Ascorbic Acid Alleviates Damage from Heat Stress in the Photosystem II of Tall Fescue in Both the Photochemical and Thermal Phases.

Ke Chen,Qing Zhu,Meiyu Huang,Huihui Zhu,Jinmin Fu,Xiaole Han,Diyong Tang,Jie Sun,Minna Zhang,Jinlin Li

doi:10.3389/fpls.2017.01373

Abstract

L-Ascorbate (Asc) plays important roles in plant development, hormone signaling, the cell cycle and cellular redox system, etc. The higher content of Asc in plant chloroplasts indicates its important role in the photosystem. The objective of this study was to study the roles of Asc in tall fescue leaves against heat stress. After a heat stress treatment, we observed a lower value of the maximum quantum yield for primary photochemistry (φPo), which reflects the inhibited activity of the photochemical phase of photosystem II (PSII). Moreover, we observed a higher value of efficiency of electron transfer from QB to photosystem I acceptors (δR0), which reflects elevated activity of the thermal phase of the photosystem of the tall fescue. The addition of Asc facilitate the behavior of the photochemical phase of the PSII by lowering the ROS content as well as that of the alternative electron donor to provide electron to the tyrosine residue of the D1 protein. Additionally, exogenous Asc reduces the activity of the thermal phase of the photosystem, which could contribute to the limitation of energy input into the photosystem in tall fescue against heat stress. Synthesis of the Asc increased under heat stress treatment. However, under heat stress this regulation does not occur at the transcription level and requires further study.

Highlights

Grasslands occupy about twice the land area of grain crops throughout the world (Mian et al, 2008) and play important ecological roles in the biosphere
Tall fescue leaves were subjected to heat stress and Asc treatment to study the role of Asc in photosystem II (PSII) against heat stress using the OJIP fluorescence transient method
Compared 44Ct curve, the 44Asc curve showed a lower K step, which indicates that Asc treatment alleviated the damage from heat stress

Summary

Introduction

Grasslands occupy about twice the land area of grain crops throughout the world (Mian et al, 2008) and play important ecological roles in the biosphere. Grasslands influence the carbon cycle, as well as the nitrogen cycle. Tall fescue (Festuca arundinacea Schreb) grows in temperate regions of the world, which is a major cool season forage and turf grass species (Chen et al, 2013; Wang and Huang, 2017). Heat stress limits the growth and Ascorbic Acid Improve PSII Activity development of tall fescue in transitional and warm climatic regions, especially in summer, when high temperature can constrain growth, reduce turf quality, induce leaf withering and inhibit photosynthesis (Sun et al, 2015)

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