Responses of photosystem to long-term light stress in a typically shade-tolerant species Panax notoginseng

Zhu Cun; Xiang-Zeng Xu; Jin-Yan Zhang; Sheng-Pu Shuang; Hong-Min Wu; Tong-Xin An; Jun-Wen Chen

doi:10.3389/fpls.2022.1095726

Responses of photosystem to long-term light stress in a typically shade-tolerant species Panax notoginseng

Front Plant Sci. 2023 Jan 12:13:1095726. doi: 10.3389/fpls.2022.1095726. eCollection 2022.

Authors

Zhu Cun^{1

2

3}, Xiang-Zeng Xu^{1

2

3

4}, Jin-Yan Zhang^{1

2

3}, Sheng-Pu Shuang^{1

2

3}, Hong-Min Wu^{1

2

3}, Tong-Xin An¹, Jun-Wen Chen^{1

2

3}

Affiliations

¹ College of Agronomy & Biotechnology, Yunnan Agricultural University, Kunming, China.
² Key Laboratory of Medicinal Plant Biology of Yunnan Province, Yunnan Agricultural University, Kunming, China.
³ National & Local Joint Engineering Research Center on Germplasm Innovation & Utilization of Chinese Medicinal Materials in Southwestern China, Yunnan Agricultural University, Kunming, China.
⁴ Research Center for Collection and Utilization of Tropical Crop Resources, Yunnan Institute of Tropical Crops, Xishuangbanna, China.

Abstract

Photosynthetic adaptive strategies vary with the growth irradiance. The potential photosynthetic adaptive strategies of shade-tolerant species Panax notoginseng (Burkill) F. H. Chen to long-term high light and low light remains unclear. Photosynthetic performance, photosynthesis-related pigments, leaves anatomical characteristics and antioxidant enzyme activities were comparatively determined in P. notoginseng grown under different light regimes. The thickness of the upper epidermis, palisade tissue, and lower epidermis were declined with increasing growth irradiance. Low-light-grown leaves were declined in transpiration rate (Tr) and stomatal conductance (Cond), but intercellular CO₂ concentration (C _i) and net photosynthesis rate (P _n) had opposite trends. The maximum photo-oxidation $P_{700}^{+}$ (P _m) was greatly reduced in 29.8% full sunlight (FL) plants; The maximum quantum yield of photosystem II (F _v/F _m) in 0.2% FL plants was significantly lowest. Electron transport, thermal dissipation, and the effective quantum yield of PSI [Y(I)] and PSII [Y(II)] were declined in low-light-grown plants compared with high-light-grown P. notoginseng. The minimum value of non-regulated energy dissipation of PSII [Y(NO)] was recorded in 0.2% FL P. notoginseng. OJIP kinetic curve showed that relative variable fluorescence at J-phase (V _J) and the ratio of variable fluorescent F _K occupying the F _J-F _O amplitude (W _k) were significantly increased in 0.2% FL plants. However, the increase in W _k was lower than the increase in V _J. In conclusion, PSI photoinhibition is the underlying sensitivity of the typically shade-tolerant species P. notoginseng to high light, and the photodamage to PSII acceptor side might cause the typically shade-tolerant plants to be unsuitable for long-term low light stress.

Keywords: Panax notoginseng; chlorophyll fluorescence; photoprotection; photosynthesis; photosystem.

Grants and funding

This research was supported by the National Natural Science Foundation of China (81860676 and 32160248), the Major Special Science and Technology Project of Yunnan Province (202102AA310048), the National Key Research and Development Plan of China (2021YFD1601003), and the Innovative Research Team of Science and Technology in Yunnan Province (202105AE160016).