Effect of NO3:NH4ratio and light intensity on nitrogen partitioning in pepper plants

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Abstract
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.