关键词: 夏蜡梅, 美国蜡梅, 属间杂交, 杂交障碍, 花粉萌发和花粉管生长, 杂种胚发育

Abstract: For an intergeneric cross between Sinocalycanthus chinensis and Calycanthus floridus var. oblongifolius，a pollen-pistil interaction using fluorescence microscopy and hybrid embryo development through a paraffin section were conducted to reveal intergeneric cross-compatibility. Results showed that，with or without reciprocal crosses，pollen grains of male parents could adhere and further germinate on stigmas of female parents and that pollen tubes could reach the embryo sacs. The process of pollen germination and pollen tube growth was more consistent when S. chinensis was used as the female parent with most of the pollen tubes entering the embryo sacs approximately 36 h after pollination. However，with or without reciprocal crosses，the hybrid embryo development through the paraffin section caused post-fertilization barriers that led to a very low seed set. Although double fertilization was observed，most hybrid embryos aborted in the early developmental stage. The barrier mechanism between reciprocal crosses，though，differed，with the reproductive barrier for S. chinensis × C. floridus var. oblongifolius being due to hybrid embryo abortion or degeneration in the early developmental stage，and the reproductive barrier for C. floridus var. oblongifolius × S. chinensis being due to a high percentage of abnormal megagametophytes together with hybrid embryo abortion in the early developmental stage. Thus the cross between S. chinensis and C. floridus var. oblongifoliushad no barriers from pollen adherence and germination，but post-fertilization barriers meant poor seed set.

Key words: Sinocalycanthus chinensis, Calycanthus floridus var. oblongifolius, intergeneric cross, reproductive barrier, pollen germination and growth, hybrid embyo development