Interactive Effects of Vermicompost and Salicylic Acid on Chlorophyll and Carotenoid Contents of Petunia Hybrid Under Drought Stress

This study was conducted to investigate the effects vermicompost, drought stress, and salicylic acid on chlorophyll and carotenoid contents of petunia plants. Experimental treatments were drought stress including two levels with and without stress, four salicylic acid concentrations including 0, 50, 100, and 200 ppm and three levels of vermicompost (0, 10, and 20% w/w). The experiment was carried out as a completely randomized design with 3 replications. The application of vermicompost resulted in significant increases in contents of chlorophyll a, total chlorophyll and carotenoid compared to control. The content of chlorophyll a and total chlorophyll in 50 ppm salicylic acid was significantly greater than that in other treatments. However, the chlorophyll b and carotenoid content was lower in the in 100 ppm salicylic acid than in other treatments. The results indicated that drought stress significantly reduced these pigments. The highest the content of chlorophyll a was observed at the rate of 10% vermicompost, 50 ppm salicylic acid, and no-stress condition. The treatment of 200 ppm salicylic acid at no-stress condition and rate of 20% vermicompost had the highest of chlorophyll b content. The highest the content of total chlorophyll was observed at the rate of 10% vermicompost, 50 ppm salicylic acid, and no-stress condition. The treatment of without salicylic acid and vermicompost at stress condition had the highest of carotenoid content. Based on the results of this experiment, application of salicylic acid and vermicompost improved the contents of chlorophyll a, total chlorophyll, and carotenoid of Persian petunia under drought conditions.