Influence of foliar urea on the antioxidant response and fruit color of sweet pepper under limited N supply

Abstract

Abstract BACKGROUND: Foliar fertilizer methods could provide a rapid and efficient response when uptake by plant roots is limited. This work studies the effect of foliar urea sprays (15 g L −1 ) at different frequencies on the antioxidant metabolism and fruit quality of sweet pepper fruits under N‐limited nutrient solution (3.5 mmol L −1 NO 3 − ) and fully N‐supplied (12.5 mmol L −1 NO 3 − ) plants. RESULTS: Foliar applications of urea in root N‐limited plants increased the total N concentration in the fruits and no significant differences were found with respect to control fruits (plants fully supplied with N by the roots). Fruit color was significantly affected by the urea sprays, and at the highest frequency (twice a week) the largest overall color difference (Δ E ) with respect the non‐sprayed fruits was obtained. Foliar urea increased anthocyanin concentration to control values but flavonoids were only affected at the highest application frequency. N deficiency induced oxidative stress but foliar application of urea altered this response, significantly diminishing catalase and ascorbate peroxidase activity. CONCLUSION: Sweet pepper fruits showed a significant and positive response to foliar fertilization on the studied parameters, compensating to a major extent the reduction of N by the roots. In addition to the environmental issues in reducing N contamination, fully monitored automatically sprayed foliar fertilizer could utilize N more efficiently and at lower cost than applying the full recommended rate of other N fertilizers to the nutrient solution, providing flexibility in correcting N nutrition in the plant, and especially the control of nutrient supply independent of the water supply. Copyright © 2008 Society of Chemical Industry