Interaction Between Root Endophytes and Plants: Their Bioactive Products and Significant Functions

Root endophytes exist in almost every identified plant species. Their capability of entering and flourishing in the plant tissues make them distinctive, which indicates their multidimensional connections within the host plants. Root endophytes influence various significant processes of the host. They trigger the growth of the plants, stimulate defensive response against pathogens, and mitigate abiotic stresses. Several studies have confirmed that endophytes interaction with the host plant is the same as that of the plant growth-promoting (PGP) microbes reside in the rhizosphere. Besides, these endophytes play crucial role in stimulating the productivity of plants and in boosting up their resistance against temperature, salinity, heavy metals, drought, and biotic stresses. Furthermore, root endophytes have potential to synthesize myriad of bioactive compounds including antioxidants, antibiotics, anticancer and antimicrobial agents, immune-suppressive compounds, and insecticides. Such compounds comprise a broad range of organic molecules such as peptides, carbohydrates, aromatics hydrocarbons, etc. and these compounds play vital role in host–microbe relationship. This chapter aimed to give background knowledge of the developments in endophyte biology, functions of root endophytes, and bioactive compounds synthesized by them.