Abstract: Three varieties were used for studing the effects of low temperature stress on the photosynthetic characteristics and chlorophyll fluorescence of Solenostemon scutellarioides after 4 d stress under 2℃ and 5℃，and recovery in 25℃. The results showed that low temperature increased the photo inhibitions of photosynthesis. With the extension of low temperature treatment time，photosynthetic rate（Pn），transpiration rate （Tr） and stomatal conductance（Gs）were decreased with the extension of low temperature treatment time，but intercellular CO2 concentration（Ci） was increased with the extension of low temperature treatment time.The result suggested that non-stomatal limitations were the key factors for the decrease of Pn during the 2℃ and 5℃stress. Three varieties showed consistent rule，but the difference could be found in the response of each cultivar to the same stress，the Pn of“Meihonglvbian”decreased least while that of “Shenhongjinbian”decreased most. About the chlorophyll fluorescence，the maximal photochemical yield（Fv/Fm） decreased，the actual photochemical efficiency of system II（φPSII） and photochemical quenching coefficient（qP）increased after 4 d stress，and the non-photochemical quenching coefficient（NPQ）showed increasing trend. A small number could recover after the elimination of 5℃，while none could recover which endured 2℃，show that the heavy photoinhibitions have led to non-recoverable harm or inactivation in the structure of PSII.

Key words: Solenostemon scutellarioides, low temperature stress, photosynthesis, chlorophyll fluorescence