Meconopsis horridula var. racemesa Prain, is a famous alpine flower and medicinal plant native to high elevations in the Himalayas, but cultivating it at lower altitudes presents great challenges. The photosynthetic gas exchange and chlorophyll fluorescence of M horridula were investigated at three temperatures to evaluate its photosynthetic performance and the relative importance of biochemical limitation, stomata] limitation, and mesophyll limitation to photosynthesis under different temperature regimes. Meconopsis horridula grown at 20 degrees C could obtain the highest photosynthetic rate and photochemical efficiency among the three temperatures, and photosynthetic performance at low temperature was better than at high temperature. Non-photochemical quenching was an important mechanism protecting the photosynthetic apparatus of M. horridula under temperature stress conditions. Although mesophyll conductance was the dominant factor for limiting photosynthesis of M. horridula both at low temperature and high temperature, the photosynthesis at high temperature was also limited by stomatal conductance and biochemical efficiency. The poor photosynthetic performance at high temperature may be what limits M. horridula cultivation at low altitude.