Nitrogen and Amino Acid Content of the Various Parts of Andropogon Ischaemum L.

Knowledge of the nitrogen metabolism of plants is of importance for an understanding of the growth and development of the plants themselves and for their evaluation as food for grazing animals. Of particular significance with respect to the latter use is the amino acid composition of the grass proteins. Although a few studies have been made of the amino acid composition of grass proteins (CHIBNALL, 2; LUGG, 8) no studies have ever been made of the amino acid compostion of grasses of range importance in the Southwest. FUDGE and FRAPS (5) have, however, made a fairly extensive study of the total nitrogen composition of certain Texas grasses. A somewhat more limited study involving rye grass, along with certain cereal grasses, has been made by MACVICAR (9). A study of the amino acids in alfalfa made by STEWARD et al. (11), employing the chromatography method, indicated that several amino acids in addition to the amides, glutamine and asparagine, could be extracted with alcohol. This study further lists a number of amino acids which were detected after acid hydrolysis. Radioautography of amino acids containing S35 aided in the identification of various.sulphur containing amino acids. One of the most important considerations with respect to range grasses is the modification of nitrogen content associated with regrowth following grazing. The physiological effects of clipping certain pasture grasses to simulate grazing have been reported by LEUKEL et al. (7). Leukel and his co-workers concluded that frequent clipping reduces the carbohydrate and nitrogen content and favors vegetative rather than reproductive growth. A detailed study of the carbohydrate and nitrogen composition of the roots, stubble, and tops of clipped perennial rye grass plants was made by SULLIVAN and SPRAGUE (13). HOLSCHER (6) has reported decreased growth and dry weight in clipped western wheatgrass, Agropyron Smithii Rydb. and blue grama grass, Bouteloua gracilis (H.B.K.) Lag. BUKEY and WEAVER (1) made a similar study of little bluestem, Andropogon scoparius Michx., and big bluestem, Andropogon furcatus Muhl. The present study deals with both total nitrogen and amino acid content of the King Ranch strain of Andropogon ischaemum L. The investigation was aimed, in part, at determining whether or not the amino acid content remains constant during the growth cycle.