Tropical Spiderwort (Commelina benghalensis L.) Increases Growth under Elevated Atmospheric Carbon Dioxide

Although considerable effort is being spent studying exotic plant pests, little consideration his been given as to how invasive plants might react to the increasing concentration of CO2 in the atmosphere. Tropical spiderwort (Commelina benghalensis L) is considered one the world's worst weeds and is becoming more of it problem in agricultural settings of tire Southeastern USA, Growth responses of tropical spiderwort were evaluated using plants grown in containers with a soilless potting medium under ambient and elevated (ambient + 200 mu mol mol(1)) levels of CO2 in open-top field chambers. Although plant height was unaffected by CO2 leaf and flower number tended to increase (approximately 23%) when exposed to elevated CO2 Aboveground plant parts exhibited significant increases in dry weight when exposed to high CO2; leaf, flower, stein, and total shoot (try weights were increased by 36, 30, 48 and 44%, respectively. Total plant dry weight was increased by 41% for plants grown under high CO2. Root dry weight and root length were unaffected by CO2 concentration, Tropical spiderwort allocated more biomass to stems and tended to allocate less to roots when plants were exposed to high CO2. Plant carbon concentration and content tended to be higher in CO2-enriched plants, whereas plant nitrogen concentration tended to be lower; thus, elevated CO2-grown plants had higher C/N ratios. Also, the amount of biomass produced per unit nitrogen was higher for plants exposed to elevated CO2. The growth response of this plant is in the upper range typical for C3 plants.