Reduction of High Temperature Inhibition in Tomato Fruit Set by Plant Growth Regulators

The effects of plant growth regulators on fruit set of tomato (Lycopersicon esculentum Mill.) under high temperature were examined in a controlled environment and a field under rain shelter. Tomato plants exposed to high temperature (34/20ºC) had reduced fruit set. Treatments of plant growth regulators reduced the fruit set inhibition by high temperature to some extent, especially treatment with mixtures of 4-chlorophenoxyacetic acid (4-CPA) and gibberellins (GAs). In the field experiment,tomatoes treated with a mixture of 4-CPA and GAs showed increased fruit set and the numbers of normal fruits (excluding abnormal types such as puffy fruit) were more than the plants treated with 4-CPA alone during summer.