Why is it that most C4 plants are tropical plants?

As far as I am aware the C4 cycle does not prevent water loss; so having it exist in tropical areas does not serve these plants any good other than preventing photo-respiration. Hence I do not understand why it is solely found in tropical plants and not plants from other areas as photo-respiration is a problem not limited to tropical areas

Reference: http://lifeofplant.blogspot.sg/2011/10/c4-and-cam-photosynthesis.html?m=1

  • $\begingroup$ See c4 cycle occurs in bundle sheath cells which are impermeable to gases. And rubisco affinity for O2 is increased with temp. Tropical regions have high temperatures So therefore co2 is given to rubisco in these gas impermeable cells in the form of maleic acid in order to reduce photorespiration $\endgroup$
    – Khushi
    Jan 4, 2019 at 9:00

1 Answer 1


This is not my field, so the following is based solely on a brief reading of Internet sources.

The Wikipedia entry on C4 carbon fixation states:

When grown in the same environment, at 30°C, C3 grasses lose approximately 833 molecules of water per CO2 molecule that is fixed, whereas C4 grasses lose only 277.

However it does not explain why this is so.

In contrast, the section in Berg et al. focuses on the energy losses caused by photorespiration and makes the following initial point:

…the oxygenase activity of rubisco increases more rapidly with temperature than does its carboxylase activity. How then do plants, such as sugar cane, that grow in hot climates prevent very high rates of wasteful photorespiration?

The answer to this (didactic) question is the C4 pathway (as described in full in that text), but the answer to the question posted here is that “tropical plants employ the C4 pathway because of this increased wastage of energy through photorespiration at the higher temperatures in which they live.”

  • $\begingroup$ Thank you. This response pretty much sums up my question $\endgroup$
    – user35897
    May 1, 2018 at 17:10
  • $\begingroup$ Now I think of it, maybe the increased rate of carbon dioxide uptake due to increased light intensity in tropical areas also play a part $\endgroup$
    – user35897
    May 1, 2018 at 17:11

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