We examined the response of antioxidant system in ascorbic acid mutant of Arabidopsis to salt stress so as to reveal the biological function of ascorbic acid. The results showed that the contents of MDA and H_2O_2 increased more dramatically in vtc-1 than that in wt under salt stress. The activities of SOD, and CAT decreased under salt stress, and that of APX increased in first 24 h and decreased after 24 h in vtc-1, but all these enzymatic activities were enhanced in wt by 100 mmol/L NaCl treatment. The am...