Application of phytohormones as attenuators of salt stress in Tropaeolum majus L. (Tropaeolaceae)

The salinity of the soil and irrigation water isone of the great challenges of agriculture. Salinity can have harmful effectson physiological processes and plant growth, including Tropaeolum majus L. (Tropaeolaceae). The application ofphytohormones can be a strategy to mitigate these effects. The aim of thisstudy was to evaluate the application of jasmonic acid, salicylic acid,cytokinin and polyamine as attenuators of salt stress in T. majus . Threelevels of salt stress were used: 0 mM NaCl (no stress), 50 mM NaCl (moderatestress) and 100 mM NaCl (severe stress). Four phytohormones and a controltreatment were used: control (deionized water), jasmonic acid (200 µM),salicylic acid (2 mM), cytokinin (6-benzylaminopurine – 10 µM) and polyamine(spermine – 1 mM). Growth and gas exchange parameters were evaluated. Appliedin conditions of moderate salt stress, all the phytohormones wereefficient in improving plant height andleaf area (except salicylic acid); cytokinin and polyamine improved the number of flowersas well as gs, A and iCE; jasmonic acid improved the stem dry mass andtotal dry mass. In relation tosevere salt stress, applications of jasmonic acid and polyaminewere efficient in improving plant height; cytokinin improved leaf dry mass as well as gs, A, E, WUE, iWUE and iCE. Theapplication of cytokinin, polyamine and jasmonic acid can be used to mitigatemoderate salt stress in T. majus.