The Nitrogen Nutrition of The Peach Tree I. Seasonal Changes in Nitrogenous Constituents in Mature Trees

Abstract

Seasonal changes in the concentration of total N, free amino acid N, arginine, and glutamine plus asparagine in flower buds, flowers, fruit, leaves, roots, new shoots, and 2-3-yr. old shoots of 25-yr. old peach trees have been studied over an annual cycle. Peak concentrations of each constituent were found in tree tissues before growth commenced and after growth ceased (woody tissues only), while a minimum was found at the end of the growing season. In most tissues this pattern of change was not influenced by the amount of N supplied or by the time of application of the nitrogenous fertilizer, but the concentration of the constituents was usually proportional to N supply. From the evidence available, it is suggested that N accumulates in proportion to supply in woody tissues of mature peach trees after the cessation of shoot growth in late summer, and that this stored N is mobilized for new growth during the next growing season. Since dormant storage tissues usually contained high concentrations of arginine but only low concentrations of glutamine plus asparagine, it is suggested that arginine is a more important constituent of the storage N of mature peach trees than are the amides.