Influence of Relative Humidity on Germination and Metal Accumulation in Vigna radiata Exposed to Metal-based Nanoparticles

The effect of single (0.1, 1, and 10 mg L −1 ) and binary mixtures (0.1 + 0.1, 1 + 1, and 10 + 10 mg L −1 ) of metal-based nanoparticles (CdO and CuO) on the germination of Vigna radiata was studied under two humidity ranges (70% and 80%). Filter paper-based tests were conducted. The surface-sterilized seeds were exposed to CdO and CuO under controlled environmental conditions (70% and 80% humidity at 35 °C). Germination rates were scored after 24 h and 48 h. The accumulation of metals was tested in seedlings after 48 h using inductively coupled plasma mass spectrometry. Compared with 70% humidity, the germination rate was higher under 80% humidity in all tested conditions. The germination rate of the CdO + CuO treatment was less than that of the single metal exposure under both humidities (70% and 80%) at 48 h. By two-way analysis of variance (ANOVA), we found that germination was greatly influenced by humidity. The accumulation of metal was higher in the CuO test than in the CdO test. Metal accumulation was concentration and humidity dependent, except for Cd accumulation in the CdO + CuO treatment. Here we show that the germination of seeds depends on the humidity and concentration of metal oxide nanoparticles. Understanding these strategies in seeds might help to avoid environmental and chemical stress and improve crop yield.