCl2, H2O2, Vc, ABA on the chilling resistance of banana seedlings.Effects of low temperature and light on the membrane-lipid peroxidation of banana seedlings were studied. At 5 C the banana seedlings had a serious damage; the permeability of cytoplasmic membranes and the malondialdehyde (MDA) contents were significantly increased; the activities of POD, CAT and the chloropyll contents were declined evidently. At 10 C, the damages of banana seedlings were light; the permeability of cytoplasmic membranes and the MDA contents were increased slightly; the activity of POD was increased; the activity of CAT was quite close to that of the control; the chloropyll content was not evidently declined. In addition, light had evident effects on the indexes that tested above,and it intensified the damages that caused by 5 C but decreased the damages that caused by 10 C.It proved that the chill-temperature photohibition intensified the damages of banana seedlings.The dynamic states of activities of enzymes (SOD, POD, CAT), the permeability of the cytoplasmic membranes, the membrane lipid peroxidations, the soluble protein contents of banana seedlings under cold acculimation were studied.The results showed that feasible time of cold acculimation not only increased the activities of enzymes, but also decreased the membrane injuries, All the indexes that above mentioned were different between varieties of banana seedlings.During the periods ofcold acculimation, the trends of the changes of three enzymes were increasing before descending, and the changes were closely related to the chilling resistance of banana seedlings.Therefore, the results of cold stress showed that cold acculimation really increased the chilling resistance of banana seedlings.Cold stress restrained the growth of banana seedlings, the activities of SOD, POD and the soluble protein contents were declined; the permeability of the cytoplasmic membranes and the membrane-lipid peroxidations were increased. Pretreatments of the banana seedlings with spraying CaCl2, H2O2, Vc at feasible concentrations before subjecting them to cold stress retarded the descent of activities of SOD, POD, and weakened the increasements of the permeability of the cytoplasmic membranes and the membrane-lipids peroxidation, but the soluble protein contents in the two varieties of banana seedlings (Musa AAA Group cv. Dazhong Gaoba and Musa ABB Group cv. Aiba Dajiao) didn't have the same current. The results showed that CaCl2, H2O2 had perfect effects, and the effect of Vc was worse compared to the other two, The banana seedlings (Musa ABB Group cv. Aiba Dajiao) had strong chilling resistance, so the injuries and the descents of activities of enzymes were less.When banana seedlings were exposed to cold stress at 5 for 24 hours, the activities of enzymes (SOD, POD, CAT) in them were declined; the membrane-lipid peroxidations and the permeability of cell membranes were increased. Pretreatment of the banana seedlings with spraying exogenous ABA at feasible concentration before subjecting them to cold stress retarded the decline of activities of enzymes, and weakened the increasement of membrane-lipid peroxidations and the permeabilitiy of cell membranes at 5 conditions for 24 hours. The results showed that 5 + 10-4 M exogeno...
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