Ribonuclease activity in the developing seeds of normal and opaque-2 maize

During development, the ribonuclease activity of maize endo sperm homozygous for the opaque-2 gene increased earlier and, after a longer period of exponential increase, was much higher finally than in normal endosperm. The maximum difference was about sixfold and occurred 22 to 25 days after pollination. Heterozygotes on day 23 did not show a comparable in crease in endosperm activity. No differ ence in the activity ratio (pH 6.0: pH 5.2) was found between normal and opaque-2 endosperm, indicating that the increase in activity in opaque-2 was due solely to an increase in ribo nuclease A. The ribonuclease activity of opaque-2 embryos increased more rapidly than that of normal embryos, but the final activity was the same in each case.