Studies on the sex expression of flowers in Cucumis Melo L. (I)

Abstract

Experiments have been continued to investigate the sex expression in Cucumis Melo L. In the present paper, the structure of flower and the inheritance of andromonoeciousness versus monoeciousness are described, and the result of comparison as regards function of pollen from either hermaphroditic or staminate flower is presented. The andromonoe-cious plant used in the experiment was commercial variety Earl's Favourite which represents C. Melo L, var. reticulatus, and for the monoecious plant No. 111 and No. 981, collected in Afghanistan and Pakistan by the Japanese expedition in 1955 were used, of which No. 111 is believed to belong to the snake melon, C. Melo L. var. fLexuosus (Fig. 1). The results obtained are summarized as followes. 1. The hermaphroditic flower on andromoneci-ous plant bore the pistil and the stamens filled with pollen, while the pistillate flower on monoe-cious plant bore the pistil and the rudimentary stamens (Fig. 3, 4). 2. Though there was a fare occurrence of the andromonoecious plant bearing pistillate flower and of the monoecious plant bearing hermaphroditic flower, it was confirmed that the monoeciousness differed from the andromonoeciousness in a single dominant allele (Table 1. 2). 3. Pollen grains of the hermaphroditic flower as well as those of the staminate flower within the same vine germinated on the artificial media (1 agar, 5% sucrose and pH 6. 5) in different degree. The difference of germination percentage of the pollen of hermaphroditic and staminate flower was significant at 5 per cent level, i.e. 75.8 per cent and 66. 2 per cent respectively after one hour of culture. No significant difference was shown in the elongation of pollen tubes, and moreover, the rate of normal pollen was as high as 95 per cent or more in either hermaphroditic or staminate flower (Table 3). 4. Either through the intra self pollination or through the neighbour pollination with pollen of staminate flower within the same vine, the yield and the market value of the mature fruit from hermaphroditic flower were the same. Comparing the character of hermaphroditic flower with those of staminate flower, no significant difference was found with regards the function of pollen, i.e. the rate of fruit setting, the number of germinable seed, and the weight of fruit or seed. From the results, it is suggested that the intra self pollination on hermaphroditic flower facilitates practical procedure of pollination, with an advantage of securing the strict inbred seed.