Environmental Effects on Dynamics of Fruit Growth and Photoassimilate Translocation in Tomato Plants

I. Effects of Irradiation and Day/Night Air Temperature

Abstract

Dynamics of fruit growth and photoassimilate translocation in tomato plants (Lycopersicon esculentum Mill.) as affected by irradiation and day/night air temperature were analyzed in relation to respiration, photosynthesis and transpiration of the fruit and the leaf. Fruit growth was explained by about 80% of sap flux imported into the fruit and was scarcely affected by transpirational water loss from the fruit. Irradiation clearly enhanced fruit growth and photoassimilate translocation, and about 70% of fruit growth and about 80% of photoassimilate translocation were brought during the light period with highly activated leaf photosynthesis and fruit respiration under day/night air temperature of 25/15°C. In particular, when air temperature around fruits rose to 25°C in the light period, remarkable increases in fruit growth and photoassimilate translocation were found with the activated fruit respiration. On the other hand, decreases in fruit growth and photoassimilate translocation were found during the dark period without effects of air temperature. From these results, it was suggested that energy-dependent transport process of sugar in fruits is one of the determinant processes regulating fruit growth and photoassimilate translocation in tomato plants under light.