Limited information is available on the effects of foliar boron (B) application on soybean seed composition. The objective of this research was to investigate the effects of foliar B on seed composition (protein, oil, fatty acids, and sugars). Our hypothesis was that since B is involved in nitrogen and carbon metabolism, it may impact seed composition. A repeated greenhouse experiment was conducted where half of the soybean plants was exposed to water stress (WS) and the other half was well-watered. Foliar boron (FB) in the form of boric acid was applied twice at a rate of 1.1 kg ha-1. The first application was during flowering stage, and the second application was during seed-fill stage. Treatments were water stressed plants with no FB (WS-B); water stressed plants with FB (WS+B); watered plants without FB (W-B), and watered plants with FB (W+B). The treatment W-B was used as a control. Comparing with WS-B plants, B concentration was the highest in leaves and seed of W+B plants (84% increase in leaves and 73% in seed). Seeds of W+B plants had higher protein (11% increase), oleic acid (27% increase), sucrose (up to 40% increase), glucose, and fructose comparing with W-B. However, seed stachyose concentrations increased by 43% in WS-B plants seed compared with W-B plants. Cell wall (structural) B concentration in leaves was higher in all plants under water stress, especially in WS-B plants where the percentage of cell wall B reached up to 90%. Water stress changed seed δ15N and δ13C values in both B applied and non-B applied plants, indicating possible effects on nitrogen and carbon metabolism. This research demonstrated that FB increased B accumulation in leaves and seed, and altered seed composition of well-watered and water stressed plants, indicating a possible involvement of B in seed protein, and oleic and linolenic fatty acids. Further research is needed to explain mechanisms of B involvement in seed protein and fatty acids. © 2013 Bellaloui, Hu, Mengistu, Kassem and Abel.
Bellaloui, N., Hu, Y., Mengistu, A., Kassem, M. A., & Abel, C. A. (2013). Effects of foliar boron application on seed composition, cell wall boron, and seed δ15N and δ13C isotopes in water-stressed soybean plants. Frontiers in Plant Science, 4(JUL). https://doi.org/10.3389/fpls.2013.00270