ABSTRACT
Salicylic compounds occur widely in plants. Salicylic alcohol and its glucosides characteristically occur in such species of salix as willow, spirea, and filipendula.1 However, salicylic acid is the dominating form in botany, and is frequently found in medical herbs. Free salicylic acid was first demonstrated in hyacinth, tulip, and violet, and later on in orange, plum, grape, and other cultivated plants.2 In a systematic investigation, Raskin et al.3 found salicylic acid in 20 out of 27 cultivated
plants. It is instructive to study the effects of salicylic acid and other salicylic compounds in the plants where they are produced:2
● Improved resistance. When microorganisms such as viruses, fungi, and bacteria attack plants, the systemic acquired resistance (SAR) is strengthened by salicylic acid. Exogenous supply of salicylic acid also seems to affect SAR. By the injection of a 0.2% solution of salicylic acid, White4 demonstrated that he could protect tobacco plants against the infection of the tobacco mosaic virus.
