engleski

The influence of increased salinity on the early stress response of Brassica seedlings

Among the various abiotic stresses limiting the crop productivity, salinity stress is one of the major problem. Increased soil salinity affects growth and development of plants depending on their capacity to overcome stress effects. Brassicaceae crops are important contributors to total vegetable and oilseed production, and their yield and quality may be highly affected by increased soil salinity. Literature data indicate that over 6% of the world’s total land and approximately 20% of irrigated land is affected by high salinity, and it is particular problem in Mediterranean, semi-arid, and arid climates. Thus, there is an urgent need to understand how do different Brassica species/varieties struggle with increased soil salinity. The aim of our research was to investigate an early response of seedlings of three Brassica species/varieties exhibiting different tolerance to salinity stress (Brassica rapa spp. pekinensis, B. oleracea var. capitata, and B. oleracea var. acephala). In order to determine salinity stress effects, 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. Content of ROS (SO, H2O2) and GSH in seedlings were determined in vivo by fluorescent microscope after staining the seedlings with specific dies (dihydroethidium (DHE), dichlorodihydrofluorescein diacetate (DCFH-DA), and monochlorobimane (MCB)). UV/VIS spectrophotometry was used for determination the level of proline and specialized metabolites, while phenolic acids profiles were determined by UHPLC-MS/MS. To be able to determine seedlings ability to cope with stress condition we also measured the antioxidant activity of seedlings by DPPH and FRAP methods. Results indicate that stress response is species specific, but also depends on the salt concentration. Treatments of seedlings with various concentrations of NaCl caused 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. Stressed seedlings produced a high level of ROS molecules (SO and H2O2) in comparison to the control, mostly in a dose dependent manner. Stress treatments had also impact on levels of osmoprotectant proline, GSH as well as phenolic antioxidants. Results of ROS and antioxidant capacities were discussed in relation to seedlings growth inhibitions and stress tolerance of three Brassica species.

Brassicaceae ; ROS molecules ; salinity stress ; seedlings ; specialized metabolites

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