Exogenous Melatonin Promotes the Salt Tolerance by Removing Active Oxygen and Maintaining Ion Balance in Wheat (Triticum aestivum L.).

Zhihui Zhang,Hongye Li,Shaocong Zhang,Xiaoyi Fu,Dongxiao Li,Xiuzhen Zhai,Liantao Liu,Na Yang,Jiaming Shen,Ruiqi Li

doi:10.3389/fpls.2021.787062

Abstract

Melatonin (MT) is a small molecule indole hormone that plays an important role in the regulation of biological processes and abiotic stress resistance. Previous studies have confirmed that MT promotes the normal development of plants under stress by mediating physiological regulation mechanisms. However, the physiological mechanism of exogenous MT regulating seed germination and seedling growth of wheat under salt stress is still unclear. In this study, NaCl stress decreased germination rate and inhibited seedling growth of wheat, but shoot length, root length, and plant weight of SM15 did not change significantly. The addition of 300 μM MT in the cultivation solution directly promoted the germination rate of SM15 and ZM18, and lateral root production, but decreased the germination rate of JM22 and inhibited the length of germ and radicle of three varieties under salt stress. For wheat seedling, application of MT could increase proline content, soluble protein, soluble sugar, Ca2+ content, and vital amino acid content in leaves to keep high water content, low level of H2O2 content, and low [K+]/[Na+] ratio. MT increased root vigor and [K+]/[Na+] ratio and decreased H2O2 content in root induced by salt stress. In conclusion, MT enhanced salt tolerance in wheat seeds and seedlings by regulating the synthesis of soluble protein and sugar, ion compartmentation in roots and leaves, enhancement of enzymatic systems, and changes in amino acid levels. Salt resistance varied with different varieties under the same environmental condition. SM15 was a higher salt-resistant variety and JM22 was a salt-sensitive one. In wheat production, the application of exogenous MT should consider the differences among varieties of wheat during the sowing and seedling stages.

Highlights

Soil salinization, a geologically environmental problem all over the world, is one of the main factors resulting in the decrease in grain production (Liang et al, 2018)
The germination rate of wheat treated with NaCl increased rapidly in the first 3 days and showed differences: Aminoacyl Derivatization Three solutions including 100 μL mixed standards, 200 μL buffer solution (0.5 mol/L sodium bicarbonate solution, 0.5 mol/L sodium carbonate solution, pH value = 9.0), and 100 μL 2,4dinitrochlorobenzene (100 mg/mL) were swirly mixed and reacted at 90◦C for 90 min in dark
Our results provided the evidence that MT increases the ability for the leaves of different wheat varieties to keep high water status and accumulate high soluble protein, soluble sugar, and proline content under NaCl stress (Table 3 and Figures 4, 5)

Summary

Introduction

A geologically environmental problem all over the world, is one of the main factors resulting in the decrease in grain production (Liang et al, 2018). It is expected that 50% of arable land will be under salinealkali stress by 2050 due to environmental pollution, lack of freshwater, improper irrigation methods, and other factors (Dou et al, 2019; Yang et al, 2021). Excessive reactive oxygen species (ROS) are accumulated which will cause cell damage, DNA damage, and oxidative stress to plants, disrupting the physiological balance and leading to reduced photosynthesis and production yield (Zhang et al, 2016; Tripathi et al, 2020). High Na+ accumulation in plant cells leads to osmotic stresses and limits uptake and utilization of other nutrition ions, which causes moisture loss and electrolytic leaching due to cell membrane damage (Abbas et al, 2015; Ahmed et al, 2015; Rebey et al, 2017)

Methods

Results

Discussion

Conclusion