Growth, Biomass and Nickel Accumulation Assessments of Amaranthus hybridus and Celosia argentea grown in Nickel Contaminated Soil

Agricultural lands used in the cultivation of vegetables are prone to contamination with heavy metals of different degrees, which could impact significantly the physiological performance of the plants, and amassing of these metals. This study was conducted at the botanical garden of the Department of Plant Biology, University of Ilorin, to appraise the effects of nickel contamination on identified growth parameters of Amaranthus hybridus and Celosia argentea, their biomass and nickel accumulated in the vegetables. The treatment comprised of varying concentrations of nickel (100, 200 and 400 mg/kg) used to pollute soil, while control soil were not contaminated. Growth parameters (stem length and girth, leaf length and breadth, number of leaves; and wet and dry weights) were evaluated. Elemental concentrations of nickel in both plants were determined using Atomic Absorption Spectrophotometer. Celosia argentea planted on soil polluted with 100 mg/kg of nickel recorded peak values for leaf length and breadth and number of leaves at 3 weeks after transplanting (WAT) (4.77 cm, 2.68 cm and 11.83) respectively. Amaranthus hybridus grown on untreated soil recorded the maximum stem length at 1, 2 and 3 WAT (3.50, 3.80 and 5.15 cm) respectively. Celosia argentea and Amaranthus hybridus grown on soil polluted with 200 and 100 mg/kg of nickel recorded the highest dry weights of 0.06 and 3.87 g respectively at 1 WAT. The highest values of nickel concentrations in Celosia argentea and Amaranthus hybridus were recorded in those planted in soil polluted with 200 mg/kg of nickel (3.90 and 3.87 mg/kg respectively). The study revealed that nickel pollution may promote the performance of Celosia argentea and Amaranthus hybridus when cultivated below the threshold of 200 mg/kg which has been established in this study to also enhance build up of nickel in the tissues of the botanicals.