Pyrene distribution dynamics and its possible degradation pathways in proso millet tissues: an experimental approach

This study investigates whether plants can uptake, accumulate, and detoxify polycyclic aromatic hydrocarbons (PAHs), hazardous pollutants that can harm soil fertility and the environment. To test this hypothesis, hydroponic system was used to examine the distribution dynamics and potential degradation pathways of pyrene (PYR) in proso millet (Panicum miliaceum) tissues at varying concentrations (0, 500, 1,000, 1,500, and 2,000 ppm). Results indicated that higher PYR concentrations adversely affected plant growth, but plant-assisted dissipation removed 29-43% of PYR over 30 days. While PYR levels in the roots increased with exposure, concentrations in the shoots significantly decreased at higher PYR levels. By the end of the experiment, PYR concentrations were higher in roots than in shoots. Bioconcentration and translocation factors peaked at 500 ppm, with translocation to shoots evident on day 15 but primarily restricted to roots by day 30. Furthermore, three main steps in PYR degradation in P. miliaceum were proposed: (A) ring cleavage and oxidation reactions forming epoxides, (B) enzymatic transformations of epoxides and other intermediates, and (C) synthesis of terpenoids and phthalates.