Effect of salinity, seaweed extract and salicylic acid on growth, essential oil and chemical composition of plectranthus amboinicus (lour) Spreng plant

This investigation was carried out at Faculty of Agriculture, Cairo University and the Experimental Farm of Medicinal and Aromatic Plant Research Department, Horticulture Research Institute, Agricultural Research Center, Dokki, Giza, during two successive seasons of 2015 and 2016.This work was designed to investigate the effect of salinity (control, 1500 and 3000 ppm), seaweed extract at the rates of (250, 500 and 1000 ppm) and salicylic acid at the rates of (150, 300 and 450ppm) on vegetative growth and chemical composition of Plectranthus amboinicus (Lour) Spreng plant. The results indicated that salinity decreased fresh, dry weight, essential oil yield/plant. Also, N, P, K and total carbohydrates contents in plant parts were greatly reduced under saline water. Essential oil %, P- cymene, beta-caryophyllene and alpha-humulene contents in the essential oil, sodium and proline contents were increased with increasing salinity concentrations. However, using the seaweed extracts and salicylic acid significantly increased all the studied characters. Salicylic acid was superior in its significant effect. Foliar application of salicylic acid reduced prominently the hazard effects of salinity and improved all the previous characters under salinity treatments.