Effect of wortmannin (WM) on BL-induced chloroplast responses and on the actin cytoskeleton in tobacco leaves. (A) Amplitudes: ΔT(+) of weak (wBL, 0.4 Wm-2), and ΔT(-) of strong (SBL, 10 Wm-2) blue light-induced responses after 1.5 h incubation with 10 μM WM. The leaves were subsequently treated with 5 mM Ca2+ or Mg2+ for 3 h (right columns). Averages of 5–7 measurements. Error bars represent SD. Asterisks denote the significance of differences (p-value calculated with the unpaired t-test, * p = 0,05–0,001; ** p = 0,001–0,0001; *** p < 0,0001). The network of actin bundles in the mesophyll cells of the transgenic tobacco after 1,5 h incubation with 10 μM (B), and 50 μM (C) WM. Note the chloroplast clustering and disturbances of AC integrity (arrowheads) at the higher WM concentration. Scale bars, 10 μm.