The presence in the incubation medium of sucrose, at a 2% concentration was found to almost completely inhibit the rapid decrease of RNA occurring in excised Potato leaf discs and in Avena leaf fragments. Also the drop of chlorophyll and of photosynthetic activity was efficently prevented by the sugar. The effect of sucrose in preventing the RNA and chlorophyll decrease during incubation in the dark appeared to be the same order as that of 10-5 M kinetin. The rate of 32P phosphate incorporation into RNA was very significantly increased by sucrose. In the leaf fragments incubated in the light (ca. 4,000 lux) the protection of RNA and of chlorophyll and of the photosynthetic capacity after 24 and 48 hours appeared of the same order as the one performed by sucrose. This effect of light was almost completely suppressed by the presence of 10-4 M DCMU, a specific inhibitor of photosynthetic CO2 fixation. These findings are interpreted as indicating that the level of sugars is an important factor in regulating the balance between RNA (and thus protein) synthesis and degradation in the excised leaves as well as, quite probably, in the leaf under physiological conditions.
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Con il contributo del Ministero per i Beni e le Attività Culturali