Wood characteristics of nine eucalypt species grown under partial substitution of potassium by sodium

Mineral fertilization with K is essential for the optimal growth of eucalypts. Research has demonstrated that Na can partially substitute for K, yielding beneficial outcomes in certain contexts, such as enhanced water-use efficiency and photosynthetic activity. However, the existing studies have predominantly focused on hybrids of Eucalyptus grandis and Eucalyptus urophylla, with limited knowledge regarding other economically significant species within the genus.

Despite the potential advantages, it is unknown if the replacement of K with Na may adversely affect wood quality. Here, we replaced 40% of K needs with Na and the anatomical structure of the cell wall, its constituents, wood density, the localization of Na and K within the stem, and the expression of various genes governing cell-wall polymer deposition and carbon metabolism. The findings indicate that substituting K with Na at a rate of 40% did not significantly alter most parameters evaluated. However, the partial substitution influenced the basic density characteristics of E. brassiana and E. globulus. In contrast, no discernible effects were detected in species such as Corymbia maculata, C. citriodora, E. tereticornis, E. globulus, E. grandis, E. camaldulensis, or E. urophylla. Our data support the conclusion that K can be partially replaced by Na without significant variations in xylem vessel diameter, lignin concentration, or the expression of genes related to stem lignin metabolism across all newly studied eucalypt species.