Effects of Anaerobiosis on Chlorophyll Fluorescence Yield in Spinach (Spinacia oleracea) Leaf Discs.
When spinach (Spinacia oleracea) leaf discs were incubated in a dark anaerobic environment, the chlorophyll fluorescence yield was much increased relative to the aerobic control. Occasionally, the fluorescence yield of the darkened anaerobic samples approached 80% of the maximum fluorescence. The anaerobic incubation period also induced in a leaf disc the capacity to exhibit a low light-mediated chlorophyll fluorescence induction phenomenon. This involved a rapid and slow increase in fluorescence yield, followed by a slow quenching. This could be induced by light levels as low as 400 [mu]W m-2. The anaerobic-dependent increase in chlorophyll fluorescence yield could be relaxed by either far-red light, O2, or a saturating pulse of white light. It was concluded that the anaerobic-dependent increase in chlorophyll fluorescence yield was due to a dark reduction of the plastoquinone pool and its relaxation by reoxidation. Darkened isolated chloroplasts did not exhibit a fluorescence yield increase under anaerobic conditions. Fluorescence slowly increased only when dithiothreitol or dithionite was added.
Harris
G. C.
GC
Biology Department, Wellesley College, Wellesley, Massachusetts 02181 (G.C.H.).
Heber
U.
U