Studies on the growth behaviour of cucumber, Cucumis sativus L. I. : The types of sex expression and its sensitivity to various daylength and temperature conditions

1. Study on the sex expressions in cucumbers, Cucumi.s sativus L., the nodal phase of male and female flowers and its mode of variation has been performed under variou s combinations of the daylength and temperature in the Phytotron at Kyushu University. 2. 25 cultivars of cucumber from 4 ecotypes were used for this study. 3. The types of sex expression were divided into the following four types: a) Monoecious type; some flowers were female and others were male. The distal part of stem tended to increase the female nodes, but did not show the gynoecious state. b) Mono-gynoecious type; the proximal part of the stem showed the monoecious state and the distal part the gynoecious one. c) Gynoccious type ; the flowers were usually female. But a few male ones were produced under certain definite cnvironment. d) Andro-monoecious type; the type which has both male and hermaphroditic flowers. 4. The promotive effect of low temperature for the female flower development could not observed on the cultivars, “Improved Long Green,” “Lemon,” “MSU 713-5” and “Higan-fushinari (only in long-day).” Most cultivars except above ones, regardless of their origin and formation, were faciliated for the formation of female flowers by low temperatures. 5. A definite differentiation of the sensitivity to the daylength was observed as following : a) Short-day sensitives ; flower development was promoted by short-day. b) Daylength insensitives ; the sex diflerentiation was not affected by the daylength. c) Long-day sensitives; female flower development was promoted under the long-day and high temperature conditions. 6. Cucumber cultivars used were classified with the types of sex expressions and the sensitiveness to daylengths and temperatures as shown in Table 13. 7. Cultivars which are considered to belong to the South Chinese variety-complex (See Fig. 1.) were low temperature and short-day sensitive. 8. Cultivars which belong to the North Chinese variety-complex (See Fig. 1.) and to the European one, i. e., “Klinskij mestnyj,” “Nezhinskij mestnyj” and “Galakhovskij,” were low temperature sensitive and daylength insensitive. 9. Cultivar “Higan-fushinari” showed the “Gynoecious” sex expression by low temperatures, the “monoecious” one by high temperature in shortday. It remained at “gynoecious” type by long-day even under the high temperature conditions