Modulation of Cellular Redox Status and Antioxidant Defense System after Synergistic Application of Zinc Oxide Nanoparticles and Salicylic Acid in Rice (Oryza sativa) Plant under Arsenic Stress.

Mohammad Faizan,Shadma Afzal,Vishnu D Rajput,Mohammad Faisal,Ahmad Faraz,Firoz Akhter,Fangyuan Yu,Abdulrahman A Alatar,Shafaque Sehar,Svetlana Sushkova,Muhammad Faheem Adil,Tatiana Minkina

doi:10.3390/plants10112254

Abstract

The objective of this research was to determine the effect of zinc oxide nanoparticles (ZnONPs) and/or salicylic acid (SA) under arsenic (As) stress on rice (Oryza sativa). ZnONPs are analyzed for various techniques viz., X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). All of these tests established that ZnONPs are pure with no internal defects, and can be potentially used in plant applications. Hence, we further investigated for better understanding of the underlying mechanisms and the extent of ZnONPs and SA induced oxidative stress damages. More restricted plant growth, gas exchange indices, significant reduction in the SPAD index and maximum quantum yield (Fv/Fm) and brutal decline in protein content were noticed in As-applied plants. In contrast, foliar fertigation of ZnONPs and/or SA to As-stressed rice plants lessens the oxidative stress, as exposed by subordinate levels of reactive oxygen species (ROS) synthesis. Improved enzymatic activities of catalase (CAT), peroxidase (POX), and superoxide dismutase (SOD), proline and total soluble protein contents under ZnONPs and SA treatment plays an excellent role in the regulation of various transcriptional pathways participated in oxidative stress tolerance. Higher content of nitrogen (N; 13%), phosphorus (P; 10%), potassium (K; 13%), zinc (Zn; 68%), manganese (Mn; 14%), and iron (Fe; 19) in ZnONPs and SA treated plants under As-stress, thus hampered growth and photosynthetic efficiency of rice plants. Our findings suggest that toxicity of As was conquering by the application of ZnONPs and SA in rice plants.

Highlights

Exposure to arsenic (As) is a threat to humans, and the main source of exposure is water contaminated with As
In As containing plants, combined application of salicylic acid (SA) and zinc oxide nanoparticles (ZnONPs) increased the all aforesaid parameters by 24%, 18%, 25%, and 21%, respectively over non-treated plants (Figure 1)
For scanning electron microscopy (SEM) analysis, the NPs was fixed on an aluminum stub using carbon double-sided glue tabs and enclosed with thin conductive palladium film, while a 200-mesh carbon-coated copper grid was used for transmission electron microscopy (TEM) analysis

Summary

Introduction

Exposure to arsenic (As) is a threat to humans, and the main source of exposure is water contaminated with As. Arsenic contaminated groundwater is reported in many parts of the world, and the most serious problems have been observed in different parts of India [1]. Arsenic contaminated groundwater is reported in many parts of the world, and the most serious problems have been observed in different parts of India [1] It exists in the environment both in inorganic [(Arsenate (AsV), arsenite (AsIII)] and organic forms. Plants can develop symptoms of toxicity when exposed to excess As, either in the soil state or in solution cultures. It inhibits seed germination, root development, photosynthesis, and leads to plant death [3]. As an active redox metal, it stimulates the generation of reactive oxygen species (ROS) that lead to lipid peroxidation, disturbance of cellular redox states and linked toxicity [4]

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