Control of starch and exocellular polysaccharides biosynthesis by gibberellic acid with cells of sweet potato cultured in vitro.

The regulation of starch synthesis and exocellular polysaccharide synthesis by GA3 was studied with cells of sweet potato grown as suspension in glycerol medium. In the presence of GA3, and under normal cell growth, starch formation was inhibited. The incorporation activity (starch synthesis) from ADP-[(14)C] glucose or UDP-[(14)C] glucose with GA3 treated cells was reduced. On the other hand, the synthesis of exocellular polysaccharides composed of glucose, galactose, mannose and arabinose etc., was stimulated and a clear increase of the Man/Ara ratio was observed in the presence of GA3. These results may indicate that GA3 affects the regulation of starch synthesis and exocellular polysaccharide synthesis.