The water-water cycle is not a major alternative sink in fluctuating light at chilling temperature

Plant Sci. 2021 Apr:305:110828. doi: 10.1016/j.plantsci.2021.110828. Epub 2021 Jan 13.

Abstract

The water-water cycle (WWC) has the potential to alleviate photoinhibition of photosystem I (PSI) in fluctuating light (FL) at room temperature and moderate heat stress. However, it is unclear whether WWC can function as a safety valve for PSI in FL at chilling temperature. In this study, we measured P700 redox state and chlorophyll fluorescence in FL at 25 °C and 4 °C in the high WWC activity plant Dendrobium officinale. At 25 °C, the operation of WWC contributed to the rapid re-oxidation of P700 upon dark-to-light transition. However, such rapid re-oxidation of P700 was not observed at 4 °C. Upon a sudden increase in light intensity, WWC rapidly consumed excess electrons in PSI and thus avoided an over-reduction of PSI at 25 °C. On the contrary, PSI was highly reduced within the first seconds after transition from low to high light at 4 °C. Therefore, in opposite to 25 °C, the WWC is not a major alternative sink in FL at chilling temperature. Upon transition from low to high light, cyclic electron transport was highly stimulated at 4 °C when compared with 25 °C. These results indicate that D. officinale enhances cyclic electron transport to partially compensate for the inactivation of WWC in FL at 4 °C.

Keywords: Dendrobium officinale; Electron transfer; Photoprotection; Photosynthesis; Photosystem I.

MeSH terms

  • Adaptation, Ocular / physiology*
  • Cold Temperature*
  • Dark Adaptation / physiology*
  • Dendrobium / physiology*
  • Electron Transport / physiology*
  • Heat-Shock Response / physiology*
  • Photosynthesis / physiology
  • Photosystem I Protein Complex / physiology*
  • Plant Leaves / physiology

Substances

  • Photosystem I Protein Complex