Impact of elevated atmospheric CO2 concentration on pea and white melilot at three levels of nitrogen fertilization

Abstract

Future environmental conditions will include elevated concentrations of nitrogen in the soils and elevated concentrations of carbon dioxide in the atmosphere. Increasing CO2 concentrations are expected to enhance growth of agricultural C3 crops. However, little is known about what are the consequences of a direct CO2 fertilization's effect for weeds and much more attention should be given to the combined effect of elevated CO2 and N supply on plants. In order to study their interactions on both types of plant performance, growth chamber experiments were performed with C3 crop pea (Pisum sativum L.) and weed white melilot (Melilotus alba Medik.) from the same family grown in a controlled conditions at different CO2 levels (400 versus 700 and 1400 ppm) combined with three levels (3, 6 and 12 g/m2 of nitrogen) of fertilization. The photosynthetic rate, transpiration rate, stomatal conductance, water-use-efficienc and dry overground biomass were investigated at the end of an experiment after 10-day duration of treatment. Higher stimulatory effects of elevated 700 and 1400 ppm CO2 concentrations were on photosynthetic parameters and growth of pea than of melilot. Contrarily, higher stimulatory effects of nitrogen supplies were on investigated parameters of melilot than of pea, but statistically significant only for transpiration rate, stomatal conductance and water-use-efficiency, at ambient and elevated CO2 levels. The consistent response to both these factors identified in the plants was increased nitrogen use efficiency, who also revealed the dependence of the CO2 response on N supply, as identified by a significant CO2 × N interaction. According to these results, we concluded, that under future elevated CO2 and nitrogen condition, both type of plants will be more efficient in resource use efficiency, but the ability of pea to assimilate additional carbon and the competitive advantage might increase more, compared to melilot.