A type of nutrition in which organisms synthesize the organic materials they require from inorganic sources. Chief sources of carbon and nitrogen are carbon dioxide and nitrates, respectively. All green plants are autotrophic and use light as a source of energy for the synthesis, i.e. they are photoautotrophic (see photosynthesis). Some bacteria are also photoautotrophic; others are chemoautotrophic, using energy derived from chemical processes (see chemosynthesis). Compare heterotrophic nutrition; mixotrophic.