Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

ABSTRACT

This work studied the behavior of different iron (Fe)-chelates as substrates of ferric chelate reductase (FCR) and their ability as Fe suppliers for mildly chlorotic plants. FCR activity and Fe concentration in xylem sap were determined in green stressed cucumber plants with different stress levels using different synthetic chelates as substrates. Both reduction and Fe concentration in the xylem sap were higher for the less-stable Fe chelates, except for Fe-EDTA, which presented a relatively low Fe concentration in sap. It was concluded that a high stability of the chelate in the nutrient solution reduces the Fe reduction, but other factors, such as the complexation of the Fe(II) by the chelating agents, should be considered when the complete process of Fe uptake is studied. The use of both indexes together, i.e., FCR determination and xylem sap concentration, is useful for understanding the Fe uptake from different Fe chelates.

Keywords:

• iron
• chelate
• chlorosis
• reductase
• Cucumis sativus

ACKNOWLEDGMENTS

The authors gratefully acknowledge the technical assistance of Carrie E. Green and Francisca Blas for their help in conducting the experiments, and thank Dr. M. Gómez-Gallego for her helpful review of the manuscript. This work was performed during a research visit by J. J. Lucena to the USDA, which was supported by a MEC-CICyT grant. Part of the work was supported by projects AGL2001-1142 from the Spanish Ministry of Sciences and Technology.