# Corn C4 Photosynthesis

**URL:** <https://boards.straightdope.com/t/corn-c4-photosynthesis/631013>\
**Category:** Factual Questions\
**Created:** [August 9, 2012, 11:21pm UTC](https://boards.straightdope.com/t/corn-c4-photosynthesis/631013 "2012-08-09T23:21:30Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![IceQube](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@IceQube](https://boards.straightdope.com/u/IceQube)\
**Post date:** [August 9, 2012, 11:21pm UTC](https://boards.straightdope.com/t/corn-c4-photosynthesis/631013/1 "2012-08-09T23:21:30Z")

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Is corn an obligate C4 plant?

:dubious:

Edit: A corollary to the above question is where does the majority of photosynthesis occur in corn?

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**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\
**Post date:** [August 10, 2012, 12:35am UTC](https://boards.straightdope.com/t/corn-c4-photosynthesis/631013/2 "2012-08-10T00:35:23Z")

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[This page](http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html) makes it sounds as if C4 photosynthesis is only used as a supplementary pathway and C3 photosynthesis can still be used (some plants, such as cacti, do use a third form known as [crassulacean acid metabolism](http://en.wikipedia.org/wiki/Crassulacean_acid_metabolism), and some are [obligate](http://en.wikipedia.org/wiki/Crassulacean_acid_metabolism#Use_of_CAM_by_plants) in that regard):

> [@](#):
>
> They all use a \*\*supplementary \*\*method of CO2 uptake which forms a 4-carbon molecule instead of the two 3-carbon molecules of the Calvin cycle. Hence these plants are called C4 plants. (Plants that have only the Calvin cycle are thus C3 plants.)

(emphasis theirs)

As for which parts of the plant are responsible for [photosynthesis](http://en.wikipedia.org/wiki/Photosynthesis), it would be the leaves and stem, pretty much any green part (yes, stems can photosynthesize too as [this source](http://www.life.illinois.edu/govindjee/encyc/encarta.htm) says; “Plant photosynthesis occurs in leaves and green stems”, but probably a relatively minor contributor except for cacti and similar plants).