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The present study shows the effect of salinity on the functions of thylakoid membranes from two hybrid lines of Paulownia : Paulownia tomentosa x fortunei and Paulownia elongate x elongata , grown in a Hoagland solution with two NaCl concentrations (100 and 150 mM) and different exposure times (10 and 25 days). We observed inhibition of the photochemical activities of photosystem I (DCPIH 2 → MV) and photosystem II (H 2 O → BQ) only after the short treatment (10 days) with the higher NaCl concentration. Data also revealed alterations in the energy transfer between pigment-protein complexes (fluorescence emission ratios F 735 /F 685 and F 695/ F 685 ), the kinetic parameters of the oxygen-evolving reactions (initial S 0 -S 1 state distribution, misses (α), double hits (β) and blocked centers (S B )). Moreover, the experimental results showed that after prolonged treatment with NaCl Paulownia tomentosa x fortunei adapted to the higher concentration of NaCl (150 mM), while this concentration is lethal for Paulownia elongata x elongata . This study demonstrated the relationship between the salt-induced inhibition of the photochemistry of both photosystems and the salt-induced changes in the energy transfer between the pigment-protein complexes and the alterations in the Mn cluster of the oxygen-evolving complex under salt stress.

Functions of the photosynthetic apparatus of C3 ( Pisum sativum L.) and C4 ( Zea mays L.) plants under physiological conditions and after treatment with different NaCl concentrations (0-200 mM) were investigated using chlorophyll a fluorescence (pulse-amplitude-modulated (PAM) and JIP test) and P 700 photooxidation measurement. Data revealed lower density of the photosynthetic structures (RC/CSo), larger relative size of the plastoquinone (PQ) pool (N) and higher electron transport capacity and photosynthetic rate (parameter R Fd ) in C4 than in C3 plants. Furthermore, the differences were observed between the two studied species in the parameters characterizing the possibility of reduction in the photosystem (PSI) end acceptors (REo/RC, REo/CSo and δRo). Data revealed that NaCl treatment caused a decrease in the density of the photosynthetic structures and relative size of the PQ pool as well as decrease in the electron transport to the PSI end electron acceptors and the probability of their reduction as well as an increase in the thermal dissipation. The effects were stronger in pea than in maize. The enhanced energy losses after high salt treatment in maize were mainly from the increase in the regulated energy losses (Φ NPQ ), while in pea from the increase in non-regulated energy losses (Φ NO ). The reduction in the electron transport from Q A to the PSI end electron acceptors influenced PSI activity. Analysis of the P 700 photooxidation and its decay kinetics revealed an influence of two PSI populations in pea after treatment with 150 mM and 200 mM NaCl, while in maize the negligible changes were registered only at 200 mM NaCl. The experimental results clearly show less salt tolerance of pea than maize.