Tree height and not climate influences intraspecific variations in wood parenchyma fractions of angiosperm species in a mountain forest of eastern China

Abstract
Premise: Parenchyma is an important cell type in the secondary xylem of angiosperm
trees, with considerable variability in its abundance. However, the functional significance of these variations and their roles in plant ecological strategies is poorly
understood at the inter‐ and intraspecific levels.
Methods: For this study, fractions of axial parenchyma cells (AP) and ray parenchyma
cells (RP) in xylem tissue were quantified for 156 individuals of 45 tree species along
an elevational gradient from 600 to 1600 m a.s.l. in eastern China. Environmental
factors and height of sampled trees at each sampling site were also measured. Linear
mixed models were employed to assess the relative extent of both intraspecific and
interspecific variations in parenchyma cells in xylem tissue fractions and to identify
intraspecific variations along environmental gradients (e.g., temperature and
humidity) and tree heights.
Results: Interspecific variations explained the large diversity in AP fractions. Conversely, intraspecific variations accounted for ~50% of the overall variations in RP
fractions. Further, intraspecific variations in the RP and the total AP and RP fractions
exhibited negative correlations with tree heights but showed no significant relationship with climate.
Conclusions: Intraspecific variations in parenchyma cells in xylem tissue fractions are
not necessarily an adaptation or acclimation to changes in the environment but are
coordinated with tree heights.