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Control of Ribonuclease and Acid Phosphatase by Auxin and Abscisic Acid during Senescence of Rhoeo Leaf Sections ¹

^a Department of Botany, California State College, Los Angeles, California 90032

We report the effects of abscisic acid and auxin (-naphthalene acetic acid) on regulation of enzyme synthesis during senescence of leaf sections of Rhoeo discolor Hance. Abscisic acid always accelerates the onset of and enhances the magnitude of the increase in activity of acid phosphatase; this is followed by an acceleration of the onset of a rapid increase in free space.

RNase activity increases 2- to 5-fold after cutting of leaf sections. Abscisic acid increases RNase activity and inhibits the rate of incorporation of uridine and leucine in leaf sections removed from plants grown under stress but not favorable conditions. Auxin inhibits the increase in RNase and acid phosphatase and suppresses the effects of abscisic acid. The increase in activity of RNase and acid phosphatase is inhibited by inhibitors of RNA and protein synthesis. This and other evidence suggests that the increases in hydrolase activity could result from new enzyme synthesis. The possible significance of the results in respect of hormonal regulation of enzyme activity and senescence is discussed.

¹ This investigation was supported by National Science Foundation Grant GB-8316 to J. A. Sacher.