Bacterial pathogens are diverse and abundant on plants in nature.  Infection by these pathogens causes the induction of defense responses, for which the central requirement of salicylic acid is well known.  While salicylic acid is also required for plant cold tolerance, much less is understood about this functional role or about interactions between the biotic and abiotic environment in determining salicylic acid concentrations.  Here, I compare salicylic acid concentrations for plants from source populations of Arabidopsis thaliana along latitudinal and elevational gradients.  In addition, I assess salicylic acid concentrations in sympatric plants with different life history strategies, focusing on a specific contrast between three summer annuals (Brassica nigra, Capsella bursa-pastoris, and Thlaspi arvense) and four winter annuals/ perennials (Arabidopsis thaliana, Barbarea vulgaris, Cardamine pensylvanicum, and Draba verna).  

Results/Conclusions

In common garden experiments, salicylic acid concentrations do tend to be higher for plants that experience colder environments in nature, with some exceptions.  These patterns are likely to be important for understanding the interactions between plants and bacterial pathogens and the distribution of plant bacterial diseases in nature.