Response mechanism of interaction between Rhododendron hainanense and microorganisms to heat stress

Heat stress is a major limitation to Rhododendron cultivation in tropical and subtropical regions. Microbial community plays an important role in plant resistance to heat stress, however the microbial mechanism is poorly understood. We conducted a pot culture experiment on Rhododendron hainanense to reveal the mechanism of root microorganisms and soil microorganisms in response to heat stress, using an artificial climate simulation. The experimental control (CK) was set as day (25 ℃, 14 h) /night (20 ℃, 10 h), treatments were medium temperature stress (MTS, 35/30 ℃), and severe temperature stress (STS, 40/35 ℃). The result showed that compared with CK, MTS treatment considerably increased malondialdehyde content, and STS treatment significantly increased proline, and both heat stress treatments significantly decreased chlorophyll content. In comparison to CK, MTS considerably reduced soil nitrate nitrogen, soil microbial biomass carbon, and soil water-soluble organic carbon content. STS dramatically increased soil available nitrogen, soil water-soluble organic carbon, and soil microbial biomass carbon. Heat stress also significantly affected soil microbial community and root endophytic microbial community. Soil microbial and root bacterial community significantly correlated with soil nitrate nitrogen content, and root endophytic fungi significantly correlated with proline and soilwater-soluble organic carbon content. Therefore, soil microorganisms impacted soil nitrogen availability under heat stress, root endophytic bacteria impacted the ability of R. hainanense to absorb nitrogen, and root endophytic fungi controlled the physiological traits of R. hainanense by modifying Pro content to increase the resistance of R. hainanense to heat stress.