ALTERATION OF GROWTH AND FLOWERING HABIT IN CUCUMBER BY CHLORFLURENOL

Abstract

Chlorflurenol (methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate) was applied to four cultivars of cucumber (Cucumis sativus L.) grown in the greenhouse to determine its effect on sex expression, fruit set, and plant growth habit. The chlorflurenol was applied at three stages of growth, the first, second and fourth true-leaf stages, at concentrations of 0, 0.1, 1.0, 10.0 and 100 ppm. At 0.1 ppm or 1 ppm, chlorflurenol promoted male flower development in predominantly female (PF) Pioneer and monoecious Galaxy. However, at 10 or 100 ppm, chlorflurenol reduced male flower development in monoecious cultivars Galaxy and Wisconsin SMR 58 and in PF Explorer. The effectiveness of chlorflurenol in doing this was dependent on the stage of growth applied. Chlorflurenol did not affect female flower formation. Black-spined Pioneer and Wisconsin SMR 58 produced twice as many fruit per plant as white-spined Explorer and Galaxy when 100 ppm chlorflurenol was applied at the fourth-leaf stage. Plant growth was terminated in all cultivars at the 100-ppm concentration. It was proposed that yields of pickling cucumbers harvested once-over could be improved by increasing plant populations and applying chlorflurenol in the fourth-leaf stage to limit growth and promote fruit set.