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The incidence of poplar mosaic virus evidenced by foliage symptoms, enzyme-linked immunosorbent assay (ELISA) or bioassay (infectivity) was greater in stooled clones having Aigeiros (especially as the female) parents than in those of Tacamahaca parentage. The overall prevalence of the virus in clones growing in England was less (84/344, 24 %) than in clones growing in Poland (143/256, 56 %). Whereas symptoms in PMV-infected P. deltoides were prominent and common, in P. nigra, another species assigned to the Section Aigeiros they were indistinct and rare. Evidence of poplar mosaic virus inferred from ELISA alone was found in only one aspen of 52 tested clones in the Sections Leuce, Leuce x Leuce or Leucoides.

Summary.The patterns of radial distribution of copper, lead, zinc and cadmium in two species of poplar, growing under polluted conditions near a copper smelter, were investigated. Populus marilandica is very resistant to such pollution, but P. balsamifera is sensitive. Soils were examined for concentrations of these metals, and only a surface layer of soil was polluted with copper and lead. P. balsamifera absorbed much more cadmium than P. marilandica under the same conditions. P. marilandica shows a pattern of copper radial distribution with significantly increased concentration of the meral in the layers in the middle of the trunk compared to P. balsamifera. Zinc and cadmium have a pattern with increased metal concentration from the bark towards the pith of the tree. In the case of copper and lead the pattern indicates increased concentrations of these metals in the rings adjacent to the pith while the pattern in other parts of the tree remains unconfirmed due to poor precision. Poplar xylem seems to accumulate zinc and cadmium while the content of lead in xylem is much lower than in the adjacent soil.