Role of flavonoids and proline in the protection of photosynthetic apparatus in Paulownia under salt stress

Abstract

The effects of different NaCl concentrations (0–150 mM) for different periods of time (10 days and 25 days) on Paulownia tomentosa x fortunei and Paulownia elongata x elongata were analyzed. The decrease of the pigment composition, an inhibition of the photochemistry of both photosystems as well as an increase of the antioxidant activity (FRAP assay), the antiradical activity (DPPH assay), the total flavonoids and the proline levels were affected only at short salt treatment (10 days) with high NaCl concentration (150 mM). These changes correspond with some decrease of the maximum quantum yields of photosystem II (Fv/Fm), the effective quantum yield of photochemical energy conversion (ФPSII) and the photochemical quenching (qP) as a result of a restriction of electron flow from QA to QB as well as an influence on the oxidation reduction properties of P700. The role of the carotenoids and levels of flavonoids and proline during the first days of salt stress for the prevence of the functions of the photosynthetic apparatus and adaptation of plants to different high salt contents are dicussed.