Response Of Molecular And Physiological Basis Of Photosynthetic Characteristics Of Stipa Grandis To Grazing

Stipa grandis, a specie of Stipa in the family Gramineae, is known as a specific dense plexus xerophyte in the typical grassland of Central Asia. S. grandis is mainly distributed in eastern Inner Mongolia, Northeast China, Ningxia, Gansu and Qinghai in China. The basal leaves rich and well preserved to winter and spring, S. grandis with abundant base foliation survived over next spring can support a lot of forage for livestock.Photosynthesis is the precondition of the herbage’s growth and development, Study on the photosynthetic characteristics of S. grandis under grazing has important significance for the regeneration and growth of grass. In this study, S.grandisas was selected as research material in Inner Mongolia Autonomous Region Xilinhot, Baiyinxile pasture. Under different grazing intensity including no grazing (NG), light grazing (LG), moderate grazing (MG), and heavy grazing (HG), the photosynthetic physiological index of S.grandis were determined and analyzed, five key enzyme genes(PEPC, rbcL, SUS1, SUT1, SUT2) related to photosynthetic physiology were screened on the basis of sheep eating transcriptome data, the relative expression amount of five genes were measured by using the method of real-time fluorescence quantitative PCR, and the correlation analysis between gene expression amount and physiological index was carried out. The results are as follows:1. Under different grazing intensities, net photosynthetic rate, transpiration rate, stomatal conductance of S.grandis increased at first and then decreased with the increase of grazing intensity, in heavy grazing appears a significant rise (P<0.05)2. In fruit after nutrition period, the content of chlorophyll in the leaves of S.grandis increased with the increase of grazing intensity.3. With the increase of grazing intensity, Soluble sugar content in leaf increased with the increase of grazing intensity (only declined under moderate grazing conditions). Soluble sugar content in root increased under light grazing, decreased significantly under moderate grazing conditions, then increased significantly in heavy grazing.4. The expression of PEPC, SUS1, SUT1, SUT2 in moderate grazing and heavy grazing was significantly different (P<0.05).5. The relative expression of PEPC was significantly positively correlated with net photosynthetic rate(P<0.01). The relative expression of SUS1 was significantly positively correlated with sucrose content(P<0.05), and the relative expression of SUT1 was positively correlated with the soluble sugar content of root(P<0.05).