Light Quality Effects on Flower Sex Expression in Cucumber and Spinach

Abstract

Using spectral filters to reduce the amount of far-red (FR) light perceived by plants has been shown to effectively reduce internode elongation of many floriculture crops. It is theorized that gibberellin (GA) function is inhibited in some way by the increase in the red: far-red light ratio. Sex expression of flowers are effected by exogenous applications of gibberellin and cause a shift in flower sex expression towards maleness. The use of growth regulators (GA inhibitors) have demonstrated a shift towards femaleness. Flowering of spinach, a dioecious species, and cucumber (staminate and pistillate lines), a monoecious species, were surveyed for shifts in flower sex expression, indicating a suppression of GA. Male: female flower ratio decreased from 7.6:1 to 4.06:1 when comparing the controls and –FR for the staminate cucumber line and 1:13 to 1:40 for the gynecious cucumber line. The decrease in male flowers on plants grown in a –FR environment are an indication that the function of GA is inhibited. There was no significant effect on the male: female flower ratios of the spinach.