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Environmental and Stress Physiology

Polysomes from Winter Rye Seedlings Grown at Low Temperature ¹

I. Size Class Distribution, Composition, and Stability

Department of Plant Sciences, University of Western Ontario, London, Ontario, Canada N6A 5B7

We have studied the influence of growth at low temperature on size class distribution, stability and composition of leaf cytoplasmic polysomes from rye seedlings (Secale cereale, cv Puma) grown at 5°C and at 20°C. Leaves of seedlings grown at 5°C contain 2.7 times more cytoplasmic polysomes (expressed on a DNA basis) and the polysome size class distribution is skewed toward larger polysomes. These changes were more pronounced in the free polysome fraction than in the membrane-bound fraction. The melting point of the total ribosome fraction from cold-grown leaves was decreased by 3.7°C. Electrophoresis did not reveal any difference in the rRNA or in core-ribosomal proteins (KCl nondissociable) following growth at low temperature. Some differences were noted in peripheral ribosomal proteins. This study is the first to examine the effect of growth at low and high temperatures on polysome metabolism using plants of similar developmental stage. Polysome quantity, polymerization, melting point and peripheral ribosomal proteins in rye seedlings are modified during growth at low temperature.

¹ Supported by a grant in aid of research from the Natural Sciences and Engineering Research Council, Canada. This work forms part of a dissertation by A. Laroche in partial fulfillment of the requirements for the Ph.D. degree in the Department of Plant Sciences, University of Western Ontario, London, Ont., Canada.