Effects of metals on the tube morphology. Pollen tubes were cultured in standard medium (A), or treated with 10 μM CdCl2 (B), 20 μM CuCl2 (C), 2 μM Na2HAs4O.12H2O (D), 20 μM CrCl3 (E), and 5 μM HgCl2 (F), respectively. DIC (Differential Interference Contrast) pictures were obtained using a ZEISS Axiovert 200 M microscope equipped with a Q imaging RETIGA-SRV CCD. Bars = 10 μm.