Resumen

CORASPE-LEON, Héctor M et al. N-nh₄⁺ and n-no₃  uptake by potato in the tuber seed production. Agronomía Trop. [online]. 2009, vol.59, n.1, pp.45-58. ISSN 0002-192X.

The nitrogen is the structural constituent of proteins, several metabolites involved in the synthesis and trans­ference of energy and also of nucleic acids. It is absorbed by plants in the nitrate (NO₃^-) or ammonium (NH₄⁺) form. The nitrate uptake varies with cultivar and light intensity. The objective of this research was to determine the preferential form of N (N-NH₄⁺ or N-NO₃^-) absorbed by the potato plants in seed tuber productions, using ¹⁵N isotope. The experiment was carried out in the greenhouse of Centro de Energia Nuclear na Agricultura (CENA) / USP, Brazil, using 2.3 l plastic pots, with expanded clays as substrate. The experimental design used was a completely randomized with five treatments, corresponding to the labeled NH₄ or NO₃ (¹⁵NH₄ or ¹⁵ NO₃) application time: 14, 28, 42, 56 and 70 days after transplanting (DAT), and three replicates. An IAC nutrient solution was used, modified to supply N, K and Ca, substituting calcium nitrate and potassium nitrate by ammonium nitrate labeled with ¹⁵N. The preferential form of nitrogen absorption at the initial developing stage was the ammonium, changing to nitrate after 56 DAT (tuber formation). The N utilization by the plants, however, was always higher with ammonium form applied in all stages, with the exception at 28 DAT and at the end of cycle.

Palabras clave : Solanum tuberosum L; nitrogen absorption; mineral nutrition; nutrient solution; ¹⁵N; expanded clay; seed tuber.