PLANT PHYSIOLOGY , Vol 106, Issue 3 983-990, Copyright © 1994 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Effects of a Short-Term Shift to Low Temperature and of Long-Term Cold Hardening on Photosynthesis and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase and Sucrose Phosphate Synthase Activity in Leaves of Winter Rye (Secale cereale L.)
V. M. Hurry, G. Malmberg, P. Gardestrom and G. Oquist
Department of Plant Physiology, Umea University, S-901 87 Umea, Sweden
The effect of a short-term (hours) shift to low temperature (5[deg]C) and
long-term (months) cold hardening on photosynthesis and carbon metabolism
was studied in winter rye (Secale cereale L. cv Musketeer). Cold-hardened
plants grown at 5[deg]C exhibited 25% higher in situ CO2 exchange rates
than nonhardened plants grown at 24[deg]C. Cold-hardened plants maintained
these high rates throughout the day, in contrast to nonhardened plants,
which showed a gradual decline in photosynthesis after 3 h. Associated with
the increase in photosynthetic capacity following cold hardening was an
increase in ribulose-1,5-bisphosphate carboxylase/oxygenase and sucrose
phosphate synthase activity and 3- to 4-fold increases in the pools of
associated metabolites. Leaves of nonhardened plants shifted overnight to
5[deg]C required 9 h in the light at 5[deg]C before maximum rates of
photosynthesis were reached. The gradual increase in photosynthesis in
leaves shifted to 5[deg]C was correlated with a sharp decline in the
3-phosphoglycerate/triose phosphate ratio and by an increase in the
ribulose bisphosphate/3-phosphoglycerate ratio, indicating the gradual
easing of aninorganic phosphate-mediated feedback inhibition on
photo-synthesis. We suggest that the strong recovery of photosynthesis in
winter rye following cold hardening indicates that the buildup of
photosynthetic enzymes, as well as those involved in sucrose synthesis, is
an adaptive response that enables these plants to maximize the production
of sugars that have both cryoprotective and storage functions that are
critical to the performance of these cultivars during over-wintering.
