ANTHER STRUCTURE IN <i>CRASSULA ERICOIDES</i>, <i>C. INTERMEDIA</i> AND <i>C. MULTICAVA</i> (CRASSULACEAE)

Abstract

The development and structure of the anther wall in Crassula intermedia, C. multicava and C. ericoides was studied for the first time. In the studied species, the presence of basic features of the Crassulaceae family associated with reproduction processes was confirmed. These include: tetrasporangiate anther, parietal tapetum, simultaneous microsporogenesis, predominantly tetrahedral tetrads of microspores, 2-celled and 3-colporate mature pollen grains. The microsporangium wall is 4-layered (epidermis, endothecium, middle layer and tapetum) and its development occurs within a typical variation of the centrifugal type. Tannins accumulate in epidermal cells: in C. intermedia, along the periphery of the cell protoplast, and in C. multicava and C. ericoides, the cell protoplasts are completely filled with tannins. The tapetum develops without reorganization (typical parietal tapetum). The study has shown that Crassula species are characterized by a number of unique features. They form an eccentric connective displaced from the central position towards the abaxial microsporangia, while the connective tissue does not develop between the adaxial microsporangia. Fibrous thickenings were found not only in the endothecium cells, but also in the cells around the vascular bundle of the connective tissue. The number of cell layers with fibrous thickenings and their location differ in the studied species. In C. ericoides, they are arranged in one layer in the form of a ring in the anther part completely fused with the filament. In C. intermedia and C. multicava, 2–3 layers are formed there. As regards the anther part free from the filament, in C. ericoides cells with fibrous thickenings are formed only in the endothecium, while in other two species not only in the endothecium, but also in 2–3 underlying layers of the connective tissue. In the structure of the stamen and anther of Crassula species, there are features common with Sedum and Aeonium species (the presence of cells with fibrous thickenings in the anther part free from the filament) and Kalanchoe (the stamen is wide at the base and narrow at the junction with the anther). Our data indicate that additional studies are needed, and the position of the Crassula clade continues to be controversial on the phylogenetic tree of the Crassulaceae family.