Control of chlorophyll synthesis by phytochrome : II. The effect of phytochrome on aminolevulinate dehydratase in mustard seedlings.

The activity of aminolevulinate dehydratase in mustard (Sinapis alba L.) seedlings increases in continuous far-red light. The light effect can be attributed to phytochrome. The same was found for the accumulation of protochlorophyll(ide) if the seedlings were treated with 5-aminolevulinate. This result could indicate that a considerable portion of the aminolevulinate dehydratase is located in the plastids. No correlation exists between aminolevulinate dehydratase activity and the capacity of the mustard seedlings to form chlorophyll. In conclusion, the increase in enzyme activity is probably not involved in the phytochrome-mediated control of chlorophyll biosynthesis.