Effect of Zinc Oxide Nanoparticles (ZnO-NPs) on Seed Germination Characteristics in Two Brassicaceae Family Species: Camelina sativa and Brassica napus L

Introduction. Zinc is one of the essential micronutrients for living organisms; so, the right performance of several enzymes depends on this element. This micronutrient is a regulator of phytohormones and chlorophyll synthesis, and also, it is an essential element for the carbohydrates' metabolisms in plants. Considering the relatively high solubility of ZnO-NPs and also the ability of plants to uptake and accumulate these nanoparticles in their biomass, ZnO-NPs can be used as an effective nanofertilizer for plants' growth. Methods. In the present study, zinc oxide nanoparticles synthesized using chemical method and the effect of ZnO-NPs (as a nanofertilizer) on seeds' germination, seedlings' rootlet, seedlings' plumule, and seedling's vigour index in two oilseed crops from the Brassicaceae family, including Brassica napus L. and Camelina sativa, were investigated. After treating the seeds with different concentrations of ZnO-NPs (from 0.1 to 1000 ppm) for 6 days, the germination percentage (GP) of each treatment was measured. Results. The results indicated an increase in GP for both plants treated with 10 ppm ZnO-NPs. For B. napus, the maximum GP occurred in treated seeds with 5 ppm ZnO-NPs which showed a 30% increase of GP compared with the control condition. For Camelina, this maximum GP was observed in 0.1 ppm concentration of ZnO-NPs which showed a 15% increase compared with the control condition. After the germination test, germinated seedlings were planted in Hoagland hydroponic solution and treated with ZnO-NPs again for a week. For both species, treatment with ZnO-NPs showed a great effect on rootlet growth, while the effects of these treatments on plumule were negligible. The maximum rootlet length was observed in treated B. napus seedlings with 5 ppm ZnO-NPs which showed a 32% increase in this parameter compared with the control condition. In contrast, the high concentrations of ZnO-NPs showed toxic effects on B. napus seedlings' rootlets. Results showed a 41% decrease in B. napus seedlings treated with 50 ppm ZnO-NPs compared with control seedlings. Similar results were observed in the treated seedlings of Camelina. For Camelina seedlings treated with 1 ppm ZnO-NPs, 15% increase in rootlets' length was observed, while treated Camelina seedlings with 50 ppm ZnO-NPs showed a 68% decrease in rootlet length compared with the control condition. The results of this study indicated the potential of using ZnO-NPs as nanofertilizer for B. napus and Camelina in low concentrations (lower than 10 ppm). In addition, these results suggest the toxicity effects of these nanoparticles on both species in concentrations higher than 50 ppm.

Automated summary

This study investigated the effects of ZnO-NPs on Brassica napus L. and Camelina sativa. Treatment with 10 ppm ZnO-NPs significantly increased germination percentage in both plants. ZnO-NPs showed a positive effect on rootlet growth, while the effects on plumule were negligible. Low concentrations of ZnO-NPs (lower than 10 ppm) have the potential to be used as nanofertilizer for these oilseed crops, while high concentrations (higher than 50 ppm) showed toxic effects.