Field experiments were conducted for two years to evaluate the effect of growth regulating substances such as p-chlorophenoxyacetic acid (CPA), gibberellic acid (GA3), and N6-benzyladenine (BA) on the fruit set and yield of tomato plants treated by high temperature.
In the first year a high temperature of 40°C for five hours markedly reduced the fruit set and yield. Fruit set of flower when treated by high temperature at anthesis recovered after CPA spray (50ppm), whereas when treated at bud formation they failed to respond to CPA spray and did not develop further. BA spray (10ppm) before high temperature treatment combined with CPA spray showed a remarkably favorable effect on fruit set of flowers treated by high temperature not only at anthesis, but also at bud formation. Consequently, the spray with CPA and BA increased considerably the yield of high temperature treated plants.
In the second year high temperature of 40°C applied for four hours reduced the fruit set and yield only of the first flower cluster of plants subjected to high temperature when its first flower just began to open. The spray with CPA or CPA plus BA remarkably increased the yield of the first and second clusters of plants treated by high temperature. There was no favorable effect of combination of CPA plus BA over CPA alone.
Occurrence of puffy fruits increased by CPA or CPA plus BA spray regardless of high temperature treatment in both years.