BSC 196 Lecture Notes - Lecture 26: Crop Rotation, Root Nodule, Mycelium
Document Summary
Plants and soil microorganisms often have a mutualistic relationship. Secretions from living roots support a wide variety of microorganisms in the near-root environment: microorganisms often make some nutrients from soil more available to plants. The layer of soil closely surrounding the plant"s roots is the rhizosphere. Rhizobacteria are free-living bacteria that occupy the rhizosphere. Endophytes are nonpathogenic bacteria that live between the cells of host plant tissues. Endophytes and rhizobacteria depend on nutrients secreted by plant cells and, in return, help to enhance plant growth: produce chemicals that stimulate plant growth, produce antibiotics that protect roots from disease, absorb toxic metals or increase nutrient availability. Nitrogen can be an important limiting nutrient for plant growth: nitrogen is needed for protein & nucleic acid synthesis. Most soil nitrogen comes from actions of soil bacteria. The nitrogen cycle transforms nitrogen and nitrogen-containing compounds.
