Salicylic Acid

​We rightfully watch and care about the corn plants as they grow in our fields.  We observe the field as a whole for uniformity of stand and expected growth rate.  We may note some individual plants that are behind others or perhaps show some differences, perhaps with disease symptoms.  We don’t see the individual cells within any of the plants where the real action is occurring.  One of those things was described in this Corn Journal blog written in June 2016.
 
Corn plants now in much of the US corn belt are stretching upwards, for the most part showing little signs of stress.  We have little cognizance, however, of the internal battles that are going on in each of those plants. All plant parts are exposed to potential invaders, through injuries, through stomata or other openings and through direct enzymatic attack from pathogens outside the plants.  Plants have systems to fight the invaders by responding with anti-microbe chemicals or even initiating cell death to limit the damage. 
 
One of the key components of that mechanism is salicylic acid. This chemical was known by Hippocrates about 2400 years ago in an extract from willow bark that could relieve humans with headaches. Yes, it is the main component of aspirin.   Salicylic acid production in plants increases when cells are stressed from pathogens, drought, or toxins.  It functions as a signal molecule, triggering the production of a series of proteins to limit the damage.  Of course, the response time for salicylic acid production and consequential protein production to stop the potential pathogen is dependent on the plant genetics and nutrition.  Pathogens, no slouches in evolution either, often include mutations to slow down the production of salicylic acid by either tying up its component compounds or interfering with the production of the resistance compounds.  It’s a battle out there!