title: Effects of foliar boron application on seed composition, cell wall boron, and seed δ(15)N and δ(13)C isotopes in water-stressed soybean plants.
abstract: 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 δ(15)N and δ(13)C 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.
authors.affiliation: Crop Genetics Research Unit, Plant Physiology, USDA-ARS Stoneville, MS, USA.
authors.forename: Nacer
authors.initials: N
authors.lastname: Bellaloui
authors.forename: Yanbo
authors.initials: Y
authors.lastname: Hu
authors.forename: Alemu
authors.initials: A
authors.lastname: Mengistu
authors.forename: My A
authors.initials: MA
authors.lastname: Kassem
authors.forename: Craig A
authors.initials: CA
authors.lastname: Abel
keywords: boron; carbon; cell boron; fatty acids; nitrogen; oil; protein