Exposure of the roots of Populus nigra L. cv. Loenen to PAHs and its effect on growth and water balance.

Poplar cuttings were cultivated for 4 weeks in a substrate, which consisted of a combination of sand and nutrient solution. The plants were treated for 24 days with BaP, Chr, Ant, Phen, P and Flt, single or in combination. The concentration of the PAHs ranged from 0.1-200 mg/kg substrate. The results of the pollution experiments can be summarized as follows: 1. The most significant deviations between the test groups and the control can be observed for transpiration, nutrient solution uptake, and root mass. 2. Although transpiration and nutrient solution uptake are significantly lower for all the treated groups than for the control group, the water content of the leaves was not affected by PAHs. 3. The biomass of the shoots and the growth in shoot length do not react as strongly to exposure to PAHs as transpiration, nutrient solution uptake and the volume of the roots. 4. The differences in leaf weight and leaf surface area are significantly less pronounced compared to the control groups. Growth inhibition is most evident with Flt. Growth and absorption of the nutrient solution dropped with just Flt 0.1 mg/kg substrate. When the substrate concentration was increased, growth and nutrient solution uptake dropped considerably and at a concentration of Flt 200, 5 of the 11 test plants died before the end of the period of exposure. Nutrient solution uptake and shoot development of the test plants decreased in the following order: BaP H approximately = Chr > Ant > Phen > Pyr > Flt.