Artisanal stone-mining impacts on leaf microstructures and biochemical parameters of some plants at Eziani, Nsukka, Nigeria

Plants are determinant of air quality and are useful in mitigating air pollution and biomonitoring of the pollution stresses.  Present study assessed the effect of stone-mining dust accumulation on foliar parameters and air pollution tolerance index (APTI) of five plants (Annona senegalensis, Bridelia ferruginea, Ficus capensis, Nauclea latifolia and Protea madiensis) commonly growing around an artisanal stone-mining site at Eziani Nsukka and Botanic Garden of the University of Nigeria, Nsukka, the control. Dust load was estimated gravimetrically. The foliar analysis carried out on the epidermises was obtained by clearing method and studied under microscope and all photomicrographs were taken with Moticam Camera 2.0 attached to the microscope. Biochemical parameters and APTI were determine following standard methods.   Dust accumulated on polluted plant leaves was high and resulted in distortion and deformation of the epidermal and guard cells. The cells appeared stretched and broken compared to the control plants. Quantitative stomatal indices such as length, width, size and density were also significantly affected by dust pollution. Polluted plants showed increase in ascorbic acid, reduction in pH values, relative water content and total chlorophyll content, and produced low tolerance index than the controls. Highest and lowest APTI were found in A. senegalensis and B. ferruginea. At polluted site, A. senegalensis had APTI (17.14 ± 0.24) and B. ferruginea had (11.38 ± 0.07) which differed significantly from the APTI of A. senegalensis (18.92 ± 0.24) and B. ferruginea (13.49 ±0.28) at the control site. A. senegalensis was the most tolerant to air pollution while other plants were intermediate tolerant plants. The abnormalities in artisanal stone-mining plants may be due to prolonged exposure to dust. However, ability of the plants to tolerate air pollution makes them potential good environmental cleaners and as such, are recommended as choice plants around stone-mining and dust-polluted sites for safer environments and better health of both miners and the inhabitants.