Effect of nickel on pollen germination and pollen tube length in Arabis alpina (Brassicaceae)

Abstract

In this work we studied and compared the toxic effect of nickel (Ni) on pollen germination and pollen tube length in Arabis alpina L. collected from serpentine and non-serpentine populations distributed in the Rila mountains, Bulgaria. Pollen grains were treated with prepared standard solutions of 100, 300, 500, and 700 μM Ni as NiCl2 in distilled water. A nutritional medium was also used to assess pollen germination. Nickel inhibited pollen germination and pollen tube elongation in both serpentine and non-serpentine plants. The percentage of germinated pollen in serpentine plants treated with Ni was higher than in non-serpentine plants but there was no difference in pollen tube elongation between groups. However, pollen tubes showed abnormalities such as coiling and swelling of the tip, or burst, and varied considerably among the samples. A complete break of pollen tube elongation is due to such abnormalities. Also, decreased pollen fertility in both populations was found. The plants from serpentines were less sensitive to (i.e. more tolerant of) elevated Ni concentrations commonly found in serpentine soils.