Orientation of tracheids in the knot region of Pinus wood

Abstract

Developing trees are subject to various biotic and abiotic factors that can determine variations in the size of cells and arrangement of the anatomical elements, especially in the transition region of knot-wood. This work was done with the objective of analyzing the orientation of the tracheids in knot and wood without knot of Pinus elliottii var. elliottii Engelm. It was used five trees of commercial planting in Agudos-SP and extracted along the trunk, discs in each section (base, half and top) with knot insertion. From each section and type of wood with knot and without knot, histological blades were made. Was evaluated tracheids of each section/type with the aid of scanning electronic microscopy images. Growth with spiral orientation of the tracheids was observed at the beginning of the formation of the knot of the top region and in the middle region of the trunk. At the base of the trunk it was not possible to identify the “twist” of the cells. Most gradual and uniform thickness of the tracheids was noticed in the transition knot in the base region and more heterogeneous thickening in the middle and top regions. Tracheids in knots have a lower increase with growth different from wood free from knots. The spiral growth of structures that form the branch was larger in the region closer to the top.