Protein and oil concentration of soybean seed cultured in vitro using nutrient solutions of differing glutamine concentration

Oil and protein are the most valuable components of soybean seed. Evidence indicates that growth and composition of soybean seed are controlled by supplies of carbon and nitrogen provided by the maternal plant to the seed, but it is difficult experimentally to control and quantify the precise amount of carbon and nitrogen provided to the seed by the whole plant. To examine whether oil and protein concentrations are affected by the supply of nitrogen to the seed, immature soybean seeds (Glycine max cv. Williams 82) were grown in vitro in nutrient solutions containing 20, 40, 60 or 80 mM of glutamine. The seeds were incubated in Erlenmeyer flasks for 8 days at 25°C. The rate of dry matter accumulation changed from 7.2 to 8.3 mg seed^?1 day^?1 as the glutamine concentration increased from 20 to 80 mM but the differences were not significant (P 0.05). Seed protein concentration increased as glutamine concentration increased from 294 mg g^?1 at 20 mM glutamine to as high as 445 mg g^?1 at 80 mM glutamine. Typical in vivo protein concentration of mature soybean seeds is about 400 mg g^?1. Oil and protein concentrations were negatively correlated (r²= 0.44), which indicates that oil and protein synthesis are interrelated. Protein synthesis was favoured over oil synthesis when nitrogen became more abundant. The seeds used in this study clearly demonstrated a capacity to respond to nitrogen availability with changes in seed protein concentration.