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UBC Theses and Dissertations

The effects of indolebutyric acid and irradiation on tomato fruit set and yield Taper, Charles Daniel


During the winters of 1946 to 1947 and 1947 to 1948 one hundred and twenty-eight tomato plants of the varieties Vetomold 121 and Ailsa Craig, growing in a greenhouse at the University of British Columbia, were subjected to irradiation from 200 watt fluorescent lamps, and treated with organic acids, applied to foliar and floral parts, in an attempt to increase fruit set and yield. The plants were grown in soil in 10 inch pots placed in randomized positions. During the first winter they were treated in groups of eight; and, during the second, in groups of six. Control groups were maintained. Sixty-seven days of irradiation from 200 watt fluorescent lamps, used to increase the normal photoperiod by six hours, produced, in Vetomold 121, prounced damage to foliage and an inhibition of flowering. Pre-irradiation of seedlings of Vetomold 121 for four hours daily, following the greening of the cotyledons, resulted in a significant increase in set of 29.6 per cent for first clusters. A combination of this treatment and a water spray, on flowers, of indolebutyric acid, 5000 p.p.m., was, for first clusters, significantly the most effective treatment applied to the variety. The initiation of flowering in tomatoes, it was found, is governed by the length of the photoperiod; and is not influenced by food relationships within the plant. Foliar sprays of indolebutyric acid 50, 100, 250 and 500 p.p.m., applied to Vetomold 121, prior to flowering, had no effect. Indolebutyric acid 100 p.p.m. and 200 p.p.m. in water were ineffective in influencing fruit set. "Fix", "Seed-Less-Set", and indolebutyric acid 5000, 3000 and 500 p.p.m., applied in water, significantly improved fruit set 20.9 to 37.1 per cent on first clusters of the varieties. Hormodin No. 1, in talc, used on the second clusters of Vetomold 121, increased set by 22.8 per cent. No treatment was better than any other in influencing set, but indolebutyric acid produced fruits of better shape than the commercial preparations "Fix" and "Seed-Less-Set". No treatment caused plant injury. Total yields were significantly increased by effective treatments; but average fruit sizes were not increased. There was no difference due to variety, year, or time of planting. A delayed spray appeared to be the most convenient method of application; i.e., one application made to each cluster when most of the flowers are open, with earlier flowers on the point of dropping. Parthenocarpic fruits were sweeter than seeded fruits. Applications of effective concentrations of indolebutyric acid resulted in the production of bands of uniformly sized fruits maturing at nearly the same time. Fruits from flowers treated with acid ripened five to seven days earlier than fruits developed from untreated flowers. Where acid treatments were effective the formation of abscission layers was retarded and, as a result, there was no fruit drop. Of the materials and concentrations tested, indolebutyric acid 500 p.p.m. in water, applied as a delayed spray to floral parts, appeared to be the most valuable.

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