Abstract: Effects of exogenous polyamines and their biosynthesis inhibitor MGBGon fruit set and the contents of the endogenous hormones and polyamines during flowering and fruit setting were studied with Red Fuji apple. The results showed that application of Spd at 1 ×10^-5mol·L^-1 at full bloom could increase fruit set and the contents of GA3 and ZR in the flowers and fruitlets of Red Fuji apple , but reduced IAA and ABA contents. MGBG basically had an opposite effects. The Spd treatment could also increase endogenous Put , Spd and Spm contents in the fruitlet of Red Fuji apple , but reduced their contents in the flowers , MGBG treatment decreased the endogenous Spd contents but increased Put contents.

Key words: Apple, Polyamines, Hormones, Fruit setting