Seasonal Changes in Total, Soluble, Soluble-Protein, Non-Protein, and Insoluble Nitrogen in Current Year's Shoots of Bartlett Pear

Abstract

Not only are proteins very closely connected with the phenomena of life, but unlike other essential constituents of the living cell, they are in all probability characteristic of the animal or plant species in which they are found. The physical properties of the proteins apparently adapt them to the performance of functions essential to the activities of life. Notwithstanding this unique position which these nitrogenous compounds occupy in the plant metabolism, but little is known as to the part they play in the metabolic cycle of the higher plants.Owing to the difficulties involved in separation and identification of various nitrogenous compounds, earlier investigators could not proceed much beyond the determination of total nitrogen in their material. Recent advances in protein chemistry have made a further study of these nitrogenous compounds possible. OSBORNE'S work on proteins in spinach leaves (7) closely followed by a series of papers by CHIBNALL on proteins in leaves of various annuals, including studies on runner bean leaves (3), stimulated interest in the study of nitrogen metabolism of the higher plants by nitrogen fractionation methods. THOMAS (8) was the first to undertake a rather complete nitrogen fractionation of woody tissue like apple twigs.This work was undertaken to determine the seasonal variations in the nitrogenous compounds in the bark and the wood of the current year's growth in Bartlett pear trees. This paper deals with fractionation of total nitrogen into water-soluble and insoluble nitrogen and further division of water-soluble into soluble protein and non-protein nitrogen. Fractionation of soluble non-protein and insoluble nitrogen will be taken up in later papers.Material The samples were taken from twelve 6-year-old Bartlett pear trees grown at the University Farm, Davis, California. These trees were fairly uniform and may be considered as representative trees for their age on a well-managed farm in that locality.Samples were collected at intervals of approximately one month from

Studies on the Chemistry of the Living Bark of the Black Locust Tree in Relation to Frost Hardiness. IV. Effects of Ringing on Translocation, Protein Synthesis and the Development of Hardiness

“…RIPPEL (19) in 1921 and COMBES (3) in 1925 showed that nitrogen migrates from the leaves in fall and accumulates in the branches and trunk of the tree. Others (8,14,15,17,18,25) have reported the occurrence of this phenomenon. LooMIs (13) in the course of certain ringing experiments, demonstrated accumulation of protein in the bark of trees in winter.…”

The Nitrogen Distribution in Alfalfa Hay Cut at Different Stages of Growth

“…5. Scheme of analysis employed by Mulay (1931) Consequently methods should be used which permit of studying this material without further modification by hydrolysis.…”

Seasonal Changes in the Composition of the Insoluble Nitrogen Fraction in the Current Year's Shoots of Bartlett Pear

“…In a previous paper (1), it was shown that there were considerable variations in the quantity of insoluble nitrogen, both in bark and wood, during the growth cycle of pear shoots. It was also shown in another paper (2) that seasonal variations in the water-soluble nitrogen fraction in pear shoots are not only quantitative but qualitative also.…”