The process by which plants, algae and some bacteria convert light energy, water and carbon dioxide into chemical energy stored as sugar, releasing oxygen as a byproduct. It is the foundation of nearly every food web on Earth, since almost all other life either eats a photosynthetic organism directly or eats something that did, and it is the source of essentially all atmospheric oxygen and, over geological time, the fossil fuels formed from ancient photosynthetic life. Most plants use a standard photosynthetic pathway that loses significant water through open leaf pores during the heat of the day, but desert plants such as the saguaro cactus instead use a variant called CAM photosynthesis, opening their pores only at night to take in carbon dioxide while conserving water, then completing the light-driven reactions internally during the following day.
Facts
PeriodicityContinuous whenever daylight and adequate carbon dioxide, water and chlorophyll are available; the process stops at night and slows sharply in cold or drought conditions. 1 ScaleCellular and organismal in mechanism, but planetary in cumulative effect: it forms the base of nearly every terrestrial and marine food web and is the dominant source of Earth's atmospheric oxygen. 1 First DescribedThe overall conversion of light, water and carbon dioxide into sugar and oxygen was worked out across the late 18th and 19th centuries. Jan Ingenhousz demonstrated in 1779 that only the green parts of plants, in sunlight, release oxygen, correcting an earlier, incomplete 1771 observation by Joseph Priestley. 1 Connections
Associated With
Source Photosynthesis (Wikipedia)
Source Nitrogen Cycle (Wikipedia)
Source Symbiosis (Wikipedia)
Source Photosynthesis (Wikipedia)
Demonstrated By
Source Encyclopaedia Britannica
Source National Oceanic and Atmospheric Administration
Source Encyclopaedia Britannica
Sources
1. Encyclopaedia Britannica
Photosynthesis (Wikipedia)
Opening section, discovery of photosynthesis
Photosynthesis was discovered in 1779 by Jan Ingenhousz who showed that plants need light, not just soil and water.
Lead section, atmospheric oxygen sentence
Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth.
Photosynthetic membranes and organelles section
In plants and algae, photosynthesis takes place in organelles called chloroplasts.
Light-dependent reactions section, photolysis sentence
The chlorophyll molecule ultimately regains the electron it lost when a water molecule is split in a process called photolysis, which releases oxygen.
Associated With: Carbon Cycle, Lead section, Calvin cycle sentence
In this process, atmospheric carbon dioxide is incorporated into already existing organic compounds, such as ribulose bisphosphate (RuBP).
Associated With: Water Cycle, Lead section, photoautotroph sentence
Most photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide and water using energy from light.
View the SourcePhotosynthesis (National Geographic Education)
Opening paragraph, first sentenceQuote, Opening paragraph, first sentence
Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric AdministrationDemonstrated By: Kelp ForestsView the Source Nitrogen Cycle (Wikipedia)
Associated With: Nitrogen Cycle, Assimilation sectionQuote, Associated With: Nitrogen Cycle, Assimilation section
If nitrate is absorbed, it is first reduced to nitrite ions and then ammonium ions for incorporation into amino acids, nucleic acids, and chlorophyll.
Symbiosis (Wikipedia)
Associated With: Symbiosis, Obligate versus facultative section, photosymbiosis sentenceQuote, Associated With: Symbiosis, Obligate versus facultative section, photosymbiosis sentence
When one of the participants in a symbiotic relationship is capable of photosynthesis, as with lichens, it is called photosymbiosis.
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