Variation in the Response of Pasture Plants to Carbon Dioxide

The percentage increases in growth resulting from a doubling of atmospheric CO2 concentration were measured for 37 common pasture plants under strictly controlled conditions of temperature, nutrient supply and irradiance. A wide range of variation in potential response lo CO2 was detected in the day/night temperature range 12n°c to 28/ 23°C. C4 species responded litlle to elevated CO2 The mean ± standard deviation of the distribution of c3 species responses ranged from l±21% at 1m•c to 90±40% at 28/23°C. These responses varied with the stage of plant development. The response by Lolium perenne cv. Grasslands Nui was of intermediate size when compared with the whole sample of plants, suggesting that the proportion of perennial ryegrass in New Zealand pastures might decrease in the future.