Study On The Influence Of Chitoson On Physiological- Biochemical Characteristics Of Pepper (Capsicum Annuum L.) Seedings Under Low Temperature Stress

Pepper (Capsicum annuum L.)seedlings (Longjiao NO.2) were used as materials to investigate effects of Chitosan on physiological and biochemical characteristics in cucumber seedlings under low temperature. An optimal concentration of chitosan in the experiment was selected by measuring of relative electrolytic leakage. Photosynthesis, Chlorophyll fluorescence, osmotic adjusting substance, resistant-oxidation enzyme activities and growth index were studied after low temperature treatment. The main results obtained are as follows:The electrolytic leakage of pepper leaves in 50 mg·L-1Chitosan-treated under low temperature treatment for five days was lowest, it is suggested that Chitosan may enhance the cold resistance in pepper under low temperature.The contents of MDA, soluble sugars and proe in pepper seedlings under low temperature stress were raised; the content of soluble sugars and pro in chitosan-treated pepper seedlings were raised obviously,and loss of material in cell through the cytoplasmic membranes was reduced.With the increase of stress time, the activity of cell defense enzymes, super-oxide dismutase (SOD), and catalase (CAT) were gradually decreased, peroxidase (POD)was decreased.The activities of antioxidant enzymes SOD, POD and CAT in chitosan-treated pepper seedlings were all higher. It showed that Chitosan could protect the integrity and stability of themembrane, and enhance the cold resistance of pepper seedling.The net photosynthetic rate and stomatal conductance were decreased,however intercellular CO2 concentration increased.The cause of reduction of net photosynthetic rate in pepper seedlings under low temperature stress might be mainly non-stomata limitation. Fv/Fm,фPS, qP and Fv '/Fm' decreased with degree decreased after low temperature, but Fo are increasing.Chla content, Chlb content and Chl (a+b) contentall was decreased under low temperature. Exogenous CS did not significantly increase the contents of Chla, Chlb and Chl (a+b). Height of pepper and stem diameter, fresh weight of root and top, dry weight of root and top, dry weight to fresh weight of root and top of pepper all decreased under the low temperature stress, Therefore, Chitosan is benefit to the grow of pepper. The ability of tolerance to low temperature in chitosan-treated pepper seedlings was stronger.