Factors responsible for the sex expression of Japanese cucumber. III

Abstract

The purpose of this study was to determine whether or not the auxin level in the cucumber plant might be responsible for or associated with the sex expression of the flower. To control the auxin level of the plant, 2, 3, 5-triiodobenzoic acid (TIBA), 2, 4-dichlorophenoxy-acetic acid (2, 4-D), in doleacetic acid (IAA), naph-thaleneacetic acid (NAA), and maleic hydrazide (MH-30) spray were applied. Spraying with growth substances was begun when the cotyldon expanded fully and repeated at 4 days interval for 30 days in the cold bed. The concentration of each substances used were as follows: TIBA at 10 ppm, MH-30 at 100 ppm, 2, 4-D at 5 ppm, IAA at 30, 100, 250 and 500 ppm, and NAA at 0.2 and 10 ppm. These growth substances, all retarded the plant growth. Male flower formation was unaffected by TIBA, but retarded by 2, 4-D, IAA and NAA. Female flower formation was slightly retarded by TIBA, but accelerated by 2, 4-D, IAA and NAA. NAA was found to be most effective for the sex control. The sprayings with the growth substances always restrict the plant growth. The results with NAA treatments show that the sex reversion thoroughly associates with the growth retardation. The re-sult with TIBA, however, show that the sex reversion does not always follow the trend of the growth retardation.