Effects of Heating Bearing Shoot near Fruit on Cell Size, Sucrose Metabolizing Enzymes and Sugar Accumulation in Watermelon Fruit

Abstract

Shoots near fruits of watermelon (Citrullus lanatus Matsumu. et Nakai) were continuously heated from 5 days after anthesis (DAA) to a minimum of 30°C during night. Temperatures in a plastic greenhouse during 0 a.m. to 6 a.m. fluctuated between 12.7-17.2°C, and the temperature of the surface of the fruit, whose near shoots were heated (designated as a heated fruit) during these hours, was higher by 0.8°C on the average than that of the control, and also the temperature of the flesh of the heated fruit was 1.0-1.5°C higher than that of the control fruit. Pigmentation of the flesh of the heated fruit was accelerated. Cell size of the heated fruit was smaller than that of the control fruit. Higher sucrose phosphate synthase (SPS) activity of the heated fruit resulted in the higher mean sucrose and fructose content of the heated fruit. Therefore, it is reasonable to consider that heating bearing shoots near fruits can accelerate the rate at which cells enlarge and mature, which causes an increase in SPS activity and an increase in the sucrose content in the fruit, especially the outer portions of the fruit.

Local Temperature Control in Greenhouse Vegetable Production

“…On the other hand, the effectiveness of fruit heating was reported in the melon (Cucumis melo L.) and watermelon (Citurullus lanatus Matsum. et Nakai), in which sucrose accumulation was promoted in fruits (Kano, 2006;Kano et al, 2008Kano et al, , 2012Matsumoto et al, 2012). The effects of fruit heating may therefore differ among crops.…”

Regulation of phytochemicals in fruits and berries by environmental variation—Sugars and organic acids

“…In contrast, no impact of temperature was found on the concentrations of fructose and glucose in satsuma mandarins (Marsh, Richardson, & MacRae, ). In view of sucrose content, it increased in fruits of melon (Kano, ; Matsumoto, Kano, Madachi, & Aoki, ) and watermelon (Kano, Matsumoto, Aoki, & Madachi, ) but decreased in bilberries (Uleberg et al, ) and purple passion fruits (Utsunomiya, ) as temperature increased. The total sugar content showed a decreasing trend in strawberry (Davik et al, ; Wang & Camp, ) and watermelon (Fukuoka, Masuda, & Kanamori, ) as temperature increased, while it did not vary in apple (Yamada et al, ).…”