Analysis of Polyphenol Metabolism and Antioxidant Capacity of Tobacco Seedlings under Cold Stress

In order to study the relationship between metabolism of polyphenols and the antioxidant capacity of tobacco seedlings under cold stress, 7th-leaf stage tobacco seedlings of K326 were used to measure the physiological indicators of tobacco seedlings at chilling stress (4℃), the changes of polyphenol contents, metabolism related enzyme activities, and gene expression were detected during the stresses of chilling. The results showed that after the treatment of chilling stress, leaf wilting, cell membrane damage and relative electrolytic leakage of tobacco increased, while total polyphenol content was less affected by low temperature stress, and lignin content increased significantly (p<0.05). The activity of superoxide dismutase (SOD) was significantly increased (p<0.05), the activity of catalase (CAT) and total antioxidant capacity (T-AOC) decreased and lower than control treatment. PAL, HCT and POD enzyme activities were increased and the expression levels of PAL, HCT and POD genes were all increased under chilling stress. The above results indicated that the metabolism of polyphenols shifted to the downstream biosynthesis of lignin, and enhancing the hardness of cell walls by increasing lignin content might be an important factor for plants to improve their cold resistance.