Effects of ammonium on the root architecture and nitrate uptake kinetics of two typical lettuce genotypes grown in hydroponic systems.

摘要

To relate the characteristics of root architecture and the kinetic parameters of nitrate (NO₃) uptake, two typical lettuce cultivars (Lactuca sativa L.), 'Sx1' and 'Nrnct', were exposed to different nutrient solutions: 100% NO₃-N (T1), 10% ammonium (NH₄)-N+90% NO₃-N (T2), 10% NH₄-N+100% NO₃-N (T3). The results obtained indicate that total root surface area, root volume, total root length and root number increased with the increased of NH₄-N; the NH₄-N in the nutrient solution had significant effects on the rates of NO₃- uptake, Vmax of NO₃- uptake kinetics in T1 was significantly higher than with T2 and T3, Km of NO₃- uptake kinetics in T1 was lower than that of T2 and T3, but the difference was not significant, NH₄-N inhibited NO₃- uptake mainly due to the higher Vmax. Based on the NO₃- uptake rate, NO₃- content, Vmax and Km, the different cultivars differed in their nitrate uptake characteristics.