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To Longjiao pepper seedlings as test materials , the use of artificial climate chamber to simulate the low temperatures , by foliar application of different concentrations of 5 - aminolevulinic acid ( ALA ) , spermidine ( Spd ) , calcium chloride ( CaCl2 ) , chitosan ( CS ) , polyethylene glycol (PEG) and sucrose , comparative study of six kinds of exogenous substances on the cold resistance of pepper . Mainly made ??the following findings : 1 foliar application of different concentrations of ALA , SPD , CaCl2 , PEG , CS and sucrose, seedlings grown and extreme low temperature ( 5 ° C ) can reduce the chilling injury index , mortality and electrolyte leakage rate, and improve the blade Fv / Fm , filter out the appropriate concentration of 0.5mg · L-1, 0.5mmol · L-1, 10mmol · L-1, 0.25%, 25% and 20% , respectively . Suitable concentration of ALA , SPD , CaCl2 , PEG , CS and sucrose treatment can significantly alleviate mild hypothermia ( 22 / 12 ° C ) stress accumulation of pepper MDA content , relative permeability to reduce the low temperature in Pepper Seedlings under plasma membrane , and induction of SOD , POD , CAT activity increased significantly improved Pro and Pr content, improve the antioxidant and osmotic adjustment of the blade , reducing the low-temperature - induced membrane lipid peroxidation injury . 3 . Mild hypothermia pepper seedling leaf chlorophyll fluorescence parameter Fv / Fm , ΦPS II , Fv ' / Fm ' , qP and Ch1 ( ab ) content decreases , the suitable concentration of ALA , Spd , CaCl2 , PEG , CS and sucrose treatment significantly improve the chili leaf chlorophyll fluorescence parameters Fv / Fm , ΦPS II , Fv '/ Fm ' , qP and CH1 ( ab ) content and increase pepper Leaves photochemical activity in low temperatures . 4 hypothermia leads to pepper seedling leaf net photosynthetic rate (Pn), stomatal conductance ( Gs ) and transpiration rate ( E ) decreased in varying degrees , and intercellular CO2 ( Ci ) increased ; suitable concentration of ALA , SPD , CaCl2 PEG , CS and sucrose treatment significantly improved the pepper leaves Pn , Gs , E , reduce the CI .
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