Free amino acids in walnut kernels and young seedlings

We investigated the composition of free amino acids in walnut (Juglans regi a L.) seeds (embryo and cotyledons). We also examined xylem transport of fr ee amino acids in young seedlings grown in the absence of external nutrient s. A relatively high concentration of free alanine was found in seed tissue , whereas a relatively high concentration of citrulline was detected in you ng seedlings. Citrulline was the main free amino acid transported in the xy lem to stem and leaves. The negligible presence of citrulline, a non-protei n amino acid, in the kernel and its presence in high concentrations in all of the tissues of young seedlings, including cotyledons, embryonic axis, ta proot and stem, suggest that citrulline is synthesized during walnut germin ation. We conclude that citrulline plays an important role in nitrogen tran slocation during walnut germination.