Trypsin Inhibitor in Corn (Zea mays L.) as Influenced by Genotype and Moisture Stress 1

This study was undertaken to evaluate the distribution of trypsin inhibitor in kernels of genetically different strains of corn (Zea mays L.) and to determine the levels of the inhibitor in kernels as affected by water stress conditions. Crude extracts of endosperms and embryos (including scutellum) were separately analyzed for trypsin inhibitor activities. Corn kernels contained more trypsin inhibitor in endosperms than embryos. The endosperm inhibitor level varied widely from line to line. Endosperms containing the opaque-2 gene exhibited much higher concentrations of trypsin inhibitor than normal corn, but the reverse was the case for endosperms containing the floury-2 gene. Trypsin inhibitor activities varied within strains when plants were subjected to differential water stress at different growth stages. Generally, there was less inhibitor in endosperms of all lines when irrigation was discontinued at pollination time, but when irrigation was discontinued about 21 days before pollination some genotypes had increased inhibitor activities. However, the increase was not significantly different from that under highest water conditions for most varieties. Trypsin inhibitor in embryos seemed to be influenced little by water stress. The amounts and pattern of trypsin inhibitor activities of corn strains suggest that both genotype and environmental stress influenced formation of inhibitors, particularly in the endosperms.