Effect of tris(3-hydroxy-4-pyridinonate) iron(III) complexes in iron deficiency chlorosis

Title : Effect of tris(3-hydroxy-4-pyridinonate) iron(III) complexes in iron deficiency chlorosis

Abstract:

Successful cultivation of crops with the best nutritional properties is an issue of paramount importance in the Agricultural and Health fields. Iron (Fe) is an essential mineral nutrient and legumes are one of the major sources of Fe. However the absorption of Fe by the roots of plants is compromised when grown in alkaline soil. As a consequence, plants may suffer from Fe deficiency chlorosis (IDC), characterized by chlorosis, yield losses, and lower concentrations of Fe in edible plant parts. Soil application of synthetic Fe(III) chelates  (e.g. Fe-EDTA or FeEDDHA) remains one of the most common measures to correct IDC.

Here, we tested the capacity of two tris(3-hydroxy-4-pyridinonate) Fe(III) complexes, [Fe(dmpp)₃ and Fe(mpp)₃], to amend IDC in hydroponically grown soybean (Glycine max) plants, and we compared them to FeEDDHA. Plants treated with 20 µM of [Fe(dmpp)₃ and Fe(mpp)₃] were significantly greener (Fig. 1), bigger and had 47% and 55% higher total Fe content (respectively) than those treated with the same amount of FeEDDHA. Plants supplied with [Fe(mpp)₃] were able to translocate 64% more Fe to the shoots than Fe(dmpp)3-supplied plants, which tended to accumulate Fe in the roots. Given the positive results obtained with 20 µM Fe(mpp)3, we hypothesized that even lower concentrations, such as 5 and 10 µM, could also be effective in preventing IDC, and a second trial was performed. Plants supplied with 20 µM and 10 µM [Fe(mpp)₃] presented two expanded trifoliate leaves whereas plants grown with 5 µM had only one expanded trifoliate leaf. Total fresh weight (TFW) was not significantly different between 10 and 20 µM supplied plants, but was different to 5 µM grown plants, which had about 30% lower TFW. Chlorosis development was assessed using SPAD measurements and total chlorophyll quantification. SPAD values were 10% higher in 20 µM-supplied plants when compared to the other two concentrations (p<0.05), although no significant differences were found in total chlorophyll leaf accumulation. Also, the accumulation of antioxidant defense related pigments - carotenoids and anthocyanins- was not significantly different between treatments. The amount of Fe was quantified in roots and leaves, using atomic absorption spectroscopy, and in both tissues no differences were detected. This work indicates that [Fe(mpp)₃] has potential as an Fe fertilizer that, even at low doses, is able to avoid IDC symptoms development, and that could be economically and environmentally favorable in agricultural contexts. The presentation is focused on the development of a new Fe fertilizer. We will explain the concept. The new compound is part of a set of compounds that are made in our laboratory and we have the possibility to tailor-made the compounds to adjust their properties and improve efficacy. The new compound improves Fe content both in roots and in leaves. Application of the new fertilizer can be made either in soil or sprayed on leaves.

Biography:

Maria Rangel is an Associate Professor at University of Porto. She is a Bioinorganic Chemist whose research interests are focused in the role of metal ions in living organisms. In recent years she has worked on the design of Iron chelators for: (a) novel strategies to fight Infection through Fe deprivation; (b) treatment of Fe Overload and (c) Fe Sensing. Her interest in Iron Biology has been extended to Plant Nutrition and she is currently developing projects that aim the understanding of mineral nutrition processes and the design of Fe-chelates to address agricultural problems related with Fe deficiency.