Effects of CO₂ enrichment on growth partitioning of Chloris gayana in the arid environment of the UAE

Grass species are impacted by increases in atmospheric carbon dioxide (CO₂). Grass species such as rhodesgrass (Chloris gayana) respond in a variety of ways to CO₂ enrichment. Some species spend more resources in the above-ground parts while others invest in below root system. The extent of growth responses and growth portioning in C. gayana as affected by increases in CO₂ was assessed. Pot trials were set up to compare plant growth parameters (e.g. plant height and number of leaves) between conditions mimicking the ambient (about 350 ppm) and enriched (650 ppm) CO₂ concentrations. Plants grown under the high CO₂ concentration had significantly higher plant height than those grown under the ambient CO₂ concentration for days 8 and 18 and to some extent for day 45. Plants grown under CO₂ enrichment, however, had a lower number of leaves than those grown under the ambient CO₂ level 28 days into the trial and to some extent on day 31. Overall, plants grown under CO₂ enrichment had a lower shoot/root ratio than those grown under ambient CO₂ levels. It is believed that biomass (shoots and roots) allocation into reproductive growth was a key phenomenon affecting C. gayana growth.