Salicylic Acid and viruses

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Ernie

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Saw a neat poster at the WOC. This might be common knowledge to the plant biologists (I'm a fish biologist by training now doing pharmacy stuff), but apparently salicylic acid plays a very important role in disease resitance in plants. It can be used to induce plants (ie orchids) to fight off viruses essentially by scaring their immune system much like an immunization does in mammals. A young lady presented a nicely done set of experiments at the WOC showing that salicylic acid in concentrations from 0.5-2.0 millimolar were equally very effective (damn near 100%) at preventing two clones of Phals from getting introduced virus over controls. The salicylic acid solution was applied BEFORE the plants were "infected" and then every couple weeks throughtout the experimental period.

What does this mean to us? Ever buy cut flowers and get a little packet of powder with them? That packet is basically ground aspirin.
Well, aspirin is acetylsalicylic acid and we can "break" of the acetyl group by simple hydrolysis (dissolving the aspirin in water). To get the aproximate amount of salicylic acid, one would use about one 81 mg aspirins per quart of water (~1 liter). This would give just over her lowest dose of 0.5 mM, BUT there is *no added benefit* from using the 2 mM dose other than wasting aspirins. I forget the exact timing of her administration, but I recall deciding spraying once a month would be about right from talking with her. I think her intended application was in large, high production commercial operations with a large in/outflux of plants. Less frequent application might be effective in hobby collections? Two things I asked her about were pH of the solutions and phytotoxicity. She did not measure pH, but sal acid is a weak acid and these are low concentrations- check pH before applying, I would NOT apply a solution to my plants if the pH was less than say 4.5 or 5.0. She did not notice any phytotox during the experimental period- doesn't mean years and years of applying aspirin won't catch up with the plants, the jury's still out. Will reduce the risk of heart attacks in your orchids though. :) Note that "pure" salicylic acid was used in the original experiments and I have not tried the apsirin solution- I'm not endorsing this practice, just sharing what I read and my interpretation of a hobbyist application.

-Ernie
 

Sirius

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Wow, this is fascinating reading Ernie. I will be interested to see if this becomes a common practice.
 

Leo Schordje

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One asprin for me, one for the plants. Lower risk of stroke and lower risk of virus. Amazing.
I doubt phytotoxicity would be a problem, salicylic acid is a common metabolic product in many unrelated groups of plants, mostly dicots - ie. willows, alders, certain eriacea - think wintergreen. The metabolic pathways must be there for handling it.
Leo
 
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John D.

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Ernie
Was her application method a spray to just wet the foliage or enough excess spray to saturate the medium as well and allow uptake through the roots?

Thanks
John
 
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Ernie

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It was a foliar spray. Good point and reminds me that she used a little bit of Tween 80 as a wetting agent. Hobbyists could sub in a drop or two of Dawn dish detergent per quart as a "spreader sticker".

My man Leo comes through with the science for us. As always, the poison is in the dose. I'd bet at some point it would be phytotoxic, BUT probably not at the 0.5 mM dose.

BTW, this and other various treatments/remedies/prophylaxes *should NOT be substitutes* for proper care and sound long term culture!

-Ernie
 

Hien

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I thought that only animals have immune system that can destroy virus? And plants do not?
 
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Mrs. Paph

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I can't remember all of my plant phys., but salicylic acid is involved somehow in the stress responses. I think water stress in tomatoes is the commonly given example w/ asprin solutions - didn't work/wasn't statistically significant in that case if I recal, nor did it seem to work in the in-class example we did w/ cold stress in mums - but virus is a different stressor, and a plant's response to a virus isn't the same as water stress or cold, so it's an interesting idea to look at.
Somebody asked about immune systems - it's not the same as animals, no, but for example if an area of a plant is wounded, bacteria or something gets in, a process called the hypersensitive response can start to kill the area of healthy cells around the damaged ones, thereby (hopefully) containing spread throughout the plant inside a small area of dead tissue - it doesn't always work though of course. If a plant doesn't recognize that there is a problem, it doesn't do anything and a disease can spread. Asprin wouldn't make it recognize a virus, but maybe it somehow primes the system and allows a faster reaction against a virus? If I ever get my proposal done I need to take a break to snoop through the databases for orchid-related papers...I like my topic, but there are soooo many papers spread all over my living room right now, and I'm typing by reaching over a pile of books and papers too! Eek!
 
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Ernie

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Asprin wouldn't make it recognize a virus, but maybe it somehow primes the system and allows a faster reaction against a virus?
Yeah, this was the impression I got. Essentially, one would use the sal acid spray just before introducing a group of new plants to the main collection- eg plants freshly into compots from flasks etc. That way, if those already residing there were infected, the newbies would be "primed" to defend themselves. Might also be useful at "high handling times" like at repotting- give 'em a dose a week or so before a major repotting event (still no substitute for gloves and a torch!).

-Ernie
 

Ray

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Plants do have primitive immune systems, but they are far less sophisticated and complex than in animals.

One of the more general responses is the generation of phenols, which are phytotoxic. They are often seen when a plant feels there is a threat, whether that be competition (one of the reasons some add charcoal to seed-sowing agar), a stress on the root system (seen as the brown coloration in damaged roots), or diseases.

I have heard that salicylates do illicit a response, but I don't know if it's a curative one. As was mentioned, the treatment reduced/prevented viral infection in plants that had none to start with, so my question is, how common are they?
 
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