Stefanov Martin A, Rashkov Georgi D, Borisova Preslava B, Apostolova Emilia L
Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria.
Plants (Basel). 2024 Apr 3;13(7):1025. doi: 10.3390/plants13071025.
Salt stress significantly impacts the functions of the photosynthetic apparatus, with varying degrees of damage to its components. Photosystem II (PSII) is more sensitive to environmental stresses, including salinity, than photosystem I (PSI). This study investigated the effects of different salinity levels (0 to 200 mM NaCl) on the PSII complex in isolated thylakoid membranes from hydroponically grown pea ( L.) and maize ( L.) plants treated with NaCl for 5 days. The data revealed that salt stress inhibits the photochemical activity of PSII (HO → BQ), affecting the energy transfer between the pigment-protein complexes of PSII (as indicated by the fluorescence emission ratio F/F), Q reoxidation, and the function of the oxygen-evolving complex (OEC). These processes were more significantly affected in pea than in maize under salinity. Analysis of the oxygen evolution curves after flashes and continuous illumination showed a stronger influence on the PSIIα than PSIIβ centers. The inhibition of oxygen evolution was associated with an increase in misses (α), double hits (β), and blocked centers (S) and a decrease in the rate constant of turnover of PSII reaction centers (K). Salinity had different effects on the two pathways of Q reoxidation in maize and pea. In maize, the electron flow from Q- to plastoquinone was dominant after treatment with higher NaCl concentrations (150 mM and 200 mM), while in pea, the electron recombination on QQ- with oxidized S (or S) of the OEC was more pronounced. Analysis of the 77 K fluorescence emission spectra revealed changes in the ratio of the light-harvesting complex of PSII (LHCII) monomers and trimers to LHCII aggregates after salt treatment. There was also a decrease in pigment composition and an increase in oxidative stress markers, membrane injury index, antioxidant activity (FRAP assay), and antiradical activity (DPPH assay). These effects were more pronounced in pea than in maize after treatment with higher NaCl concentrations (150 mM-200 mM). This study provides insights into how salinity influences the processes in the donor and acceptor sides of PSII in plants with different salt sensitivity.
盐胁迫显著影响光合机构的功能，对其组成成分造成不同程度的损害。与光系统I（PSI）相比，光系统II（PSII）对包括盐度在内的环境胁迫更为敏感。本研究调查了不同盐度水平（0至200 mM NaCl）对水培生长的豌豆（L.）和玉米（L.）植株经NaCl处理5天后分离的类囊体膜中PSII复合物的影响。数据显示，盐胁迫抑制了PSII（HO→BQ）的光化学活性，影响了PSII色素 - 蛋白复合物之间的能量转移（如荧光发射率F/F所示）、Q再氧化以及放氧复合体（OEC）的功能。在盐胁迫下，这些过程在豌豆中比在玉米中受到的影响更显著。闪光和连续光照后氧气释放曲线的分析表明，对PSIIα中心的影响比对PSIIβ中心的影响更强。氧气释放的抑制与缺失（α）、双击中（β）和被阻断中心（S）的增加以及PSII反应中心周转速率常数（K）的降低有关。盐度对玉米和豌豆中Q再氧化的两条途径有不同影响。在玉米中，用较高NaCl浓度（150 mM和200 mM）处理后，从Q - 到质体醌的电子流占主导，而在豌豆中，Q上的电子与OEC的氧化S（或S）的重组更为明显。77 K荧光发射光谱分析显示，盐处理后PSII的捕光复合体（LHCII）单体和三聚体与LHCII聚集体的比例发生了变化。色素组成也有所下降，氧化应激标记物、膜损伤指数、抗氧化活性（FRAP测定）和抗自由基活性（DPPH测定）有所增加。在用较高NaCl浓度（150 mM - 200 mM）处理后，这些影响在豌豆中比在玉米中更明显。本研究为盐度如何影响不同盐敏感性植物中PSII供体侧和受体侧的过程提供了见解。
