Effects of fusicoccin and indole‐3‐acetic acid on the levels of ascorbic acid and dehydroascorbic acid in the apoplast during elongation of epicotyl segments of Vigna angularis

Abstract

The levels of ascorbic acid (AA) and dehydroascorbic acid (DHA) in the apoplast of epicotyl segments from Vigna angularis L. cv. Erimoshouzu decreased to nearly zero and about 35%, respectively, of their initial levels, 3 h after the preparation of the epicotyl segments. The decreased level was kept nearly constant between 3 and 7 h. Fusicoccin (FC) and indole‐3‐acetic acid (IAA) slightly amplified the initial decrease in the level of AA, but suppressed the initial decrease in the level of DHA while enhancing elongation growth. During incubation for 3 and 7 h, FC then increased the levels of both AA and DHA, whereas IAA did so only with DHA. By the addition of FC 4 h after the start of incubation, the levels of both AA and DHA were also increased. The uncoupler carbonylcyanide m‐chlorophenyl hydrazone increased the levels of both AA and DHA in the apoplast inhibiting elongation growth. These results suggest that the electrochemical proton gradient across the plasma membrane is one of the factors that control the apoplastic levels of AA and DHA.