Acclimation of Photosynthetic Traits of Caragana Species to Desert Environment in Inner Mongolian Plateau

Abstract

Caragana species are commonly distributed in desert regions. We hypothesized that the photosynthetic traits of desert Caragana species could acclimated well to the desert environments, which are characterized by high temperature, intense radiation, and low moisture. To test our hypothesis, we studied the responses of photosynthesis to light, temperature and humidity, and fluorescence parameters of four Caragana species from desert region and one Caragana species from steppe region in Inner Mongolian Plateau. The desert Caragana species had higher light compensation point, light saturation point, optimum temperature for photosynthesis, and lower optimum relative air humidity for photosynthesis than the steppe Caragana species, and their net photosynthesis rates (Pn) were higher under high temperature, intense sunlight, and low humidity. The nonphotochemical quenching efficiency (NPQ) and minimal fluorescence (Fo) of the desert Caragana species were higher, and the values of maximum fluorescence (Fm), maximum quantum yield (Fv/Fm), relative quantum yield (ΦPSII), and photochemical quenching coefficient (qP) were lower, except for C. korshinskii. The electron transport rate (ETR) of the desert Caragana species was greater or similar to that of C. microphylla. In summary, the photosynthetic traits of the desert Caragana species acclimated well to desert environment, although such acclimation might be still not sufficient. The order of photosynthetic acclimation of the four species to desert environment is: C. korshinskii > C. stenophylla > C. tibetica > C. roborovskyi.