Salicylic acid
Salicylic acid is a phenolic phytohormone, and is found in plants with roles in plant growth and development, photosynthesis, transpiration, and ion uptake and transport. Salicylic acid is involved in endogenous signaling, mediating plant defense against pathogens. It plays a role in the resistance to pathogens (i.e. systemic acquired resistance) by inducing the production of pathogenesis-related proteins and other defensive metabolites. Exogenously, salicylic acid can aid plant development via enhanced seed germination, bud flowering, and fruit ripening, though too high of a concentration of salicylic acid can negatively regulate these developmental processes.