How Long Do Wood Parenchyma Cells Live in the Stem of a Scots Pine (Pinus sylvestris L.)? Studies on Cell Nuclei Status along the Radial and Longitudinal Stem Axes

Mirela Tulik,Katarzyna Marciszewska,Joanna Jura-Morawiec,Anna Bieniasz

doi:10.3390/f10110977

Abstract

This paper deals with the spatial distribution of heartwood in Scots pine stems (Pinus sylvestris L.), determined on the basis of the absence of nuclei in parenchyma cells. Samples were collected at several heights from two Scots pine stems growing in fresh coniferous stand as codominant trees. Transverse and radial sections were cut from the samples and stained with acetocarmine to detect the nuclei and with I2KI to show starch grains. Unstained sections were also observed under ultraviolet (UV) light to reveal cell wall lignification. The shapes of the nuclei in ray and axial parenchyma cells differed: the axial parenchyma cells had rounded nuclei, while the nuclei of the ray parenchyma cells were elongated. The lifespan of the parenchyma cells was found to be 16–42 years; the longest-lived were cells from the base of the stem, and the shortest-lived were from the base of the crown. The largest number of growth rings comprising heartwood was observed at a height of 1.3–3.3 m, which signifies that the distribution of heartwood within the stem is uneven. Moreover, the distance of the cells from the apical meristem and the cambium was seen to have an effect on the presence of living parenchyma cells, i.e., those with stained nuclei.

Highlights

The presence of living parenchyma cells in wood is, in addition to the ability to conduct sap, the generally accepted basic distinction between sapwood (SW) and heartwood (HW)
Our research aims to describe, for the first time, the spatial distribution of heartwood expressed as a result of the absence of nuclei in parenchyma cells in the stem of Scots pine
This proves that both axial and radial tracheids, they differ in length, lost nuclei in the final stage of their differentiation

Summary

Introduction

The presence of living parenchyma cells in wood is, in addition to the ability to conduct sap, the generally accepted basic distinction between sapwood (SW) and heartwood (HW). According to the International Association of Wood Anatomists (IAWA) definition, heartwood consists of “inner layers of wood that have ceased to contain living cells in the growing tree, in which reserve materials (e.g., starch) have been removed or transformed into a heartwood substance” [1]. These materials provide natural durability—generally low in sapwood but much higher in heartwood—with some species being very resistant to biodeterioration [2], which is of value to the forestry and timber industry. L.), a long-lived coniferous tree, the most widely distributed pine found throughout Eurasia and a model tree for studying the mechanism of wood

Methods

Results

Conclusion