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Plant Physiol Biochem. 2015 Feb;87:45-52. doi: 10.1016/j.plaphy.2014.12.014. Epub 2014 Dec 19.

Plant-microorganism-soil interactions influence the Fe availability in the rhizosphere of cucumber plants.

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Faculty of Science and Technology, Free University of Bolzano, I-39100 Bolzano, Italy.
Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, University of Bari "Aldo Moro", I-70126 Bari, Italy.
Faculty of Science and Technology, Free University of Bolzano, I-39100 Bolzano, Italy. Electronic address:


Iron (Fe) is a very important element for plants, since it is involved in many biochemical processes and, often, for the low solubility of the natural Fe sources in soil, plants suffer from Fe - deficiency, especially when grown on calcareous soils. Among the numerous plant growth-promoting rhizobacteria (PGPR) that colonize the rhizosphere of agronomically important crops, Azospirillum brasilense has been shown to exert strong stimulating activities on plants, by inducing alterations of the root architecture and an improvement of mineral nutrition, which could result from an enhancement of ion uptake mechanisms as well as by increased bioavailability of nutrients. Some studies have also established that A. brasilense can act as biocontrol agent, by preventing the growth and/or virulence of phytopathogens, most likely through the production of microbial siderophores that sequester Fe from the soil. Despite microbial siderophores complexed with Fe could be an easily accessible Fe source for plants, the possible involvement of A. brasilense in improving Fe nutrition in plants suffering from the micronutrient deficiency has not been investigated yet. Within the present research, the characterization of the physiological and biochemical effects induced by Fe starvation and PGPR inoculation in cucumber plants (Cucumis sativus L. cv. Chinese Long) was carried out. The analyses of root exudates released by hydroponically grown plants highlighted that cucumber plants respond differently depending on the nutritional status. In addition, following the cultivation period on calcareous soil, also the root exudates found in the extracts suggested a peculiar behaviour of plants as a function of the treatment. Interestingly, the presence of the inoculum in soil allowed a faster recovery of cucumber plants from Fe-deficiency symptoms, i.e. increase in the chlorophyll content, in the biomass and in the Fe content of leaves. These observations might suggest a feasible application of A. brasilense in alleviating symptoms generated by Fe-limiting growth condition in cucumber plants.


Azospirillum brasilense; Biofertilization; Cucumis sativus L.; Fe mobilization; Fe-deficiency; Plant growth-promoting rhizobacteria; Rhizosphere

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