Abstract
Summary In order to correlate the role of endogenous inhibitors of growth of soybean plants with the inhibition of such growth by red light (R), a search for specific growth inhibitors was undertaken in the neutral and acidic fractions of acetone extracts from R- and dark-grown hypocotyls of soybean seedlings ( Glycine max L.). Two neutral and two acidic inhibitors were isolated. They were named N-I and N-II (neutral inhibitors) and A-I and A-II (acidic inhibitors), respectively, based on the order of their increasing Rf values during chromatography. Variations in the activity of the inhibitors in the hypocotyls of dark-grown seedlings after the onset of R irradiation were determined in terms of «cress units» which were defined as the activity that causes 50 % inhibition in the cress-root bioassay. The inhibitory activity of N-I and N-II tripled after exposure of plants to R for 24 h, whereas the activity of A-I and A-II remained almost unchanged. These results suggest that R-induced inhibition of growth of soybean hypocotyls may be controlled by variations in the levels of the neutral inhibitors, N-I and/or N-II, in the hypocotyls rather than by the acidic inhibitors.
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