Infrared spectroscopy-based metabolomic analysis of maize growing under different nitrogen nutrition

For metabolomic analysis of maize plants growing under different nitrogen nutrition sequential extraction of fresh biomass was used and isolated fractions were characterized and evaluated using IR spectra. The IR spectra of individual fractions were evaluated in relation to the nitrogen rates (2 g or 4 g N), to applied fertilizers (ammonium nitrogen or urea ammonium nitrate solution) and sampling period. For butanol fraction, typical bands of flavo-noids, polar phospholipids, steryl glycosides, analogues of ecdysteroids were characterized. The IR spectra of BuOH fraction showed changes of relative contents of isolated compounds mainly affected by nitrogen rates. For water fraction bands of organic acids, salts of organic acids, flavonoid glycosides and oligopeptides (phytochelatins and/ or glutathione) were the most significant. The results showed an increased induction of oxalic acid in plants after 4 g N application. Degradation of this acid induced oxidative stress, therefore strong correlation among contents of oxalic acid, flavonoids and compounds with amide nitrogen (glutathione) was observed in plants growing under 4 g nitrogen nutrition. The glutathione-ascorbate cycle protects plants against oxidative damage.