Abstract: This study was conducted with leaves collected from the test-tube plantlet of Red Fuji apple as the experimental materials. Changes of hormones，polyamines and NO during in vitro regeneration of adventitious buds were studied under light and dark culture. The results indicated that the contents of ZR，ABA and polyamines under dark culture were higher than that under light culture. The hormone（ZR，ABA and IAA）contents in leaves had the high level during the early stage of inoculation，and the higher level of ZR and ABA，the lower level of IAA were found at the stage of cell division and bud primodium formation. Meanwhile，the ratios of ZR/IAA and ABA/IAA under dark culture were both higher than that under light culture. During the initial stage of inoculation，the endogenous polyamines contents had reached peak，and the contents was also in higher level at the stage of adventitious buds differentiation. During the culture of leaves in vitro，the contents of NO under dark culture kept higher than that of light culture. It is obvious that adventitious bud formation from in vitro leaves of Red Fuji apple was closely associated with contents of endogenous hormones，polyamines and NO.

Key words: apple, leaves, regeneration of adventitious bud, endogenous hormone, endogenous polyamine, nitric oxide