Acclimation of whole-plant Acacia farnesiana transpiration to carbon dioxide concentration

Transpiration per unit leaf area of Acacia farnesiana (L.) Willd. plants gr own at a CO2 concentration ([CO2]) Of 385 mu mol mol(-1) was about twice th at of plants grown at 980 mu mol mol(-1). However, when plants grown for mo re than a year at 980 mu mol mol(-1) were exposed to 380 mu mol mol(-1) for 9 days, they transpired at half the rate of those that had been grown at 3 80 mu mol mol(-1). Similarly, plants grown at 380 mu mol mol(-1), when expo sed to 980 mu mol mol(-1), transpired at twice the rate of those grown at 9 80 mu mol mol(-1). Thus, the effects of elevated [CO2] on whole-plant trans piration, like those on photosynthesis, respiration and stomatal conductanc e, cannot reliably be extrapolated from measurements made during shortterm exposure to elevated [CO2].