| Abstract: | When young tomato plants grown in high light (400 µmolquanta m–2s–1 PAR) were transferred to low light(100 µmol quanta m–2s–1 PAR), non-cyclic electrontransport capacity was decreased and the rate of dark re-oxidationof Q–, the first quinone electron acceptor of photosystemII, was decreased within 1–2 d. In contrast, the amountof coupling factor CF1, assayed by its ATPase activity, decreasedmore gradually over several days. The total chlorophyll contentper unit leaf area remained relatively constant, although thechlorophyll a/chlorophyll b ratio declined. When young tomato plants grown in low light were transferredto high light, the ATPase activity of isolated thylakoids increasedmarkedly within 1 d of transfer. This increase occurred morerapidly than changes in chlorophyll content per leaf area. Inaddition, in vivo chlorophyll fluorescence induction curvesindicate that forward electron transfer from Q– occurredmore readily. The functional implications of these changes arediscussed. Key words: Tomato, leaves, light intensity, thylakoid membrane |
