Carbohydrate and enzymic characterization of a high sucrose sugary inbred line of sweet corn.

Reserve carbohydrates were determined on developing endosperm of a new line of sugary maize (Zea mays L.). Other entries, included for comparative purposes, were Midway (sugary), Funks G4646 (starchy), and Illini X-tra Sweet (shrunken-2). Sucrose in the new line, Illinois 677a, was more than twice that of Midway at most stages of development, and reached a maximum of 40% of dry weight at 18 days after pollination. Appreciable phytoglycogen accumulated in Illinois 677a, reaching 30% or more of dry weight as endosperm tissue matured. Thus, Illinois 677a is a typical sugary maize concerning phytoglycogen content, but it resembles shrunken-2 concerning the extent of sucrose accumulation.Enhanced sucrose accumulation by Illinois 677a was not accounted for by altered in vitro activities of invertase, sucrose synthase, UDP-glucose pyrophosphorylase, or ADP-glucose pyrophosphorylase. Its normal level of ADP-glucose pyrophosphorylase set Illinois 677a apart from shrunken-2 in which the enzyme was drastically reduced.