Crops from the family of Brassicaceae are commercially widely spread vegetables. Abiotic stresses such as salinity and drought are the primary causes of crop loss worldwide. Phytohormones are crucial for the plant ability to adapt to abiotic stress by mediating a wide range of adaptive responses: photosynthesis modification, increased antioxidant activities, secondary metabolites accumulation, changes in gene expression. Phytohormone auxin regulates the majority of plant stress responses through interactions with stress hormones salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), and brassinosteroids (BRA). The aim of this proposal is to investigate the abiotic stress responses of selected Brassica crops (Brassica rapa. ssp. pekinesis, Brassica oleracea var. capitata and Brassica oleracea var. acephala) to drought and salinity stress through integrative research approach comprising biophysical methods of photosynthesis measurements, biochemical methods of stress diagnostics, metabolomics (plant hormones and secondary metabolites) and molecular functional research. Particular focus will be placed to the role of auxin and its interactions with stress hormones (SA, ABA, JA and BRA) in stress responses and potential mechanisms of tolerance. Phytohormones auxin, SA, JA, ABA and BRA will be analyzed by UHPLC-MS/MS. Secondary metabolites, polyphenols and glucosinolates will be measured by spectrophotometry and UHPLC-MS/MS. In order to shed light on auxin homeostasis in abiotic stress, functional research will be performed by using Arabidopsis thaliana lines for genes of auxin reversible conjugation (GH3 and ILR). Results of hormonal analyses will be correlated with basic physiological and biochemical parameters (photosynthesis parameters, ROS level, antioxidant enzymes, proline, glutathione, protein carbonyl level). Finally, stress plant hormones will be investigate as potential biostimulator of abiotic stress tolerance by foliar spray and root treatment.