Calcium distribution in ovules ofTorenia fournieri was studied by electron energy loss spectroscopy and transmission electron microscopic visualization of calcium antimonate precipitates. High calcium levels were found in the ovules ofT. fournieri. Calcium is situated mainly in extracellular regions before fertilization, including the surface of embryo sac, in the mucilage, and among the cells of the egg apparatus. Intracellular calcium was found only in the nucellar cells around the embryo sac and in the epidermis of the central axis and funiculus. After pollination, a labyrinthine structure (coralloid-like cell wall formation) develops on the micropylar surfaces of the egg apparatus that contain high levels of calcium. Calcium levels increase in the degenerating synergid after the penetration of the pollen tube. Calcium-antimonate precipitates are abundant in vacuoles of the disrupted synergid and pollen tube cytoplasm.
CalciumElectron energy loss spectroscopyEmbryo sacTorenia fournieriFertilization