EFFECT OF THE APPLICATION OF PLANT BIOSTIMULANTS ON THE ACCUMULATION OF BIOACTIVE COMPOUNDS IN DIFFERENT CROPS UNDER SEMIARID CONDITIONS

Biostimulants improve the efficiency of plant metabolism and stimulate plant responses to adverse environmental conditions. Among the abiotic stresses in the Mediterranean region, high temperatures and drought are of particular importance because of their devastating effect on crop yields. In order to defend themselves against these stresses, plants produce antioxidant compounds that have beneficial effects on human health due to their known anti-carcinogenic and antioxidant properties. These compounds include glucosinolates and betalains, which are secondary metabolites characteristic of the order Brassicales and Caryophyllales, respectively. This work investigates the effect of plant biostimulants (seaweed extract, salicylic acid, brassinosteroids, chitosan and modified plant polysaccharides) applied by root or foliar application on the accumulation of glucosinolates and betalains in white cabbage (Brassica oleracea var. capitata), pak choi (Brassica rapa subsp. chinensis) and red beet (Beta vulgaris). The effect of the biostimulants depended on the species (cabbage, pak choi or beet) and the application (root or foliar). In cabbage, root treatment with salicylic acid significantly increased the levels of sinigrin, glucoraphanin, glucoiberin, 4-hydroxyglucobrassicin and glucotropaeolin compared to the control treatment, while in pak choi, foliar treatments with seaweed extract and salicylic acid significantly increased the levels of glucoalysin and brassinosteroids increased the levels of glucotropaeolin. In beetroot, chitosan increased the concentration of betanin, its isomer and both betaxanthins, and treatments with salicylic acid and brassinosteroids increased the concentration of prebetanin. The other treatments did not significantly affect the concentration of the compounds studied.