The physiological and morphological response of loblolly pine (Pinus taeda L.), green ash (Fraxinus pennsylvanica Marsh.), and hybrid poplar (Populus deltoides Bartr. x Populus nigra L.) seedlings to the uptake of cadmium and trichloroethylene

Three greenhouse phytoremediation studies were conducted at the Arthur Temple College of Forestry, Stephen F. Austin State University. In Part A, survival, morphology, and translocation following uptake of cadmium (Cd) and trichloroethylene (TCE) in loblolly pine (Pinus taeda L.) and hybrid poplar (Populus deltoides Bartr. × Populus nigra L.) were investigated April–July 1998. Poplar cuttings and loblolly pine seedlings were planted in sand and four contamination treatments were applied: (1) one-time application of 20 mg Cd kg −1 sand, (2) weekly application of 191.3 mg TCE kg −1 sand, (3) both Cd and TCE treatments, and (4) control (water and fertilizer only). In Part 8, the effect of Cd uptake from sand and bark potting media treated with 0, 7, and 11 mg Cd kg−1 on root morphology of loblolly pine and green ash (Fraxinus pennsylvanica Marsh.) seedlings was evaluated from March–June 2000. Loblolly pine and green ash seedlings were planted in Cd-treated soil in individual rhizotrons. In Part C, the effect of uptake of Cd from soils treated with 30 mg Cd kg−1 on root morphology of loblolly pine was studied from June–November 2000.; Hybrid poplar, loblolly pine, and green ash all developed highest Cd concentrations in root tissue. TCE treatments resulted in higher loblolly pine mortality after one year. Loblolly pine shoots had higher Cd content than green ash shoots, even though loblolly pine shoots had lower dry weights. Leaf water relations and net photosynthesis were not affected by Cd treatments. However, high temperatures in the greenhouse may have influenced these results. Soil Cd reduces the root elongation rate of both loblolly pine and green ash. Qualitatively, root systems of both species appeared to develop fewer fine roots and had increased suberization after Cd exposure. Mitotic index results were not statistically significant, but suggest that green ash root elongation rates may have been reduced due to Cd effects on the rate of cell division.