Fig. 2

Anther development of flowers of Cylindropuntia wolfii. A) Anther of staminate flowers shows four layers at pre-meiosis of the microspore mother cells (MC). (B) Tetralocular male anther in pre-anthesis with young pollen grain (YPG) developing with tapetum fully disintegrated but endothecium (EN), epidermis (EP) and connective tissues (CT) intact. (C) Male anther in late pre-anthesis with stomium (ST) initiation indicating that the anther is about to dehisce. (D) Male anther at anthesis releasing fully mature pollen grains. (E) Female flower anther in pre-anthesis with MiMC (MC) developing. All cells in the anther wall such as tapetum (T), middle layer (ML), endothecium (EN) as well as the MiMC start showing hyper-vacuolization. (F) Microspore mother cells and tapetum show complete disintegration by this stage and only few tapetal cells are visible. (G) Female anther in late pre-anthesis showing the disintegration of the MiMC, nuclei are visible in cells of the anther wall. (H) Aborted anther in female flower at anthesis lacking nuclei in most remaining cells