Wednesday, January 25, 2012

Do Plants Breathe? How do Plants Breathe?

Plants breathe quite the opposite of the way we breathe.  They do breathe though, and they do it through tine holes called stomata located on their leaves.
Oops, I thought I posted this on Monday.  But here you go, better late than never!

It’s common knowledge that humans and animals inhale oxygen and exhale carbon dioxide in a process called respiration.  A lot of people also know that plants do just the opposite, “inhaling” carbon dioxide and “exhaling” oxygen, in a process called photosynthesis.  As a result plants and animals cycle oxygen and carbon dioxide between each other, one producing a waste that is used by the other and so on.  Obviously, animals breath through their mouths and nostrils but the way plants breath is far less obvious.  Nothing on a plant resembles a mouth or nose in the way animals breath.  And if we look at the chemical reaction for photosynthesis and respiration we will see they are sort of opposites, or reflections, to one another.  What one produces the other consumes.  So because of the differences we should expect totally different ways of breathing between the two.

Water + Carbon Dioxide + Light → Sugar + Oxygen

Sugar + Oxygen → Carbon Dioxide + Water

Stomata are the round holes in the photo above.  This is a microscopic image of a fingernail polish peel taken from a leaf surface.  Most plants open these during the day in order to breathe.  Only cacti and agaves open them at night to breathe
The only way to find the structures through which plants breathe is by searching microscopically.  Very simply, by painting a square inch or so of a leaf with clear fingernail polish, then peeling it off and viewing it under a microscope we should be able to find the stomata, which are tiny microscopic holes through which plants breathe.  The dried fingernail polish retains the cellular imprint of the leaf surface so when viewed under a microscope every structure on the leaf surface can be seen.  On the fingernail polish peal, the stomata appears as a tiny hole with two crescent shaped cells on either side. These crescent cells are known as guard cells being they open and close the stomata in order to let “breathing” to occur or not, and to preserve water.  Stomata can be found on any green surface of a plant, but typically are located in the highest concentrations on the underside of leaves.  Location on leaf undersides prevents exposure to the sun which helps prevent excess water loss through the stomata.  

Different types of plants have different patterns and forms of stomata.  Most trees have lots of relatively small oval stomata evenly spaced all over their leaves.  Desert trees and shrubs generally have fewer stomata to conserve water.  Corn and other grasses often have more rectangular stomata organized in rows along vessels.  Cacti have relatively few round stomata located in pits, but they are huge compared to other plants.  Types and shapes of stomata generally depend on how much water a plant has available and its general physiology.  Plants with lots of stomata have lots of water while plants with fewer stomata have less water.  If you have a microscope try making a fingernail polish peal to view the stomata, it takes a few tries but after that becomes extremely easy. 

Here is a website with more details on how to do this experiment:  Stomata Experiment

Sorry, I completely forgot to update the blog on Monday.  I became so busy with writing things up for this site that I thought I posted something new!


  1. Thank you it helped alot !

  2. thank you very much it was very interesting

  3. This article is very interesting and well written. Could you explain,, please, why do plants continue breathing during the night when stamata are closed? Thank you.

    1. Plants need to continue to conduct respiration in order to live through the night. In respiration they actually consume oxygen and produce carbon dioxide. With daylight however, light allows for photosynthesis to happen, reversing this process to where oxygen is produced and carbon dioxide consumed.

  4. All this is great info except for the fact that the word "breathe" only applies to animals. Plants don't breathe.

    1. If you can prove to us that plant don't breathe. I will prove that they do breathe

  5. thanks this helped lots on my science fair project anyone want to date im 11