Hemming I. Virgin

CHLOROPHYLL b FORMATION IN DARKNESS AFTER PHOTOTRANSFORMATION OF PROTOCHLOROPHYLLIDE AND DURING A PERIOD OF INTERMITTENT LIGHT

ABSTRACT Chlorophyll (Chl) b formation in leaves of wheat (Triticum aestivum L. cv. Starke II Weibull) after a short light pulse was followed for 5 h in darkness. Prior to this the leaves were kept in darkness or in continuous far-red light. The far-red light used activated the phytochrome system but did not cause any phototransformation of the protochlorophyllide present. The Chl b/a ratio increased faster in dark-grown leaves than in far-red pretreated ones, i.e. Chl b formation was slower in the latter. Thus, continuous far-red light appears to counteract Chl b formation. When comparing 5- and 7-day-old leaves the Chl b formation was faster in the younger leaves during the first hours after phototransformation. Formation of Chl b in darkness continues for several hours after the initial photo transformation has taken place. Formation of Chl b in wheat in this phase does not seem to depend on the level of chlorophyllide (Chlide), as Chl b formation continues long after Chlide could be detected. Chl b fo...