PLANT PHYSIOLOGY , Vol 108, Issue 2 761-767, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Factors Associated with Depression of Photosynthetic Quantum Efficiency in Maize at Low Growth Temperature
M. J. Fryer, K. Oxborough, B. Martin, D. R. Ort and N. R. Baker
Department of Biology, University of Essex, Colchester CO4 3SQ, Essex, United Kingdom (M.J.F, K.O., N.R.B.)
The photosynthetic productivity of maize (Zea mays) in temperate regions is
often limited by low temperatures. The factors responsible for the
sensitivity of photosynthesis in maize to growth at suboptimal temperature
were investigated by measuring (a) the quantum yields of CO2 fixation and
photosystem II (PSII) photochemistry, (b) the pigments of the xanthophyll
cycle, (c) the concentrations of active and inactive PSII reaction centers,
and (d) the synthesis of core components of PSII reaction centers.
Measurements were made on fully expanded leaves grown at 14[deg]C, both
before and during the first 48 h after transfer of these plants to
25[deg]C. Our findings indicate that zeaxanthin-related quenching of
absorbed excitation energy at PSII is, quantitatively, the most important
factor determining the depressed photosynthetic efficiency in
14[deg]C-grown plants. Despite the photoprotection afforded by
zeaxanthin-related quenching of absorbed excitation energy, a significant
and more persistent depression of photosynthetic efficiency appears to
result from low temperature-induced inhibition of the rate at which damaged
PSII centers can be replaced.
