Exogenous Silicon Enhanced Salt Resistance by Maintaining K+/Na+ Homeostasis and Antioxidant Performance in Alfalfa Leaves.

Yuanfa Meng,Kai Fan,Jianming Niu,Zhijian Yan,Jie Zhang,Yuqing Wang,Qiang Yin

doi:10.3389/fpls.2020.01183

Abstract

Silicon (Si) has been known to enhance salt resistance in plants. In this experiment, 4-weeks-old alfalfa seedlings were exposed to different NaCl concentrations (0–200 mM) with or without 2 mM Si for two weeks. The results showed that NaCl-stressed alfalfa seedlings showed a decrease in growth performance, such as stem extension rate, predawn leaf water potential (LWP) and the chlorophyll content, potassium (K+) concentration, as well as the ratio of potassium/sodium ion (K+/Na+). In contrast, NaCl-stressed alfalfa seedlings increased leaf Na+ concentration and the malondialdehyde (MDA) level, as well as the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in alfalfa leaves. Besides, exogenous Si application enhanced photosynthetic parameters of NaCl-stressed alfalfa seedlings, which was accompanied by the improvement in predawn LWP, level of chlorophyll content, and water use efficiency (WUE). The Si-treated plants enhanced salinity tolerance by limiting Na+ accumulation while maintaining K+ concentration in leaves. It also established K+/Na+ homeostasis by increasing K+/Na+ radio to protect the leaves from Na+ toxicity and thereby maintained higher chlorophyll retention. Simultaneously, Si-treated plants showed higher antioxidant activities and decreased MDA content under NaCl stress. Our study concluded that Si application enhanced salt tolerance of alfalfa through improving the leaves photosynthesis, enhancing antioxidant performance and maintaining K+/Na+ homeostasis in leaves. Our data further indicated exogenous Si application could be effectively manipulated for improving salt resistance of alfalfa grown in saline soil.

Highlights

Soil salinization is a major abiotic stress that hinders plant growth and crop production in the world (Ahmad et al, 2019)
The shoot DW, root DW, and stem extension rate significantly decreased as the NaCl concentration increased (Tables 1 and 2)
The total chlorophyll concentration showed a significant decrease with the rise of NaCl concentration from 0 to 200 mM (Figure 1)

Summary

Introduction

Soil salinization is a major abiotic stress that hinders plant growth and crop production in the world (Ahmad et al, 2019). The accumulation of Na+ in photosynthetic tissue will reduce photosynthetic carbon assimilation (Munns et al, 2020), resulting in loss of yield (Roy et al, 2014; Rubio et al, 2020) Salt stress disturbs K+ homeostasis and harms plant performance Both osmotic pressure and ionic effects destroy the cell’s metabolism, leading to excessive accumulation of reactive oxygen species (ROS), which adversely affects tissue structure and cell metabolism (Chaves and Oliveira, 2004; Chaves et al, 2009)

Methods

Results

Discussion

Conclusion