Effects of elevated nickel and cadmium concentrations on growth and nutrient uptake of mycorrhizal and non-mycorrhizal Pinus sylvestris seedlings

The effects of Ni and Cd on growth and nutrient uptake of mycorrhizal and n on-mycorrhizal Pinus sylvestris L. seedlings were investigated in a pot exp eriment. Seedlings were either inoculated with Laccaria bicolor (Maire) Ort on or left uninoculated before being planted in pots containing a mixture o f sandy soil from the B-horizon of a coniferous forest, small stones and pu re quartz sand. The pots were supplied with small amounts of a balanced nut rient solution every 24 h using peristaltic pumps. Nickel or Cd were added as chlorides to the nutrient solution at levels of 85 muM Ni (Ni 1), 170 mu M Ni (Ni 2), or 8.9 muM Cd. Mycorrhizal colonisation of the roots was nearl y 100% in the mycorrhizal treatments. The mycorrhizal seedlings grew signif icantly better than the non-mycorrhizal ones. The weight of mycorrhizal see dlings in the Ni 2 treatment was 29% lower than that of the mycorrhizal con trols, but still 34% greater than that of the non-mycorrhizal seedlings not exposed to metals. There was an overall, statistically significant, negati ve effect of metals on plant yield. Mycorrhizal plants had lower root:shoot (R:S) ratios than non-mycorrhizal plants and the R:S ratio was increased b y metal exposure, particularly in the non-mycorrhizal seedlings. Plant conc entrations of Cd or Ni were not affected by mycorrhizal colonisation, but t otal uptake of Cd and Ni was higher in bigger mycorrhizal seedlings. Nickel decreased P concentration in all seedlings and Cd decreased P concentratio n in the non-mycorrhizal seedlings. Generally, the mycorrhizal seedlings gr ew better than non-mycorrhizal ones and had better P, K, Mg and S status. R oot growth was not significantly affected by the metal treatments. The redu ction in mean shoot growth of non-mycorrhizal plants, relative to the metal -free control, appeared higher than in mycorrhizal plants but was not stati stically significant due to high variation in the non-mycorrhizal plants no t exposed to metals. The main mycorrhizal effect was thus increased nutrien t uptake and growth of the seedlings.