Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure

With increasing interest in the effects of elevated atmospheric CO2 on plan t growth and the global carbon balance, there is a need for greater underst anding of how plants respond to variations in atmospheric partial pressure of CO2. Our research shows that elevated CO2 produces significant fine stru ctural changes in major cellular organelles that appear to be an important component of the metabolic responses of plants to this global change. Nine species (representing seven plant families) in several experimental facilit ies with different CO2-dosing technologies were examined. Growth in elevate d CO2 increased numbers of mitochondria per unit cell area by 1.3-2.4 times the number in control plants grown in lower CO2 and produced a statistical ly significant increase in the amount of chloroplast stroma (nonappressed) thylakoid membranes compared with those in lower CO2 treatments. There was no observable change in size of the mitochondria. However, in contrast to t he CO2 effect on mitochondrial number, elevated CO2 promoted a decrease in the rate of mass-based dark respiration. These changes may reflect a major shift in plant metabolism and energy balance that may help to explain enhan ced plant productivity in response to elevated atmospheric CO2 concentratio ns.