Abstract:

【Objective】 The effects of different nigh low temperatures on carbohydrate metabolism in melon fruit were studied in this paper. 【Method】 Each carbohydrate content and sugar-metabolizing enzymes activities in fruits grew under normal and night low temperature circumstance simulated by climate room were analyzed. 【Result】 Effects of different night low temperatures on carbohydrate contents in melon fruit were different to some degrees. Fructose and glucose decreased after treatment of 9℃ in night for 3 d while significantly decreased sucrose content occurred in middle and later period, yet galactinol content had no change. Meanwhile, total carbohydrate content was lower than the control with markedly significant difference after treatment of 9℃ in night for 3 d, and the difference was more obvious as the time prolonging. Otherwise, compared with the control, starch content increased obviously on 3-12 d after treatment of 9℃ in night, however, after treatment of 12℃ in night, starch content increased in evidence while each carbohydrate content was almost invariable. Meanwhile, the change of sugar-metabolizing enzymes activities in fruit indicated that acid invertase (AI), netutral invertase (NI) and ?-galactosidase activities enhanced, but sucrose synthase (SS) activities and sucrose phosphate synthase (SPS) activities declined with very significant difference after treatment of 9℃ in night. What was more, the effects of 12℃ in night on sugar-metabolizing enzymes activities were small, with no significant difference. 【Conclusion】 Sugar accumulation and sugar-metabolizing enzymes activities were affected seriously after treatment of 9℃ in night, but 12℃ in night did not altered the carbohydrate metabolism, which was the critical low temperature to restrict sugar accumulation. These results suggested that the decreased metabolism including sucrose, stachyose and starch may affect melon fruit expansion and quality after treatment of 9℃ in night.

Key words: melon, night low temperature, carbohydrate, sugar-metabolizing enzymes