Influence of Cotyledons upon alpha-Amylase Activity in Pea Embryonic Axes

alpha-Amylase activity remained relatively low in the axes of intact etiolated pea seedlings; the activity was predominantly confined to the epicotyl. Starch accumulated slightly. When the cotyledons were removed and the axes cultured on medium containing no carbon source, the starch reserve in the axes disappeared within a few days. This was accompanied by a 10- to 15-fold increase in alpha-amylase activity, in the absence of additional epicotyl growth. The phenonemon was observed for axes throughout early growth, although the relative accumulation of alpha-amylase activity in cultured axes was less for older seedlings. This change was attributed to a reduced response by nongrowing tissues. There was no corresponding change in beta-amylase activity. These observations, described for several varieties of peas, demonstrate the control of cotyledons upon the utilization of stored reserves within the axis, with alpha-amylase as a key enzyme.