Southern Nigeria is a major cassava producing area that has been subjected to air pollution from increasing industrial activities and population explosion in the coastal towns and cities. The level of pollution is not expected to change drastically in the immediate future. Investigations were carried out to study the changes in the morphology, survival, growth and yield of TMS 96/1672 cultivar of cassava Manihot esculenta (Crantz) to simulated acid rain. The plants were exposed to simulated acid rain of pH 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0 (control) respectively. Simulated acid rain induced morphological changes including chlorosis, early leaf senescence, necrosis, leaf abscission, leaf folding and death. Plant height, leaf area, fresh weight, dry weight, relative growth rate, chlorophyll content and the harvest index was the highest at pH 7.0 (control) and significantly (p<0.05) decreased with increasing acidity. The results indicates that TMS 96/1672 cultivar of Manihot esculenta exhibited growth stimulation at low acidity of pH 2.0 and it is likely to be retarded in future due to rapid and uncontrolled industrialization.

The rain forest belt in Southern Nigeria is potentially susceptible to problems related to acid rain because of the increase in the consumption of petroleum oil products, such as diesel, gasoline and coal, used to produce energy for different sectors of the economy. The effect of simulated acid rain on the plant growth component of cowpea, Vigna unguiculata was studied.

This study was designed to investigate the effect of crude oil pollution on the morphology, growth and heavy metal content of maize (Zea mays L.) by analyzing selected physicochemical parameters and heavy metals in soil samples and plant parts using standard field experimental methods. Results from this study show that all the growth parameters of Zea mays planted in the polluted soil were adversely affected by crude oil pollution. The highest mean height for treatments 50 ml, 100 ml and 150 ml were 33.54 cm, 31.34 cm and 27.44 cm respectively while that of the control was 87.58 cm. The pH of the soil increased as the volume of the crude oil increased. Chlorophyll content of the Zea mays leaves reduced with increase in the volume of crude petroleum. Of the plant parts examined, root had the highest content of chromium (Cr) with 0.22 ppm (150 ml), nickel (Ni) with 0.46 ppm (150 ml), lead with 0.06 ppm (150 ml) and cadmium (Cd) with 0.02 ppm (150 ml) while the highest copper (Cu) value of 0.28 ppm (150 ml) was recorded in the leaves (150 ml). Heavy metals concentration significantly increased (P < 0.05) with the increase in volume of crude oil pollution. This study has shown that crude oil polluted soil brings about reduction in the growth, yield and leaf chlorophyll of maize plant. Coupled with increasing heavy metal concentration, this could lead to scarcity and safety concerns in maize consumption in areas impacted by crude oil pollution.

Toxicity of heavy metals above the normal threshold constituted a threat to humanity and biodiversity. Phytoremediation has become a novel and emerging technology of cleaning polluted sites through the use of plants. A study was carried out at the screen house located besides the academic building of the Federal University of Technology, Akure, Nigeria, to evaluate the phytoremediation potential of Amaranthus hybridus L. (Caryophyllales: Amaranthaceae) on a brewery effluent. The parameters investigated include chlorophyll content, the concentration of the metals in the plants, Bioconcentration Factor (BCF) and Translocation Factor (TF) was studied. Three different concentrations of brewery effluent were used at 50, 100 and 150 mL/5 kg of soil, respectively. The results of this study under controlled conditions indicate that effluent application increased chlorophyll content, reduced plant height and stem girth. Three heavy metals (iron, cadmium, and chromium) were detected in the shoots and leave of both plants after the experimental period. The translocation factor (less than 1) and bioaccumulation factors (greater than 1) were below the permissible limits hence indicating a possible bio-accumulator for the heavy metals investigated. Brewery effluent reduce the plant height but increase the leaf area of A. hybridus under high concentrations which possibly suggest an adaptive mechanism developed by the plant under stress.

A screen house study was conducted to evaluate the effect of gemstone mining on the growth behaviour of maize Zea mays L. A completely randomized design involving two samples of soil (FUTA (control) and Ijero (mined soil)), two varieties of the maize (TMZ234 and Sammarz 39) was used. The seeds were sown into experimental pots containing the soils and the whole set up was left for eight weeks. Growth parameters (plant height, leaf area and stem girth were taken at a weekly basis up till the eight week. Eight heavy metal (Cd, Cu, Cr, Fe, Ar, Zn, Pb and Ni) concentration in the soils, roots and shoots of the plants was determined at the end of the experiment using atomic absorption spectrophotometer. Baseline data indicates that the mined soil is acidic (pH 4.12), with low organic carbon (0.92), low organic matter (1.59) and low total nitrogen (0.76). Results obtained from this study show that all growth parameters were negatively affected by the mined soil. Plant height was significantly higher in the control varieties (82.28 and 40.46, respectively) when compared with the mined soil varieties (30.5 and 29, respectively) at 8 weeks after planting (WAP). Leaf area also followed the same pattern with varieties grown on control soil having significantly higher leaf area (48.22 and 25.22, respectively) than varieties grown on mined soil (19.08 and 19, respectively). Stem girth of variety TMZ234 in control soil was also significantly higher than the rest (2.24 as against 1.68, 1.5 and 1.74). Heavy metals concentration in the soil, shoot and root of the plants grown in mined soils were all higher than in those grown on control soils. In the soil, Cr, Ni and Pb were 0.24, 0.15, 0.10 and 0.20, 0.13, 0.10, respectively, in both varieties grown on mined soils as against 0.03, 0.01, 0.00 and 0.03, 0.08, 0.00 for Cr, Ni and Pb, respectively, for both varieties grown on control soils. Bioaccumulation and translocation factors for the metals were less than 1 in all the soils except for Ni which had BCF of 2.80 and 6.90 for both varieties grown in the control soils. The results from this study has shown the negative effect of gemstone mining activities on the growth of two varieties of Zea mays.