Factors responsible for the sex experssion of Japanese cucumber. II

Anatomical studies on the sex experssion and the transformation of the cucumber flowers induced by pinching

Abstract

To detect any factors occurring in the early development of the cucumber flower that might contribute to our knowledge of sex determination, it seemed desirable to follow the growth of the flower bud from differentiation, with special reference to the stamen and pistil formation.
Figs. 1 and 2 show the staminate flower buds, growing successively.
Fig. 3 shows the pistillate flower buds, the growth of the second flower bud being far restricted.
The modes of the growth succession of the flower buds as above related show the first sign of the nodal sex expression.
Fig. 4 shows the prominent growth of the stamens, indicating the staminate flower formation.
Fig. 5 shows the maximal growth of the pistil of the staminate flower.
Fig. 6 shows the first sign of the pistillate flower, the pistil is progressively growing and the growth of the stamen is inhibited.
Fig. 7 shows the maximal growth of the stamen in the pistllate flower.
It will thus be observed that all cucumer flowers in the primordial stages bear both sets of sex organs, and hence are apparently potentially herma-phroditic.
Fig. 8 shows the staminate flower buds and the primordia of the lateral branch.
Fig. 9 shows the pistillate flower buds and the primordia of the lateral branch.
The stem is pinched for the purpose of inducing the sex reversion of the staminate flower buds. The staminate flower buds are transformed into the bisexual flower and the pistillate flower and also into the lateral branch somewhat malformed at the basal portion.
Fig. 10 shows the bisexual flower and the fruiting of the pistillate flower which is developed through the sex reversion of the staminate flower buds, induced by the pinching of the stem.
Fig. 11 shows the induced pistil development in the staminate flower bud. Fig. 12 shows the stamens filled with the pollens and the developing pistil in the bisexual flower bud induced by the stem pinching.
Fig. 13 shows the development of the pistil in the staminate flower buds as induced by the stem pinching.
Fig. 14 shows the normal lateral branch (left) and the induced lateral branch (rlgbt) transformed from the staminate flower primordia, showing the malformed leaves and the short internodes.
Fig. 15 shows the transforming flower primordia to develop to form the induced lateral branch.
It may be concluded that the sex determination of the flower buds was induced before the morpho-logical expression became appreciable with respect to the stamen and pistil development. Application of the growth substance and the stem pinching bring about the sex reversion and even the transformation of the staminate flower buds to the lateral branch.