ABSTRACT
Soil pollution with copper or arsenic is detrimental to Capsicum annuum growth. Arsenic is non-essential to plants while copper is an essential plant nutrient. Both metals are however toxic to Capsicum annuum at high concentrations. Capsicum annuum was cultivated in soil contained in bowls placed in a field and treated with arsenic and copper solutions of a concentration range of (0 ppm – 40 ppm) for 10 weeks, and the heights, girth size, leaf length and germination rates of the plants were measured within the period. Based on the results derived, the plants showed decreased growth and germination rates with increasing concentration of arsenic, and later death at conceentrations ranging from 20 – 40 ppm. Plants cultivated on copper-treated soils showed increased growth and germination rates at concentrations ranging from 5 – 25 ppm and decreased growth and germination rates at the 30 – 40 ppm concentration range. Prior to the potted field experiments, a laboratory germination analysis of C. annuum seeds was conducted during which seeds were placed in petri dishes, some containing arsenic solutions at concentrations of 0 – 40 ppm and others containing copper solutions at concentrations of 0 – 40 ppm, and left to germinate. The radicle and plumule lengths of the germinating seedlings were measured, as well as the number of germinated seeds for each concentration of metal in solution. The results of the experiment showed a decrease in germination rate with increasing concentration of arsenic, and a sigmoid germination rate with increasing copper concentration, that is, an increase in germination rate of seeds within the 0 – 25 ppm range of copper concentration, and a decrease in germination rate at the range of 30 – 40 ppm. Copper is essential to plants for growth, but inhibits lateral root growth in C. annuum and other plants at high concentrations, since it is a trace plant element, that is, it is required by plants in small amounts for a healthy metabolism. Arsenic at high levels induces stress in plants by causing the production of free radicals which invariably cause lipid peroxidation and destruction of plant cells and, ultimately, the death of plants. Arsenic accumulation in plants also leads to the overproduction of stress proteins in plants. Stress protein overproduction impedes seed germination and plant growth. Hence, soils polluted with copper and arsenic are not favourable to C. annuum growth and development.
