What do the plants got from the symbiosis? how could this happen?

In plants, symbionts play significant roles in plant growth, development, and health by providing nutrients and increasing tolerance to biotic and abiotic stress factors. For example, endophytic fungi are very common in plants and many studies have shown that they increase growth and development of colonized plants (Rodriguez, White, Arnold, & Redman, 2009). This is mainly achieved by promoting root growth through the allocation of resources to the expanding root system before stem growth (Rodriguez, Freeman, McArthur, Kim, & Redman, 2009). Indeed, evidence suggests that some of these effects are due to epigenetic effects of plant symbiotic fungi or bacteria on their hosts. Conversely, during the course of the establishment of endosymbiosis, genetic and/or epigenetic changes occur in the interacting microorganisms with plant hosts.

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