Background: Phytoremediation is determined as an emerging green technology suitable for the safe remediation and restoration of polluted terrestrial and aquatic environments. In this study, the assessment of an ornamental plant, Vinca rosea L., as a phytoremediator of crude oil in polluted soils was conducted. In an open greenhouse experiment, plants were raised in sandy-clayey soils treated with 1, 3, 5, and 7% oil by weight. The experiment was conducted over 5 months.
Results: Total petroleum hydrocarbon (TPH) degradation percentage by V. rosea after a 5-month growth period ranged from 86.83 ± 0.44% to 59.05% ± 0.45% in soil treated with 1 and 7%, respectively. Plants raised in polluted soils demonstrated a dramatic reduction in germination rates, in addition to growth inhibition outcomes shown from decreased plant height. An increase in branching was observed with an increase in oil pollution percentages. Moreover, the phytomass allocated to the leaves was higher, while the phytomass witnessed lower values for fine roots, flowering and fruiting when compared to the controls. Apart from the apparent morphological changes, there was a decrease in chlorophyll a/b ratio, which was inversely proportional to the oil pollution level. The contents of carotenoids, tannins, phenolics, flavonoids, and antioxidant capacity were elevated directly with an increase in oil pollution level. The start codon-targeted (SCoT) polymorphisms and inter-simple sequence repeat (ISSR) primers showed the molecular variations between the control and plants raised in polluted soils. The genetic similarity and genomic DNA stability were negatively affected by increased levels of crude oil pollution.
Conclusions: The ability of V. rosea to degrade TPH and balance the increased or decreased plant functional traits at the macro and micro levels of plant structure in response to crude oil pollution supports the use of the species for phytoremediation of crude oil-polluted sites. The genotoxic effects of crude oil on V. rosea still require further investigation. Further studies are required to demonstrate the mechanism of phenolic, flavonoid, and antioxidant compounds in the protection of plants against crude oil pollution stress. Testing different molecular markers and studying the differentially expressed genes will help understand the behavior of genetic polymorphism and stress-resistant genes in response to crude oil pollution.
Keywords: Antioxidants; FRAP; Phenolics and flavonoids; Photosynthetic pigments; Plant growth; SCoT and ISSR markers; Tannins.
© 2022. The Author(s).