Partial Reversal of Temperature‐dependent Inhibition of Soybean Hypocotyl Elongation by Cotyledon Excision1

The effect of removal of cotyledonary tissue on the subsequent hypocotyl elongation at 25 C of four soybean (Glycine max L. Merr.) cultivars was studied. Following a 24‐hour imbibltion period, cotyledonary tissue was removed from seed of “short” hypocotyl ‘Amsoy’ and ‘Beeson’ and “long” hypocotyl ‘Corsoy’ and ‘Hawkeye.’ Seed were then grown on paper towels for 7 days at 25 or 31 C. Inhibition of Amsoy and Beeson hypocotyl elongation at 25 C was reduced by this technique. Hypocotyl dry weight decreased, but hypocotyl length increased with increasing percentage removal of cotyledons. Removal of 50% gave the greatest reversal of the inhibition; at 75% removal, limited food reserves apparently decreased hypocotyl length. Hawkeye and Corsoy hypocotyl length did not increase with increasing cotyledon removal. Resuits suggested that inhibition of Amsoy and Beeson hypocotyl elongation at 25 C may be due to an inhibitory substance, or its precursor, located in the cotyledons.