Gibberellic Acid and Starch Breakdown in Pea Cotyledons

The stimulation of starch breakdown in the cotyledons of dwarfpea cultivars (Progress No. 9 and Dark Skin Perfection) whentreated with gibberellic acid (GA³) is mediated through theremoval of metabolites by the axis. When applied to excisedcotyledons, GA³ had only a minor effect on starch breakdown,as it did in the cotyledons of a tall pea (cv. Alaska) irrespectiveof whether they were attached to the plant or excised. Enzyme activity appears to be controlled by the level of solublesugars in the cotyledons, and GA³delays the increase in amylolyticactivity in the cotyledons through a direct effect on cotyledonmetabolism.