Abstract

                                The present study was aimed at evaluation of the toxicity potential ofnanoceria 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 quantumyield (terrestrial ecosystem). The study examined the differences in toxicityamong a different concentration of nanoceria to each organism anddifferences 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 soilmicrobes, aquatic organisms and terrestrial plants at lower concentration (upto 25 mg L-1). However, above 25 mg L-1 concentration, differential responsesbetween 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 causedby nanoceria could be associated with the concentration of nanoceria,differences in interactions with the cell with nanoceria, and oxidative damagecaused by nanoceria. Among the assays, pollen germination was found tobe more sensitive to the nanoceria in the medium, followed by photosystemII quantum yield.

Key words : Azolla; Ecotoxicity; Microalgae; Nanoceria; Phosophobacteria; Pollen germination