Chin J Plant Ecol ›› 2021, Vol. 45 ›› Issue (4): 404-419.DOI: 10.17521/cjpe.2021.0013

• Research Articles • Previous Articles     Next Articles

Photodamage to photosystem in a typically shade-tolerant species Panax notoginseng exposed to a sudden increase in light intensity

WU Hong-Min1,2, SHUANG Sheng-Pu1,2, ZHANG Jin-Yan1,2, CUN Zhu1,2, MENG Zhen-Gui1,2, LI Long-Gen1,2, SHA Ben-Cai1, CHEN Jun-Wen1,2,*()   

  1. 1National & Local Joint Engineering Research Center on Germplasm Innovation & Utilization of Chinese Medicinal Materials in Southwestern China, Key Laboratory of Medicinal Plant Biology of Yunnan Proince, Yunnan Agricultural University, Kunming 650201, China
    2College of Agronomy and Biotechnology, Yunnan Agricultural University, Kunming 650201, China
  • Received:2021-01-12 Accepted:2021-03-14 Online:2021-04-20 Published:2021-04-14
  • Contact: CHEN Jun-Wen
  • Supported by:
    National Natural Science Foundation of China(81860676);National Natural Science Foundation of China(81360609);Key Science and Technology Project of Yunnan Province(2016ZF001);Key Science and Technology Project of Yunnan Province(2017ZF001)


Aims Photodamage to a shade-tolerant species is common due to a sudden increase in growth light intensity. However, it is unknown about the underlying mechanism of the sensitivity of the shade-tolerant species to high light. The objective of the present study was to elucidate the mechanisms involved in the inability of the typically shade-tolerant species Panax notoginseng to survive under natural full-light condition.

Methods The relative chlorophyll content (SPAD), photosynthetic parameters and chlorophyll fluorescence parameters were continuously examined in P. notoginseng when transferred from shade (10% of full sunlight) to full sunlight for three days.

Important findings The net photosynthetic rate (Pn) of P. notoginseng exposed to full sunlight condition showed a “double-peaked” diurnal curve, and Pn decreased with the prolonged days of full light treatment. The SPAD value, water utilization efficiency and light use efficiency were significantly decreased under full sunlight condition. Furthermore, the maximum fluorescence signal of the P700 reaction center, electron transfer rate of photosystem II (PSII), the maximum quantum efficiency of PSII under dark adaptation and maximum quantum efficiency of PSII under light adaptation were significantly lower in full sunlight than those under shading condition, while the fraction of energy passively dissipated in the forms of heat and fluorescence, energy dissipation due to acceptor side limitation of PSI, and cyclic electron flow were significantly higher under the full light condition. Moreover, the sudden increase in growth light intensity caused a significant change in the fluorescence induction kinetic curve and significantly increased the fluorescence yield on the donor and acceptor side of PSII. The oxygen-evolving complex activity in the donor side of PSII was impaired under full sunlight. Furthermore, the electron transfer in the acceptor side of PSII was inhibited and the over-reduction of the acceptor side of PSI was caused by PSI photoinhibition. The study reveals that the full sunlight might induce the irreversible damage to PSII and the moderate photoinhibition to PSI in shade-tolerant species, and it may be an important underlying mechanisms why the shade-tolerant speciesP. notoginseng cannot survive under full sunlight.

Key words: shade-tolerant species, full sunlight, photosynthesis, photosystem, photoprotection, Panax notoginseng