Tissue interactions in the developing locule of Gasteria verrucosa during microgametogenesis

We investigated the development of the locule tissues of Gasteria verrucosa (Mill.) H.Duval using electron microscopy and summarized it in detailed pen-drawings. Most of the anther opening processes take place in the epidermis and the endothecium. The starch in these two layers is used for different steps of the dehiscence process. The (single) middle layer is isolated from the endothecium and finally degenerates. This process is related to tapetal functions. Sporopollenin-containing structures arise on both the tapetum and the microspores, for pollen dispersal and protection, respectively. In the tapetum, starch turns into part of the pollenkitt. During the microspore mitosis the starch of the microspores is deposited in the vegetative cell. The polarity in the microspores is related to the formation and development of the generative cell. Ultrastructural changes in the different cell layers are discussed in relation to their development and interaction.