Nutrient distribution among metabolic fractions in 2 Atriplex spp

Abstract

The seasonal variations in nitrogen and phosphorus fractions and cations in 2 species of Atriplex common to Western Australia (Atriplex amnicola P.G. Wilson and Atriplex nummularia Lindl.) were investigated. Both species contain high concentrations of nitrogen (N) in winter as compared with summer when both species contain high concentrations of sodium. The sum of soluble protein-N, amino acid-N, nucleic acid-N and nitrate-N is about half of the total nitrogen. The remainder includes non-soluble protein-N and other N associated with cell membranes and walls. Phosphorus was more uniformly distributed among pools of inorganic-P, phytate-P, nucleic acid-P and other (residual) fractions. We suggest that interpretation of animal nutrition studies based on similar trichloroacetic acid (TCA) fractionations might be improved by independent estimation of soluble proteins. Fractionation using TCA provides valuable information about the subcellular distribution of both N and P in foliage tissues for study of plant physiology and animal nutrition. Concentrations of major nutrients in foliage of both species were significantly and negatively correlated with monthly maximum temperature and significantly and positively correlated with monthly rainfall. In summer and early autumn the apparent nutritive value of both species is well below the basic requirement of sheep or other grazing ruminants such as goats.