Chromium toxicity in Coleus amboinicus Lour.: morphological, physiological, and ultrastructural changes

Intensive industrial activities have led to increased chromium concentrations in soil and water, posing significant environmental and health risks due to its cytotoxic and carcinogenic nature. Present study is aimed to elucidate the sequel of chromium toxicity on structural and functional properties of Coleus amboinicus Lour. The experimental set up consisted of cultivation of rooted propagules of C. amboinicus in nutrient solution artificially contaminated with 150 µM potassium dichromate in which the plants exhibit visible growth retardation and maintaining their survival. Structural alterations of plants treated with Cr studied in terms of anatomy as well as tissue ultra structure using Scanning Electron Microscopy. Presence of Cr was observed in the form of stained masses in the sections of root, stem and leaf, indicating the translocation of Cr to the plant body. Qualitative and quantitative detection of elemental composition of both control and experimental were made by energy dispersive X-ray analysis. Cr influence the macro and micro-elemental distribution in plant tissues. Plants exhibited structural modifications like increase in the trichomes of leaves and stem of Cr treated C. amboinicus. Presence of cell structural distortions and Cr deposit inclusions in the inner parenchyma cells were distinct. Cr stress induced the reduction in pigment content and metabolites like proteins, proline, phenol and malondialdehyde marked a significant increase. The low BCF and TF values, combined with its coping mechanisms for metal stress, indicate that C. amboinicus lacks the potential for chromium hyperaccumulation.