STRONG SYNERGISTIC EFFECTS OF GIBBERELLINS WITH THE SYNTHETIC CYTOKININ N-(2-CHLORO-4-PYRIDYL)-N-PHENYLUREA ON PARTHENOSCARPIC FRUIT-SET AND SOME OTHER FRUIT CHARACTERISTICS OF APPLE
F. Bangerth et M. Schroder, STRONG SYNERGISTIC EFFECTS OF GIBBERELLINS WITH THE SYNTHETIC CYTOKININ N-(2-CHLORO-4-PYRIDYL)-N-PHENYLUREA ON PARTHENOSCARPIC FRUIT-SET AND SOME OTHER FRUIT CHARACTERISTICS OF APPLE, Plant growth regulation, 15(3), 1994, pp. 293-302
The induction of parthenocarpic fruit set was investigated using the a
pple cvs. Golden Delicious and Jonagold. The gibberellins GA(3), GA(4)
, GA(5) and GA(7) and the synthetic phenylurea-type cytokinin CPPU (N-
(2-chloro-4-pyridyl)N-phenylurea), were applied alone and in combinati
on to unpollinated flowers at the end of petal fall. Gibberellins indu
ced only a marginal final set of parthenocarpic fruits. CPPU sprays we
re more effective, particularly in the first year. When applied in com
bination, CPPU and gibberellins had a positive synergistic effect on p
arthenocarpic fruit set and fruit size, but a negative effect on flowe
r induction the next year. After CPPU + GA sprays, percent fruit set w
as similar, or greater, compared to natural pollinated trees. The part
henocarpic fruits induced by CPPU + GA had an increased length to diam
eter ratio. CPPU stimulated, and GA(4) and GA(7) reduced, the russetin
g of the parthenocarpic fruits. The internal quality of the fruits was
hardly affected, but Ca-deficiency symptoms occurred more frequently
in parthenocarpic fruits.