Embryogenesis in Crassulaceae: structural aspect of suspensor development

Abstract

The suspensor in the majority of angiosperms is an evolutionally conserved embryonic organ functioning as a conduit that connects ovule tissues with the embryo proper for nutrients and growth regulators flux. In this article the present knowledge on the embryo-suspensor ultrastructure and function in representatives of Crassulaceae genera: Sedum, Jovibarba, Sempervivum, Aeonium, Monanthes, Aichryson and Echeveria. The role of the suspensor in the transport of nutrients from the tissues of the ovule to the proper embryo is confirmed by the structure of the basal cell, especially the nature of the micropylar part of its wall, the "transfer wall". The basal suspensor cell is a site of intense metabolic activity. The special attention is paid to the plasmodesmata. The correlation between types of suspensors and structure of plasmodesmata was investigated. Final conclusions are given and the presented data summarized.