High temperature injuries in tomato. II

Effect of duration of high temperature on fruit setting and yield

Abstract

Tomato seedlings (var. Fukuju No. 2) were exposed to temperatures of 40°C and 45°C for 1, 3 (in one day), 6 (3 hours each in two days), or 15 hours (3 hours each in five days). The high temperature treatment was given when the first flower of the first cluster had just begun to bloom.
These temperature treatments induced no visible injuries on the plants and did not affect the plant growth.
Treatment of 40°C for 1 hour did not actually reduce both percentage of fruit setting and yield, but all other treatments reduced yields, and the reduction in yield was enhanced with increasing temperature and duration of treatment. Reduction in yield at the temperature of 40°C and 45°C for 3 hours was remarkable as compared with those for 1 hour.
Germination test of pollen on artificial medium revealed that the treament of 40°C for 1 hour was enough to decrease percentage of pollen germination.
Considering the effect of high temperature on various stages of flower development, the buds of 8 to 9 days before anthesis were highly susceptible to high temperature, and the percentage of fruit setting at that stage was reduced by even the treatment of 40°C for 1 hour. From this fact, together with the result of pollen germination, it was suggested that even 40°C for 1 hour was injurious, and might reduce the percentage of fruit setting in tomato.