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Response of the Brassicaceae seedlings on short-term salt stress and role of specialized metabolites

Brassicaceae crops are among the oldest known cultivars and their use is widespread. Abiotic stress, such as increased salinity, and oxidative stress are serious threats to agriculture and the natural status of the environment. Increased salinity may cause nutrient deficiencies or imbalances, as well as reduced yield, growth and development of plants depending on their ability to overcome the effects of stress. The ability of plants to tolerate salt is determined by multiple biochemical pathways, those that lead to synthesis of specialized metabolites and support scavenging of reactive oxygen species (ROS). For this reason it is important to understand how Brassicaceae crops struggling against increased salinity. The aim of our research was to evaluate the short-term stress responses of three Brassica species/varieties (Brassica rapa spp. pekinensis, B. oleracea var. capitata, and B.oleracea var. acephala) exposed to saline stress. In order to determine the impact of the salt stress, one-day old seedlings were treated with NaCl (in range of conc. 50- 200 mM), in comparison to corresponding controls, during 24h. The physiological effect of treatments was determined in vivo using the rooth growth assay. The amount of ROS (SO, H2O2) and GSH in seedlings is determined in vivo using a fluorescent microscope connected to the camera after the seedlings are stained with specific dies (dihydroethidium (DHE), dichlorodihydrofluorescein diacetate (DCFH-DA), and monochlorobimane (MCB)). Proline and specialized metabolites were determined used UV/VIS spectrophotometry, while phenolic acids profiles were determined by UHPLC-MS/MS. Ultimately, results indicate that stress response is species specific and depends on the salt concentration. The treatment of seedlings with different concentrations of NaCl cause gradual inhibition of biomass accumulation and root growth where B. rapa spp. pekinensis proved to be the most sensitive species while B. oleracea var. acephala the most tolerant one. Seedlings which are under stress conditions produce higher levels of ROS molecules (SO, H2O2) in comparison to the control, mostly in a dose dependent manner. Stressful conditions also affect at the level of osmoprotectant proline, GSH as well as phenolic antioxidants. Profile of phenolic acids were determined and their fluctuations upon salinity stress were disscussed in comparison to seedlings growth inhibitions and stress tolerance of three Brassica varieties.

ROS molecules ; salinity stress ; three Brassica seedlings types ; UHPLC-MS/MS ; UV/VIS spectrophotometry

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