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Submitted to: The Scientific World
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/26/2014 Publication Date: 2/1/2014 Citation: Bellaloui, N., Mengistu, A. 2014. Effects of boron nutrition and water stress on nitrogen fixation, seed d15N and d13C daynamics, and seed composition in soybean cultivars differing in maturities. The Scientific World. 2015(407872):1-11. Interpretive Summary: Boron is an essential nutrient for crop growth, production, and seed quality. Water stress is a major abiotic stress factor, resulting in a major yield loss and poor seed quality. Little information is available on the effects of foliar boron fertilizer on soybean seed composition (protein, oil, fatty acids, and sugars) under water stress. Therefore, the objective of the current research was to evaluate the effects of foliar boron fertilizer on seed protein, oil, fatty acids (palmitic, stearic, oleic, linoleic, and linolenic), and sugars (sucrose, raffinose, stachyose, glucose, and fructose) under water stress conditions. A repeated greenhouse experiment was conducted using two soybean cultivars of maturity group 3 (III) and two of maturity group 5 (V). The results showed that seed protein, sucrose, fructose, and glucose were higher in well watered-plants with the application of foliar boron than in well-watered plants without foliar-applied boron or water-stressed-plants with or without foliar-applied boron. Foliar boron application resulted in higher nitrogen fixation, but water stress changed the source of nitrogen and carbon metabolism and indicated by changes in nitrogen and carbon natural isotopes. Our results showed that foliar boron application altered seed composition, had positive effects on nitrogen fixation, but water stress resulted in physiological and metabolic changes in carbon and nitrogen pathways. Limited movement of boron from leaves to seed under water stress may explain a possible mechanism of boron deficiency under drought conditions. This research is beneficial to growers for fertilizer management and seed quality, and for breeders to use natural nitrogen and carbon isotopes and stachyose sugar to select for drought tolerance soybean. Technical Abstract: Water stress is a major abiotic stress factor, resulting in a major yield loss and poor seed quality. Little information is available on the effects of B nutrition on seed composition under water stress. Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using two cultivars of maturity group (MG) III and two of MG V. Plants were well-watered with no foliar B (W-B), well-watered plants with foliar B (W+B), water-stressed plants with no foliar B (WS-B), and water-stressed plants with foliar B (WS+B). Foliar B was applied at rate of 0.45 kg•ha-1 and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W+B treatment than in W-B, WS+B, and WS-B. The increase in protein in W+B resulted in lower seed oil, and the increase of oleic in WS-B or WS+B resulted in a decrease in linolenic acid. Foliar B resulted in higher nitrogen fixation in W+B and W-B than in WS+B or WS-B. Water stress resulted in seed d15N and d13C alteration, but not in well-watered plants. Our results showed that foliar B application altered seed composition and had positive effects on nitrogen fixation. Altered seed d15N and d13C under water stress conditions indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources. Limited translocation of B from leaves to seed under water stress may explain the possible mechanism of B deficiency under drought. This research is beneficial to growers for fertilizer management and seed quality, and for breeders to use 15N/14N and 13C/12C ratios and stachyose sugar to select for drought tolerance soybean. |
