Effects of gibberellin on cellulose biosynthesis and membrane-associated sucrose synthase activity in pea internodes

The gibberellic acid (GA(3))-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 GA(3)-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 GA(3)-treated internodes enzyme activity was 70% higher than in the water control. These results indicate that the membrane-bound sucrose synthase may play a role in GA(3)-mediated cellulose biosynthesis by supplying UDP-glucose as substrate.