The influence of nitrogen and potassium supply on the ammonium content of maize (Zea mays L.) leaves including a comparison of measurements made in vivo and in vitro
Gerendás J., Ratcliffe RG., Sattelmacher B.
Maize seedlings were grown on either nitrate or ammonium, at two different potassium levels, and the growth analysis revealed that ammonium supply reduced shoot dry matter particularly under conditions of limited potassium supply. The ammonium content of the leaves was determined in vitro, using continuous flow analysis of plant extracts, and in vivo using 14N nuclear magnetic resonance (NMR) spectroscopy. The conventional continuous flow analysis procedure was modified by the inclusion of a gas dialysis step across a PTFE membrane and control experiments showed that this provided an effective method for avoiding the overestimation of the ammonium content of leaf tissue extracts, by eliminating interference from amino acids and amides. Excellent agreement was obtained between the non-invasive NMR method and the modified continuous flow analysis technique, and it was concluded that leaf ammonium levels are unlikely to affect growth in plants grown with an adequate potassium supply. © 1995 Kluwer Academic Publishers.