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

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