What was done
Turions of Vallisneria spinulosa Yan were collected from Liangzi Lake, Hubei Province, China and planted in fertile lake sediment 15 cm deep topped with 40 cm of lake water in each of a number of tanks placed in two glasshouses, one of which was maintained at the ambient atmospheric CO2 concentration of 390 ppm and one of which was maintained at an elevated concentration of 1000 ppm for a period of 120 days, after which the plants were harvested and the dry weights of their various organs determined.

What was learned
Yan et al. report that "total biomass accumulation of plants grown in the elevated CO2 was 2.3 times that of plants grown in ambient CO2, with biomass of leaves, roots and rhizomes increasing by 106%, 183% and 67%, respectively." Most spectacularly of all, "turion biomass increased 4.5-fold," because "the mean turion numbers per ramet and mean biomass per turion in elevated CO2 were 1.7-4.3 and 1.9-3.4 times those in ambient CO2," All in all, these several changes resulted in a greater allocation of biomass to belowground structures. In addition, it was determined that nitrogen concentrations in leaves and turions were reduced by 13% and 16%, respectively, while phosphorus concentrations were increased in all plant organs by between 35% and 147%.

What it means
The three Chinese researchers concluded that because "both the number and the size of turion, the most important storage and reproductive organ, increased significantly" in the elevated CO2 treatment, this phenomenon would enhance the "population-increasing rate of V. spinulosa ... in the next growth season and would benefit its dominant species role."