Capillary electrophoresis for the determination of major amino acids and sugars in foliage: application to the nitrogen nutrition of sclerophyllous species

Amino acids and sugars are probably the most commonly measured solutes in p lant fluids and tissue extracts. Chromatographic techniques used for the me asurement of such solutes require complex derivatization procedures, analys is times are long and separate analyses are required for sugars and amino a cids. Two methods were developed for the analysis of underivatized sugars a nd amino acids by capillary electrophoresis (CE), Separation of a range of sugars and amino acids was achieved in under 30 min, with good reproducibil ity and linearity. In general, there was dose agreement between amino acid analyses by CE and HPLC with post-column derivatization. An alternative, mo re rapid method was optimized for the common neutral sugars. Separation of a mixture of fructose, glucose, sucrose, and fucose (internal standard) was achieved in less than 5 min. How the source of N applied (nitrate or ammon ium) and its concentration (8.0 or 0.5 mM) affects the amino acid and sugar composition of leaves from Banksia grandis Willd. and Hakea prostrata R. S r. was investigated. The amino acid pool of Banksia and Hakea were dominate d by seven amino acids (aspartic acid, glutamic acid, asparagine, glutamine , serine, proline, and arginine), Of these, asparagaine and glutamine domin ated at low N-supply, whereas at high N-supply the concentration of arginin e increased and dominated amino-N. Plants grown with nitrate had a greater concentration of proline relative to plants with ammonium. In Banksia the c oncentration of amides was greatest and arginine least with a nitrate N-sou rce, whereas in Hakea amides were least and arginine greatest with nitrate N-source. The concentration of sugars was greater in Banksia than Hakea and in both species at greater N-supply.