Growth reduction in American sycamore ( Plantanus occidentalis L.) caused by PbCd interaction

Abstract

Seedlings of American sycamore ( Plantanus occidentalis L.) were grown in Drummer silty clay loam soil treated with various concentrations of Pb, Cd, or Pb plus Cd. Plant growth and heavy metal content were measured at the end of 90 days. Heavy metal accumulation by plant parts increased with soil treatment levels but was much lower than values previously reported in the literature. Root growth, woody stem diameter increment, new stem growth and foliage growth were found to be synergistically affected by the PbCd treatment. Whilst treatment with Pb or Cd alone caused a reduction in photosynthesis and transpiration, the addition of Cd to Pb-treated plants did not reduce rates of photosynthesis and transpiration below that observed for plants treated with Pb alone. A method is proposed to quantitate the concept of synergism.