photosynthesis definition | Dictionary.com

pho⋅to⋅syn⋅the⋅sis

[foh-tuh-sin-thuh-sis]

–noun Biology, Biochemistry.

(esp. in plants) the synthesis of complex organic materials, esp. carbohydrates, from carbon dioxide, water, and inorganic salts, using sunlight as the source of energy and with the aid of chlorophyll and associated pigments.

Origin:
1895–1900; photo- + synthesis

Related forms:

pho⋅to⋅syn⋅thet⋅ic [foh-tuh-sin-thet-ik]

, adjective

pho⋅to⋅syn⋅thet⋅i⋅cal⋅ly, adverb

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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Link To photosynthesis

pho·to·syn·the·sis (fō'tō-sĭn'thĭ-sĭs)

n. The process in green plants and certain other organisms by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.
pho'to·syn·thet'ic (-sĭn-thět'ĭk) adj., pho'to·syn·thet'i·cal·ly adv.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Photosynthesis

Pho`to*syn"the*sis\, n. (Plant Physiol.) The process of constructive metabolism by which carbohydrates are formed from water vapor and the carbon dioxide of the air in the chlorophyll-containing tissues of plants exposed to the action of light. It was formerly called assimilation, but this is now commonly used as in animal physiology. The details of the process are not yet clearly known. Baeyer's theory is that the carbon dioxide is reduced to carbon monoxide, which, uniting with the hydrogen of the water in the cell, produces formaldehyde, the latter forming various sugars through polymerization. Vines suggests that the carbohydrates are secretion products of the chloroplasts, derived from decomposition of previously formed proteids. The food substances are usually quickly translocated, those that accumulate being changed to starch, which appears in the cells almost simultaneously with the sugars. The chloroplasts perform photosynthesis only in light and within a certain range of temperature, varying according to climate. This is the only way in which a plant is able to organize carbohydrates. All plants without a chlorophyll apparatus, as the fungi, must be parasitic or saprophytic. -- Pho`to*syn*thet"ic, a. -- Pho`to*syn*thet"ic*al*ly, adv.

Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
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photosynthesis

Use by green plants of the energy in sunlight to carry out chemical reactions, such as the conversion of carbon dioxide into oxygen. Photosynthesis also produces the sugars that feed the plant.

Note: Green plants depend on chlorophyll to carry out photosynthesis.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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photosynthesis

1898, loan-translation of Ger. Photosynthese, from photo- "light" + synthese "synthesis." Another early word for it was photosyntax.

Online Etymology Dictionary, © 2001 Douglas Harper
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Main Entry: pho·to·syn·the·sis
Pronunciation: "fOt-O-'sin(t)-th&-s&s
Function: noun
Inflected Form: plural -the·ses
: synthesis of chemical compounds with the aid of light sometimes including the near infrared or near ultraviolet; especially : the formation ofcarbohydrates from carbon dioxide and a source of hydrogen (as water) in chlorophyll-containing cells (as of green plants) exposed to light involving a photochemical release of oxygen through thedecomposition of water followed by various enzymatic synthetic reactions that usually do not require the presence of light —pho·to·syn·the·size /-"sIz/ also British pho·to·syn·the·sise intransitive verb -sized also British -sised; -siz·ing also British -sis·ing
—pho·to·syn·thet·ic /-sin-'thet-ik/ adjective —pho·to·syn·thet·i·cal·ly /-i-k(&-)lE/ adverb

Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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photosynthesis pho·to·syn·the·sis (fō'tō-sĭn'thĭ-sĭs)
n.
The process in green plants and certain other organisms by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source.

pho'to·syn·thet'ic (-sĭn-thět'ĭk) adj.

photosynthesis (fō'tō-sĭn'thĭ-sĭs) Pronunciation Key

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The process by which green plants, algae, diatoms, and certain forms of bacteria make carbohydrates from carbon dioxide and water in the presence of chlorophyll, using energy captured from sunlight by chlorophyll, and releasing excess oxygen as a byproduct. In plants and algae, photosynthesis takes place in organelles called chloroplasts. Photosynthesis is usually viewed as a two-step process. First, in the light reactions, the energy-providing molecule ATP is synthesized using light energy absorbed by chlorophyll and accessory pigments such as carotenoids and phycobilins, and water is broken apart into oxygen and a hydrogen ion, with the electron of the hydrogen transferred to another energy molecule, NADPH. The ATP and NADPH molecules power the second part of photosynthesis by the transfer of electrons. In these light-independent or dark reactions, carbon is broken away from carbon dioxide and combined with hydrogen via the Calvin cycle to create carbohydrates. Some of the carbohydrates, the sugars, can then be transported around the organism for immediate use; others, the starches, can be stored for later use. Compare chemosynthesis. See Note at transpiration.

Our Living Language : Almost all life on Earth depends on food made by organisms that can perform photosynthesis, such as green plants, algae, and cyanobacteria. These organisms make carbohydrates from carbon dioxide and water using light energy from the Sun. They capture this energy with various pigments which absorb different wavelengths of light. The most important pigment, chlorophyll a, captures mainly blue and red light frequencies, but reflects green light. In plants, the other pigments are chlorophyll b and carotenoids. The carotenoids are usually masked by the green color of chlorophyll, but in temperate environments they can be seen as the bright reds and yellows of autumn after the chlorophyll in the leaves has broken down. The energy gathered by these pigments is passed to chlorophyll a. During the light reactions, the plant uses this energy to break water molecules into oxygen (O₂), hydrogen ions, and electrons. The light reactions produce more oxygen than is needed for cellular respiration, so it is released as waste. All of the oxygen in the Earth's atmosphere today was produced as waste by photosynthetic organisms, especially cyanobacteria, which have been producing oxygen for some three billion years, since their first appearance in the Precambrian Eon. During the dark reactions, the plant uses hydrogen ions and the electrons to make carbon dioxide into carbohydrates. Within the leaf of a green plant, photosynthesis takes place in chlorophyll-containing chloroplasts in the columnlike cells of the palisade layer and in the cells of the spongy parenchyma. The cells obtain carbon dioxide from air that enters the leaf through holes called stomata, which also allow excess oxygen to escape. Water from the roots is brought to the leaf by the vascular tissues called xylem, while the carbohydrates made by the leaf are distributed to the rest of the plant by the vascular tissue called phloem.

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