PLANT PHYSIOLOGY , Vol 102, Issue 3 903-910, Copyright © 1993 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Changes in the Activities of Anti-Oxidant Enzymes during Exposure of Intact Wheat Leaves to Strong Visible Light at Different Temperatures in the Presence of Protein Synthesis Inhibitors
N. P. Mishra, R. K. Mishra and G. S. Singhal
School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
Changes in activities of the enzymes involved in the metabolism of active
oxygen species were followed in homogenates prepared from wheat leaves
(Triticum aestivum L.) exposed to strong visible light (600 W m-2). The
activities of superoxide dismutase (SOD), ascorbate peroxidase, and
monodehydroascorbate reductase increased significantly on prolonged
illumination of the leaves, indicating an increase in the rate of
generation of active oxygen species. This increase was further exacerbated
when high light stress was combined with low temperature (8[deg]C). Our
results indicate that the increase in activities of SOD and ascorbate
peroxidase involved de novo protein synthesis that was sensitive to the
nuclear-directed protein synthesis inhibitor cycloheximide. The activity of
catalase, on the other hand, decreased on exposure to strong light, which
could be due to its photolability, particularly at lower temperatures.
Ascorbate and total carotenoid contents also increased on light treatment
of the leaves. The induction of the enzymes except for catalase and
increase in the levels of ascorbate and total carotenoids in response to
the stress conditions indicate that they play an important role in the
protection of higher plants from the damaging effects of toxic active
species.
