Response of Seed Composition of Soybean Genotypes to Over-Supplying Amino N

【Objective】 This study was to test whether amino-N supply during rapid seed filling could stimulate seed protein accumulation without a negative impact on the accumulation of other valuable seed components. 【Method】The seeds of three genotypes (Evans, PI132.217, and Proto) with various seeds protein contents were grown under optimal conditions in a growth chamber until 18 days after flowering. Then the seeds collected from plant in the middle node of plant, the cotyledons were cultured in liquid medium with different concentrations of glutamine (0, 37, 75, 150 mmol·L-1). The seed and cotyledon were harvested respectively in the day after flower (DAF) of 24, 30, 36 and 42 in vivo and 6 d, 12 d, 18 d and 24 d in vitro. 【Result】 The accumulated rate of cotyledon FW and DW in vitro was more rapidly than those in plant. Under supplying amino-N at 37 mmol·L-1 or over, Evans and Proto cotyledons grew more rapidly and accumulated more protein N. At amino-N concentration above 75 mmol·L-1, Evans and Proto accumulated more non-protein-N, decreased oil accumulation. But there was no response to supplying amino-N in PI132.217 cotyledons. While supplying amino N at 37 mmol·L-1 glutamine decreased oil and starch accumulation. Therewas a difference in supplying N for seed development in planta among three genetic lines of soybean. In planta, Evans and Proto can not provide seeds with demanded N, they were very sensitive to supplying N. But PI132.217 can get enough demanded N from planta, it was not response to supplying N. 【Conclusion】 Increasing N supply from the plant could lead to a modest increase in seed protein content in low protein genotypes. Then, over supplying N will negatively impact on metabolism of available C into oil and starch. Because there is a genetic difference in N-supplying and N utilization in genetic lines of soybean, genetic breeding may be a good way for improving N-supplying and ability of N metabolism to enhance protein content of seed.