[The increase of phytochrome-mediated anthocyanin synthesis in the mustard seedling (Sinapis alba L.) by chloramphenicol].

Chloramphenicol (CAP) within a certain range of concentration (about 20-30μg/ml) increases the rate of far-red mediated anthocyanin accumulation in the mustard seedling (Sinapis alba L.) (Fig. 1). The lag-phase after the onset of far-red and the time of termination of anthocyanin synthesis are not influenced by the presence of the antibiotic (Fig. 2). With and without CAP we observe a constant rate of anthocyanin accumulation over a period of at least 24 hours after the lag-phase at all far-red intensities investigated (Fig. 2). The percentage increase of the rate of anthocyanin accumulation which is due to CAP (20 μg/ml) is independent of the far-red intensity applied and always amounts to about 25% (Table). Formally one can conclude that CAP and far-red seem to act as two independent factors in a multiplicative system. On the "molecular" level the observations can possibly be explained as follows: CAP at a concentration of 20 μg/ml inhibits protein synthesis of the plastids. This inhibition leads to an increase of the pool of phenylalanine in the cotyledons. Because the small concentration of CAP does not interfere with protein synthesis (enzyme synthesis) in the cytoplasm, far-red mediated anthocyanin synthesis can proceed normally. Since phenylalanine acts as a precursor of flavonoids the increased pool of this substance will lead to an increase in the rate of anthocyanin accumulation.