Effects of Gibberellin on Cellulose Biosynthesis and Membrane-associated Sucrose Synthase Activity in Pea Internodes

The gibberellic acid (GA3)-induced growth of the second internode in 4- to 8-day-old light-grown pea seedlings (Pisum sativum L. var. Senator) was analysed. During hormone-mediated growth and after cessation of elongation the rate of cellulose biosynthesis was much larger than in the water control. In GA3-treated stems the concentration of UDP-glucose was higher than in the control. The specific catalytic activity of the plasma membrane-associated form of the enzyme sucrose synthase was determined in growing and mature stems. In GA3-treated internodes enzyme activity was 70 % higher than in the water control. These results indicate that the membrane-bound sucrose synthase may playa role in GA3-mediated cellulose biosynthesis by supplying UDP-glucose as substrate.