Mineral concentrations in soybean seed produced under high day and night temperature

Abstract

Environmental stress during reproductive growth can alter the mineral composition of soybean [Glycine max (L.) Merr.] seed, which can affect nutritional value, functional quality, and seed quality. This study was conducted to determine the impact of different combinations of day and night temperatures during reproductive growth on the final mineral concentrations in soybean seed. Day/night temperatures of 30/20, 30/30, 35/20, and 35/30°C were imposed during flowering and pod set (R1 to R5), seed fill and maturation (R5 to R8), and during the entire reproductive growth period (R1 to R8). The soybean seed was harvested at maturity and analyzed for elemental concentration of P, K, Ca, Mg, Mn, Fe, B, Cu, Zn, Al, and Na. Calcium and Mn declined and Na increased as mean day temperature during R1-R5 increased from 30 to 35°C. Phosphorus, K, Ca, and Mg became more concentrated in the seed with increased temperature during R5 to R8. The concentration of several minerals was increased by temperature treatments during R1 to R8. The exceptions were Mg and Fe, which declined, and Mn and Al, which were unchanged. Phosphorus, K, Fe, Cu, and Zn concentrations were negatively correlated with seed size. Concentrations of these minerals in seed may be greater in soybean grown in high temperature environments that limit seed size. The changes in mineral concentrations resulting from high temperature may alter soybean nutritional quality and modify its end-use properties for oil processing and tofu production. Key words: Soybean, Glycine max, mineral composition, temperature