The effect of kinetin on nucleic acids and nucleases of excised barley leaves.

Recent work from several laboratories (6, 7, 9, 11, 12, 13) has shown that in excised green leaves floated on water there are rapid declines in the level of RNA, DNA, protein and chlorophyll which are retarded if the leaves *are floated on kinetin solution. Furthermore, the local application of kinetin on detached tobacco leaf causes the maintenance of the protein level and color of the treated area which has been suggested to act as a metabolic sink (6). The stimulation of both RNA and protein synthesis by kinetin in tobacco (8) and Xanthiumwl (7) leaves has been reported, and McCalla, Moore and Osborne (5) using another kinin, the benzyladenine-CG4, have obtained tentative evidence that label was incorporated into RNA although at a very low rate. Wollgiehn and Parthier (13) have recently shown that chloramphenicol and thiouracil accelerated the yellowing of detached tobacco leaves and the breakdown of RNA and protein which was prevented by kinetin. All these findings have indicated that kinetin in some way maintains the level of RNA and thus keeps protein synthesis going in detached leaves. Since the level of RNA and DNA in detached leaves may depend not only on the rate of synthesis, but also on the rate of breakdown, it was thought desirable to investigate the effect of kinetin on the amount of RNA, DNA and chlorophyll, on the rate of incorporation of p32 into RNA and DNA, and on the activity of soluble ribonuclease and deoxyribonuclease in excised barley leaves. The present paper describes the results of this investigation. Materials and Methods