Abstract
In the previous paper, it was reported that tomato seedlings were severely injured in relatively short time when they were exposed to 50°C. It was also found that fruiting and germination of pollen were remarkably affected when seedlings were exposed to 45°C for three hours each in five days, though their vegetative parts were hardly affected.
Expriments were conducted to determine the effect of different temperatures on tomato seedlings (Fukuju No. 2 variety) of various stages of growth. Seedlings were exposed to 30 (control), 35, 40 or 45°C for three hours daily lasting over five days. The stages of seedlings during high temperature treatment were cotyledon expanded, two to three leaves, five leaves, eight leaves, 11 leaves, and 14 to 15 leaves expanded.
Temperature lower than 45°C generally induced no visible injuries on the plants, but in 14 to 15 leaves expanded stage, high temperature of 45°C induced necrosis in leaves and stem of some plants.
Even the temperature as high as 45°C did not reduce yield when the seedlings were in the first three stages (till five leaves expanded). But the treatment of high temperature reduced both percentage of fruit setting and yield when plants were in the older three stages. In these three stages, the higher the temperature, the less the yield, also the older the seeding, the severer the effect. At eight leaves expanded stage yield was reduced only in the first cluster, while at 11 leaves expanded stage reduction in yield extended to the second cluster, and at 14 to 15 leaves expanded stage it was from first to third clusters.
Considering the effect of high temperature on various stages of flower development, high temperature (40 to 45°C) resulted in overall reduction of fruit setting, when flower buds were treated in the stages 15 days prior to anthesis to nine days after anthesis. Reduction was especially severe in the flower buds five days before anthesis to one day after anthesis. It may, however, be mentioned that 40°C temperature treatment given one to two days before anthesis did not adversely affected fruit setting.
A considerable number of small fruits of less than 50 grams in weight were obtained from the flower buds treated during and after anthesis, but no other types of abnormal fruits such as puffy or green gelatinous ones were obtained.
