Abstract:

The paper aims to clarify the problem that low light reduces the quality of watermelon fruit. In this study, watermelon variety ‘Sumi 8’ was used as the test material. Through the field 50% shading treatment simulated low light test, the sugar composition and the activities of key enzymes of sucrose metabolism in different growth and development stages of watermelon fruit under low light stress were determined by liquid chromatography and spectrophotometry. The results showed that shading significantly reduced the content of soluble solids in watermelon. In the early stage of fruit development (0-12 days), low light promoted the accumulation of sucrose in watermelon fruit, and then low light significantly inhibited the accumulation of sucrose in watermelon fruit. In the development stage of watermelon fruit, low light stress inhibited the accumulation of fructose and glucose in watermelon fruit. The decrease of sucrose phosphate synthase activity and invertase activity was the main reason for the inhibition of sucrose content accumulation, sugar content and sugar composition change under low light stress. This study provides a scientific basis for the management of light environment and the research and development of high-quality cultivation techniques in protected watermelon production in early spring and autumn.

Key words: watermelon, low light, fruit quality, sucrose metabolism, dynamic study