Resumo

HERNANDEZ-PEREZ, Armando et al. Tolerance of lisianthus (Eustoma grandiflorum (Raf.) Shinn) to high ammonium concentrations in nutrient solution. Rev. Mex. Cienc. Agríc [online]. 2015, vol.6, n.3, pp.467-482. ISSN 2007-0934.

Lisianthus (Eustoma grandiflorum (Raf.) Shinn) is an ornamental species grown to produce cut flowers or potted plants and has a trade potential for its variety of colors. The use of soilless cultivation technology in ornamental species allows defining and clarifying the demand and optimal levels of nutrition. The present study aimed to evaluate the effect of the relationship NO₃^-: NH₄⁺ in the nutrient solution, keeping constant total concentration of nitrogen to define the maximum tolerance to NH₄⁺ in function of the phenological stage. The solutions under study consisted on four ratios of NO₃^-: NH₄⁺: 100: 0, 75:25, 50:50 and 25: 75%. Most variables responses allowed defining an optimal ratio of NO₃^-: NH₄⁺ between 75:25 and 50: 50% in vegetative and reproductive stage, interval that in most plant species would be toxic at these levels of NH₄⁺. This was observed in parameters such as plant height, stem diameter, leaf area and total dry weight of plant. Excessive concentration of NH₄⁺ (75%) caused a reduction in plant height, flower diameter, and total dry weight of plant. The increase in ratio of NH₄⁺ was associated with increased concentrations of N, P, K, Ca and Mg in leaf and stem, but in flower was less marked for K and Mg. The extraction of these macronutrients showed the same trend.

Palavras-chave : nitrate /ammonium; nutrition; nutrient solution; ornamental; tezontle; toxicity.