Cytology of the Ray Cells in Sapwood and Heartwood

Mineral nutrient concentrations in sapwood and heartwood: a literature review

“…Secondly, the differences among elements and the correlation pattern among them (N-P on the one hand and Ca-Mg on the other hand) are consistent with the well-known differences in mobility and chemical form of these elements in the xylem. Thus, a high proportion of N, P and K is located in the symplast of parenchyma ray cells [50,64,72] which is thought to be withdrawn during sapwood senescence [27,66,76]. In contrast, a substantial proportion of Ca and Mg in wood is located in the cell wall either adsorbed on negatively charged exchange sites or incorporated in the form of pectates or in the lignin matrix [17,44,48].…”

“…In most if not all, tree species, inner sapwood rings are eventually converted into heartwood. Heartwood no longer contains living cells, often has vessels blocked with tyloses and can accumulate secondary compounds [9,27,32,60,67,77]. The cause and function of heartwood formation are disputed.…”

Aspects of the Aging Process in Cambium and Xylem

“…Too little is äs yet known of the actual changes in the living tissue of these types in the vicinity of the pith, but we have good evidence of that the cytological aging of cells (A. Frey-Wyssling and H. H. Bosshard, 1959) at advanced tree ages is basically the same äs in heartwood forming woods, with the exception that it begins later. Apart from these so-called sapwood trees, the transformation into heartwood usually begins regularly, but at least three modifications requiring to be observed: (i) woods havinglightheartwood(cf.…”

Electron microscopy of elm infected with Ceratocystis ulmi (Buism) C Moreau

“…The term "polyphenol" has been used to refer to a wide variety of The accumulation of phenols has been shown to accompany the tran sition of sapwood to heartwood (Frey-Wyssling and Bosshard, 1959). The oxidation of accumulated phenols progresses in many tree species to form the dark brown pigments responsible for the darkened heartwood.…”