Abstract
PurposePhytosiderophores (PS) from grasses solubilize sparingly soluble iron (Fe), and the resultant PS-Fe is an Fe source even for dicots. Recently, the synthetic PS proline-2′-deoxymugineic acid (PDMA) has been developed as a moderately biodegradable Fe fertilizer for grasses. We aimed to investigate whether PDMA-Fe is also a good Fe source for dicots.MethodsThe availability of PDMA-Fe to cucumber was evaluated in a calcareous substrate and hydroponic cultures at pH 7.0–9.0 by determining chlorophyll level, PSII activity, and Fe uptake. EDDHA-Fe, EDTA-Fe, and citrate-Fe were used as controls. The reducibility of Fe chelates by roots was measured to determine the mechanism underlying differences in availability. Expressions of Fe deficiency-inducible genes were analyzed to estimate the Fe status in plants.ResultsThe application of PDMA-Fe and EDDHA-Fe to a calcareous substrate reduced Fe-deficient chlorosis to a similar extent; however, the shoot Fe concentration was higher in the PDMA-Fe treatment. In the hydroponic culture, the availability of PDMA-Fe was higher than that of the other chelates at all pH levels, and this was confirmed by higher PSII activity and lower expression of Fe deficiency-inducible genes. The reducibility assay revealed that the reduction level of PDMA-Fe was greater than that of EDTA-Fe and citrate-Fe under alkaline pH.ConclusionsPDMA-Fe is utilized by cucumber roots more efficiently than traditional synthetic chelates in both calcareous substrate and hydroponic cultures. The higher availability of PDMA-Fe may be attributed to its higher reducibility. Our findings suggest that PDMA-Fe could be a good Fe fertilizer for dicots.
Highlights
Iron (Fe) is the fourth most abundant element in the Earth’s crust; under aerobic conditions, the concentrations of Fe3+ and Fe2+ ions in soil solution are below 10− 15 M at pH > 6, limiting plant growth at neutral or alkaline pH (Lindsay and Schwab 1982; Guerinot and Yi 1994)
We investigated the effects of PDMAFe application on a calcareous substrate and the availability depending on pH in hydroponic cultures, and revealed that proline-2′-deoxymugineic acid (PDMA)-Fe could be an alternative to the traditional synthetic chelates, even for Strategy I plants
At 4 d after the treatment, plants treated with Cit-Fe and with no Fe showed Fe-deficiency chlorosis, whereas plants treated with PDMA-Fe and EDDHA-Fe did not (Fig. 1a)
Summary
Iron (Fe) is the fourth most abundant element in the Earth’s crust; under aerobic conditions, the concentrations of Fe3+ and Fe2+ ions in soil solution are below 10− 15 M at pH > 6, limiting plant growth at neutral or alkaline pH (Lindsay and Schwab 1982; Guerinot and Yi 1994). Plants have developed two mechanisms for Fe acquisition (called “Strategy I” and “Strategy II”) to cope with this limitation (Marschner and Römheld 1986). Strategy I plants, including non-grass monocots and dicots, release organic compounds including flavins and iron-mobilizing coumarins in response to Fe deficiency to mobilize rhizosphere Fe through reduction and/or chelation (Römheld and Marschner 1983; Jin et al 2007; Sisó-Terraza et al 2016; Tsai and Schmidt 2017). The acidification of the rhizosphere by H + release is required to increase Fe solubility and to ensure Fe(III) reductase activity in this strategy (Römheld and Nikolic 2007). Based on the difference in mechanisms, sparingly soluble Fe(III) is considered a substrate for the Strategy II system, whereas Fe(III) chelates are the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
