Background:Bisphenol A(BPA)and diisobuthylphthalate(DIBP)have found wide applications as plasticizers;however,they are covalently bonded to materials and are subsequently leached into the environment.Methods:This study evaluated the effects of BPA,DIBP and mixtures of BPA and DIBP on the antioxidant enzymes[superoxide dismutase(SOD),peroxidase(POD)]activities using standard methods and DNA profile of earthworm(Hyperiodrilus africanus)using randomly amplified polymerase chain reaction(RAPD-PCR)method.A total of 2 kg soil samples collected from FADAMA Farm,Federal University of Agriculture,Abeokuta were spiked to obtain 1,2.5,5 and 10 ppm of BPA,DIBP and mixtures of BPA and DIBP.Earthworms were exposed to the unpolluted and spiked soil samples and were collected on the 7th and 14th day for SOD,POD and DNA analysis.Results:SOD activity was more pronounced at 5 and 10 ppm concentrations.POD activity was increased in all concentrations,including the control,meanwhile POD activity induced by BPA and DIBP was significantly higher(p<0.05)at 10 ppm compared to other concentrations.RAPD-PCR analysis revealed varying DNA fragment lengths due to excessive oxidative stress generated by the treatments,resulting in DNA damage.BPA and DIBP mixtures generated more fragments of DNA on day 14 than other treatments.Conclusions:This study established that antioxidant activity decreases with exposure time to BPA and DIBP,while DNA damage increases with exposure time.
Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by silicon (Si) with respect to salt tolerance. The experiment was undertaken consisting of two treatments with 3 replicates: (i) 120 mmol@L?1 NaCl alone (referred to as Si(NaCl+), (ii) 120 mmol@L?1 NaCl + 1.0 mmol@L?1 Si (as potassium silicate) (referred to as Si+NaCl+). Plant root tips were harvested for microanalysis using an energy dispersive X-ray microanalyzer (EDX) 30 d after transplanting. Higher Cl and Na X-ray peaks were recorded in the root epidermal, cortical and stelar cells of roots for the treatment Si(NaCl+ with the majorities of Na and Cl being accumulated in epidermal and cortical cells, while relatively low K peaks were observed regardless of the barley cultivars used. By contrast, considerably higher K peaks were detected in the epidermal, cortical and stelar cells of the roots for the treatment Si+NaCl+, but lower Cl and Na peaks were also observed for this treatment with both Na and Cl ions being evenly distributed in the epidermal, cortical and stelar cells. These findings directly support our previous finding, which showed that Si depressed the uptake of sodium but enhanced the uptake of potassium by salt-stressed barley. We believe that one of the possible mechanisms involved in Si-enhancement of salt tolerance in barley is attributed to the Si-induced changes in the uptake and microdistribution of mineral ions in plants.
