PLANT PHYSIOLOGY , Vol 111, Issue 3 867-875, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Chloroplast Movement in the Shade Plant Tradescantia albiflora Helps Protect Photosystem II against Light Stress
Y. I. Park, W. S. Chow and J. M. Anderson
Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, G.P.O. Box 1600, Canberra, Australian Capital Territory 2601, Australia
The role of high-light-induced chloroplast movement in the photoprotection
of the facultative shade plant Tradescantia albiflora was investigated by
comparison with pea (Pisum sativum L.) leaves, both grown in 50 [mu]mol
photons m-2 s-1. Photoinactivation of photosystem II (PSII) in vivo was
induced in 1.1% CO2 by varying either duration (0-2 h) of illumination
(fixed at 1800 [mu]mol m-2 s-1) or irradiance (0-3000 [mu]mol m-2 s-1) at a
fixed duration (1 h) after infiltration of leaves with water or lincomycin
(an inhibitor of chloroplast-encoded protein synthesis). At all photon
exposures, PSII of T. albiflora leaves showed a greater resistance to light
stress than pea leaves, although both utilization of absorbed light by
photosynthesis and psbA gene product synthesis were smaller than for pea
leaves. This greater tolerance was not due to differences in PSII antenna
size or the index of susceptibility of PSII to light stress, because these
two parameters were comparable in both plants. However, the transmittance
increase mediated by chloroplast movement was greater in T. albiflora than
pea, resulting in a 10% decrease of absorbed light at high light. We
suggest that the greater tolerance of PSII against light stress in T.
albiflora may be partly ascribed to its light-induced chloroplast
rearrangement.
