식물 영양에서 박테리아와 곰팡이의 역할

Though plants derive their food through photosynthesis, they also require minerals and nutrients. Some plants rely on soil-dwelling organisms to efficiently acquire resources from the soil.

Rhizobacteria are prokaryotes that live in association with plant roots. This diverse class of organisms receives nutrition from plant roots while providing support for the plant in a variety of ways. They might, for instance, produce antibiotics to protect the plant, absorb unwanted chemicals from the soil, or facilitate the acquisition of essential nutrients.

Nitrogen is a critical component of proteins and nucleic acids. However, plants cannot use atmospheric nitrogen, as they lack the machinery to convert it into biologically useful forms. 

During a process called nitrogen fixation, prokaryotes convert atmospheric nitrogen to ammonia, which is modified to ammonium. Other prokaryotes convert ammonia to nitrate. Nitrate and ammonium can be taken up and used by plants.

In legumes, like pea and bean plants, nitrogen fixation occurs at specialized root structures called nodules. In this symbiotic relationship, Rhizobia fix atmospheric nitrogen and make it bioavailable to plants, while the bacteria receive critical nutrients from the legume they are associated with. 

Most plant species are also associated with fungi in a mutually beneficial relationship. The fungi, called mycorrhizae, receive nutrition from the plant. In return, mycorrhizae can access soil stores of nutrients that would be otherwise unavailable to plants. For instance, fungi facilitate the acquisition of phosphate, copper, and zinc. 

Fungi may also function as a physical barrier against pathogens or produce antibiotics to protect the plant.