Do plants have immune systems?

[Gungalley]

I can't fathom plants having antibodies and stuff, but logic tells me that they ought to have some sort of defences against microbes and stuff. Well do they? I haven't heard anything about such a topic.

[Empress Meg]

Sure they do. I am sure there is a more scientific explanation, but as I just despised biology in high school I've not the nerve to open my old text books. However, from a gardeners point of view, something I do enjoy dabbling in from time to time, one does get to see the immune system at work. It is not something akin to the type humans have; a plant once it develops a virus of some kind cannot really fight it off like the human can the common cold, but a plant does have many defenses before that stage which have bee very successful for them for some eons.

If they did not, we'd all be toast as there are many viruses the prey on the plant life on our planet just as the animal life too is consumed by microorganisms. But despite this, plants have a natural defensive line that is both quietly ingenious and deviously humble.

Plants have an intrinsic immunity to many insects and virus "bugs". A dependence on other species of plants is sometimes a must for certain parts of the plant defensive line. Ah, let me explain that before I go off on a tangent. Basil, the yummy herb used for salads, lends itself to be an excellent repellent of those bugs and pests that would devour a tomato or other juicy vine fruit. So if you plant basil about your vining plants you've very few bugs to worry about. The tomatoes too for that matter, so a symbiotic relationship sometimes forms between certain species of plants to help one another out when it comes time for a bug chow down.

Mint, dill, and rosemary, and the devil's trumpet has a very nasty smell which many birds find unappealing to eat and thus help to drive away these pests. Humans tend to find them aromatic and tasty however (well not the devil's trumpet don't eat that it will kill you) so I guess it is not a full proof system - yet.

Many plants, like the aforesaid devil's trumpet are extraordinarily toxic or poisonous which keeps most bugs, animals and birds away. Humans are not as smart with the warnings as animals in some cases.

Oh, the bark on trees is also a deterrent from larger animals biting and pecking at the tender insides of a tree. Not as cool as the skin organ on a person, but perhaps more resilient.

Plants are also able to resist many forms of disease due to their watery insides, or ooze as some have as not. Keeps in the moisture but keeps out many harmful diseases which may not like the oily, oozy insides. Like my Aloe plants for instance, that sucker has never gotten a brown spot in its life. Great for burns and rashes for people too, but again don't eat them.

Plants which develop spots on some of their leaves can easily survive a pruning of the damaged leaves with little fuss. Something a human would find less easy to do should an arm need to be taken off. So in an off themselves they are pretty darn tough when it comes to whacking off their limbs, some even require it for better growth.

If a plant does get ill though, there is very little one can do. Sometimes removing a damaged limb or leaves helps, but you cannot "cure" an unhealthy plant. Quarantine is the only solution I've found once the defenses are down- which is very rare. Remove the ill leaves or cut the plant in half and get the diseased parts away from the healthy parts. I suppose then there is no active system, no defender cells like we have, but they have developed outside redoubts instead and internal deterrents to keep many bugs away.

Devoirs The Empress

[pannonian]

Oh, the bark on trees is also a deterrent from larger animals biting and pecking at the tender insides of a tree. Not as cool as the skin organ on a person, but perhaps more resilient.

Sap also works to wall over any physical damage, in a similar manner to clotting blood.

[Bernem]

have a look here:

http://www.nature.com/nature/journal...ture05286.html

[Ummon]

But not based on antibody production.

[Bernem]

antibodies are part of the adaptive immune system that is unique to vertebrates, so no, plants don't have them

[Chaigidel]

viruses can affect plants and animals, and fungi-- In fact they are likely the reason organic life exists as we know it at all; the nucleus of every cell is a remnant of the virus that integrated itself into early bactieria.

but since we all "grew up together" cells of all stripes have various methods of defense and offense, within systems and without.

[Francebunkerer]

IIRC, Plants can even activate defence mechanism of other nearby plants of the same species, using airbourne messenger compounds.

[Bernem]

yes this is called systemic reaction. the plant activates its defense mechanisms by releasing eg. jasmonic acid. this works as an alarm messenger for its own organs as well as with other plants of the same species (often even with different species). It causes for example the production of toxins. But the plants' ultimate response to a pathogen is the hypersensitive reaction, where the part invaded by the pathogen and the surrounding parts simply die and leave 'burnt earth'. That works well bio biotrophic pathogens, but not so well with necrotrophic wo live the dead plants' parts.

[Gungalley]

Then for diseases that wipe out entire fields, is there no adaptive immunity for that?

[Bernem]

there's a 'strategy' that works in an evolutionary way... for many pathogene genes there are countered by plant defense genes, but these develop in an evolutionary process.

tit for tat

[Sphere]

for many pathogene genes there are countered by plant defense genes, but these develop in an evolutionary process.

Thats the key difference, plant "immune" systems adapt through evolution. The verterbrate immune system is adaptive on an individual basis (as well as evolutionary). A single plant can never become immune to a disease, but a single human can develop resistance to specifiic viruses over a lifespan.

[Ummon]

A wonderful example of how many other things in our body work. Infact Edelman started as an immunologist (Nobel prize at that).