Cell wall structure in the xylem parenchyma of Cryptomeria.

Abstract

Cell wall structure in ray and axial parenchyma cells in the wood ofCryptomeria was shown to be typically crossed polylamellate and dissimilar to the characteristically layered wall of fibers and tracheids. Ray cells differed from axial cells in terms of form and also in the relative inclination of crossed microfibrillar helices in the cell wall. This feature was reflected by positive birefringence in ray cells and negative birefringence in axial cells. Localized wall thickenings,viz. transverse “bars” in ray cells and longitudinal “ribs” in axial cells, also displayed crossed polylamellate structure. This observation contrasts with the exclusively longitudinal microfibrillar orientation previously reported for longitudinal ribs in elongated parenchyma cells of primary tissue. On the basis of similar microfibrillar orientations between outer and inner wall lamellae, the cell walls ofCryptomeria parenchyma were judged to be predominantly secondary. Lignin was heterogeneously distributed in lamellate fashion and a high concentration characterized the thin middle lamella. Both types of parenchyma suggested a higher lignin content than adjacent longitudinal tracheids.