[The effect of kinetin on protein, amino acid, and RNA metabolism in Lemna minor L].

Lemna minor L. was cultivated on nutrient medium with kinetin (10(-5) m) for 3 hours at 28°C and ca. 5,000 lux. Samples were taken at different times and their amino acid, protein and RNA content was determined.The amino acid content in the cultures with kinetin corresponds to that in the cultures without kinetin. The amino acid concentration seems to be regulated by mechanisms independent of kinetin. On the other hand, kinetin increases the quantity of protein immediately i.e., within the first two minutes. This increase stops after ca. 30 minutes, but the excess of protein remains for a long time. In the first 30 minutes the RNA concentration also rises. This increase is not as strong as that of the protein nor does it remain. After 30 minutes, when the rise of protein content stops, the RNA concentration begins to drops within 1 hour to that of the control cultures without kinetin.The extent of the protein and RNA increase induced by kinetin depends strongly upon the physiological state of the plants. This may be because the plants produce different quantities of endogenous cytokinins under different conditions.The protein induced by kinetin was then examined after centrifugation at 100,000 x g. In samples taken during the first 5 minutes, the quantity of protein in the supernatant and in the sediment is increased. In samples taken after this period, the increase of protein in the supernatant disappears and only that in the sediment remains. After some time, therefore, all the excess protein consists of structural protein, which is found in the sediment. The findings are compared with those of other authors and an unspecific stimulation of RNA is suggested.