Humic Acid Alleviates the Toxicity of Nanoplastics towards Solanum lycopersicum

Abstract

Nanoplastics (NPs) are emerging pollutants that contaminate agricultural produce. The present study investigates the impact of polystyrene (PS) and humic acid (HA) individually and in combination on the germination and growth of seeds of Solanum lycopersicum (tomato). Here we report the formation of eco-corona upon the interaction of PS with humic acid at 24 h with a significant increase in hydrodynamic size. Seed germination, plant growth, and chlorophyll content increased in the coronated PS. In addition, we report that the treatment of seeds with PS + HA resulted in the germination of 90% of seeds, while treatment with only PS resulted in the germination of only 65.8% of seeds. A quantitative analysis of chlorophyll (a, b, and a + b) revealed that HA-treated groups and PS + HA-treated groups showed significantly high chlorophyll (a, b, and a + b) contents of (PS: 3.48 mg g−1, 2.12 mg g−1, and 4.19 mg g−1, HA: 5.76 mg g−1, 3.88 mg g−1, and 6.41 mg g−1, PS + HA: 4.17 mg g−1, 3.23 mg g−1, and 6.58 mg g−1)respectively compared to PS treated groups. Similarly, ROS levels were comparatively low in HA and PS + HA-treated groups than in only-PS-treated groups. Furthermore, we observed a decline in the level of antioxidant enzyme (superoxide dismutase and catalase) activity in HA and PS + HA treated groups than that in only-PS treated groups. The results indicate that HA significantly reduces PS-induced toxicity and improves germination and growth of seeds of Solanum lycopersicum; the corresponding reduction in toxic effects may be due to eco-corona formation on the PS. We understand that eco-corona is a way to protect plants from xenobiotics concerning nanoplastics.