Hormonal Control of Nuclease Level in ExcisedAvenaLeaf Tissues1

In excised Avena leaves, kinetin and benzyladenine decreased, while abscisic acid and benzimidazole increased the over-all nuclease level. Significant effects were observed as early as 2 h after treatment. Not all the nucleases of the Avena leaf were affected by the growth regulators. Changes in over-all nuclease activity were accounted for almost entirely by changes in the amount of a relatively purine-specific endo-ribonuclease, which produces 2′,3′-cyclic phosphates as breakdown products. Slight changes induced by the growth regulators were also detected in the amount of a sugar non-specific endo-nuclease which produces 5′-nucleotides and has a relative specificity for adenylic acid. The level of an alkaline phosphodiesterase, an exo-nuclease which produces 5'-nucleotides, was not affected by any of the growth regulators tested. Gibberellic acid and indol-3yl-acetic acid did not influence the level of Avena nucleases.