Effect of air pollutants on some heavy metals and biochemical constituents of leaves of some plants at Bangalore city: A case study

Abstract

Rapid urbanization in India has necessitated for undertaking remedial measures to minimize the alarming air pollution levels and consequent health effects. Promotion of vegetation that is tolerant to air pollutants is considered as an ecological sustainable strategy for mitigation of ill effects of particulate matters. In this regard the levels of four heavy metals viz. zinc (Zn) , lead (Pb), copper (Cu) and chromium (Cr) and its effects on antioxidants levels (Catalase activity), phytochemicals (Protein, Proline, Gallic acid) and lipid peroxidation were studied in six commonly growing plants- O.sanctum, L. aspera, L.camara, V. rosea, B. spectabilis and R. communis from polluted (Zone I) and unpolluted (Zone 2) environments of Bangalore. Mean levels of heavy metals were comparatively higher in plants from polluted environments. Mean levels of Total protein (6.57±1.71 v/s 8.35±1.27 mg/g), gallic acid (15.79 ± 22.51 v/s 22.95 ± 25.66mg/g) and Catalase activity (66.72±17.95 v/s 78.94± 15.24 mU/g) was comparatively decreased in plants from polluted sites compared to non polluted control sites. Mean Proline (3.11±0.46 v/s 2.63±0.66 mg/g) and Malonaldehyde (19.07±13.86 v/s 16.62±13.49 nmol/g) levels, indicators of oxidative stress, was comparatively increased in plants from polluted sites. Positive correlation of lipid peroxidation in leaves was observed with heavy metals copper (r=0.961, P<0.005 in control sites; r=0.881, P<0.05 in polluted sites) and chromium (r=0.792 in control sites; r=0.758 in polluted sites). Zn levels showed statistically significant (P<0.05) positive correlation with gallic acid content in plant leaves (r= 0.871 in control sites: r= 0.937 in polluted sites). Total protein content showed significant negative correlation (P<0.005) with Cu (r=-0.846) and Cr (r=-0.943) in control sites, but non-significant negative correlation in plants from polluted sites. The study revealed that plants responded to stress induced by air pollutants and produced phenolic compounds to tolerate and mitigate the oxidative stress.