Study On The Reproductive Biology Of Catalpa Bungei C.A.Meyer

The breeding system and sexual reproduction process of cultivated Catalpa bungei C. A.Meyer in Yuntaishan National Forest Park in Lianyungang City were investigated for the firsttime. The reason for its barrenness was analyzed from aspects of individual, population andenvironment, and histological observation was performed for characterizing its self-incompatibil-ity. The main results are concluded as follows:1. The differentiation procedure of flower organs in C. bungei were as follows: sepal formation,stamen formation, petal formation, and pistil formation. The development of anther wall wasclassified as dicotyledonous, and the tapetum was of glandular heterotypic. Meiotic divisions inmicrospore mother cells were followed by smiultaneous cytokinesis and resulted in tetrahedraltetrad. The mature pollen grains were2-celled and nonaperturate. The species showed superiorovary,2-locules, and axial placenta with many ovules. The ovule was anatropous, unitegmic andtenuinucellatae. The development of embryo sac was of polygonum type, and hybrid embryo wascruciferous type. Zygote displacement occurred during the dormancy, and division taken place atabout20days after pollination. Endosperm was cellular and eventually developed intohaustorium cell with typical structure in both mycropyle and chalazal.2. The processes of flower bud differentiation, microsporogenesis, and megasporogenesis werenormal. It shows that male or female sterility wasn't the reason for barrenness happened in C.bungei. Self-sterility happened in C. bungei caused by its self-incompatibility. Self pollen tubeswere inhibited at different parts of pistil, especially in the stigma and ovary. The site of pollentube incompatibility reactions taken place was in the ovary, and the time was pre-zygotic, whichindicates the occurrence of pre-zygotic late-acting self-incompatibility in C. bungei.3. The breeding system of C. bungei was self-incompatibility, predominantly outcrossing butmixed with selfing, and the likely evolutionary tendency was from outcrossing to selfing. Theflower was entomogamy type whith typical entomophilous pollination syndrome. Blossom was"mass-flowering blomming" pattern. The full-bloom stage lasted for a long time in the populatio-n, and blossoms were synchronized between individuals.4. It is concluded that one reason for barrenness of C.bungei in Yuntaishan National ForestPark in Lianyungang City is self-incompatibility happened in the individuals, and the other ispollen-limitation caused by population composition, pollination models, and environmentalfactors.