Identification of Ca2+ in olive pistils by using the pyroantimonate (PA) method. (A) Numerous electron-dense precipitates are present in the vacuole and in the intracellular spaces of the stigmatic cells (arrows). (B) Negative controls were the pistils fixed without the addition of PA; there is a lack of electron-dense precipitates in the stigmatic cells. V - vacuole. Bars = 1 μm;. (C) Energy dispersive x-ray analysis of the electron-dense deposits present in the ultrathin sections of stigma cells (area marked as square in A). (D) Overlapping peaks of Ca and Sb confirm the identity of calcium antimonite precipitates. The spectrum of the material reveals peaks for Ca and Sb.