Ammonium uptake kinetics and protons efflux in corn varieties

Abstract

The analysis of kinetic parameters for absorption of ions (NO3? e NH4+) is the main experimental procedure for the differentiation of the efficiency of absorption of these nutrients between corn species and cultivars. This work had the aim of evaluating the kinetic parameters of ammonium uptake to elucidate metabolic strategies of corn cultivars at environments with low and high nitrogen concentrations. The selected cultivars were: Catetão, Sol da Manhã, Eldorado and BR 473. The plants were cultivated in pots with N solutions of 1.43 and 8.57 mM at green house conditions. The following kinetic parameters were evaluated 28 days after germination: Vmax, KM and N-amino soluble fraction in the water, nitrate and ammonium. Fresh mass of above groud part and roots, and N-total, P, and Mg in the dried material were determined. Sol da Manhã cultivar presented high development at high affinity uptake systems, while Catetão and Eldorado cultivars presented high development at the low affinity and high capacity of NH4+ uptake system. Sol da Manhã cultivar presented high adaptation at low nitrogen availability conditions. The values of NH4+ uptake kinetic parameters, Vmax and KM can justify the high productivity of this cultivar described in the literature as efficient in nitrogen use.