The elemental composition, the microfibril angle distribution and the shape of the cell cross-section in Norway spruce xylem

Relationships between the elemental composition, the microfibril angle (MFA) distribution and the average shape of the cell cross-section of irrigated-fertilised and untreated Norway spruce (Picea abies [L.] Karst.) earlywood were studied. Sample material was obtained from Flakaliden, Sweden. The elemental composition was studied by determining the relative mass fractions of the elements P, S, Cl, K, Ca and Mn by X-ray fluorescence and by determining the mass absorption coefficients for X-rays. X-ray diffraction was used to determine the MFA distribution and the average shape of the cell cross-section. The latter was also determined by light microscopy. In transition from juvenile wood to mature wood, a decrease of the mode of the MFA distribution from 13°–24° to 3°–6° was connected to a change in the shape of the cell cross-section from circular to rectangular. The irrigation-fertilisation treatment caused no change in the MFA distribution or in the shape of the cell cross-section, whereas the mass absorption coefficient was higher and the density was smaller in irrigated-fertilised wood. Larger proportion of the elements S, Cl and K, but smaller proportion of the element Mn, were observed due to the treatment. The results indicate that the shape of the cell cross-section or the MFA distribution are not directly linked to the growth rate of tracheids or to the nutrient-element content in the xylem and only show notable changes as a function of the cambial age.