Nitrogen and carbon partitioning in soybean under variable nitrogen supplies and acclimation to the prolonged action of elevated CO2

This study was conducted to determine reciprocal effects of low to high doses of nitrogenous fertilizer (N-30, N-40, N-50, N-60 and N-70-30, 40, 50, 60 and 70 kg center dot ha(-1) respectively) and CO2 enriched environment on C and N partitioning in soybean (Glycine max (L.) Merril cv JS-335). Plants were grown from seedling emergence to maturity inside open top chambers under ambient, AC (350 +/- 50 mu mol center dot mol(-1)) and elevated, EC (600 +/- 50 mu mol center dot mol(-1)) CO2 and analyzed at seedling, vegetative, flowering, pod setting and maturity stages. Soybean responded to both CO2 enrichment and N supply. Leaves, stem and root reserves at different growth stages were analyzed for total C and N contents. Consistent increase in the C contents of the leaf, stem and root was observed under EC than in AC. N contents in the different plant parts were found to be decreased under EC-grown plants specially at seedling and vegetative stage despite providing N doses to the soil. Significant increase observed for C to N dry mass ratio under EC in the root, stems and leaves at seedling and vegetative stage was decreased in the middle and later growth stages possibly due to combined impact of N doses to the soil and increased N-2 fixing activities due to EC conditions. Critical analysis of our findings reveals that the composition and partitioning of C and N of soybean under variable rates of N supply and CO2 enrichment alter according to need under altered metabolic process. These changes eventually may lead to alteration in uptake of not only N but other essential nutrients also under changing atmosphere.