Optimization of Growth and Biochemical Production in Dracocephalum moldavica L. through Biochar and Salicylic Acid Application in a Pot Experiment

Abstract

This study examines the impact of biochar and salicylic acid on the morphological and biochemical characteristics of Moldavian balm (Dracocephalum moldavica L). A pot experiment was conducted usig a factorial experiment basd on CRD with two factors: salicylic acid applied as a foliar spray at concentrations of 0, 0.5, and 1 mM, and biochar incorporated into the soil at 0, 50, and 100 g/kg in 3 replication at scientific greenhouse at Imam Khomeini International University. The findings reveal that salicylic acid significantly promotes plant growth, with notable increases in height, branching, and biomass, and boosts chlorophyll a and b, essential oil percentage, carotenoids, total phenolic content (TPC), total flavonoid content (TFC), and DPPH radical scavenging activity, especially at the 1 mM concentration. Biochar also positively influences plant height, branching, and biomass, and increases chlorophyll, essential oil percentage, carotenoid content, and TFC, although it has no significant effect on TPC or essential oil composition. The combined application of biochar and salicylic acid produces a synergistic effect, with the highest treatment combinations (1 mM & 100 g/kg) yielding the most significant improvements. Essential oil analysis indicates that salicylic acid markedly enhanced main components such as geraniol, geranial, geranyl acetate, and borneol, while biochar's influence on these compounds is minimal. The interaction between biochar and salicylic acid is particularly effective in boosting chlorophyll content and essential oil composition. These results underscore the potential of integrating biochar and salicylic acid to optimize plant growth and secondary metabolite production in Moldavian balm.