Injury and physiological responses of Larrea tridentata (DC) coville exposed In situ to sulphur dioxide

Abstract The response of shrubs of Larrea tridentata (DEC) Coville (creosotebush) exposed to sulphur dioxide (SO 2 ) was evaluated using in situ plants of the Majove Desert. Larrea was exposed to acute levels of 0·3 to 2·0 μl litre −1 SO 2 for periods up to 13 days using field chambers or an open-air fumigation system. Plants exposed in the spring exhibited considerable leaf injury (necrosis and defoliation) when exposed to 2·0 μl litre −1 SO 2 , and in the autumn had leaf injury when exposed to > 0·4 μ l litre −1 SO 2 . Injured plants had higher transpiration rates, less negative water pressure potentials, and/or lower photosynthetic rates than control plants. It is likely that Larrea would not be injured by the typically low SO 2 concentrations and dry environmental conditions of the Mojave Desert. However, if injury were to occur, it would be accompanied by changes in plant-water relations and photosynthesis, followed by recovery after the SO 2 stress was removed.