Cadmium Accumulation, Phosphorus Concentration and Growth Response of Cd-treated Ectomycorrhizal Poplar Cuttings

We investigated whether cadmium (Cd) toxicity affects phosphorus (P) concentration and growth of poplar, which might be related to the ectomycorrhizal associations. Populus ${\times}$tomentoglandulosa cuttings were treated with 0.1 mM and 0.4 mM $CdSO_4$ and inoculated with ectomycorrhizal fungus, Pisolithus tinctorius (Pt) and grown in autoclaved peat vermiculite mixture for five months under greenhouse conditions. Ectomycorrhizal plants showed significantly higher Cd concentration in leaves, stems and roots than in non-mycorrhizal plants. Likewise, P contents in leaves and roots of ectomycorrhizal plants were higher than those of non-mycorrhizal plants. Acid phosphatase activity in leaves of ectomycorrhizal plants, however, was significantly lower than that of non-mycorrhizal plants. 0.1 mM Cd significantly increased P content in leaves and stems of non-mycorrhizal plants. In spite of high P concentration, which is accompanied by lower acid phosphatase activity, plant growth was not improved by inoculation with P. tinctorius. Total plant dry weight was lower than the non-mycorrhizal counterpart. The results imply that this might be caused by the large amount of energy consumption to alleviate Cd toxicity resulted from high Cd accumulation in their tissues.