CHARACTERISTICS OF CARBOHYDRATE-METABOLISM IN SWEET CORN (SUGARY-1) ENDOSPERMS

Metabolic characteristics of developing sugary-1 maize (Zea mays L.) e ndosperms were investigated. In the later stages of development (>30 d ays postpollination), sugary-1 kernels maintained higher levels of man y enzyme activities and retained more moisture than normal kernels. Hi gher enzyme activities were attributed to moisture retention and were not associated with any increase in dry weight accumulation. Of enzyme activities measured at 20 days postpollination, that of ADP-glucose p yrophosphorylase was higher in sugary-1 kernels than in normal, wherea s total amylase, alpha-amylase, and pullulanase activities were lower. Experiments testing the effects of zero, one, two, and three doses of the sugary-1 gene in OH43 endosperms indicated that the sugary-1 phen otype was not expressed until three doses of the sugary-1 gene were pr esent. Decreased activities of amylases. but not of pullulanase, were attributed to an interference in detection by phytoglycogen. Increased ADP-glucose pyrophosphorylase activity is attributed to a response by the maize endosperm cells to increased sucrose concentrations.