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Summary • A common response of plants to elevated atmospheric CO2 concentration (CO2 ) is decreased leaf conductance. Consequently, leaf temperature is predicted to increase under elevated CO2 . • Diurnal patterns of leaf conductance and temperature were measured for three desert perennials, the C3 shrub Larrea tridentata , C3 tussock grass Achnatherum hymenoides and C4 tussock grass Pleuraphis rigida , at the Nevada Desert FACE facility. Measurements were made on ambient and c . 550 µmol mol-1 CO2 plots through both a wet and dry year. • Reductions in conductance were 35%, 20% and 13% for Pleuraphis , Achnatherum and Larrea , respectively. Decreased conductance occurred throughout the day only for Pleuraphis . Both C3 species had smaller CO2 effects during dry periods than wet. Leaf temperature did not differ significantly between elevated and ambient CO2 for any species. Comparisons of blower-control and nonring plots indicated that the FACE apparatus did not confound our results. • All three species exhibited decreased leaf conductance under elevated CO2 , although reductions were not uniform during the day or among years. Nonetheless, leaf energy balance was only minimally changed for these microphyllous desert perennials. [ABSTRACT FROM AUTHOR]