INVESTIGATIONS OF SEX EXPRESSION OF CUCUMIS SATIVUS BY GRAFTING AND COPPER APPLICATION

The cucumber (Cucumis sativus) with its diversity of sex types represents a perfect model plant for studying sex expression. Besides environmental factors, three major genes, Acr/acr, M/m, and A/a are responsible for the different sex types of cucumber. According to the one-hormone hypothesis, formation of the four sex types of cucumber can be explained in connection with the genes M/m and Acr/acr. In contrast to the gene Acr/acr that links to an ACC synthase (a key enzyme during ethylene synthesis), nothing is known about the function of the gene M/m. Grafting experiments between different M/m genotypes (gynoecious and hermaphroditic) and different Acr/acr genotypes (gynoecious and androecious) were conducted. The results excluded a transport of the product from the gene M/m. These are in agreement with the assumption that this gene is responsible for an ethylene receptor. Results of experiments of copper applications indicated that copper probably protects the ethylene receptors before their inactivation by silver ions. However, femaleness could not be enhanced by copper, so that copper did not increase the sensitivity of the receptors.