Summarizing Nutritional Adaptations of Plants

Summary

Atmospheric nitrogen is the largest pool of available nitrogen in terrestrial ecosystems. However, plants cannot use this nitrogen because they do not have the necessary enzymes. Biological nitrogen fixation (BNF) is the conversion of atmospheric nitrogen to ammonia. The most important source of BNF is the symbiotic interaction between soil bacteria and legumes. The bacteria form nodules on the legume’s roots in which nitrogen fixation takes place. Fungi form symbiotic associations (mycorrhizae) with plants, becoming integrated into the physical structure of the root.

Through mycorrhization, the plant obtains minerals from the soil and the fungus obtains photosynthate from the plant root. Ectomycorrhizae form an extensive dense sheath around the root, while endomycorrhizae are embedded within the root tissue. Some plants—parasites, saprophytes, symbionts, epiphytes, and insectivores—have evolved adaptations to obtain their organic or mineral nutrition from various sources.

Glossary

epiphyte

plant that grows on other plants but is not dependent upon other plants for nutrition

insectivorous plant

plant that has specialized leaves to attract and digest insects

nitrogenase

enzyme that is responsible for the reduction of atmospheric nitrogen to ammonia

nodules

specialized structures that contain Rhizobia bacteria where nitrogen fixation takes place

parasitic plant

plant that is dependent on its host for survival

rhizobia

soil bacteria that symbiotically interact with legume roots to form nodules and fix nitrogen

saprophyte

plant that does not have chlorophyll and gets its food from dead matter

symbiont

plant in a symbiotic relationship with bacteria or fungi