The pine stems were cut from three different polluted environments – Ist trees degradation degree (weak pollution), IInd trees degradation degree (strong pollution) and IIIrd trees degradation degree (connected with very strong pollution). On the basis of obtained results it was stated that environmental pollution caused changes in late wood participation, as well as distribution of cellulose on the stem cross- and longitudinal section. It also changed cellulose content in bark from the butt-end section, which was about 26% regardless the degradation degree. The environmental pollution caused also an increase of viscometric average polymerization degree of cellulose in heartwood in relation to heartwood adjacent sapwood and sapwood from butt-end section. Regardless the degradation degree, cellulose polymerization degree in heartwood adjacent sapwood from the middle part of the stem was higher in comparison to sapwood and heartwood. Moreover, the environmental pollution caused the increase of viscometric average polymerization degree of cellulose in bark. The polymerization degree of cellulose in bark from the butt-end section of IIIrd degradation degree stems was 22% and 23% higher in comparison to the Ist and IInd degradation degree.

The chemical composition of poplar wood in relation to the species and age of trees. The contents of the following substances: mineral substances, extractives, cellulose, lignin, holocellulose, in wood from fastgrowing poplar species (Populus deltoides x maximowiczii and Populus trichocarpa Torr and A.Gray) aged 2.5, 3, 5 and 7 years were compared to the contents of the abovementioned substances in Populus nigra L. and Populus alba L. wood, aged about 30. According to other publications, the cellulose and lignin contents increase in parallel with the tree's age. On the other hand, the comparison of cellulose content in poplar wood showed that its content did not depend from the species of tree, age and growth environment. Whereas, the content of extractives in poplar wood was dependent from the species of tree, age and growth environment. The lignin content increased slightly as a tree age, but its content in 7-year-old wood was already similar to the level to be found in the wood at the age of about 30 years. About 30-year-old wood of P. nigra and P. alba contained less holocellulose as compared to its contents in P. deltoides x maximowiczii and P. trichocarpa wood, regardless of its age.

The chemical composition of poplar wood in relation to the species and age of trees. The contents of the following substances: mineral substances, extractives, cellulose, lignin, holocellulose, in wood from fastgrowing poplar species (Populus deltoides x maximowiczii and Populus trichocarpa Torr and A.Gray) aged 2.5, 3, 5 and 7 years were compared to the contents of the abovementioned substances in Populus nigra L. and Populus alba L. wood, aged about 30. According to other publications, the cellulose and lignin contents increase in line with the tree's age. On the other hand, the comparison of cellulose content in studied poplar wood showed that its content did not depend from the species of tree, age and growth environment. Whereas, the content of extractives in poplar wood was dependent from the species of tree and growth environment. The lignin content in Populus deltoides x maximowiczii and Populus trichocarpa wood did not depend from its age and was similar to the lignin content in 30-year-old P. nigra wood. 30-year-old wood of P. nigra and P. alba contained less holocellulose compared to its contents in P. deltoides x maximowiczii and P. trichocarpa wood, regardless of its age.

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