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Indoleacetic acid protection against microplastic induced oxidative stress in Pinellia ternata antioxidant enzyme and secondary metabolite regulation
Summary
This plant science study found that microplastics in soil reduced the growth and altered the secondary metabolite chemistry of Pinellia ternata, a medicinal plant used in traditional Chinese medicine. Applying the plant hormone indole-3-acetic acid (IAA) partially counteracted the microplastic stress, restoring some growth parameters and enzyme activities. The research suggests that microplastic pollution in agricultural soils could affect the quality and pharmacological properties of medicinal crops — an underexplored consequence of plastic contamination. It also points to potential mitigation strategies using plant growth hormones.
Microplastic (MP) has emerged as a potential threat to crops and agro-ecosystems. The research on their impact on secondary metabolism in medicinal plants and functional foods is limited. Pinellia ternata is a medicinal plant, and its pharmacological characteristics are related to its secondary metabolites. Indole-3-acetic acid (IAA) has been proven to enhance plants' resistance to various abiotic stresses. This study investigated the effects of MP, IAA, and their combination on P. ternata growth, secondary metabolites, reactive oxygen species (ROS) levels, endogenous hormones, and the ascorbic acid-glutathione (AsA-GSH) cycle. Compared with the control group (CK), IAA significantly increased the contents of secondary metabolites, nutrients, ascorbic acid (AsA) and glutathione (GSH). The MP group reduced plant height, tuber weight, ascorbic acid peroxidase (APX), dehydroascorbic acid reductase (DHAR), and soluble protein of P. ternata over the CK. MP + IAA increased tuber weight, APX, DHAR, and soluble protein by 10.3, 26.6, 7.7, 18.2, and 12.5%, respectively, compared with MP. MP elevated the rate of O2·- production, flavonoids, alkaloids, β-sitosterol, and PAL compared to CK. MP + IAA significantly declined the alkaloids, soluble sugar contents, and PAL compared with the MP group. MP reduced DHAR, MDHAR, and APX activities by 30.5, 12.5, and 16.1%, respectively, over the CK. While MP + IAA increased DHAR and APX activities by 18.2 and 7.7%, respectively, compared with MP. Summarily, IAA alleviated the oxidative stress induced by MP and maintained the levels of secondary metabolites, highlighting its potential in protecting the quality of medicinal plants under MP stress.