Z. Kristof et al., Changes of calcium distribution in ovules of Torenia fournieri during pollination and fertilization, PROTOPLASMA, 208(1-4), 1999, pp. 149-155
Calcium distribution in ovules of Torenia fournieri was studied by electron
energy loss spectroscopy and transmission electron microscopic visualizati
on of calcium antimonate precipitates. High calcium levels were found in th
e ovules of T. fournieri. Calcium is situated mainly in extracellular regio
ns before fertilization, including the surface of embryo sac, in the mucila
ge, and among the cells of the egg apparatus. Intracellular calcium was fou
nd only in the nucellar cells around the embryo sac and in the epidermis of
the central axis and funiculus. After pollination, a labyrinthine structur
e (coralloid-like cell wall formation) develops on the micropylar surfaces
of the egg apparatus that contain high levels of calcium. Calcium levels in
crease in the degenerating synergid after the penetration of the pollen tub
e. Calcium-antimonate precipitates are abundant in vacuoles of the disrupte
d synergid and pollen tube cytoplasm.