| Abstract: | The structure of ovule in Gastrodia elata Blume was very simple. Functional megaspore occurred at the chalazal end. Callose was absent at megasporocyte stage. It first appeared at the chalazal wall during the first meiotic prophase and exhibited continuous fluorescence. Soon later callose fluorescence disappeared in some part of the chalazal wall and many noncallosic dark areas took place, subsequently these nonfluorescence areas became larger and the callose fluorescence appeared discontinuous granulose distribution. This fluorescence maintained until the megaspore formed. The callose of micropylar wall appeared later and usually disappeared before megaspore formation. In the cross walls between the functional and the two degenarated megaspore callose fluorescence was very strong, continued and kept for a long time. But the side walls usually lacked callose. Accoding to the morphological character of simple ovule in G. eiata and the localization of acid phosphatase and polysaecharide grains, the transfer of vegetative materials from surrounding tissues into megasporocyte mainly passing through the chalazal end of megasporocyte. Thus a continuous callose wall deposited at the ehalazal end of megasporocyte, and it in reality caused the “isolation” of meiocyte. It was possible that a reduced form of callose disposition existed in parasetic orchids. |
