Despite the importance of nitrogen for plant performance, few studies have addressed the nitrogen assimilation and amino acid metabolism of Neotropical trees. This study analyzed the nitrogen use strategies of tree species native to the Brazilian Atlantic Forest with different degrees of shade tolerance: Heliocarpus popayanensis (a shade-intolerant species), Cariniana estrellensis (a shade-tolerant canopy species) and Eugenia brasiliensis (a shade-tolerant understory species). We analyzed the growth and nitrogen uptake, assimilation and translocation of seedlings cultivated hydroponically with nitrate (NO₃⁻) or ammonium (NH₄⁺). ¹⁵N incorporation into amino acids was monitored after incubation with ¹⁵NO₃⁻ or ¹⁵NH₄⁺. H. popayanensis showed a preference for NO₃⁻, characterized by high NO₃⁻ uptake rates and intense NO₃⁻ assimilation occurring primarily in the leaves. E. brasiliensis assimilated NO₃⁻ primarily in the roots and showed a preference for NH₄⁺ uptake. The canopy species C. estrellensis assimilated NO₃⁻ predominantly in the leaves and absorbed NO₃⁻ and NH₄⁺ at similar rates. Both shade-tolerant species were highly tolerant to NH₄⁺ and showed glutamine and compounds related to nitrogen remobilization as important nitrogen carriers in their xylem sap. In contrast, H. popayanensis seedlings had their growth reduced by NH₄⁺ and showed asparagine as the major amino acid translocated in the xylem sap. Variations in root and leaf amino acid metabolism among the species were also observed. The canopy species has nitrogen use strategies intermediate to shade-intolerant and understory species. The different responses might be related to adaptations to the different light conditions of their habitats, since high light intensities could favor the use of NO₃⁻.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.