Effects of Kinetin and Different Light Qualities on the Content of Carbohydrates

Abstract

Summary The effects of kinetin on the content of soluble redueing sugars, starch, soluble proteins and various components of the photosynthetic apparatus were studied with primary leaves of Sinapis alba, which were grown under different light qualities (white, red, blue Jight conditions). It was especially the content of soluble reducing sugars that was most influenced by kinetin. The enhancement of the sugar content was dependent on the duration of application as well as on the concentration of kinetin. The doseresponse curve shows that the sugar content strongly increased at low kinetin eoneentrations (0.01 to 1 mg · 1-1), whereas from 1 mg · 1-1 onwards the inerease was slower and linear. The enhancement of the sugar synthesis by kinetin was, however, different at the three light qualities: The highest increase was observed under blue light conditions and the smallest effect under red light conditions, whereas the response under white light conditions was in between. An opposite effed of the light qualities could be observed with respect to the starch content: The starch synthesis remained uninfluenced by kinetin under blue light conditions; under white light conditions it was slightly and under red light conditions strongly inereased, If the sum of both the content of soluble reducing sugars and the eontent of starch (calculated in units of glucose) is plotted against the concentration of kinetin, it beeomes evident that the earbohydrate synthesis was equally enhaneed by kinetin at all three light conditions. Thus, the light quality decides whether the enhaneed synthesis of carbohydrates by kinetin is direetcd to the synthesis of stareh or to the synthesis of soluble reducing sugars.