Differences in the Responses to Water Stress of Growing and Non-Growing Regions of Maize Mesocotyls: Protein Synthesis on Total, Free and Membrane-Bound Polyribosome Fractions

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Abstract
The growing and non-growing regions of the mesocotyl of young maize seedlings show different responses to water stress with respect to their ability to retain polyribosomes. The growing region shows a marked reduction in total polyribosomes, although some are retained within the stressed tissue. In the non-growing region there is little stress-induced change to the total polyribosome content. These results support the contention that physiologically younger, growing tissues are more sensitive to water stress than more mature tissues that have ceased to grow. The free (FP) and membrane-bound (MBP) polyribosome content of the growing mesocotyl region is considerably greater than that of the non-growing region, which is indicative of their more active metabolism. Both the MBP and FP fractions decline when the cells of the growing region are subjected to stress: no differential sensitivity is evident. Hence any qualitative changes in protein synthesis induced by stress must be expected to result from changes in activity of both polyribosome fractions. In the stressed non-growing region, FP decline slightly, but MBP exhibit no consistent changes.

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