Indian Agricultural Research Institute, New Delhi
Effects of four concentrations of MH (200, 400, 600 and 800 ppm) and two concentrations each of NAA (100 and 200 ppm), IAA (100 and 200 ppm) and 2, 4-D (5 and 10 ppm) on the sex expression and sex ratio in cucumber (Cucumis sativus L. var. Straight Eight) were studied. MH-200 ppm and NAA-100 ppm increased the number of female flowers significantly over the control. All treatments induced appearance of first female flower on comparatively lower nodes of the main axis when compared with the control. MH-600 and 800 ppm, NAA-100 and IAA-200 ppm and IAA-100 ppm suppressed the number of male flowers significantly over the control. All the plant regulators increased the female to male flower ratio when compared with the control. NAA-100 ppm recorded the highest female to male flower ratio.
Observation on pollen fertility immediately after the second spray was also reported. MH-800 ppm recorded the highest pollen sterility. This effect however was temporary.
IAA-100 and 200 ppm and NAA-200 ppm stimulated the growth of the plants. MH in all concentrations suppressed the apical growth. This effect was temporary in all the concentrations except 800 ppm.
It was concluded that even under long days and high temperature conditions it was possible to modify the sex expression and ratio in cucumber by spraying certain plant regulators.
