Seasonal free amino acid fluctuations in red pine and white spruce needles

Abstract

Eighteen free amino acids were quantified biweekly from the needles of 3-year-old bare-root red pine (Pinusresinosa Ait.) and white spruce (Piceaglauca (Moench) Voss) seedlings over a 3-year period. In both species, concentrations of alanine, serine, aspartic acid, glutamic acid, asparagine, threonine, valine, glutamine, and proline increased during summer. Phenylalanine, lysine, and leucine accumulated in red pine during the summer but not in white spruce. During the winter tyrosine and histidine accumulated in white spruce but not in red pine. Only tryptophan consistently exhibited a significant trend in both species, rising from a low concentration in summer to a peak in fall and then returning to a low concentration in the spring. Thirteen amino acids in red pine and 15 in white spruce exhibited significant coefficients of determination with photoperiod and daily air temperature together. Fourteen amino acids in red pine and 10 in white spruce had significant photoperiod partial regression coefficients, while three amino acids in red pine and six in white spruce exhibited significant temperature partial regression coefficients. Total amino acid concentration exhibited significant coefficients of determination, with only the photoperiod partial regression coefficients being significant for both species.