Effect of NO3:NH4 ratio and light intensity on nitrogen partitioning in pepper plants

Pepper plants were hydroponically grown in a growth chamber with two levels of light intensity (300 and 240 w/m²) and two NO₃:NH₄ ratios (100:0 and 80:20). Plants grown with both N forms (80:20) under high light regime displayed greater concentrations of free NH₄, organic soluble N and insoluble N than NO₃, treated plants, this effect was more pronounced for stem, petioles and root. By contrast, nitrate‐ammonium fed plants with light reduced over 25% presented similar concentrations of organic N (soluble and insoluble) as compared to plants supplied with NO₃ as sole source of N, however, the amount of free NH₄ in stem and root was increased. Results indicat that NH₄ supplied at low concentration was more deletereous for pepper plants grown under high light conditions, when light was reduced, plants presented an alleviation of toxic effect of NH₄ supply. Finally, nitrogen use efficiency is related to form of N nutrition and the light supplied to crop.