Abstract
Experiments were carried out to investigate the effect of hormone sprays on the plant growth and pigment and carbohydrate contents of tomato fruits, in 1959 at Shinshu University farm. The variety Aichi-tomato was used. Hormones and their concentrations used were þ-chlorophenoxyacetic acid, 30 ppm; gibberellin, 50 ppm; α-naphthaleneacetic acid, 50 ppm; 2, 4-dichlorophenoxyacetic acid, 10 ppm. Aqueous solutions of these hormones were sprayed on the flowers from the first to the third cluster at each flowering time.
1. Plant height of hormone sprayed lots increased over that of control plant, but there was no difference in the number of leaves between the control and the hormone sprayed lots.
2. The numbers of flowers and of fruits set in each flower cluster of hormone sprayed lots did not increase, but on the total of three flower clusters, the gibberellin sprayed lot was the greatest and the 2, 4-D sprayed lot the smallest. The fruit set percentage of PCPA sprayed lot was the highest of all lots. The fruit development, in the hormone sprayed lots except in the gibberellin lot was accelerated over that of the control lot, but the gibberellin sprayed fruits were smaller than the control, and their development was checked.
3. The fruits of PCPA and 2, 4-D sprayed lots were seedless as the result of parthenocarpy, but the gibberellin and NAA sprayed fruits produced seeds. Among the seed-containing fruits, the larger the fruits, the more seeds they contained.
4. The fruit yield of gibberellin sprayed lot was greater than that of the control, but among the other hormone sprayed lots, there was hardly any difference. The early yield was greater in PCPA, NAA and 2, 4-D sprayed lots, but gibberellin spray delayed the harvest.
5. Chlorophyll content of fruits sprayed with PCPA, NAA and 2, 4-D decreased, but carotene, lycopene and xanthophyll contents of these fruits increased compared with the control. In the gibberellin sprayed lot the disappearance of chlorophyll was slower, and carotene and xanthophyll contents were less than the control fruits.
6. Differences in sugar contents of fruits between the hormone sprayed and control lots were not significant, and the sugar content increased as the fruits matured. Starch content of fruit decreased in all lots as the fruits matured.
