Photoresponse Characteristics of Chamaenerion spp. in Mount Shergyla

Chamaenerion spp. (Onagraceae) are a class of ecological restoration medicinal herbs. Mount Shergyla has three species and one variant of Chamaenerion. Studying their photoresponse characteristics and elucidating their adaptation and physiological response to the photosynthetic characteristics of the environment is the basis for the development and protection of the plant resources of the genus Chamaenerion. In this experiment, Li-6400 portable photosynthesis instrument was used to study the photoresponse characteristics of Chamaenerion spp. in Mount Shergyla, and the photoresponse curves were fitted using a right-angle hyperbolic correction model. The results showed that Chamaenerion conspersum has low light compensation point (4.931 μmol/(m2.s)), high light saturation point (1 000 μmol/(m2.s)), and strongest adaptability to light, which is one of the determinants of its distribution at each elevation of Mount Shergyla. Chamaenerion angustifolium subsp. circumvagum has higher light compensation point (11.848 μmol/(m2.s)), low light saturation point (800 μmol/(m2.s)), and weakest adaptability to light, and it is a typical sciophilous plant. This result is consistent with the habitats (Rhododendron wardii shrub and spruce forest margin) that C. angustifolium are distributed in Mount Shergyla. Chamaenerion angustifolium and Chamaenerion latifolium have higher light compensation points and higher light saturation points, suggesting that the adaptability of C. angustifolium and C. latifolium to the light environment is weak. This can also explain the narrow distribution of C. angustifolium and C. latifolium in Mount Shergyla. There are certain degree of differences in the responses of net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), stomatal conductance (Gs) and transpiration rate (Tr) of the three species and one variant of Chamaenerion to different photosynthetically active radiation (PAR). With the increase of light intensity, the Pn, Gs and Tr of Chamaenerion spp. increased significantly, and the Ci decreased. The Pn of C. conspersum and C. latifolium differed insignificantly, but they were both higher than that of C. angustifolium. The Pn of C. angustifolium subsp. circumvagum was the lowest. The Gs of C. conspersum and C. latifolium differed insignificantly, but they were both higher than that of C. angustifolium subsp. circumvagum. The Gs of C. angustifolium was the lowest. There was no obvious difference in Ci between C. angustifolium and C. latifolium, of which the Ci was both higher than that of C. conspersum. The Ci of C. angustifolium subsp. circumvagum was the lowest. C. angustifolium subsp. circumvagum had the highest Tr, followed by C. angustifolium and C. conspersum (no obvious difference), and C. latifolium had the lowest Tr. The light utilization efficiency of Chamaenerion spp. ranked as C. angustifolium subsp. circumvagum < C. angustifolium < C. latifolium < C. conspersum. The light suppression phenomenon was evident in C. angustifolium, C. angustifolium subsp. circumvagum and C. latifolium. C. conspersum is most suitable for application under high light intensity conditions in Tibet. C. angustifolium, C. angustifolium subsp. circumvagum and C. latifolium should be shaded properly under conditions of high light intensity in the cultivation process, while C. conspersum needs to be supplemented with light during the cultivation process.