The Form in Which Nitrogen Is Supplied Affects the Polyamines, Amino Acids, and Mineral Composition of Sweet Pepper Fruit under an Elevated CO2 Concentration.

We investigated the effect of supplying nitrogen, as NO3- or as NO3-/NH4+, on the composition of fruits of sweet pepper (Capsicum annuum L. cv. Melchor) plants grown with different CO2 concentrations ([CO2]): ambient or elevated (800 μmol mol-1). The results show that the application of NH4+ and high [CO2] affected the chroma related to the concentrations of chlorophylls. The concentrations of Ca, Cu, Mg, P, and Zn were significantly reduced in the fruits of plants nourished with NH4+, the loss of Fe being more dramatic at increased [CO2], which was also the case with the protein concentration. The concentration of total phenolics was increased by NH4+, being unaffected by [CO2]. Globally, the NH4+ was the main factor that affected fruit free amino acid concentrations. Polyamines were affected differently: putrescine was increased by elevated [CO2], while the response of cadaverine depended on the form of N supplied.