Conceptual Model for the Analysis of Plant–Endophyte Symbiosis in Relation to Abiotic Stress
Probably no plant in nature is ever completely devoid of microbial symbionts living both in and on it. The term endophyte literally means “within plant” and is used to refer to organisms such as bacteria and fungi that live inside a host (Wilson, 1995). The term implies nothing as to whether or not the endosymbiont grows within or between host cells. Typically, the endosymbiont is obligatorily dependent on its host, while the host can survive without its endosymbiont. Although in the past, use of the term endophyte had sometimes been restricted to mutualistic associations (Wilson, 1995; Stone et al., 2000), it is now mostly presumed not to imply anything about the nature of the endosymbiotic relationship. In Wilson’s (1995) de nition, endophytes were also presumed to be “unapparent and asymptomatic infections” that did not cause disease symptoms. However, because there are examples of fungal endophytes that can behave like plant pathogens at least during some portion of their life cycle, it is unnecessarily restrictive to limit the use of the term in this way.