Mild Potassium Chloride Stress Alters the Mineral Composition, Hormone Network, and Phenolic Profile in Artichoke Leaves

There is a growing interest among consumers and researchers in the globe artichoke\r\n[Cynara cardunculus L. subsp. scolymus (L.) Hegi] leaf extract due to its nutraceutical\r\nand therapeutic properties. The application of an abiotic stress such as salinity\r\ncan activate the stress-signaling pathways, thus enhancing the content of valuable\r\nphytochemicals. The aim of this study was to assess the metabolic changes in\r\nartichokes by probing the leaf metabolome of artichoke plants grown in a floating\r\nsystem and exposed to a relatively mild (30 mM) potassium chloride (KCl) salt stress.\r\nPotassium chloride treatment decreased the leaf dry biomass of artichoke, macro- and\r\nmicroelements in leaves (e.g., Ca, Mg, Mn, Zn, and B) but increased the concentrations\r\nof K and Cl. Metabolomics highlighted that the hormonal network of artichokes was\r\nstrongly imbalanced by KCl. The indole-3-acetic acid conjugates, the brassinosteroids\r\nhormone 6-deoxocastasterone, and even more the cytokinin precursor N6-(Delta-\r\n2-isopentenyl)-adenosine-50-triphosphate, strongly increased in leaves of KCl-treated\r\nplants. Moreover, KCl saline treatment induced accumulation of GA4, a bioactive form\r\nadditional to the already known GA3. Another specific response to salinity was changes\r\nin the phenolic compounds profile, with flavones and isoflavones being decreased by\r\nKCl treatment, whereas flavonoid glycosides increased. The osmotic/oxidative stress\r\nthat salinity generates also induced some expected changes at the biochemical\r\nlevel (e.g., ascorbate degradation, membrane lipid peroxidation, and accumulation\r\nof mannitol phosphate). These latter results help explain the molecular/physiological\r\nmechanisms that the plant uses to cope with potassium chloride stress exposure.