Do trees have some sort of "immune system"?

Question

I know this may seem odd, but think about it. Scientists can tell by tree growth rings is it was previously disease or infested by parasites. They can also tell by later rings that the tree was healthy. Why did the tree not sucumb? This makes me think a tree possess some sort of immune system

Answer 1

Plants have two tiers of defenses. First they try to keep the pathogen or herbivore away then they try to fight with an innate immune system. This does not trigger an adaptive immune response like humans have, they do not carry antibodies and they have no circulatory system. They do have a large repertoire of immune receptors that recognizing classes of pathogen surface patterns in every part of the plant. Once triggered the plant releases antimicrobial compounds and will restructure itself with thicker cell walls or even walling infected regions off to prevent spread into uninfected tissue.
< www.blackwell-synergy.com/doi/pdf/
10.1111/j.1462-5822.2006.00829.x >
http://en.wikipedia.org/wiki/Innate_immune_system
You have noticed some plants listed as disease resistant. Tomatoes have the Fen gene. This is an example of a protein encoded by the class of pathogen specific resistance genes.
http://www.isb.vt.edu/proceedings99/proceedings.keen.html
http://www.news.cornell.edu/chronicle/03/5.22.03/BTI-plant_gene.html
http://www.news.cornell.edu/stories/July07/plantPathogens.kr.html
http://ipmworld.umn.edu/chapters/eigenbr.htm
They also have RNA silencing to block viral infection.
http://en.wikipedia.org/wiki/RNA_interference

Plants produce secondary metabolites to act in primary defense from herbivory. These metabolites produce reactions in whoever eats the plant. They can be psychoactive, poisonous, just nasty or reduce the digestability but the point is to discourage diners. With plants the herbivorous insect causes more problems than large bodied herbivores. Further leaves often releases volatile molecules that signal the presence of feeding damage. The volatiles are produced just prior to release so are released in blends that imply a different response to feeding by different species, even closely related species.

To protect against soil organisms that can cause harm plants form mutual symbiosis with mycorhizal fungi and bacteria. Plants cultivate their zoo for support and defense. Protozoa are the primary predators of bacteria and are necessary in releasing the nitrogen held by the bacteria. Thus they close the symbiotic loop between plants and nitrogen fixing rhizobacteria plus controlling the soils microfauna balance.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1559669
http://www.organicgardening.com/feature/0,7518,s1-3-78-1559,00.html
http://www.cababstractsplus.org/google/abstract.asp?AcNo=20043093218

Answer 2

Sap helps protect them when damaged and the tendrils of mycellium fungus growing underneath them helps their survival the two can not survive with out each other.
This is what I am lead to believe.

Bee's take the tree sap for building their immune system because the propolis it contains gives them a boost.

Everything has some sort of defence mechanism otherwise it would not survive for long.

Answer 3

wow this is a tough question and i dont think i can get the best answer for this one lol.however,in my opinion,it is not called as immune system.(thank God u put those ".....").It sort of like system that usually functions to carry on prooves.Like our body,when we got pimples,or chicken-pox.It will leaves scar or spots after we gets it.

well i dont know..lol