Some Morphogenic Differences between Monoecious and Gynoecious Cucumber Seedlings as Related to Ethylene Production.

Exposure of gibberellic acid-treated seedlings of a monoecious cucumber cultivar ;Chipper' (Cucumis sativus L.) to ethylene caused thickening of the hypocotyl, inhibited longitudinal growth, and had no effect on fresh weight. Downward curvature of cotyledons was increased by the presence of ethylene. A gynoecious breeding line, ;Gy 3,' had thicker hypocotyls and displayed its cotyledons in a more downward position than ;Chipper'. Excised hypocotyls of the gynoecious seedlings produced three times as much ethylene as did the monoecious Chipper hypocotyls. Thus, ethylene may play a role in the regulation of cucumber seedling morphology.