PLANT PHYSIOLOGY , Vol 111, Issue 3 713-719, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Effect of Cold Hardening on the Components of Respiratory Decarboxylation in the Light and in the Dark in Leaves of Winter Rye
V. Hurry, O. Keerberg, T. Parnik, G. Oquist and P. Gardestrom
Cooperative Research Centre for Plant Science, The Australian National University, G.P.O. Box 475, Canberra ACT 2601, Australia (V.H.)
In the dark, all decarboxylation reactions are associated with the oxidase
reactions of mitochondrial electron transport. In the light,
photorespiration is also active in photosynthetic cells. In winter rye
(Secale cereale L.), cold hardening resulted in a 2-fold increase in the
rate of dark respiratory CO2 release from leaves compared with nonhardened
(NH) controls. However, in the light, NH and cold-hardened (CH) leaves had
comparable rates of oxidase decarboxylation and total intracellular
decarboxylation. Furthermore, whereas CH leaves showed similar rates of
total oxidase decarboxylation in the dark and light, NH leaves showed a
2-fold increase in total oxidase activity in the light compared with the
dark. Light suppressed oxidase decarboxylation of end products of
photosynthesis 2-fold in NH leaves and 3-fold in CH leaves in air. However,
in high-CO2, light did not suppress the oxidase decarboxylation of end
products. Thus, the decrease in oxidase decarboxylation of end products
observed in the light and in air reflected glycolate-cycle-related
inhibition of tricarboxylic acid cycle activity. We also showed that the
glycolate cycle was involved in the decarboxylation of the end products of
photosynthesis in both NH and CH leaves, suggesting a flow of fixed carbon
out of the starch pool in the light.
