Growth response and antioxidant enzyme capability of Helianthus annuus L. in lead contaminated soil under organic and urea fertilizer applications

Abstract

<p><strong>Background: </strong>Indiscriminate dumping of wastes, including heavy metals such as lead (Pb) on Nigerian soils is increasing. <em>Helianthus annuus</em> has been found to have ability to clean up contaminated soils, but with paucity of information on the effect of Pb stress on the plant’ antioxidant enzymes activities when fertilizers are applied as soil enhancers, hence this study.<strong></strong></p><p><strong>Methods: </strong>The experiment consisted of four levels (0, 400, 800, 1200 mg Pb kg<sup>-1</sup>) using [Pb (CH<sub>3</sub>COO)<sub>2</sub>.3H<sub>2</sub>O], three rates (0, 5 and 10 t ha<sup>-1</sup>) of organic and two rates (0 and 2 t ha<sup>-1</sup>) of urea fertilizers, and each treatment was replicated thrice to give a total of 72 experimental units in pot culture. Each pot contained 10 kg of sieved topsoil and arranged in a complete randomized design. The <em>H. annuus</em> seeds were sown, fertilizers were applied and stands of <em>H. annuus</em> were collected for antioxidant enzymes (SOD, CAT, POX and APX) activities determination in the roots and shoots using standard methods.<strong></strong></p><p><strong>Results: </strong>Soil<strong> </strong>pH<strong> </strong>was slightly acidic and soil texture was loamy sand. Biomass yield of <em>H. annuus </em>increased with increase in organic fertilizer, but decreased with increase in Pb contamination. There was significant (p<0.05) increase in detoxification responses in the shoots than the roots of <em>H. annuus</em> against oxidative stress caused by Pb toxicity when<em> </em>organic fertilizer was applied to soil.</p><p><strong>Conclusions: </strong>The study concluded that addition of organic fertilizer increased biomass yield and had superior enhancing detoxification responses on <em>H. annuus</em> against oxidative stress by Pb toxicity.</p>