Figure 3.

Patterns of Ca²⁺ elevation following hypo-osmotic treatment in dividing cells. (A) Calcium Green to Texas Red ratio images during the onset of a hypo-osmotically induced Ca²⁺ wave (100% SW to 50% SW) shows an initial elevation of Ca²⁺ in the rhizoid apex which declines before the onset of Ca²⁺ elevation arising in the apical nucleus region (n = 40). (B) A variation in this pattern was evident in a minority of cells where Ca²⁺ elevations were observed to arise in subapical nucleus simultaneous with the apical Ca²⁺ elevation (n = 10). (C) Confocal sections of ER stained with 1.0 μM DiOC₆ (Molecular Probes) for 10 min show ER distributed in the rhizoid apex and perinuclear regions. (D) The number of cell divisions was significantly reduced following more severe hypo-osmotic shocks (e.g., 100% SW to 70% SW) that cause elevated nuclear Ca²⁺. (E and F) Polarized rhizoid growth was unaffected by hypo-osmotic treatments up to 50% SW (E) compared with control untreated embryos (F). (Bar = 15 μm.)