Effect of Light on Auxin Binding, Cell Fractionation, and Ultrastructure of Etiolated Soybean Hypocotyls

Abstract

Illumination of dark-grown seedlings of soybean (Glycine max [L] Merr) just prior to and during cell fractionation affected auxin binding and the distribution of cell components, especially rough endoplasmic reticulum (ER) Fluorescent illumination of dark-grown seedlings depressed overall auxin binding compared with dark-grown controls. Rough ER isolated in dim green light from dark-grown hypocotyls passed through 14 M sucrose, whereas rough ER isolated from dark-grown hypocotyls exposed to ordinary laboratory fluorescent lighting collected at the 1.0/1 2 M sucrose interface. A detailed examination of the ultrastructure of subhook cells of the cortex of dark-grown seedlings and dark-grown seedlings exposed to light revealed no marked change in the total amount of ER There was, however, in dark-grown hypocotyls harvested and fixed in dim green light, a preponderance toward endoplasmic cisternae associated with the plasma membrane. Following 20-min exposure to laboratory fluorescent lighting, these endoplasmic cisternae associated with the plasma membrane were virtually absent The most marked change, ultrastructurally, was a 10-fold increase in microtubule profiles in the subplasma membrane region of the cytoplasm The findings are of interest in terms of potential effects of light on cell fractionation experiments with plants, auxin binding, microtubule assembly, and ER-plasma membrane associations related to growth