Salt Priming Protects Photosynthetic Electron Transport against Low-Temperature-Induced Damage in Wheat.

Hui Li,Zongshuai Wang,Xiangnan Li,Shengqun Liu,Huawei Li,Yanjie Lv,Yongjun Wang,Xiancan Zhu,Caiyun Xin,Fengbin Song

doi:10.3390/s20010062

Abstract

Low temperature limits the photochemical efficiency of photosystems in wheat plants. To test the effect of salt priming on the photosynthetic electron transport in wheat under low temperature, the germinating seeds of a winter wheat cv. Jimai44 were primed with varying concentrations of NaCl solutions (0, 10, 30, and 50 mM NaCl, indicated by S0, S10, S30, and S50, respectively) for 6 d, and after 11 d of recovery, the seedlings were subsequently exposed to 24-h low-temperature stress (2 °C). Under low temperature, the S30 plants possessed the highest absorption flux per reaction center and higher density of reaction center per cross-section among the treatments. In addition, S30 plants had higher trapped energy flux for reducing QA and fraction of QA-reducing reaction centers and non-QB reducing center than the non-primed plants under low temperature, indicating that S30 plants could maintain the energy balance of photosystems and a relatively higher maximum quantum efficiency of photosystem II under low temperature. In addition, the low temperature-induced MDA accumulation and cell death were alleviated by salt priming in S30 plants. It was suggested that salt priming with an optimal concentration of NaCl solution (30 mM) during seed germination enhanced the photochemical efficiency of photosystems in wheat seedlings, which could be a potential approach to improve cold tolerance in wheat at an early stage.

Highlights

Low-temperature stress limits wheat plant growth (Triticum aestivum L.), mainly due to the inhibition of photochemical efficiency in photosystems [1,2]
A significant difference was found in fluorescence transients (OJIP curves) between salt primed and non-primed plants under low temperature (Figure 1A)
The chlorophyll fluorescence transients in salt primed wheat plants were less affected by low temperature, in relation to non-primed plants, indicating that salt priming alleviated the low-temperature-induced damage to photosystems

Summary

Introduction

Low-temperature stress limits wheat plant growth (Triticum aestivum L.), mainly due to the inhibition of photochemical efficiency in photosystems [1,2]. The photochemical process in photosystems is triggered when light is absorbed by the antenna, and excitation energy transferred from absorbed energy is either trapped at a reaction center for QA -reducing and electron transport or dissipated as heat and emitting radiation-fluorescence [3]. Sensors 2020, 20, 62 the dark-adapted photosynthetic process by saturating light, is called OJIP (rapid fluorescence transient) curve [4,5]. This curve shows a sequence of phases from the initial (Fo ) to the maximal (FM ) fluorescence value, which is labeled step O (all reaction centers open), J (~2 ms), I (~30 ms), P (equal to FM when all reaction centers are closed) [3,4]. Under low-temperature stress, the redundant excitation energy produces reactive oxygen species (ROS), and the oxidizing power potentially results in damage to the plant’s cell membrane [11,12]

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Discussion

Conclusion