Abstract: To probe into the response of endogenous polyamine to temperature stress and the relationship between endogenous polyamine and fruit expansion, The effects of different night temperatures on fruit expansion and polyamines were analyzed with Cucumis melo L. 'Yu Meiren' as material. The results showed that single fruit weight, transverse length and vertical length after 12 ℃ in night were biggest, that after 15 ℃ in night were the second, and the single fruit weight, transverse length and vertical length after 18 ℃ in night were significant smaller than that after the treatment of 15 ℃ in night, whereas the single fruit weight, transverse length and vertical length after 9 ℃ in night were remarkable smaller than that after the treatment of 18 ℃ in night. Meanwhile, the change of PA content in fruit indicated that the contents of total PA, Spd, Put decreased during fruit development, while the difference among night temperatures was lied. The contents of Put, Spd, Spm, total PA were lowest in six days after the treatment of 9 ℃ in night, and that of 18 ℃ in night was remarkable lower than that of 12 ℃ and 15 ℃ in night. Moreover, the difference between 12 ℃ and 15 ℃ in night was not significant . In addition, Put、Spd and total PA content in fruit was positively correlated to the increment rate of melon single fruit. These results suggested that the effect of high or low temperature on fruit expansion may be related with the change of PAs in fruit.

Key words: Melon, night temperature, fruit expansion, polyamine