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Title: VARIATION IN MN AND FE ACCUMULATION AMONG SOYBEAN GENOTYPES GROWING ON HYDROPONIC SOLUTIONS OF DIFFERING MN AND NITRATE CONCENTRATIONS.

Author
item IZAGUIRRE-MAYORAL, M. - CARACAS, VENEZUELA
item Sinclair, Thomas

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2004
Publication Date: N/A
Citation: N/A

Interpretive Summary: Manganese is an essential element required by soybean for growth and yield because it is involved in a number of physiological processes. Yields of soybean can be decreased substantially on soils that are deficient in manganese. This study, done in cooperation with a USDA-ARS scientist located at the Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL, was undertaken to examine possible variations in manganese accumulation by soybean varieties. Indeed, soybean varieties were discovered to separate into two distinct groups with one group having much greater manganese accumulation than the other. Surprisingly, these two groups had even more marked differences in iron accumulation. The group accumulating greater manganese concentrations also accumulated several-fold greater amounts of iron. These results indicated major differences in basic mechanisms for mineral uptake among soybean varieties. The varieties that have the capability to accumulate high concentrations of these two elements could be especially useful in developing improved varieties for soybean production on mineral-deficit soils.

Technical Abstract: Manganese (Mn) is an essential element of plant growth and it 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 the shoot. Variations among genotypes existed in the rate of ureide catabolism when plants were grown on nutrient solutions deficient in Mn. One possibility 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 on nutrient solutions with differing Mn and nitrate concentrations. In addition to Mn concentrations, concentrations of ureide, a-amino N, nitrate, and iron (Fe) were measured. Genotypes segregated into two distinct groups with one group having higher leaf Mn concentrations under Mn deficient conditions and much higher leaf Fe concentrations when no nitrate was added to the nutrient solution. These results indicated major differences among soybean genotypes in the mechanism for root uptake of Mn and Fe.