Microbial Symbionts of Plants

Abstract

Plants in nature always grow with soil microorganisms, and some become intimately associated with plants to form mutualistic symbiosis. Examples of such symbiotic microorganisms include mycorrhizal fungi, cyanobacteria, and N 2 -fi xing prokaryotes, especially rhizobia. Looser symbiotic associations involve bacteria and soil microfauna within the rhizosphere. Their metabolic activities increase nutrient availability. All of these symbioses may affect rates of growth and eventually reproduction of plants compared with growth in the absence of such associations. A symbiotic association is therefore a potential selection pressure that can infl uence the evolutionary success of vascular plants and hence the composition of plant communities. Application of associative bacteria for sustainable agriculture holds immense potential. These bacteria are known to enhance growth and yield of plants by fi xing atmospheric nitrogen, solubilization of phosphate, production of phytohormones and siderophores, possession of antagonistic activity, as well as reducing the level of stress ethylene in host plants. This review provides examples of associations and interactions between microorganisms and plants. The cyanobacterial association with various plants such as bryophyte, pteridophyte, gymnosperm, and angiosperm was illustrated. It also describes the actinorhizae, Frankia and Rhizobium , interaction with plants and their applications.

Reviewing bryophyte-microorganism association: insights into environmental optimization

“…Hormogonia form by chemo-attraction, and the host plant generates chemical signals that direct the hormogonia to the site of entry into the plant tissue. Host signals within the symbiotic cavity promote the establishment of heterocysts and dinitrogen fixation while inhibiting further homosexual creation (Thajuddin et al, 2015 ). There are only few genera where cyanobacterial interactions with liverworts are observed.…”