Nitrate/Ammonium Ratios and Nitrogen Deficiency Impact on Nutrient Absorption and Photosynthetic Efficiency of <i>Cedrela odorata</i>

Abstract

Nitrate (NO3−) and ammonium (NH4+) are the primary forms of nitrogen (N) taken up by plants and can exhibit different effects on plant nutrition, photosynthesis, and growth. The objective was to investigate the influence of nitrate/ammonium proportions (%) on the nutritional status, photosynthetic parameters, and the development of Cedrela odorata seedlings after 150 days of cultivation. We tested six nitrate/ammonium ratios (100/0; 80/20; 60/40; 40/60; 20/80; and 0/100 of NO3− and NH4+, respectively), plus a control treatment (without N supply). Based on the results, the species responds to the supply of N; however, the NO3− and NH4+ proportions did not show any significant effect on plant growth. The deficiency of nitrogen (N) in Cedrela odorata decreases the photosynthetic rate, nutrient absorption, and initial growth of this species. Increasing the proportion of N in the form of nitrate inhibited the absorption of S (sulfur) but did not interfere with the accumulation of N, Ca (calcium), Mg (magnesium), Mn (manganese), Zn (zinc), B (boron), and Cu (copper). Cedrela odorata apparently does not distinguish between nitrate and ammonium in the N absorption process, since the proportions between these forms of N did not affect its photosynthetic rate, nutrient accumulation, or growth.

Keywords

• ammonium toxicity
• chlorophyll index
• gas exchange
• tree seedling nutrition
• mineral nitrogen
• nitrogen forms