Amino acid composition of fractions of cultivar kentucky 31 tall fescue festuca arundinacea as affected by nitrogen fertilization and mild water stress
Belesky, D.P.; Wilkinson, S.R.; Evans, J.J.
Plant and Soil 81(2): 257-268
ISSN/ISBN: 0032-079X Accession: 004708928
Environmental and management factors can influence the protein concentration of forages, significantly altering specific amino acid content. Drought, high rates of fertilizer N and the presence of a fungal endophyte were associated with significant alterations in plant N metabolites and animal performance problems on tall fescue. A controlled environment study was conducted to examine the influence of N fertilization (10 and 110 .mu.gN/g) and water regime (low and adequate soil water availability) upon the distribution and concentration of amino acids in endophyte infected tall fescue (F. arundinacea Schreb.) herbage. Tall fescue tissue was collected from 3 replicas of each treatment, quick frozen in liquid N and lyophilized. Two insoluble (RI, structural residue; RII, membrane residue) and 2 soluble (SI, solution protein, SII, low MW N compounds) fractions were collected. Amino acid analyses of acid hydrolysates of fractions showed that application of 110 N significantly increased the concentration per unit dry wt) of all amino acids in the entire plant, with an average increase of about 55%. Application of 110 N increased the concentrations of most amino acids in fractions RI, RII and SI, but only aspartate-asparagine, glutamate-glutamine, alanine, thorenine, serine, valine and proline in fraction SII. Fraction RI contained about 65% of total amino acids under 10 N and 55% under 110 N even though N level did not alter dry matter distibution among fractions. While the amount of dry matter was least in SI, amino acids in the fraction ranged from 8% (leucine, 10 N) to 20% (lysine, 110 N) of the total amount of specific amino acids recovered. Significant increases in proline, glutamate, aspartate, serine, valine, threonine, alanine and phenylalanine concentration occurred under low soil-water availability compared with adequate water conditions. Basic amino acids including histidine, arginine and lysine increased with increased N and with water stresst at each N level. Application of N increased amounts, and water stress influenced distribution of amino acids among the fractions of tall fescue herbage. Nitrogenous components, such as non-protein amino acids which could influence plant nutritive quality, were increased in fraction SII by increased N and water stress.