Variation in Tracheid Dimensions of Conifer Xylem Reveals Evidence of Adaptation to Environmental Conditions

Abstract

Globally distributed extant conifer species must adapt to various environmental conditions, which would be reflected in their xylem structure, especially in the tracheid characteristics of earlywood and latewood. With an anatomical trait dataset of 78 conifer species growing throughout China, an interspecific study within a phylogenetic context was conducted to quantify variance of tracheid dimensions and their response to climatic and soil conditions. There was a significant difference in tracheid diameter between earlywood and latewood while no significant difference was detected in tracheid wall thickness through a phylogenetically paired t-test. Through a phylogenetic principle component analysis, Pinaceae species were found to be strongly divergent in their tracheid structure in contrast to a conservative tracheid structure in species of Cupressaceae, Taxaceae, and Podocarpaceae. Tracheid wall thickness decreased from high to low latitudes in both earlywood and latewood, with tracheid diameter decreasing for latewood only. According to the most parsimonious phylogenetic general least square models, environment and phylogeny together could explain about 21∼56% of tracheid structure variance. Our results provide insights into the effects of climate and soil on the xylem structure of conifer species thus furthering our understanding of the trees’ response to global change.

Intraspecific variation in growth‐related traits—from leaf to whole‐tree—in three provenances of Cryptomeria japonica canopy trees grown in a common garden

“…Hydraulic conductivity is governed by the morphology, dimensions (particularly the diameter), and spatial arrangements of the conducting elements (vessels and tracheids) (Hacke et al, 2017; Tyree & Zimmermann, 2002). The diameter of conducting elements varies according to tree size (Olson et al, 2014), environmental gradients (Arenas‐Navarro et al, 2021; Zheng et al, 2022), and position within trees (Petit et al, 2008; Spicer & Gartner, 2001). The latter factor determines the pattern of accumulation of hydraulic resistance along tree height, thus influencing whole‐tree hydraulic conductivity, especially in large trees (Liu et al, 2019).…”

The Variations in Tracheid Length of Pseudotsuga menziesii (Mirb.) Franco Wood in Relation to Cambium Age, Site, and Growth

“…Earlywood and latewood differ, above all, in cell size [14]. In relation to that, Zheng et al [44] confirmed differences in tracheid diameter between earlywood and latewood. Longer latewood than earlywood tracheids were measured in this study.…”

Modeling of the Statistical Distribution of Tracheids in Conifer Rings: Finding Universal Criterion for Earlywood–Latewood Distinction

“…There are significant differences between species in the shapes of scatter plots and in the location/density of earlywood and latewood clusters, reflecting the specific features of the anatomical structure. This variability reflects species-specific features with regards not only to tree size (height), but also to ecophysiological traits and species-specific adaptations to habitat conditions [46][47][48][49]. Taking into account the estimates of the threshold value k = 0.105-0.136 obtained in this work, we can conclude that the usage of one universal rigid threshold of k, as both interpretations of the Mork criterion suggest, quite often does not reflect the actual intra-seasonal variability of the anatomical structure in conifer wood.…”