Variation in Manganese and Iron Accumulation Among Soybean Genotypes Growing on Hydroponic Solutions of Differing Manganese and Nitrate Concentrations

Abstract

Manganese (Mn) is an essential element of plant growth and has been identified as a cofactor in soybean (Glycine max Merr.) leaves for catabolism of ureides, which are the main products of nitrogen fixation transported from nodules to shoot. Variations among genotypes were observed in the rate of ureide catabolism when plants were grown in nutrient solutions deficient in Mn. One possible explanation is that the differences in ureide catabolism among genotypes might be related to differences in Mn uptake from Mn-deficient nutrient solutions. Therefore, the objective of this study was to compare Mn uptake among six soybean genotypes grown in nutrient solutions with differing Mn and nitrate concentrations. Manganese concentration in various plant tissues was measured, as were concentrations of ureide, α-amino acid, nitrate, and iron (Fe). The genotypes segregated into two distinct groups under Mn-deficient conditions, with one group having higher leaf Mn concentrations and higher leaf Fe concentrations when nitrate was excluded from the nutrient solution. These results indicated that there exist major differences among soybean genotypes in the mechanism for root uptake of Mn and Fe. In addition to the benefit of sustaining ureide catabolism and nitrogen fixation, those genotypes that readily recovered Mn and Fe from the solution might be especially useful in developing cultivars for soils low in available Fe that might otherwise result in soybean Fe chlorosis.

^†Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply approval or the exclusion of other products that may also be suitable.

Keywords:

• iron
• manganese
• nitrate
• soybean
• ureide

ACKNOWLEDGMENTS

The authors thank Susan Sorrell and Justin West for diligent and competent assistance in plant preparation and sampling. This research was supported in part by a grant from the United Soybean Board.

Notes

^†Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply approval or the exclusion of other products that may also be suitable.