Phytotoxic Evaluation of Phytosynthesized Silver Nanoparticles on Lettuce

• Main Authors: Murtaza Hasan, Kinza Mehmood, Ghazala Mustafa, Ayesha Zafar, Tuba Tariq, Shahbaz Gul Hassan, Suraj Loomba, Muhammad Zia, Abeer Mazher, Nasir Mahmood, Xugang Shu
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Coatings
• Subjects: nanoecotoxicology; plant health; seedling; phytotoxicity; ultra-efficient
• Online Access: https://www.mdpi.com/2079-6412/11/2/225

The increasing metal release into the environment warrants investigating their impact on plants, which are cornerstones of ecosystems. Here, <i>Lactuca sativa</i> L. (lettuce) seedlings were exposed hydroponically to different concentrations of silver ions and nanoparticles (Ag NPs) for 25 days to evaluate their impact on plant growth. Seedlings taking Ag⁺ ions showed an increment of 18% in total phenolic content and 12% in total flavonoid content, whereas under Ag NPs, 7% free radical scavenging activity, 12% total phenolic contents (TPC), and 10% total reducing power are increased. An increase in 31% shoot length, 25% chlorophyll, 11% carbohydrate, and 16% protein content of the lettuce plant is observed in response to Ag NPs, while silver nitrate (AgNO₃) has a reduced 40% growth. The lettuce plant was most susceptible to toxic effects of Ag+ ions at a lower concentration, i.e., 0.01 mg/L, while Ag NPs showed less toxicity, only when higher concentrations >100 mg/L were applied. Further, biomolecules other than antioxidant enzymes showed higher phytotoxicity for Ag⁺ ions, followed by Ag NPs with the concentration of 25, 50, and 100 mg/L compared to the control. Thus, moderate concentrations of Ag NPs have a stimulatory effect on seedling growth, while higher concentrations induced inhibitory effects due to the release of Ag⁺ ions. These results suggest that optimum metallic contents are desirable for the healthier growth of plants in a controlled way.