Abstract: Morphology of sexual rep roduction abortion in ‘High Noon’, a distant hybridization cultivar of tree peonies ( P. delavayi var. lutea ×P. suffruticasa) , was systematically investigated with light microscopy and cross. The results indicated that: (1) The stamens matured earlier than the gynoecia and pollens
dispersed at the early stage of anthesis but the rate of normal 2-celled pollenswere merely 2.41%. No pollens germinated not only in liquid nutrition but also on its own stigmas and on other two female parents’stigmas. When flower withered, stigmas excreted a great deal of exudation and became in the best for pollination; (2) The meiosis of multi-megasporocytes were highly asynchronous in one ovule, the development of embryo sac and fertilization were retarded, and the mitosis of some free endosperm nucleiwere abnormal during the cellularization stage; (3) No seeds were produced by self- and cross-pollination in the same cultivar group, but natural pollination seeds were produced with the rate of 0.053‰ - 0.130‰. It was suggested that the main
reasons for the sexual rep roduction abortion in ‘High Noon’were that it can not form enough viable gametes and lack valid pollination.

Key words: Tree peony, Sexual reproduction, Abortion, Morphology