Effect of phenylalanine and tryptophane on chlorophyll and phenolic content, and the antioxidant activity of sweet basil (Ocimum basilicum L.) under drought conditions

Abstract

Sweet basil ( Ocimum basilicum L.) is an endemic annual mucilaginous spicy herb plant of the mint family (Lamiaceae), growing wild in subtropical and tropical areas of America, Africa, Asia, and in southern Europe. Basil belongs to the aromatic plants that are grown all over the world nowadays. To increase the amount of phenolic and other biologically active compounds in plants, safe, effective, and ecological ways to achieve this are constantly being sought. The greatest economic losses worldwide are due to the negative effects of drought stress and extreme temperatures on plant morphological, physiological, and biochemical characteristics limiting crop growth and productivity. The aim of the study was to evaluate the effect of phenylalanine and tryptophane on the content of chlorophyll and phenolic, and the antioxidant activity of basil under drought conditions. Foliar spraying with phenylalanine and tryptophane to drought-stressed plants increased the chlorophyll a and b content. Application of phenylalanine significantly increased the total phenolic content (TPC) in the cultivar ‘Aromatico Della Riviera Ligure’, while foliar spraying with tryptophane increased TPC in the drought-stressed ‘Palla Compato’ and ‘Toscano’. Foliar spraying with phenylalanine and tryptophane to drought-stressed plants increased the antioxidant activity measured by the DPPH method. Principal component analysis showed that the first factor was highly and positively related to all parameters studied. Hierarchical clustering analysis showed that the first cluster was formed due to drought-stressed ‘Aromatico Della Riviera Ligure’, ‘Cinnamon’, and ‘Lemon’. The second cluster consisted of well-watered ‘Aromatico Della Riviera Ligure’, ‘Cinnamon’, and ‘Lemon’, and drought-stressed and phenylalanine-sprayed ‘Aromatico Della Riviera Ligure’ and ‘Palla Compato’. The third cluster consisted of the combinations of other cultivars and treatments tested.