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

Abstract: Premise of the study: 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 both 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 that spanned 600 m to 1600 m asl in eastern China. The heights of individually sampled trees, as well as environmental factors of each sampling site were also measured. Linear mixed models were employed to assess the relative extent of both intraspecific (within species) and interspecific (between species) variations in parenchyma cells in xylem tissue fractions, as well as identify intraspecific variations along environmental gradients (e.g., temperature and humidity) and tree heights. Key results: The results revealed that 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 RAP (total AP and RP fractions) fractions exhibited negative correlations with tree heights but showed no significant relationship with climate. Conclusions: In conclusion, the findings suggested that intraspecific variations in parenchyma cells in xylem tissue fractions were not necessarily an adaptation or acclimation to changes in the environment but were coordinated with tree heights.KEYWORDSclimate gradient, elevation, inter-and-intraspecific variation, parenchyma, tree, woody trait, xylem anatomy