Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: Effect of light during growth on photoinhibition and recovery.
Photoinhibition of photosynthesis was induced in intact kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson) leaves grown at two photon flux densities (PFDs) of 700 and 1300 μmol·m(-2)·s(-1) in a controlled environment, by exposing the leaves to PFD between 1000 and 2000 μmol·m(-2)·s(-1) at temperatures between 10 and 25°C; recovery from photoinhibition was followed at the same range of temperatures and at a PFD between 0 and 500 μmol·m(-2)·s(-1). In either case the time-courses of photoinhibition and recovery were followed by measuring chlorophyll fluorescence at 692 nm and 77K and by measuring the photon yield of photosynthetic O2 evolution. The initial rate of photoinhibition was lower in the high-light-grown plants but the long-term extent of photoinhibition was not different from that in low-light-grown plants. The rate constants for recovery after photoinhibition for the plants grown at 700 and 1300 μmol·m(-2)·s(-1) or for those grown in shade were similar, indicating that differences between sun and shade leaves in their susceptibility to photoinhibition could not be accounted for by differences in capacity for recovery during photoinhibition. Recovery following photoinhibition was increasingly suppressed by an increasing PFD above 20 μmol·m(-2)·s(-1), indicating that recovery in photoinhibitory conditions would, in any case, be very slow. Differences in photosynthetic capacity and in the capacity for dissipation of non-radiative energy seemed more likely to contribute to differences in susceptibility to photoinhibition between sun and shade leaves of kiwifruit.
Plant Physiology Division, DSIR, Private Bag, Palmerston North, New Zealand.
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Greer
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Laing