And right here on DG:
http://davesgarden.com/guides/articles/view/730/
A most interesting article . . . .
I saw that ~ most intriguing, isn't it? And maybe a real godsend.
Ric, thanks for the heads up on that, very interesting! Just how Messenger works has never been explained satisfactorily to me till now. I've seen the various benefits of aspirin discussed from time to time too, and always been curious.
Hmmmm, I'll have to look into this plant immune system thing. Do they really have one?
Oh, yes! This is why within a genus, some species are more resistant to diseases than others, and how breeding brings those resistant qualities to hybrids.
I should have been more specific. I wonder what form of immune system they have. Animals have cells that attack invaders. I am thinking plants have some form of chemical control? Very interesting, don't know why I never looked into it...
Plant immune systems
Author: stephanie
Text: Do plants have an immune system? How does it work? Are plants
able to "fight off" infections such as Dutch Elm disease?
Response #: 1 of 1
Author: wizkid
Text: In the broadest sense, an immune system is any method an organism
has protect itself from succeeding to another organism's efforts to undermine
its health and integrity. In this sense, yes, plants have immune systems.
Plants do NOT have "active" immune systems, like humans, including
macrophages, lymls, antibodies, complements, interferon, etc., which help us
ward off infection. Rather, plants have "passive" mechanisms of protection.
For instance, the waxy secretion of some plants (cuticle) functions to help
hold in moisture and keep out microorganisms. Plants can also secrete
irritating juices that prevent insects and animals from eating it. The thick
bark of woody plants is another example of a defensive adaptation, that
protects the more delicate tissues inside. The chemical secretions of some
plants are downright poisonous to many organisms, which greatly enhance the
chances of survival for the plant. Fruits of plants contain large amounts of
vitamin C and bioflavonoids, compounds which have been shown in the lab to be
anti-bacterial and antiviral. So in these ways, plants can improve their
chances of survival. Hundreds of viruses and bacteria attack plants each
year, and the cost to agriculture is enormous. I would venture to guess that
once an organism establishes an infection in a plant, the plant will not be
able to "fight" it. However, exposure to the sun's UV light may help control
an infection, possibly even defeat it, but the plant does not have any
inherent "active" way to fight the infection.
http://www.newton.dep.anl.gov/newton/askasci/1993/biology/bio035.htm
Wizkid's response makes it sound like a plant cannot react at all to infections, and just plugs along, doing what it's always does, infection or not.
Whereas I would not attach to plants any kind of decision making process, i.e."this is bad, therefore I will do . . . ", actual reactions by plants are common. While some of these reactions seem to be in response to a pathogenic infection, more likely, I would think, they are merely preprogrammed reactions to a new "something" present only because of the presence of the pathogen. An example might be a chemical that only the pathogen produces. That chemical triggers the plant to produce an "immune response", which is preprogrammed, and not a response at all in our way of thinking, yet a reaction, nonetheless.
A walk through an old maple forest in my region will reveal many disfigured old trees. The disfiguring is from verticillium wilt infections that the trees overcame, and so continued to grow. I do not claim the trees fought off the disease. But the disease did trigger inherent functions within the trees that performed as disease defenses.
My point is that a plant is not a stagnant lifeform. It does have the ability to change, at least somewhat, according to its environment , and that may or may not include pathogenic infections. And of course, what will further study bring? We would be naive to think we know all the answers in the living world.
"but the plant does not have any
inherent "active" way to fight the infection."
I envisioned a plant popping antibiotics and rubbing ointment on the undersides of its leaves, LOL. I need to get out more, my brain is going Far Side!
I believe the main point the author was making is that plants don't have cells that seek and destroy. Something that most people probably imagine when they here "immune system".
"Plants do NOT have "active" immune systems, like humans, including
macrophages, lymls, antibodies, complements, interferon, etc."
The statement below may be true, if a person has a human type immune system in mind.
"I would venture to guess that
once an organism establishes an infection in a plant, the plant will not be
able to "fight" it."
Agreed, Intecessor. No search and destroy tactics. I think there was also call for succinctness in his answer, without getting too technical. Considering the source of many of the queries on the site, this questioner was prabably school age.
But I wouldn't be too surprise if someday, someone did find a gray area on the subject. Never say never in the living world.
Does anyone have access to the journal Nature?
There is an excerpt available that sounds interesting, but I don't have the ability to access the full article.
http://www.nature.com/nature/journal/v444/n7117/abs/nature05286.html
Review
Nature 444, 323-329 (16 November 2006) | doi:10.1038/nature05286
The plant immune system
Jonathan D. G. Jones1 & Jeffery L. Dangl2
Top of page
Many plant-associated microbes are pathogens that impair plant growth and reproduction. Plants respond to infection using a two-branched innate immune system. The first branch recognizes and responds to molecules common to many classes of microbes, including non-pathogens. The second responds to pathogen virulence factors, either directly or through their effects on host targets. These plant immune systems, and the pathogen molecules to which they respond, provide extraordinary insights into molecular recognition, cell biology and evolution across biological kingdoms. A detailed understanding of plant immune function will underpin crop improvement for food, fibre and biofuels production.