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Abstract

Wheat (Triticum aestivum L.) cv PBW 343 was grown in Hoagland solution devoid of nitrogen (-N) and with 1 mM KNO3 (+N) under two carbon dioxide levels, viz. ambient (370 μl/l, AC) and elevated (600±50 μl/l, EC) for twenty days in growth chambers. The pattern of nitrate uptake was similar under both AC and EC but, the rate of uptake was significantly higher in EC grown plants when the concentration of the nitrate in the external medium was low. The Vmax for high affinity nitrate transport system (HATS) was significantly high for the EC grown un-induced seedlings (116.36 μmol g-1 fw h-1) compared with AC grown un-induced seedlings (79.55 μmol g-1 fw h-1). The pattern of gene expression of the nitrate transporters in roots correlated with the kinetics and uptake. The rate of nitrate uptake was influenced by previous nitrate nutrition and was strongly regulated by external nitrate levels. It is possible that the HATS operates more efficiently under EC as indicated by high Vmax and the plants will be able to take up nitrate more efficiently from the soils low in nitrate in the future high CO2 world and may have better NUE.