Effects of saline stress on proline and polyphenolic compounds content in Arabidopsis thaliana

Soil salinity causes osmotic and oxidative stress in plants. Proline acts as an osmoprotector and an antioxidant in plant cells. It is known that proline accumulation in plants occurs after exposure to drought, high and low temperatures, ultraviolet radiation and high concentrations of heavy metals. Polyphenolic compounds are also part of the antioxidant system. In plants, the synthesis and accumulation of polyphenolic compounds is stimulated in response to biotic and abiotic stress. However, the role of proline and polyphenolic compounds in the early response to acute salt stress is insufficiently studied. To clarify this question we studied changes in the content of proline and polyphenolic compounds in leaves of Arabidopsis upon 50, 100, and 200 mM sodium chloride treatment for 4 and 8 hours. To ensure the rapid inflow of sodium ions in plant during treatment with NaCl 5 week-old Arabidopsis rosettes separated from plant roots were used. Our results show that treatment during 4 hours with 200 mM sodium chloride leads to the increase in proline content by 42%, whereas after 8 hours an increase of 78% was observed. A rise in concentration of polyphenolic compounds by 20% and 23% is detected only after 8 hours of treatment with 100 and 200 mM NaCl, respectively. Therefore, the increase of polyphenolic compound content in leaf tissue occurs later and the effect is weaker compared to the content of proline. The obtained data suggests the involvement of proline and polyphenolic compounds in the protective response of the plant cell to rapid increase of sodium concentration in leaf tissues (acute salt stress).