Abstract:

【Objective】 This experiment was carried out to elucidate the sugar accumulation in tomato fruit under different conditions of light and nitrogen, and make sure of the reasonable nitrogen supply in different light intensities. 【Method】 With Dongnong 708 as experimental material, the changes of sugar accumulation and activities of enzymes related to sucrose metabolism in the development of tomato fruits under four light and four nitrogen supply conditions were studied. 【Result】 At early fruit development stage, light, nitrogen and their interactions had a significant influence on tomato fruit starch accumulation, but had no significant influence on sucrose content. 70% natural light intensity treatment increased fruit SS activity, promoted accumulation of fruit starch at early fruit development stage when the nitrogen level at 8 kg/667 m2. Nitrogen had the same effects at the same light level. Light, nitrogen and their interactions had a significant influence on tomato fruit fructose accumulation at fruit development stage. At later fruit development stage, fruit AI and NI activities were the highest in 8 kg/667 m2 nitrogen treatment under 70% and 100% natural light intensity, and in 0 nitrogen treatment under less than 70% natural light intensity. And they were the highest in 70% natural light intensity in the same nitrogen. Increased fruit AI and NI activity decomposed starch and sucrose, which accumulated at early development stage, into glucose and fructose, and finally improved fruit quality. 【Conclusion】 Light, nitrogen and their interactions have a significant influence on tomato fruit fructose contents. With sufficient light, proper application of nitrogen (8 kg/667 m2 in this experiment ) could improve tomato fructose content. In shading treatment, nitrogen application could decrease tomato fructose content. SS, AI and NI were closely related to sugar accumulation in tomato fruit.

Key words: light intensity, nitrogen, tomato, sugar accumulation, sucrose-metabolizing enzymes