Plant Anatomy against crime: Araucaria angustifolia wood sawdust identification

Abstract

Teams from São Paulo Criminalistics Institute receive chainsaws allegedly involving deforestation in preservation areas. Here, we aimed to examine wood and bark sawdust from chainsaws to determine the potential of differentiating materials from Araucaria angustifolia (native), Pinus spp. and Eucalyptus spp. (exotic). Such knowledge is crucial in the elucidation of environmental crimes, particularly where occurs A. angustifolia, a species at risk of extinction. We obtained samples of adult tree trunks from A. angustifolia, Pinus spp., Eucalyptus spp., and Corymbia citriodora. Our reference samples of wood and bark came from material used in other studies by the Instituto Florestal team. In a blinded manner, we took sawdust samples of A. angustifolia, Pinus caribaea and Eucalyptus grandis and tagged with codes. We prepared all samples based on the standard methodology for wood and bark maceration. Then, we prepared histological slides and comparatively analyzed several slides under light microscopy. Results show that it is possible to obtain cell fragments useful in separating the groups of plants studied. For example, tracheids on the cell walls of A. angustifolia have polygonal pits, with two or more alternating pits, while on Pinus spp., circular pits are observed, usually with uniseriate pits on the radial walls and opposing pits in the case of more than one row. Moreover, vessel elements and fibres can only be found in the wood fragments of Eucalyptus spp. Bark cells and cells from immature tissues also serve as corroborative evidence.