Factors responsible for the sex expression of Japanese cucumber. (VII)

Abstract

1. Cucumber seedlings are set under long day (15hrs.) and high night temperature (30°C) treat-ment of two or four days duration at each stage of their development, for the purpose of detecting the influence of those environmental factors reflected upon the sex pattern of the flowers. In some plots, treatments are thrice or five times repeated-ly applied. A plot is set under the long day and high night temperature through the whole seedling stage. Control plot is set under short day (8hrs.) and medium night temperature (20°C) through the whole seedling stage. 2. Long day and high night temperature favor the staminate flower development and restrict the pistillate flower formation. As the first pistillate flower of the control plant flowered at the eighth node, the adverse influence of the long day and high night temperature treat-ment reveals its effect apparently only at the higher nodes. At the lower nodes, even on the control plants, there bloomed only the staminate flowers. 3. Treated at the fourth period, just when the primordia of the seventh to the tenth nodes are going to differentiate sexually, those primordia were all transformed into the staminate flowers. Even the treatment applied at the first period influenced on the sex differentiation of the primor dia of the seventh to the eighth nodes. The treatment at the second period influenced upon the sex of the primordia of the seventh to the ninth nodes. The treatment at the third period influenced upon the primbrdia of the seventh to the tenth nodes. 4. The effect of the treatment of four days duration always manifested itself stronger than that of two days duration applied at the same stage. 5. It seems that these environmental conditions influence the sex differentiation by inducing the physiological change around the primordia just going to differentiate sexually, being invigorated as much as the duration of the treatment elongated, or the repetition times of the treatment multiplied, and fainting as time elapses.