Ceylon Journal of Science 46(2) 2017: 39-48 DOI: http://doi.org/10.4038/cjs.v46i2.7428 RESEARCH ARTICLE Performance and remediation potential of Chrysopogon aciculatus (Retz.) Trin. grown in nickel-contaminated soils S. Oyedeji1,*, O.O. Agboola2, K.S. Olorunmaiye1 and O.M. Olagundoye1 1Department of Plant Biology, University of Ilorin, Ilorin, 240003 Nigeria 2Department of Botany, University of Lagos, Akoka, Lagos, Nigeria Received:26/08/2016-; Accepted: 01/04/2017 Abstract: The performance and remediation potential properties such as ductility, malleability, of Chrysopogon aciculatus (Retz.) Trin. grown in conductivity, cation stability, and ligand nickel contaminated soil was assessed. Six specificity. They are characterized by relatively contamination regimes of 50, 100, 150, 200, 250 and high density and high relative atomic weight 300 mg Ni/kg soil and control were set up in three with an atomic number greater than 20 (Raskin et replicates each. Chrysopogon aciculatus established from tillers were allowed to grow six weeks before al., 1994). Some of the heavy metals such as Cd, data collection started. Data were collected weekly on Pb and Hg are toxic to living organisms while ground cover, chlorophyll index and concentrations, heavy metals such as Co, Cu, Fe, Mn, Mo, Ni, V, total carotenoids and yield at maturity. Soil Ni and Zn are required in trace amounts for proper concentrations were determined at pre-plant and post- functioning of the cell (Tchounwou et al., 2012). harvest stages. Ground cover was not significantly th different among the treatments. Ni contaminated Nickel, the 24 most abundant element in treatments had the highest chlorophyll index at 10 and the Earth’s crust, comprise about 3% of the 12 weeks after planting. Chlorophyll a concentration composition of the earth. As a member of the was highest in 150 mg Ni/kg treatment (T150) at 12 transition metal series, it is resistant to corrosion WAP. T150 also had the least Chlorophyll b by air, water and alkali, but dissolves readily in concentration at 12 WAP. T200 and T250 had low total dilute oxidizing acids (Young, 1995). Nickel is a carotenoids at 12 WAP. Dried shoot and root from nutritionally essential trace metal for at least T300 had the highest Ni concentrations. Grass grown in several animal species, micro-organisms and T200 accounted for the highest soil Ni uptake (% Ni remediated) with 96.4%. Soil Ni contents were plants, and therefore either deficiency or toxicity reduced in all treatments. It is concluded that C. symptoms can occur when too little or too much aciculatus can tolerate Ni contamination in soil and Ni is taken up, respectively. Although Ni is therefore can be used as a turf grass on Ni polluted omnipresent and vital for the physiological soils. functioning of cells in many organisms, concentrations in some areas from both Keywords: Contamination, heavy metal, performance, anthropogenic release and naturally varying Port Harcourt grass, remediation, tolerance. levels may be toxic (McGrath and Zhao, 2003). High Ni concentration in the soil affect INTRODUCTION germination of seeds, retard root and shoot, decrease branching and luxuriance, deform Heavy metals are naturally present in the soil but various plant parts including flower, decrease geologic and anthropogenic activities may biomass production, induce leaf spotting, disturb increase their concentrations to levels that are mitotic root tips, and produce Fe deficiency that harmful to both plants and animals (Raskin et al., leads to chlorosis and foliar necrosis. 1994; Chibuike and Obiora, 2014). Some of Additionally, excess Ni also affects nutrient these activities include mining and smelting of absorption by roots, impairs plant metabolism, metals, burning of fossil fuels, use of fertilizers inhibits photosynthesis and transpiration, and and pesticides in agriculture, production of causes ultrastructural modifications (Ahmad and batteries and other metal products in industries, Ashraf, 2011). Soluble Ni compounds are often sewage sludge, and municipal waste disposal absorbed by plant roots passively (through a (Alloway, 1995; Shen et al., 2000). Heavy cation transport system) while chelated Ni metals are elements that exhibit metallic compound are taken up through active-transport- *Corresponding Author’s Email: [email protected] 40 Ceylon Journal of Science 46(2) 2017: 39-48 mediated means, using transport proteins such as and Chattopadhyay, 2005). The plant is permeases. Insoluble Ni compounds primarily commonly called lovegrass (English) and Port enter root cells through endocytosis. Once Harcourt grass (Nigeria). It is popular for its absorbed by roots, Ni is easily transported to good turf, especially with low mowing (Royal shoots via the xylem through the transpiration Botanic Gardens, 2005). It is usually found in stream and can accumulate in neonatal parts such sunny, dry, exposed areas such as roadsides, as buds, fruits, and seeds (Ahmad and Ashraf, lawns, pasture, river banks and water courses 2011). (Noltie, 2000). The grass is fairly drought tolerant (FAO, 2016), persisting almost Chronic exposure to Ni has been connected throughout the year and with great potentials to with increased risk of lung cancer, cardiovascular spread quickly over open areas using its creeping disease, neurological deficits, developmental rhizomes. It can tolerate grazing, mowing and deficits in childhood and high blood pressure trampling by animals (Kabir and Nair, 2009). (Chervona et al., 2012). Therefore, the Ambasta and Rana (2013) identified C. cultivation of crops in Ni-contaminated sites is aciculatus as a good soil binder that prevents soil unsafe, as the metal can be re-introduced into the erosion and difficult to eradicate when fully food chain (Ahmad and Ashraf, 2011). established. Oyedeji et al. (2014) assessed the Considering the adverse effect of Ni pollution in performance of C. aciculatus for turf in a field the environment, the need to for remediation trial and reported the species’ adaptation to low should be emphasized. mowing. Documentation on the heavy metal Remediation of metal-polluted soils by uptake by C. aciculatus is scarce. However, physical and chemical methods such as Garbisu et al. (2002) identified features solidification, stabilization, soil washing and including rapid growth rate, high biomass, and flushing are often expensive and may render the profuse root system in C. aciculatus which is soil unsuitable for plant growth (Marques et al., shared by most phytoextractors. 2009). Biological remediation using plants Although new species are added to the list (phytoremediation) and/or micro-organisms is of grasses suitable for phytoremediation, the found to be an useful application (Chaney et al., information on remediation potentials of 1997; Glass, 1999). Although heavy metals Chrysopogon aciculatus is scarce. The present cannot be degraded during phytoremediation, study aims to bridge this gap by assessing the they are transformed from one organic complex performance and remediation potential of or oxidation state to another. Due to a change in Chrysopogon aciculatus grown in nickel their oxidation state, heavy metals can be contaminated soil regimes. transformed into either less toxic, easily volatilized, more water soluble (and thus can be MATERIALS AND METHODS removed through leaching), less water soluble (which allows them to precipitate and become Experimental design and set-up easily removed from the environment) or less A pot experiment was conducted in the screen bioavailable (Garbisu and Alkorta, 1997; Garbisu house located in the Botanical Garden, and Alkorta, 2003). University of Ilorin, Ilorin, Nigeria. Ilorin lies Turf grasses have been used in remediating within the southern guinea savanna. The soils are metal-polluted soils (Jadia and Fulekar, 2008; lateritic consisting of three layers classified as Danh et al., 2009; Zhang et al., 2010; Subhashini Luvisols or Alfisols. The predominant soil in the and Swamy, 2014) and notable species including University estate is loamy sand with dark greyish Festuca arundinacea (tall fescue), Spartina brown (5YR3/2) colour (Ogunkunle et al., 2016). patens (salt meadow cord grass), Eremochloa The soil used for the experiment was ophiuroides (centipede grass), Buchloe collected from the University Botanical Garden dactyloides (buffalo grass) and Cynodon (N 08° 28’ 53.3’’, E 04° 40’ 28.9’’). The dactylon (Bermuda grass) have been tested for collected soil was air-dried for 7 days and sieved their metal-remediating potentials (Qu et al., using a 2 mm mesh to remove the debris. The 2003; Rathi et al., 2011). soil was homogenized before packing into the Chrysopogon aciculatus (Retz.) Trin. is a planting pots. A sample of 7 kg each of the perennial grass with creeping rhizomes (Paria sieved soil were weighed into plastic pots (0.40 m × 0.40 m × 0.25 m, length by width by depth) Oyedeji et al. 41 perforated (to allow aeration) and underlaid with The concentrations of chlorophylls a, b and total plastic trays (to collect and return percolates back carotenoids were also measured. Chlorophyll to the soils). Nickel contamination levels were index was determined using Atleaf chlorophyll created using anhydrous nickel chloride (NiCl2). meter (FT Green LLC, USA). Chlorophyll a, b Six contamination levels, 50, 100, 150, 200, 250 and total carotenoids were determined by and 300 mg Ni per kg soil were prepared and soaking 25 mg fresh leaf samples in 7 ml of denoted as T50, T100, T150, T200, T250 and T300 100% acetone (Analytical grade) for 72 hours respectively. The control soils were without and reading the absorbance of the supernatant at Nickle (T0). All the treatments were arranged in a wavelengths of 470 nm, 645 nm and 662 nm completely randomized design and replicated (Lichtenthaler, 1987). Concentrations (in μg ml- three times. The pots were watered for a week 1) of chlorophyll a, chlorophyll b, and total with distilled water to allow the metal to fully carotenoids (xanthophyll + β-carotene) in the leaf stabilize prior to planting of the grass. extract were determined using the equations: In each pot, nine 2 cm tillers of Chlorophyll a = 11.24A662 - 2.04A645 (1) Chrysopogon aciculatus (Retz.) Trin.