Influence of elevated carbon dioxide and ammonium nutrition on growth and nitrogen metabolism in wheat (Triticum aestivum)

Growth under elevated CO2 (EC) conditions inhibits nitrate (NO3-) assimilation in crop plants, hence ammonium (NH4+) nutrition is beneficial compared to NO3– nutrition under EC conditions. In the present study, an attempt was made to compare the suitability NH4 + vs mixed NH4 + + NO3 – nutrition in wheat (Triticum aestivum L.). Wheat seedlings supplied with NH4+ alone or with both NH4+ + NO3– as nitrogen (N) source and grown under ambient (380 μl/l, AC) or elevated (600±50 μl/l, EC) CO2 conditions were analyzed for growth and biochemical parameters. Plants receiving only NH4+ as N source showed significant reduction in growth parameters. The negative effects of NH4+ nutrition were manifested in form of reduced root length, root surface area and thinner leaves under EC. Negative effects of NH4+ nutrition were ameliorated in plants receiving mixed NH4 + + NO3 – nutrition. Supplementing NO3 – -N with NH4+ -N led to the enhancement of various morphological and biochemical parameters in EC grown plants. Activity and gene expression of the enzymes, nitrate reductase and glutamine synthetase was significantly higher in plants supplied with both NH4+ + NO3– ions and grown in EC, as compared to plants grown in AC, resulting in lesser reduction in N content of the EC grown plants. Our study indicates that mixed NH4+ + NO3– nutrition will be more suitable for wheat cultivation under high CO2 conditions in future.