Physiological Toxicity Of Silver Nanomaterials To Rice Seedlings

With the rapid development of nano-science,engineered nanoparticles are extensively used in various fields,and the most used nanomaterials are silver nanomaterials(AgNMs).The widespread applications of AgNPs in consumer makes their release to the environment inevitable,which is bound to pose potential risks to the organism.Meanwhile,rice is considered to be one of the most important crops and the staple food of more than half of the world's population.Therefore,the study of the influence of AgNMs on rice is of great significance to human food and life safety.Specifically,this research selected three kinds of commonly used silver nanomaterials(30 nm AgNPs,70 nm AgNPs,and AgNCs)to study their effects on germination,growth,and development of rice,and investigate the mechanism of AgNMs on rice seedlings.In this research,PVP stabilized silver nanoparticles(30 nm AgNPs)and silver nanocubes were successfully synthesized.And 70 nm AgNPs were obtained from Lengshi company.The study on physiological toxicity of silver nanocubes to rice seedlings found that the toxicity of AgNCs to rice seedlings presented a concentration dependent manner.The growth of rice seedlings and seed germination rate were significantly promoted when exposed to 0.5 mg/L AgNCs.With the external AgNCs increased,lipid peroxidation and electrolyte leakage were enhanced in rice seedlings,while antioxidant enzyme activities were inhibited.The growth of rice seedlings was completely inhibited under 9.5 mg/L of AgNCs exposure.Importantly,a particle-specific effect of AgNCs towards rice seedlings was the effects when AgNCs concentration below 2.5 mg/L,while the combined effects of the AgNCs and dissolved Ag were observed when AgNCs concentration excessed 5 mg/L.The toxicological studies on the effects of silver nanoparticles(AgNPs)of different sizes on rice seedlings showed that the germination rate was improved when rice seeds exposed to AgNPs.At the same concentration,30 nm AgNPs had more pronounced effects on rice seedlings than 70 nm AgNPs.Specifically,30 nm AgNPs inhibited the growth(elongation of roots and shoots)and antioxidant enzyme activity more seriously,and enhanced the lipid peroxidation and electrolyte leakage.This also confirmed that the small size effect of the silver nanomaterial itself,which means the small particle size makes it have higher activity and more obvious impacts on rice.In addition,70 nm AgNPs at 0.5 mg/L could promote the elongation of roots and shoots.