Vegetative and Fruiting Responses of Tomatoes to High Temperature and Light Intensity

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Abstract
A study, involving effects of high temp. and light intensity on growth and fruiting of tomato, was conducted in 4 phases. Two commercial vars., Marglobe and V617 Pearson, and 3 summer-setting selections, S-1112B, S-1114C, and S-1119N, were used. Flower clusters of Marglobe were sprayed with 10 ppm. para-chlorophenoxyacetic acid (CPA) during a period of increasing temp. Parthenocarpic fruits were set by the spray initially, but with the onset of the high-temp. and light intensity conditions, fruiting failed entirely. Marglobe plants in a shaded greenhouse set fruit in response to CPA sprays even under extremely high temps., but were unresponsive to CPA, sucrose, and urea sprays in an unshaded greenhouse at the same temp. Marglobe plants started outdoors during the high-temp. period were not receptive to CPA in inducing fruit-set other than on the 1st fruit spur. The summer-setting selections developed parthenocarpic fruit under high light intensities and temp. and were favored by CPA sprays. Shading also increased fruit-set without CPA. Non-fruiting Pearson plants and fruiting S-1119N plants grown in the field under the same conditions of high temp. and light intensity were analyzed. There was little evidence that the difference in fruiting was due to chemical composition. Flower abscission and style exsertion as possible causes of fruiting failure under high temp. were discussed.