Growth and essential oil yield of Basil (Ocimum basilicum L.) as affected by foliar spray of citric acid and salicylic acid

We investigated the effect of the foliar application of three levels of citric acid (0, 0.1, and 0.3% w/v) and three levels of salicylic acid (0, 2, and 4 mM) on leaf dimensions, SPAD reading, and yield indices (fresh weight, dry weight and essential oil yield) of basil (Ocimum basililcum L.). The experiment was conducted in a randomized block design factorial arrangement (3 x 3) with four replications. The factorial analysis suggested both citric acid and salicylic acid to affect only the essential oil yield. The essential oil yield for 0, 0.1 and 0.3% (w/v) of citric acid was 42.9, 52.9 and 58.8 kg/ha, respectively. Salicylic acid either had no effect or decreased the essential oil yield at a concentration of 4 mM. In most factor-levels containing citric acid, the essential oil yield was significantly higher than in the control. The highest essential oil yield was observed for 0.1 % citric acid and 0 mM salicylic acid and amounted to a mean of 73.4 kg/ha compared to 39.5 kg/ha in case of the control. The ease of availability and usage makes citric acid a promising candidate for the manipulation of secondary metabolism-related pathways in medicinal plants.