Effects of iron foliar application on the number and size of glandular trichomes and essential oil content and composition of holy basil (Ocimum sanctum L.) at first and second harvests

Holy basil (Ocimum sanctum L.), belonging to Lamiaceae family, is one of the most important medicinal plants. In order to evaluate the effect of foliar application of iron on the number and size of glandular trichomes and essential oil content, yield and composition of holy basil, an experiment was conducted at the research farm of Department of Horticultural Science, Shahid Chamran University of Ahvaz based on randomized complete block design, with six treatments and three replications. The treatments were control, nano iron chelate (0, 0.5, 1 and 1.5 g.L-1) and iron chelate (1 and 1.5g.L-1) fertilizers. Results showed that the effect of foliar application of iron fertilizers on all measured traits of holy basil was significant (p≥0.01).The highest number (19.76) and size (173.33μm2) of glandular trichomes, essential oil content (2.17%) and yield (14.74 kg.ha-1), and eugenol (33.27%) at first harvest were observed in plants sprayed with 1 g.l-1 nano iron chelate. The highest oil content (2.33%) and yield (12.75 kg.ha-1) and eugenol (41.51%) at second harvest were obtained in plant sprayed with 1 g.L-1 nano iron chelate. The lowest values of mentioned traits were obtained in control plant. Overall, since there was no significant difference between 1 and 1.5 g.L-1 nano iron chelate treatments, foliar application of plant with 1g.L-1 nano iron chelate is recommended for increasing morphological traits of holy basil.