Stress Physiology of Brassica Crops upon Drought and Salinity: Hormonal Cross-talk and Defense Response

Climate changes and their negative impacts on environment are in the focus of scientific community for the last decades. Big interest is pointed towards plant stress physiology as plant’s growth and development are highly affected upon presence of stressors. Salinity and drought are considered the major abiotic stresses resulting in decreased crop’s yields and quality. Knowledge about survival and sustained growth of agronomical important crops during severe environmental conditions presents valuable tool to cope with these issues. Within this purpose, three important Brassica cultivars (Chinese cabbage, white cabbage and kale) were selected and exposed to drought and salinity treatments. Using the interdisciplinary approach, we wanted to underline the response of selected cultivars by observation of salt ions uptake, osmotic adjustment, oxidative stress defense mechanisms and impairment of photosynthesis and biomass production. Furthermore, the fluctuations in phytohormones levels and hormonal cross-talk were the focus of the research due their role in environment sensing and mediating physiological processes. Response mediated by abscisic acid (ABA), salicylic acid (SA) and jasmonates (JAs) together with the altered levels of growth promoting hormones: indole-3- acetic acid (IAA), cytokinins (CKs) and brassinosteroids (BRs) revealed differences in tolerance of Brassicas to drought and salinity. Research conducted on different response levels enabled us to characterize selected crops from the most tolerant to the most sensitive in following order: kale, white cabbage, Chinese cabbage and conclude that drought and salinity tolerance is mostly determined by changes in endogenous levels of phytohormones. However, as the hormonal cross-talk and defense mechanism are very complex, additional research at the molecular level is necessary to shed light on the hormonal players and the interactions responsible for drought and salinity tolerance in Brassicaceae.