Physiology of Sex in Cucumis Sativus (L.) Leaf Age Patterns and Sexual Differentiation of Floral Buds

Abstract

One of the factors which control the sexual differentiation of the floral primordium in the cucumber plant may be the hormonal balance in its vicinity; a balance in favour of growth substance, like IAA, may enhance the female tendency while low concentrations of these substances or higher concentration of their antagonists may cause an increase in the proportion of male flowers. In the present work it is shown that whenever the female tendency is strong, the floral buds develop next to younger leaves; the reverse is true for plants of a stronger male tendency. This rule was found to hold true where environmental conditions— like length of day and night-temperature—affected the sex tendency, as well as in the case of the main branch of the cucumber plant, where an increasing female tendency is found. No difference in leaf age-flowerbud relations was detected when different levels of nitrogen were fed to the plants, and the different N leveb had no effect on the sex tendency of the plants. It is pointed out that a similar situation was found in earlier work where the difference in sex tendency was due to genetic factors. It is suggested, therefore, that both environmental and genetic factors, which are known to affect sex tendency in the cucumber plant, work through changing the leafage-flowerbud relationship. Presumably this is related to the hormonal balance in the vicinity of the developing floral primordium.