Effects of preconditioning on carbohydrate and amino acid composition of osmotically stressed black spruce (Piceamariana) cuttings

Abstract

The effects of preconditioning on osmotic potentials and the composition of soluble carbohydrates and free amino acids were studied in ramets of black spruce (Piceamariana Mill. B.S.P.). Plants were grown in solution culture and preconditioned by exposure to increasing concentrations of polyethylene glycol, and their osmotic potentials and composition of free amino acids and soluble carbohydrates were determined. Preconditioning increased levels of soluble carbohydrates compared with unconditioned plants. When the preconditioned and unconditioned plants were subjected to a subsequent, more severe osmotic stress with polyethylene glycol, high levels of monosaccharides and certain amino acids were observed in both preconditioned and unconditioned plants. During stress, preconditioned plants had lower (more negative) osmotic potentials and contained slightly higher levels of amino acids, but carbohydrate levels did not significantly differ from unconditioned plants. The increase in free amino acids and carbohydrates was insufficient to explain the drop in osmotic potentials resulting from preconditioning treatment.