Ultraviolet-B Radiation (UV-B) Relieves Chilling-Light-Induced PSI Photoinhibition And Accelerates The Recovery Of CO2 Assimilation In Cucumber (Cucumis sativus L.) Leaves.

Zi-Shan Zhang,Xi-Zhen Ai,Li-Qiao Jin,Mikko Tikkanen,Hui-Yuan Gao,Yu-Ting Li,Qing-Ming Li

doi:10.1038/srep34455

Zi-Shan Zhang, Xi-Zhen Ai + Show 5 more

Open Access

https://doi.org/10.1038/srep34455

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Abstract

Ultraviolet-B radiation (UV-B) is generally considered to negatively impact the photosynthetic apparatus and plant growth. UV-B damages PSII but does not directly influence PSI. However, PSI and PSII successively drive photosynthetic electron transfer, therefore, the interaction between these systems is unavoidable. So we speculated that UV-B could indirectly affect PSI under chilling-light conditions. To test this hypothesis, the cucumber leaves were illuminated by UV-B prior or during the chilling-light treatment, and the leaves were then transferred to 25 °C and low-light conditions for recovery. The results showed that UV-B decreased the electron transfer to PSI by inactivating the oxygen-evolving complex (OEC), thereby protecting PSI from chilling-light-induced photoinhibition. This effect advantages the recoveries of PSI and CO2 assimilation after chilling-light stress, therefore should minimize the yield loss caused by chilling-light stress. Because sunlight consists of both UV-B and visible light, we suggest that UV-B-induced OEC inactivation is critical for chilling-light-induced PSI photoinhibition in field. Moreover, additional UV-B irradiation is an effective strategy to relieve PSI photoinhibition and yield loss in protected cultivation during winter. This study also demonstrates that minimizing the photoinhibition of PSI rather than that of PSII is essential for the chilling-light tolerance of the plant photosynthetic apparatus.

Highlights

Ultraviolet-B radiation (UV-B) is generally considered to negatively impact the photosynthetic apparatus and plant growth
This study demonstrates that minimizing the photoinhibition of photosystem I (PSI) rather than that of photosystem II (PSII) is essential for the chilling-light tolerance of the plant photosynthetic apparatus
The leaves were irradiated with weaker UV-B during chilling-light treatment; PSI photoinhibition was alleviated in this experiment, and the PSII photoinhibition was more severe (Fig. 1b,d)

Summary

Introduction

Ultraviolet-B radiation (UV-B) is generally considered to negatively impact the photosynthetic apparatus and plant growth. The results showed that UV-B decreased the electron transfer to PSI by inactivating the oxygen-evolving complex (OEC), thereby protecting PSI from chilling-light-induced photoinhibition. This effect advantages the recoveries of PSI and CO2 assimilation after chilling-light stress, should minimize the yield loss caused by chilling-light stress. UV-B is generally considered to negatively impact plants[2,4], some research has shown that UV-B can suppress insect predation and pathogen infection in plants[5,6,7] This opinion considered only the Calvin cycle and photosystem II (PSII), while neglecting photosystem I (PSI) and the interaction between PSII and PSI. UV-B does not directly influence PSI8,9, PSI and PSII successively drive electron transfer in C3 plants; the interaction between them is unavoidable[10]. During the recovery from chilling-light stress, the limited electron transport from PSII to PSI protects PSI from further photoinhibition and accelerates the recovery of PSI13

Results

Discussion

Conclusion