STABILITY OF CHLOROPHYLL DURING GREENING

ABSTRACT Physiologically active phytochrome (Pfr) is known to determine the capacity, i.e. potential rate, of chlorophyll (Chi) accumulation in higher plants. Moreover, the photo- stability of Chi as it occurs in the thylakoid membrane is a property brought about by Pfr. We investigated whether phytochrome is also responsible for the stability of Chi in darkness following a treatment (2 h or longer) with white light (WL). In mustard (Sinapis alba L.) seedlings transferred to darkness after 72 h of WL (3500 lx), the partial disappearance of Chi b within 6 h of darkness and the virtual stability of Chi a during this period were not affected by the presence or absence of Pfr at the beginning of the dark period. The conclusion that once the initial requirement for photostability is satisfied the stability of Chi is no longer? Pfr-dependent, was confirmed in a variety of WL → darkness transition experiments with mustard and milo (Sorghum vulgare Pers.) seedlings. Circumstantial evidence was obtained in favour ...