Effect of SO₂ on growth and sulfur content of hybrid poplar

Growth of hybrid poplar clone NE-388 (Populus maximowizii Henry x trichocarpa Torr. & Gray) was significantly reduced by repeated continuous 72-h exposures to 0.12 or 0.25 ppm SO₂ for 6 or 14 weeks, respectively. Both dosages of SO₂ induced significant defoliation of the oldest leaves. The sulfur content of abscised foliage ranged from 0.90 to 1.70% S dry weight basis compared with control values of 0.24 to 0.32% S. These sulfur values may provide information on the role of hybrid poplar in removing pollutants from the atmosphere.