MULTIVARIATE ANALYSIS OF TRACHEID MORPHOLOGY IN KNOTS OF Pinus elliottii var. elliottii

During the formation of wood, cells go through developmental stages in which anatomical elements differentiate between knotted and knot-free regions. The objective of this study was to compare, dimensionally, tracheids of “knot” and “knot-free wood” regions in Pinus elliottii var. elliottii. Five trees were used, and three discs were extracted from each tree: at the base (point of insertion of the first branch), at the top (trunk with 12 cm diameter) and in the middle (between base and top) to make specimens from the “knot” and “knot-free wood” regions. Permanent slides of the material were made, and photomicrographs were taken. Dissociation and maceration of material fragments were performed, comparing the parameters total length, total diameter, lumen diameter and wall thickness, besides counting and measuring cellular elements. Parametric data were subjected to ANOVA (p ≤ 0.05) and to Bartlett’s test, and non-parametric data were subjected to Dunn’s test. Non-Metric Multidimensional Scaling (NMDS) with simple Euclidean distance was employed through Analysis of Similarity (ANOSIM) and Non-Parametric MANOVA Analysis. GraphPadPrism and PAST v. 2.17c statistical packages were used. The results indicate that the pattern of growth and increment of the longer and thicker structural tracheids from the base to the top of the trunk is not repeated in the knots. Tracheids of knots show a smaller increment in size and do not seem to have growth similar to that observed in knot-free wood.