HAUSTORIA DEVELOPMENT AND FRUIT SET IN PRUNUS

During endosperm development in Prunus species, the occurrence of haustoria is a common phenomenon. Haustoria differentiate by extension of the embryo sac, forming a connection to the chalaza. Since vascular elements end at the chalaza, haustoria are believed to have a function in the nutrition of the growing endosperm and embryo. The current studies were carried out using new microtechnical method that enabled us to study complete haustoria. Development of the embryo sac into a haustorium begins before the division of the primary endosperm nucleus. The haustorium extends basipetally through the nucellus to the chalaza. In the wall of the haustorium, circular structures with variable diameter and distribution were found rather regularly. Serial sections of the haustoria showed that these structures occur mainly in the older part of the haustorium, where they may function in the nutrient uptake by haustoria.