Abstract
Effects of different day temperatures at a constant night temperature on the relative growth rate, transpiration rate and net photosynthetic rate were investigated at 100 days after seeding in plants of four pepper varieties with immature fruits. Two varieties which belonges to the bell pepper type bore large fruits. The other two varieties which belonges to the long pepper and cone pepper types bore small fruits. Plants were grown for 7 days in phytotrons under natural light conditions in which day/night temperatures were set at 37/22, 32/22, 27/22°C.
Transpiration rate and stomatal conductance increased with the day temperature. Responses of the netphotosynthetic rate to the day temperatures differed from the responses of the transpiration rate. Changes in the net photosynthetic rate were related to the day temperatures and the presence of immature fruits in plants.
Response of the relative growth rate (RGR) to day temperatures differed among the varieties. Changes in RGR depended on the fruit growth and fruit size. In the plants from the varieties with large fruits, the maximum amount of dry matter accumulated in the fruits and the growth of the leaves was inhibited of a high day temperature. In the plants from the varieties with smaller fruits, the growth of the leaves increased with the day temperature, Dominant sink at a high day temperature was represented by immature fruits in the varieties with large fruits and leaves in the varieties with small fruits.
