The ability of low levels of elevated ozone to change the growth and phytochemical constituents of a medicinal plant Andrographis paniculata (Burm. f.) Nees.

Abstract

Ground-level ozone (O₃) is well recognized as a secondary air pollutant with detrimental effects on plant growth and biochemistry. In a field study, Andrographis paniculata (King of Bitter) was exposed to ambient O₃ and elevated O₃ (AO + 20 ppb) at three growth stages [45, 90, and 135 days after treatment, (DAT)] using open-top chambers. Elevated O₃ stress negatively impacted plant growth, increased cell damage, and induced foliar injuries. However, elevated O₃ also boosted antioxidant production such as proline, phenol, and enzymatic antioxidants, as well as certain secondary metabolites such as tannins, phytosterols, saponins, and alkaloids. This may enhance the plant's medicinal properties, including compounds limonene dioxide, phytol, palmitic acid, and androstadiene. While, certain metabolites like Citronellol, Khusenol, and tocopherol displayed an adverse reaction under elevated O₃ exposure. The novel detection of acrodiene, squalene, and neophytadiene under O₃ stress emphasizes their medicinal significance. Notably, an important bioactive compound andrographolide in A. paniculata showed increased synthesis under elevated O₃ at 45 and 90 DAT, suggesting that O₃ exposure could enhance the plant's pharmaceutical value.