Since there is limited information on the simultaneous effect of drought stress and salicylic acid on yield and mucilage content of the medicinal herb, Plantago ovata Forssk is available, a pot experiment was conducted in factorial form based on a randomized complete block design with three replications in Jiroft, Kerman Province, south of Iran. As the first factor, drought stress included four levels of irrigation: 100% field capacity (FC) (no stress), 75% FC (low stress), 50% FC (medium stress) and 25% FC (high stress). In the second factor, salicylic acid had four levels: 0, 0.01, 0.5 and 1 mM.
The results showed that maximum yield and yield components of P. ovata Forssk were obtained with 100% FC and simultaneous application of 1 mM salicylic acid. Minimum amounts of yield and yield components resulted from irrigation based on 25% FC with no application of salicylic acid. Such an outcome revealed the significant role of salicylic acid in increasing the tolerance of Plantago ovata Forssk to drought stress.