Response of Flowers of Black Corinth and Fruit of Thompson Seedless Grapes to Applications of Plant Growth-Regulators

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Abstract
Oil emulsions and/or aqueous soln. of beta-napthoxyacetic acid, alpha-napthaleneacetic acid, gamma-(indole-3)-n-butyric acid, beta-napthoxypropionic acid, 2,4,5-trichlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, alpha-(2-chlorophenoxy)propionic acid, and indole-3-acetic acid were applied separately to Black Corinth grapes by dipping clusters of the flowers. Oil emulsions of the first 6 compounds were applied to Thompson Seedless by dipping clusters of the fruit. The treatment at full bloom of flower clusters of Black Corinth with beta-naphthoxypropionic acid at 200 ppm. resulted within 12 days in berries and clusters larger than those of untreated controls. The maturation of these treated clusters was accelerated. Application of 4-chlorophenoxyacetic acid at 5 ppm. resulted in many large berries containing seeds or seedlike structures. The other compounds applied to Black Corinth resulted in no marked responses other than injury. Very young berry clusters of Thompson Seedless treated with 4-chlorophenoxyacetic acid at 20 ppm. resulted in larger clusters and berries than untreated controls. The other compounds applied to this var. produced varying amounts of injury. The young clusters were much more responsive than older ones. Some treatments resulted in only temporary curvatures of the rachis, its branches, and the pedicels; at higher concns. of the growth-regulators the rachis and its branches enlarged, split, and callused, and many berries failed to enlarged, split, and callused, and many berries failed to enlarge; some clusters were killed.