Close up of poison oak leaves.  Copyright © 2005 by Lawrence M. Kelly



The Poison Oak's biggest adaptation is obviously the urushiol poison that it releases when coming into contact with the plant.  Any part of the plant can contain the oils and even the tiniest amounts can cause an irritating reaction. Urushiol is an oil that the poison oak releases through resin ducts as soon as the plant is disturbed or touched the oil is already on you.  It can last up to a week on your clothes, shoes, or other equipment and the reaction can take a few days to appear.  The poison oak even has the oil present when the plant is dead making handling even dead plants dangerous.  To learn more about the urushiol poison see Toxicology. 
Living conditions…
Poison Oak has also adapted to numerous different environments.  Not only can they live in dry, arid climates such as the chaparral areas but also in wet, humid areas such as the mixed evergreen forests.  They're found from sea level to around 5,000 ft above sea level. 
The seeds of the poison oak are hard shelled seeds which protects it while moving through the digestive system of birds as well as the environment.  The mature seeds have a sugary coating which attracts the birds.  Not only does the coating attract birds as an adaption to spread the seeds around the environment but the poison urushiol turns to a mild laxative causing the birds to defecate sometimes as soon as 15mins after ingesting the seed. Another adaptation related to all angiosperms is the development of a protecting structure we know as fruit. 

This shows the poison oak's fruit holding its precious seeds inside.
©2002 Margo Bors

Support or no support…
Yet another adaption by the poison oak is its ability to recognize whether to become a shrub or a vine.  In a study done by B.L. Gartner who is from the Department of Biological Sciences at Stanford University found that in the presences of support the poison oak plant would grow as a vine and in the absence of support it would grow as a shrub.  This is an incredible adaption that we would not think a plant would be capable of determining or accomplishing.  With support it has no need to worry about putting energy into building a support system instead it focuses growth upward climbing closer to the sun for photosynthesis.


Poison oak in its vine form has completely engulfed this tree in the picture.
©2009 Anna Bennett


This shows the poison oak in its shrub form during the fall with its reddish orange leaves.
©1999 California Academy of Sciences

The poison oak plant being autotrophic uses internal and external stimuli to survive.  A great example was mentioned earlier in the vine versus shrub formation.  However, the most important stimuli is that of detecting light.  With the ability to detect light the plant can grow upwards or outwards to maximize its photosynthetic abilities by exposing the greatest amount of leaves possible. 


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