Fig. 3.

Localization of loosely bound Ca²⁺ by potassium antimonate precipitation in the Petunia sitt at the PP1 stage. a, b The sitt after pollination. c–f sections of germinated pollen grain (pg) with the germinal aperture (ga). g–k cross sections of different zones of the growing pollen tube (pt); apical zone with numerous vesicles (g) and sub-apical zone (h–k) containing Golgi stacks (g) and ER cisternae (er). Cartoon shows the analyzed region of the pistil at the PP1 stage. a amyloplast, ecm extracellular matrix, ex exudate, n nucleus, no nucleolus, p plastid, s sporoderm, v vesicle. Bars 1 μm (a, c, e, g, i), 500 nm (b, d, f, h, j, k)