Abstract
Fruit sweetness correlates with sugar accumulation into fruits during their development. Sugar content in tomato fruits is known to increase just as during salt- or drought-stress. These effects are interpreted as the result of water withdrawal from the fruit and transfer to the plant, thereby raising the concentration of sugars in the fruits. Another possible factor is the induction of free sugar accumulation in the leaves under abiotic-stress, with consequent movement of sugars to the fruits. We gave oxidative-stress to 4-months-old tomato and melon plants by supplying the hydrogen peroxide solution to the soil. This treatment caused an increase of sucrose-phosphate-synthase activity and subsequent free sugar content in the leaves. It also caused an increase in free sugar content of the fruits. Furthermore, the production levels of the fruits were slightly increased after supplying the hydrogen peroxide solution, although the oversupply of hydrogen peroxide prevents plant growth.
