Silicon Alleviate Hypoxia Stress by Improving Enzymatic and Non-enzymatic Antioxidants and Regulating Nutrient Uptake in Muscadine Grape (Muscadinia rotundifolia Michx.).

Zafar Iqbal,Naeem Khan,Noshin Ilyas,Ali Sarkhosh,Celina Gómez,Muhammad Adnan Shahid,Muhammad Zubair,Rashad Mukhtar Balal

doi:10.3389/fpls.2020.618873

Abstract

Flooding induces low oxygen (hypoxia) stress to plants, and this scenario is mounting due to hurricanes followed by heavy rains, especially in subtropical regions. Hypoxia stress results in the reduction of green pigments, gas exchange (stomatal conductance and internal CO2 concentration), and photosynthetic activity in the plant leaves. In addition, hypoxia stress causes oxidative damage by accelerating lipid peroxidation due to the hyperproduction of reactive oxygen species (ROS) in leaf and root tissues. Furthermore, osmolyte accumulation and antioxidant activity increase, whereas micronutrient uptake decreases under hypoxia stress. Plant physiology and development get severely compromised by hypoxia stress. This investigation was, therefore, aimed at appraising the effects of regular silicon (Si) and Si nanoparticles (SiNPs) to mitigate hypoxia stress in muscadine (Muscadinia rotundifolia Michx.) plants. Our results demonstrated that hypoxia stress reduced muscadine plants’ growth by limiting the production of root and shoot dry biomass, whereas the root zone application of both Si and SiNP effectively mitigated oxidative and osmotic cell damage. Compared to Si, SiNP yielded better efficiency by improving the activity of enzymatic antioxidants [including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)], non-enzymatic antioxidants [ascorbic acid (AsA) and glutathione contents], and accumulation of organic osmolytes [proline and glycinebetaine (GB)]. SiNP also regulated the nutrient profile of the plants by increasing N, P, K, and Zn contents while limiting Mn and Fe concentration to a less toxic level. A negative correlation between antioxidant activities and lipid peroxidation rates was observed in SiNP-treated plants under hypoxia stress. Conclusively, SiNP-treated plants combat hypoxia more efficiently stress than conventional Si by boosting antioxidant activities, osmoprotectant accumulation, and micronutrient regulation.

Highlights

Global climatic changes are predicted to cause extreme environmental conditions such as floods, heat waves, and droughts, in all parts of the world
The induced hypoxia stress led to a severe reduction of 50% in shoot dry weight and 45% in the root dry weight, whereas a decrease of 50% in the total dry weight concerning the control plants was observed
Whereas plants grown under hypoxia stress but supplemented with conventional Si had an increase in their root dry weight, shoot dry weight, and total dry weight by 125, 120, and 125%, respectively, compared to those grown under hypoxia stress without Si

Summary

Introduction

Global climatic changes are predicted to cause extreme environmental conditions such as floods, heat waves, and droughts, in all parts of the world. Damage caused by flooding is difficult to assess, primarily due to the complex nature of its occurrence. It can vary significantly, depending on the amount, intensity, duration, and spatial distribution of precipitations, all of which make ecosystems vulnerable worldwide (Ruperti et al, 2019). I.e., low oxygen conditions (usually between 1 and 5%). The cellular and physiological functions of the plants are compromised and negatively affect the developmental stages of the plants. Plants respond to hypoxia stress at morphological, physiological, biochemical, and molecular levels by modifying their metabolism, gene expression, photosynthesis, and phytohormonal balance

Methods

Results

Conclusion