Changes in Nitrogen Metabolism of Vigna Radiata in Response to Elevated CO<sub>2</sub>

Abstract

With the aim to determine the effects of CO2 on nitrogen metabolism mungbean (Vigna radiata) plants were grown from seedling emergence to maturity inside open top chambers under ambient CO2 (CA, 350 ± 25 µmol mol-1) and elevated CO2 (CE, 600 ± 50 µmol mol-1) concentrations at the Indian Agricultural Research Institute, New Delhi. Leaflet blades of the same physiological age were sampled at 20, 35 and 50 d after germination. Total nitrogen concentration in dry mass was consistently lower under CE than in CA. Non-protein nitrogen and protein nitrogen were also decreased under CE Total soluble protein content also decreased up to 35 d after germination under CE. However, a 27 % increase in protein content at 50 d after germination due to CE was observed. A significant decrease in total free amino acid under CE at 20 d after germination was observed. CE also brought about a remarkable decrease in the activity of nitrate reductase in leaves at 20 d after germination but increase at 35 d and 50 d after germination. Nitrogenase activity increased at all growth stages due to CE. Although total harvested leaves of CE plants accumulated more nitrogen, the relative amount of nitrogen on a percentage basis was low, probably due to a comparatively greater accumulation of sugars in the leaves of CE plants.