Effect of Root Temperature on the Flower Formation and Fruit Yield of Tomatoes

Abstract

In this study, the effects of root temperatures on flower formation and fruit yield of tomato plants were investigated.
1. Roots of young tomato seedlings were bathed in containers of nutrient solution kept at temperatures ranging from 10°to 35°C at 5°C intervals. The experiments ran from 14 to 21 days beginning at cotyledon expansion. Shoot and root growths of seedlings kept at root temperatures 25°and 30°C were greater than those of seedlings grown at other root temperatures. The number of flowers on the first truss of plants whose roots were exposed to 25°C was greater than those on trusses of seedlings grown at other root temperatures, whether the air temperature remained constant at 20°or fluctuated between 20°and 30°C. No difference in the number of nodes on the primary axes among plants was found in this experiment.
2. In experiments conducted during three different times of the year; spring, late spring to early summer, and late fall to early winter, roots of plants were exposed to various temperatures from anthesis of flowers on the first truss to fruit harvest on the third truss. Shoot growth of plants grown at root temperatures between 20°and 30°C was better than that of plants grown at other root temperatures. Root temperatures favorable for root growth have a range lower than that for optimum shoot growth. Fruit production from plants grown at root temperatures of 10°and 35°C was very low because of poor fruit set and growth, especially on those of second and third trusses.
3. Fruit ripening was accelerated on plants grown at root temperature of 10°and 15°C, especially in the 15°C treatment if the nutrient solution was low in nitrogen.
4. These results confirm that the optimum range of root temperatures for the growth of tomato vines widens with increasing size and age of plants from the young seedling stage to mature producing vines, that is 25°30°C during the flower differentiation period in the first truss, 20°30°C for the vegetative growth stage, and 15°30°C during fruit production.