Phytotoxicity of Silver Nanoparticles with Different Surface Properties on Monocots and Dicots Model Plants

Abstract

The aim of the research was to evaluate the effect of three types of silver nanoparticles (AgNPs) with different physicochemical properties and silver ions delivered in the form of silver nitrate (AgNO3) at the concentration of 50 mg L−1 on germination and initial growth of monocots (common wheat, sorghum) and dicots (garden cress, white mustard). The AgNPs were prepared using trisodium citrate (TCSB-AgNPs), tannic acid (TA-AgNPs), and cysteamine hydrochloride (CHSB-AgNPs). They exhibited comparable shape, size distribution, and an average size equal to 15 ± 3 nm which was confirmed with the use of transmission electron microscopy. The electrokinetic characteristics revealed that CHSB-AgNPs have positive, whereas TCSB-AgNPs and TA-AgNPs negative surface charge. First, toxicity of the silver compounds was assessed using the Phytotestkit test. Next, after transferring seedlings to pots, shoot length, leaf surface, shoot dry mass, electrolyte leakage measurement, and photosystem II (PSII) efficiency were determined. AgNPs and silver ions delivered in the form of AgNO3 reduced root and shoots length of common wheat, sorghum, and garden cress; leaves surface of garden cress and white mustard; and shoots dry mass of white mustard. The positively charged CHSB-AgNPs and silver ions delivered in the form of AgNO3 showed the greatest inhibition effect. Moreover, silver ions and positively charged CHSB-AgNPs were more toxic to PSII of model plants than negatively charged TCSB-AgNPs and TA-AgNPs. AgNPs impact differed in the case of monocots and dicots, but the size of the changes was not significant, so it concerned individual parameters. The results revealed the interaction strength, which was generally similar in all tested plants, i.e., increasing negative effect in sequence TCSB-AgNPs < TA-AgNPs < silver ions delivered in the form of AgNO3 < CHSB-AgNPs.