Experimental translocation of Primulina species provides insights into the conservation of threatened karst cave plants

Karst caves are hotspots of biodiversity and endemism, but threatened by human unsustainable activities. Many cave plants are site-endemic restricted in isolated caves and are at risk of extinction due to habitat loss. To explore the adaptability of cave plants to different karst cave habitats and confirm whether there are alternative habitats for conservation translocation, seedlings of Primulina huaijiensis, P. rubella and P. fengkaiensis were transplanted to four different sites. Comparative analysis of the environmental variables at four different sites, as well as survival rates (SR), phenotypic, photosynthetic and biochemical traits of these species showed that the three species can adapt to twilight zone of alternative caves with similar climatic conditions, but transplanting them outside caves was not conducive to their growth. This was confirmed by lower SR, poor growth status, decreased photosynthetic efficiency and increased antioxidant enzymes activities of plants outside caves. Light intensity was negatively correlated with the growth of the three species, while relative humidity was positively correlated with the growth of P. rubella and P. fengkaiensis. Moreover, soil microbial biomass carbon content and soil available Na content were correlated with the growth of P. rubella and P. fengkaiensis, respectively. The present study furthers our understanding of the physiological and ecological adaptability of Primulina species, and lays foundations for the conservation of threatened karst cave plants.