Evaluation of Ecotoxicity of Nanoceria to Organisms of Different Trophic Levels

Vidhya Bharathi K.S,Raghu R,Djanaguiraman M,Jeyakumar P,Karthikeyan S

doi:10.29321/maj.10.000490

Abstract

he present study was aimed at evaluation of the toxicity potential of nanoceria on phosphobacteria (Bacillus megaterium ; soil ecosystem), azolla (Anabaena azollae and microalgae ; Aquatic ecosystem) and sorghum (Sorghum bicolor (L.) Moench) pollen grain and photosystem (PS) II quantum yield (terrestrial ecosystem). The study examined the differences in toxicity among a different concentration of nanoceria to each organism and differences in toxicity among the organisms. In each toxicity experiment, the concentration of nanoceria used are 0, 5, 10, 25, 50, 100, 200, 400, 500, and 1000 mg L-1. The result indicated that nanoceria is not toxic to soil microbes, aquatic organisms and terrestrial plants at lower concentration (up to 25 mg L-1). However, above 25 mg L-1 concentration, differential responses between nanoceria and organisms were observed. Higher concentration (500 and 1000 mg L-1) inhibited the growth of phosphobacteria, microalgae, and pollen germination and PS II quantum yield. The adverse effect caused by nanoceria could be associated with the concentration of nanoceria, differences in interactions with the cell with nanoceria, and oxidative damage caused by nanoceria. Among the assays, pollen germination was found to be more sensitive to the nanoceria in the medium, followed by photosystem II quantum yield.

Highlights

The nanoparticles have potential applications in several sectors like medical science, electronics and biotechnology, including agriculture, where nanotechnology is used to synthesize nano fertilizers, carriers of agrochemicals and materials to mitigate abiotic stress (Prasad et al, 2017)
In-vitro pollen germination was assessed by germinating the pollen in a medium containing 150 mg H3BO3, 500 mg Ca (NO3)2.4H2O, 200 mg MgSO4.7H2O, 100 mg KNO3 and 300 g sucrose, dissolved in 1 L of deionized water to which 15 g of agar per litre and different concentration of nanoceria (0, 5, 10, 25, 50, 100, 200, 400, 500, and 1000 mg L-1) were added
It is evident that increasing the concentration of nanoceria in the medium had significantly reduced the pollen germination percentage from 62% (0 mg L-1) to 6.4 % (1000 mg L-1) (Fig. 2)

Summary

INTRODUCTION

The nanoparticles have potential applications in several sectors like medical science, electronics and biotechnology, including agriculture, where nanotechnology is used to synthesize nano fertilizers, carriers of agrochemicals and materials to mitigate abiotic stress (Prasad et al, 2017). Studies indicated that the application of titanium oxide nanoparticle under drought stress in wheat had improved the yield, gluten and starch content (Jaberzadeh et al, 2013). Cerium oxide nanoparticles (nanoceria) are extensively used in the electronics and automotive industry, and there is limited use in agriculture. It is not clear whether nanoceria act as a prooxidant or antioxidant molecule due to the conflicting reports on the toxicity of nanoceria. The controlled environmental study has shown that cerium nanoparticle can alleviate the drought stress effects in sorghum through modulating antioxidant enzymes activity and oxidant production level (Djanaguiraman et al, 2018b). We aim (i) to examine whether there are differences in toxicity among a different concentration of nanoceria to each organism and (ii) whether for the same nanoparticle, there are significant differences in toxicity among the organisms

MATERIAL AND METHODS

AND DISCUSSION

Findings

CONCLUSIONS