Tree-ring anatomy reveals climatic influence on xylem morphogenesis

During the growing season, the cambium of conifer trees produces successive rows of xylem cells, known as tracheids. Current knowledge on this process mainly stems from xylogenesis monitoring spanning a few years.

Example of a tree ring split into ten sectors (A) and representation of the anatomical features measured on each single tracheid (B). In (A), the overlay curves show the intra-ring variation of the mean 90th percentile of cell diameter (CD) and cell-wall thickness (CWT) as obtained for the ten tree-ring sectors with equal width. The coloured cells illustrate on a narrow strip how individual tracheids were assigned to the sectors.

In this investigation of the effects of long-term inter-annual climate variability on tracheid formation and wall thickening, Castagneri et al. retrospectively study tree-ring xylem anatomy in Picea abies along an altitudinal gradient in the Alps. Climate fluctuations are shown to influence morphogenesis of tracheids sequentially formed in the growing season over successive periods. Morphogenetic mechanisms responsible for different tracheid traits are affected by climate to differing degrees according to the extent of elevation. This long-term high-resolution analysis of xylem anatomy could support short-term xylogenesis observations, offering insights into the ways in which climate controls tree growth and functioning.