Abstract:Ca2+ subcellular localization in the path of pollen tube growth in Brassica napus has been determined by means of in situ precipitation with improved potassium pyruantimonate technique and electron microscopic visualization, in order to study the relation between Ca2+ and chemotropic response of pollen tube growth. The results showed that Ca-containing anti monate precipitates (CaPA) was present in the intercellular space of the transmitting tissue under the papilla, in the style and inside the septum, Ca2+ was thus present in the path of pollen tube growth. These results provide evidence tha‘ Ca2+ is an inducer of chemotropic res pome of pollen tube growth. On the other hand, a phenomenon, that secretion is produced hy papilla, may be interpreted on a structural basis as the local ingrowth of tranfer cell wall.