Department of Molecular Biology and Biochemistry, Federal University of Ceará, Fortaleza, 60440-970, Brazil.
Bioscience Institute, São Paulo State University (UNESP), São Vicente, 11330-900, Brazil.
Physiol Plant. 2019 Nov;167(3):404-417. doi: 10.1111/ppl.12908. Epub 2019 Feb 8.
Salinity commonly affects photosynthesis and crop production worldwide. Salt stress disrupts the fine balance between photosynthetic electron transport and the Calvin cycle reactions, leading to over-reduction and excess energy within the thylakoids. The excess energy triggers reactive oxygen species (ROS) overproduction that causes photoinhibition in both photosystems (PS) I and II. However, the role of PSI photoinhibition and its physiological mechanisms for photoprotection have not yet been fully elucidated. In the present study, we analyzed the effects of 15 consecutive days of 100 mM NaCl in Jatropha curcas plants, primarily focusing on the photosynthetic electron flow at PSI level. We found that J. curcas plants have important photoprotective mechanisms to cope with the harmful effects of salinity. We show that maintaining P700 in an oxidized state is an important photoprotector mechanism, avoiding ROS burst in J. curcas exposed to salinity. In addition, upon photoinhibition of PSI, the highly reduced electron transport chain triggers a significant increase in H O content which can lead to the production of hydroxyl radical by Mehler reactions in chloroplast, thereby increasing PSI photoinhibition.
盐度通常会影响全球的光合作用和作物产量。盐胁迫破坏了光合作用电子传递和卡尔文循环反应之间的精细平衡，导致类囊体中过度还原和过剩能量。过剩的能量引发活性氧（ROS）的过度产生，从而导致 PSI 和 PSII 都发生光抑制。然而，PSI 光抑制的作用及其对光保护的生理机制尚未得到充分阐明。在本研究中，我们分析了在 100mM NaCl 处理下连续 15 天对麻疯树植物的影响，主要关注PSI 水平的光合作用电子流。我们发现，麻疯树植物具有重要的光保护机制来应对盐度的有害影响。我们表明，保持 P700 处于氧化状态是一种重要的光保护机制，可以避免盐胁迫下 ROS 的爆发。此外，当 PSI 发生光抑制时，高度还原的电子传递链会引发 H2O 含量的显著增加，这可能导致叶绿体中 Mehler 反应产生羟基自由基，从而增加 PSI 光抑制。
