Impact of elevated CO₂ concentration on carbon and nitrogen metabolism of irrigated rice plants

Abstract

Rice is essential to feed the world’s population, being the most important staple food in several countries. Crop production has been directly impacted by climate change. Plants can mitigate an increase in atmospheric CO₂ concentration through photosynthetic conversion into carbohydrates. However, the potential for this conversion and plant responses to climate change remain unclear. The study was conducted from the cultivation of plants in open-top chambers (OTCs) with two concentrations of CO₂, 400 ppm (ambient – a[CO₂]) and 700 ppm (enhanced – e[CO₂])). We used rice plants of the cultivar IRGA 424 RI. Evaluations occurred in the vegetative (V5 and V11) and reproductive (R2 and R7) stages. As for gas exchange, plants grown under e[CO₂] showed increased net CO₂ assimilation rate, greater water use efficiency, and higher intercellular CO₂ concentration. On the other hand, the lowest values for stomatal conductance, chlorophyll index, nitrogen balance index, percentage of nitrogen in the leaves, and thousand-grain weight were found for this treatment. In addition, there was an increase in the activity of the glutamine synthetase and nitrate reductase enzymes in leaves and roots under e[CO₂], as well as a higher content of nitrate, starch, water-soluble polysaccharides and total soluble sugars in leaves in the first evaluated phenological stage. These results showed us that the reductions in chlorophyll levels added to the stimulation of the photosynthetic machinery elevated the nutritional demand. Due to these impacts, nitrogen and carbon metabolism were reduced, negatively reflecting on the yield components of rice plants.

Keywords:

• Climate change
• enzymatic activity
• gas exchange
• oryza sativa L.
• OTCs

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

The present work was carried out with the support of the Coordination for the Improvement of Higher Education Personnel (CAPES) – financing code 001 for S. N. Pires. S. Deuner (grant number 429531/2016-8) is supported by resources from the Brazilian National Council for Scientific and Technological Development (CNPq).  Dr. Avila is the chair to Dr. Glover B. Triplett for the Endowed.