Influence of Gibberellic Acid on Setting and Development of Fruits in Tomato

Abstract

Considering the total number of investigations concerned with gibberellic acid those dealing with fruits are relatively few (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Gibberellic acid (GA) is capable of inducing parthenocarpy (1, 3, 5, 6, 7, 13), but whether or not fruit setting is increased at the same time is not known (4,6, 12). Several investigators found no increase in fruit size with GA treatment (4, 6, 10), but investigators did find considerable increase in the size of the grape berry (8, 9, 10, 11). There is thus room for more work with GA on fruiting. In 1957 the writer set up three experiments for studying the effect of GA on setting and development of fruit in Lycopersicum esculentum Mill. var. John Baer. Early in February an experiment with 2 foot John Baer tomato plants in 6 inch pots was set up in the greenhouse. The purpose was to make a comparative study of indoleacetic acid, 2, 3, 6-trichlorobenzoic acid and gibberellic acid on induction of parthenocarpic fruits. These growth regulators were incorporated in lanolin pastes both alone and in combinations with GA in the following concentrations: 1.0 and 0.5% IAA; 0.1% 2,3,6-TCBA; 1.0 and 0.5% GA; 0.5 % IAA + 0.5 % GA, and 0.1% 2,3,6-TCBA + 0.25 % GA. These pastes were applied to the cut surface of the pistil of emasculated flower buds, ready to open. Only the first two buds in each cluster were used; the others were removed. Seventy-four mature fruits were harvested. Of these, 16 produced by pollination were seeded; all others were seedless. The seedless fruits produced by applying growth regulators were a little smaller than the seeded ones. The GA treatment alone induced parthenocarpy: adding growth regulators to the GA did not alter the percent setting or the size of the fruits. This is different from the report of Luckwill (3), in which he states that there was a synergistic effect when the growth regulators were added to GA.In late April a second experiment was started (also in the greenhouse), with 36 Several weeks later eight plants were sprayed with 35 ppm GA and eight others with water. At the time of spraying clusters, one had a few recently set fruits, flowers, and buds; clusters two had flowers and buds; and clusters three had only small buds. As the fruits matured they were harvested, counted, weighed, and sectioned for observation as to seed and pulp conditions. It is seen in table I that spraying the tomato flowers or buds increased setting but the fruits were smaller and the total yield was decreased by the GA. Many of the GA treated fruits were only partially seeded; some lacked locules.In late May, 1957, 76 John Baer tomato plants were planted in the field. By June 9 the flowers of the first cluster were opening and at that time this cluster was removed from 46 plants. The flowers and buds of 10 of the remaining 30 plants were sprayed with a solution of 70 ppm GA. A further group of ten was similarly treated with 35 ppm GA,

Fruits: A Developmental Perspective.

“…Growth factors by which pollen influence fruit set most likely include the plant hormones auxin and gibberellins (Nitsch, 1970). Gibberellins stimulate pollen germination and pollen tube growth, and exogenous application of gibberellins to flowers can result in fruit set in the absence of fertilization (Gustafson, 1960). Application of gibberellins to unpollinated tomato flowers causes an increased auxin level in the ovary (Sastry and Muir, 1963).…”

Pollination Increases Gibberellin Levels in Developing Ovaries of Seeded Varieties of Citrus

“…This concept is based mostly on three lines of evidence: (a) pollen contains plant hormones such as auxins and GAs (Nitsch, 1971); (b) exogenous auxin or GA results in fruit growth in the absence of fertilization (Gustafson, 1960); and (c) parthenocarpic ovaries contain increased amounts of auxins and GAs (Gil et al, 1972). Nevertheless, the support in the literature for a hypothetical stimulation of the hormonal synthesis promoted by pollination is scarce or indirect.…”

Producción y calidad poscosecha de tomate (Solanum lycopersicum L.) larga vida sometido a la aplicación de ácido giberélico

“…Es posible que se haya presentado un exceso con las dosis mencionadas, las cuales afectaron negativamente el desarrollo del fruto, además, con 10.000 mg L -1 de ácido giberélico se observaron lesiones en la epidermis del fruto, agrietamientos y manchas en el pedúnculo, lo cual disminuye marcadamente la calidad de los frutos, por tanto, esta dosis definitivamente no se recomienda para los frutos de tomate, así mismo, como es una dosis tan alta aumenta bastante los costos de producción, la dosis de 1.000 mg L -1 de ácido giberélico tampoco se recomienda. En concordancia, Gustafson (1960) encontró que esta hormona disminuyó el tamaño de los frutos en tomate.…”