Photosynthetic characteristics of the non-photosynthetic organs of Mikania micrantha and its ecological significance Effects of solar UV-B radiation on the efficiency of PSII photochemistry in the alpine plant Saussurea superba under different weather conditions in the Qinghai-Tibet Plateau of China Assessment of photosynthetic photo-inhibition and recovery of PSII photochemical efficiency in leaves of wheat varieties in Qinghai-Xizang Plateau