Abstract: In order to reveal the photosynthetic characteristicsof leaves of Mentha haplocalyx Briq.with officinal herbs growing at the Qing-Tibet Plateau,those at three different altitudes in Huangyuan,Xining and Minhe of Qinghai Province were comparatively studied by adopting conventional determination method of photosynthesis indices.The result showed that:(1)the thickness of leaves was the thickest in Huangyuan district and the thinnest in Xining district.And there were significant differences between Xining and Minhe,Huangyuandistrict (p＜0.01).(2)with altitude increasing,the carotenoid and chlorophyll content tended to rise,while the chlorophyll a/b and lutein/chlorophyll content tended to decline.And there were no significant differences among them (p＞0.05) except for the carotenoid content there were significant differences between Minhe and Xining (p＜0.05).(3)it was positive correlation between the photosynthetic rate and apparent quantum yield and elevation height,while the light compensation point and dark respiration rate decreased with increasing of theelevation.Simultaneity,there were no significant differences about the apparentquantum yield among three districts (p＞0.05) and there were significant the obvious differences on the dark respiration rate and photosynthetic rate between Minhe and Huangyuan (p＜0.05),but there were significant differences about the light compensation point among three districts (p＜0.05).The studyrevealed that the changes of Mentha haplocalyx Briq.in its photosynthetic characteristics was an adaptive response to adverse environments including low temperature,low air pressure,strong solar radialization,etc.

Key words: Qinghai,China, Mentha haplocalyx Briq., photosynthetic characteristics