Chromium (VI) accumulation in different plant organs of Lacy Phacelia (Phacelia tanacetifolia Benth.): Implications for phytoremediation

Lacy Phacelia (Phacelia tanacetifolia Benth.) is a very beneficial nectar source for honeybees, contributing to their foraging activities and honey production. Chromium (Cr) is a toxic metal that may be taken up by plants through roots and accumulates in different organs. The accumulation of Cr in nectars can affect nectar production and subsequently bee health. This study investigated whether Lacy Phacelia accumulates Cr in different plant organs. A pot experiment was conducted under controlled conditions with five different Cr concentrations (0, 5, 10, 20 and 40 mg kg^{- 1}). The plants were grown for 110 days, and Cr, manganese (Mn) and iron (Fe) contents accumulated in different plant organs (root, leaf, stem, flower and stamen) were examined. Similalry, the impact of different Cr concentrations on plant height, stem diameter, and dry weights of root, stem, leaf, and flower was also recorded. The highest and lowest Cr(VI) accumulation was recorded in roots and flowers respectively. The mean Cr concentration in different organs was, i.e., root (7.13 mg kg^{- 1}) > leaf (3.25 mg kg^{- 1}) > stem (2.53 mg kg^{- 1}) > flower (1.62 mg kg^{- 1}) = stamen (1.54 mg kg^{- 1}). Translocation factor was < 1 in all Cr concentrations, indicating that it is not a suitable candidate for phytoremediaiton. The Mn concentration in different organs generally increased with increasing Cr concentrations, while Fe concentration, plant height, and dry weights of root, stem, and flower decreased. Lacy Phacelia should not be grown on Cr-contaminated soils for agricultural purposes or phytoremediation. The accumulation of Cr in the stamens may possibily contaminate bee products obtained through the bees collecting nectar from Lacy Phacelia grown on Cr-contaminated soils. The transfer of Cr from Lacy Phacelia plants grown on Cr-contaminated soils to honeybee and honey products should be investigated in future studies to safeguard honeybee health.