Strong synergistic effects of gibberellins with the synthetic cytokinin N-(2-chloro-4-pyridyl)-N-phenylurea on parthenocarpic fruit set and some other fruit characteristics of apple

Abstract

The induction of parthenocarpic fruit set was investigated using the apple cvs. Golden Delicious and Jonagold. The gibberellins GAs, GA4, GAs and GA7 and the synthetic phenylurea-type cytokinin CPPU (N-(2-chloro-4-pyridyl)-N-phenylurea), were applied alone and in combination to unpollinated flowers at the end of petal fall. Gibberellins induced only a marginal final set of parthenocarpic fruits. CPPU sprays were more effective, particularly in the first year. When applied in combination, CPPU and gibberellins had a positive synergistic effect on parthenocarpic fruit set and fruit size, but a negative effect on flower induction the next year. After CPPU + GA sprays, percent fruit set was similar, or greater, compared to natural pollinated trees. The parthenocarpic fruits induced by CPPU + GA had an increased length to diameter ratio. CPPU stimulated, and GA4 and GA7 reduced, the russeting of the parthenocarpic fruits. The internal quality of the fruits was hardly affected, but Ca-deficiency symptoms occurred more frequently in parthenocarpic fruits.

Effects of Plant Growth Regulators on Fruit Set and Fruit Shape of Parthenocarpic Apple Fruits

“…The percentages of fruit set with non-pollination have been reported as 72% in 'Ohrin' (Saito et al, 2007) and 48% in 'Spencer Seedless' (Tanaka et al, 2004); however, the relationship between endogenous plant growth regulators and the growth of seedless fruits, which have no seeds to function as a source of plant growth regulators, remains unclear. Gibberellins are closely related with parthenocarpy in apples: application of gibberellins (Bukovac, 1963;Bukovac and Nakagawa, 1967;Davison, 1960;Nakagawa et al, 1967) and the combination of gibberellins with cytokinins (Bangerth and Schröder, 1994;Williams and Letham, 1969) can induce parthenocarpic fruiting. Exogenous plant hormone application to unfertilized ovaries might serve as a switch that starts the continuing autonomous development of the fruit (Bangerth and Schröder, 1994), and controls the continuity of the flow of assimilates and nutrients required for fruit growth (Treharne et al, 1985).…”

Redução de sementes do tangor 'Murcote' com a aplicação de biorreguladores durante o florescimento

“…Em tangor Murcote , apesar do GA 3 ter proporcionado redução do número de sementes, tal redução não pode ser considerada tão eficiente, apesar de ter existido. Esta eficiência pode estar relacionada com a rápida metabolização do GA 3 , principalmente para o crescimento dos frutos cítricos, pois suas taxas de crescimento são mais lentas, em relação a outros tipos de frutos, como as olerícolas, onde o ciclo reprodutivo é mais curto, e as plantas são anuais e bienais (BANGERTH & SCHRODER, 1994).…”

“…Segundo Davies (1995) e Viviam-Smith & Koltunow (1999, o fator que limita o crescimento do ovário não fertilizado está relacionado com a redução endógena dos níveis hormonais, pois as sementes viáveis são responsáveis por sintetizar altos níveis hormonais como auxinas, giberelinas e citocininas, e segundo Bangerth & Schroder (1994), a aplicação exógena de biorreguladores pode induzir autonomia de crescimento do ovário das flores não fertilizadas, podendo ou não levar à formação de frutos de qualidade ou inclusive promover crescimento rápido dos frutos, continuando ou não o desenvolvimento, que vai ser influenciado pelos níveis hormonais.…”

Induction of Parthenocarpy by Bordeaux Mixture and Its Use for Cultivation in Japanese Pear ‘Kosui’

“…On the other hand, gibberellin can induce parthenocarpy in various fruit tree species such as grapes (Fellman et al, 1991) and the Japanese pear (Nakagawa et al, 1968;Pharis and King, 1985;Vivian and Koltunow, 1999;Zhang et al, 2010). Cytokinins also induce parthenocarpy in some fruit trees (Bangerth and Schroder, 1994;Hayata et al, 1995;Iwahori et al, 1988;Lewis et al, 1996;Ogata et al, 1989;Takagi et al, 1994;Yu, 1999 seemed to be effective during any bud stages of the flower to induce parthenocarpy, from sprouting time to 4 days before anthesis. In more developed flowers, the effectiveness was different between the Bordeaux mixture and FeSO 4 solution; the former also induced fruit at and after anthesis, but the latter did not.…”