EFFECT OF GIBBERELLIN ON GROWTH, PROTEIN SECRETION, AND STARCH ACCUMULATION IN MAIZE ENDOSPERM SUSPENSION CELLS

The physiologic effect of gibberellins (GA) in seed development is poo rly understood. We examined the effect of gibberellic acid (GA(3)) on growth, protein secretion, and starch accumulation in cultured maize ( Zea mays L.) endosperm suspension cells. GA(3) (5 and 30 mu M) increas ed the fresh weight, dry weight, and protein content of the cultured c ells, but the effect of GA(3) at 50 mu M was not significantly differe nt. However, the protein content in the culture medium was increased b y these three concentrations of GA(3). The effect of GA(3) on the amou nt of cellular structural polysaccharides was not significant, but GA( 3) had a dramatic effect on the starch content. At 5 mu M, GA(3) cause d an increase in the starch content, but at 50 mu M the starch accumul ation was reduced. Chlorocholine chloride (CCC), an inhibitor of GA bi osynthesis, significantly increased the starch content and decreased t he structural polysaccharide content of the cultured cells. The effect s of CCC at 500 mu M on the starch and polysaccharide content were par tially reversed by 5 mu M GA(3) applied exogenously. Based on these re sults we suggest that GA does not favor starch accumulation in the cel l cultures and that the addition of lower concentrations of GA(3) in t he medium may provide an improved balance among the endogenous GA in t he cultured cells.