Potassium deficiency influences soybean seed mineral compositions and metabolic profiles across CO2

Authors: SING, SHARDENDU - University Of Washington; Barnaby, Jinyoung; Reddy, Vangimalla; Sicher Jr, Richard

Submitted to: Journal of Soil Science and Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2019
Publication Date: 12/6/2019
Citation: Sing, S., Barnaby, J.Y., Reddy, V., Sicher, R.C. 2019. Potassium deficiency influences soybean seed mineral compositions and metabolic profiles across CO2. Journal of Soil Science and Plant Nutrition. 10(12):2113-2133.
DOI: https://doi.org/10.4236/ajps.2019.1012149

Interpretive Summary: Impacts of potassium (K) deficiency and elevated carbon dioxide (eCO2) on seed quality traits have rarely been explored in the majority of crops. To fill in this knowledge gap, soybean was grown in a controlled environment at either sufficient or deficient levels of K under ambient and elevated CO2. Results showed that K deficiency primarily decreased seed mineral elements, oil, and essential fatty acids but enhanced protein, amino acids, simple sugars, and accumulation of stress-responsive metabolites such as sugar alcohols and proline. The eCO2 also decreased several mineral elements and essential fatty acids across K fertilization but the essential amino acids (e.g., valine, phenylalanine, leucine) declined, exclusively under the severe K deficiency. Thus, eCO2 is likely to exacerbate the negative impacts of K deficiency on soybean seed nutritional quality, especially, by reducing the levels of mineral elements and essential fatty acids. Results on the nutritional aspects of the K deficiency and eCO2 on soybean seeds will be useful to farmers and researchers to understand its impacts on seed quality and offers a prospect for quality improvement.

Technical Abstract: Impacts of potassium (K) deficiency and elevated carbon dioxide (eCO2) on seed constituents have rarely been explored in the majority of crops including soybean. A controlled environment experiment was conducted with soybean grown under a sufficient (5.0 Mm) and two deficient (0.50 and 0.02 Mm) levels of K fertilization at ambient (aCO2) and eCO2 (400 and 800 µmol mol-1, respectively). Both treatments significantly affected several constituents, with the K deficiency having stronger impacts than eCO2. Out of 49 seed constituents, K deficiency and eCO2 influenced 41 and 16 constituents, respectively. The K deficiency primarily decreased on average 16 constituents including minerals (e.g., K, P, Mg, Mn, Zn, Fe, B), oil, and essential fatty acids (e.g., linoleic and linolenic acids) but enhanced 25 constituents such as protein, amino acids, simple sugars, and stress-responsive metabolites (e.g., sugar alcohols mannitol and myo-inositol and proline). An accumulation of N while decreased C concentration resulted in the lower C:N ratio in the seeds of K-deficient plants. However, protein:oil, C:K, N:P, and N:K ratios were consistently greater under K deficiency. The eCO2 also decreased minerals such as P, S, Zn, B, and essential fatty acids but enhanced the concentration of six constituents including alanine, oleic acid, fructose, and sugar alcohols across K fertilization. In addition, the impact of eCO2 on several amino acids appeared to be dependent on the severity of K deficiency. For instance, eCO2 decreased essential amino acids (e.g., valine, phenylalanine, isoleucine) in the seeds of severely K-deficient plants but not in the other treatments leading to a K×CO2 interaction. Results showed that CO2 enrichment is likely to exacerbate the decline in the concentration of seed minerals such as P, K, S, Zn and B) and essential fatty acids and amino acids under K limited conditions.