ANATOMY AND CHEMICAL-COMPOSITION OF PINUS-PINASTER BARK

The secondary phloem of Pinus pinaster Aiton bark has sieve cells and axial and radial parenchyma, but no fibres. Resin ducts are present in fusiform rays. Stiloid crystals, starch granules and tannins occur in side sieve and parenchyma cells. The rhytidome of P. pinaster bark has a variable number of periderms forming scale-type discontinuous layer s over expanded parenchyma cells. Phellem comprises 4-6 layers of thic k walled and little suberized cells and phelloderm a layer of 2 or 3 t hickened lignified cells and a layer of expanded cells. Ash content of P. pinaster bark is low and pH slightly acid. Total extractives amoun t to 11.4% and tannins correspond to 4.5% of oven-dry weight. Content of lignin and unhydrolysable phenolic acids is 43.7% and polysaccharid es amount to 41.7% with the following monosaccharide composition: gluc ose 51.8%, mannose 13.4%, xylose 26.1%, galactose 4.1% and arabinose 4 .6%. No statistical significant differences were found between the str ucture of the bark from trees at five sites.