Functional Relationships of Wood Anatomical Traits in Norway Spruce.

Alma Piermattei,Andrea Piotti,Alan Crivellaro,Georg Von Arx,Ulf Büntgen,Giovanni Giuseppe Vendramin,Patrick Fonti,Camilla Avanzi,Holger Gärtner,Carlo Urbinati

doi:10.3389/fpls.2020.00683

Abstract

The quantitative assessment of wood anatomical traits offers important insights into those factors that shape tree growth. While it is known that conduit diameter, cell wall thickness, and wood density vary substantially between and within species, the interconnection between wood anatomical traits, tree-ring width, tree height and age, as well as environment effects on wood anatomy remain unclear. Here, we measure and derived 65 wood anatomical traits in cross-sections of the five outermost tree rings (2008–2012) of 30 Norway spruce [Picea abies (L.) H. Karst.] trees growing along an altitudinal gradient (1,400–1,750 m a.s.l.) in the northern Apennines (Italy). We assess the relationship among each anatomical trait and between anatomical trait groups according to their function for (i) tree-ring growth, (ii) cell growth, (iii) hydraulic traits, and (iv) mechanical traits. The results show that tree height significantly affects wood hydraulic traits, as well as number and tangential diameter of tracheids, and ultimately the total ring width. Moreover, the amount of earlywood and latewood percentage influence wood hydraulic safety and efficiency, as well as mechanical traits. Mechanically relevant wood anatomical traits are mainly influenced by tree age, not necessarily correlated with tree height. An additional level of complexity is also indicated by some anatomical traits, such as latewood lumen diameter and the cell wall reinforcement index, showing large inter-annual variation as a proxy of phenotypic plasticity. This study unravels the complex interconnection of tree-ring tracheid structure and identifies anatomical traits showing a large inter-individual variation and a strong interannual coherency. Knowing and quantifying anatomical variation in cells of plant stem is crucial in ecological and biological studies for an appropriate interpretation of abiotic drivers of wood formation often related to tree height and/or tree age.

Highlights

Every single cell in a tree ring is derived from the division of a cambial cell, which expands to its final size, thickens its cell wall and eventually lignifies before programmed cell death (Plomion et al, 2001)
Tree-ring width was positively correlated with the number of tracheids per radial row (r = 0.99)
Dtan was more related to tree height than Drad, and these relationships were strongest for EW (EW Dtan: R2 = 0.536, EW Drad: R2 = 0.390, and LW Dtan: R2 = 0.357, P < 0.001) (Figure 3A)

Summary

Introduction

Every single cell in a tree ring is derived from the division of a cambial cell (periclinal growth), which expands to its final size, thickens its cell wall and eventually lignifies before programmed cell death (Plomion et al, 2001). Several studies brought a new perspective on the interindividual variation of wood anatomical traits highlighting the role of tree height as the driver of wood anatomical variation along plant stem, as opposed to the classical pith-to-bark age trend (Enquist, 2002; Olson et al, 2014; Kašpar et al, 2019). This is especially true for conduits in woody species, designed to transport water from roots to leaves. In a short plant bearing narrow conduits, the increase in conduit size from pith-to-bark is a consequence of the conduits getting larger to compensate for a height increase (Carrer et al, 2015) (Figure 1)

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