Nitrogen Modulates the Diurnal Regulation of Nitrate Reductase in Wheat Plants – Projections Towards Climate Change
Institute of Natural Resources and Agrobiology of Salamanca, IRNASA–CSIC, Apartado 257, 37071 Salamanca, Spain; e–mail: rosa.morcuende@irnasa.csic.es
Abstract:
This study investigates whether the diurnal regulation of nitrate reductase activity in the flag leaf of wheat is affected by combined increases of CO2 and temperature in the air and to ascertain whether the nitrogen supply modifies these effects. Spring wheat was grown at ambient (360 μmol mol−1) or elevated (700 μmol mol−1) CO2, under ambient and 4°C warmer temperatures, and with two levels of nitrogen supply in field temperature gradient chambers. At ear emergence, NR activity reaches a maximum in the early part of the light period and declines later in the light period and during the first part of the night. Although elevated CO2 did not increase NR activity, it led to a modification of the diurnal regulation. During the last part of the photoperiod the decline of the activity was faster in plants grown in ambient CO2, in which the accumulation of amino acids was higher. The maximum reached in the first hours of the light period in plants grown in elevated CO2 and nitrogen abundance was related to a higher accumulation of soluble carbohydrates. The dark inactivation of NR was prevented in plants grown in elevated CO2 with low nitrogen. Additionally, the higher decline of NR activation in plants grown with ample nitrogen supply and higher temperatures was related to the accumulation of amino acids. It is concluded that nitrogen plays a role in the activity and post-translational regulation of NR under the future climatic scenario.
Key words:
carbohydrates, diurnal rhythm, elevated CO2, nitrate reductase, nitrogen, temperature, wheat