Cadmium Accumulation and Its Effects on Physiological Characteristics of Arundo Donax L
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Global NEST Journal, Vol 21, No 4, pp 423-429 Copyright© 2018 Global NEST Printed in Greece. All rights reserved Cadmium accumulation and its effects on physiological characteristics of Arundo donax L. in a simulated wetland Pu G.1*, Zeng D.1, Mo L.1, Liao J.1, Xu G.1, Huang Y.2 and Zhang C.3 1Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, Guangxi Institue of Botany, Guangxi Zhuang Autonomous Region and Chinese Academy of Sciences，85 Yanshan Street, Yanshan District, Guilin, 541006, P.R. China 2Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Guangxi Teachers Education University, Nanning, 530001, P.R. China 3School of Resources, Environment and Materals, Guangxi University, Nanning, 530004, P.R. China Received: 11/01/2018, Accepted: 04/09/2018, Available online: 26/09/2018 *to whom all correspondence should be addressed: e-mail: [email protected] https://doi.org/10.30955/gnj.002580 Abstract have been well studied, some questions still remain unaddressed (He et al., 2017). A simulated wetland experiment was used to investigate the effect of cadmium (Cd) on the growth of Arundo In general, excess Cd accumulation in plants can donax, as well as its photosynthetic characteristics and profoundly interfere with a series of physiological antioxidant enzyme activities. Cd accumulation in the processes such as uptake, transport, and assimilation of order of stem < roots < leaves increased gradually with mineral nutrients and photosynthesis, and thereby lead to increasing Cd concentrations. Due to the higher transport nutrient deficiency, disruption of ATPase activity, of Cd, its accumulation in the aboveground parts of decrease of photosynthesis, inhibition of various enzyme A. donax was nearly 2 times that in belowground parts. activities, induction of oxidative stress and reduce There were no differences in physiological parameters, genotoxicity (Metwally et al., 2005; Imran et al., 2008; such as the relative chlorophyll content (SPAD), the Johna et al., 2009; Chen et al., 2012; Alshaal et al., 2015; potential (Fv/Fm) or effective (Y) photochemical efficiency Çikili et al., 2016; Moussa et al., 2016; Shahid et al., 2017; of PSII, and photosynthetic rate (Pn). There were slight He et al., 2017). These studies also suggested that the changes in transpiration rate (Tr), intercellular CO2 accumulation of and tolerance to Cd in plants varied concentration (Ci) and stomatal conductivity (Gs). greatly among plant species (Çikili et al., 2016), cultivars The activity of superoxide dismutase (SOD) was stimulated (Chen et al., 2012) and genotypes (Imran et al., 2008). by Cd treatments, and the decrease in catalase (CAT) was For example, Metwally et al. (2005) reported that, in the compensated by the induction of peroxidase (POD) selected ten genotypes of Pisum sativum L., Cd toxicity suggesting these two enzymes function concurrently to expression has both similarities and distinct features. In remove H2O2. These results indicate that despite the addition, some important environment factors (such as oxidative stress involved in the mechanism of Cd toxicity soil PH, organic matter and microorganisms) have associated with the high transport of Cd in A. donax, its governed the sorption/desorption processes and chemical photosynthetic system was not harmed. This suggests a speciation of Cd in soils (Sappin-Didier et al., 2005; Liu strong tolerance of this species to increased Cd pollution et al., 2017). Obviously, plant species in different and its potential use for phytoremediation purposes in environments would show a wide range of plasticity in Cd wetland environment. tolerance. Therefore, it is important to understand the response of plants to Cd in different environments, and Keywords: Arundo donax, antioxidant enzymes, then carry out phytoremediation. chlorophyll fluorescence, gas exchange parameters. Phytoremediation is a growing field of research in 1. Introduction environmental studies due to the advantages of its Cadmium (Cd) is a typical, heavy metal pollutant with high environmental friendliness, safety, and cost-effectiveness toxicity and high solubility in water, soil and sediments; (Malik, 2007; Mirza et al., 2010; Elhawat et al., 2014). hence, it poses a serious environmental concern (Pinto Although hyperaccumulation as a tool for cleaning up et al., 2004; He et al., 2017). Cadmium, at trace levels, can metal contaminated environments has been widely undermine ecosystem functioning and human health (Zhi suggested (Leitenmaier and Küpper, 2013), the process is et al., 2016). Therefore, how to effectively control often linked with slow growth rate and low biomass cadmium pollution and restore the ecological production. As a result, net removal of metals via environment is one of the most urgent environmental phytoextraction is quite limited (Elhawat et al., 2014). problems. Although the toxicity effects of Cd2+ in plants Therefore, the use of low-cost, fast-growing indigenous Pu G., Zeng D., Mo L., Liao J., Xu G., Huang Y. and Zhang C. (2018), Cadmium accumulation and its effects on physiological characteristics of Arundo donax L. in a simulated wetland, Global NEST Journal, 21(4), 423-429. 424 PU et al. plants with efficient biomass production, such as giant 2013) and metals polluted soil (Papazoglou et al., 2005; reed (Arundo donax L.), is highly desirable for Miao et al., 2012; Shabana et al., 2012; phytoremediation of metal contaminated sites and El-Ramady et al., 2014; Liu et al., 2017). However, there is waters. A. donax is a perennial rhizomatous grass limited data on the physiological responses of A. donax to (Poaceae family) native to the freshwater regions of Cd stress in wetland environment and the capacity of Eastern Asia. Because of its large biomass, high A. donax to aid in the recovery of Cd-contaminated adaptability and unique physiological features, it readily wetlands. absorbs and concentrates toxic chemicals from Thus, our objective was to monitor the uptake and contaminated soil (Elhawat et al., 2014). Furthermore, translocation of Cd in A. donax and to investigate A. donax has gained a broad reputation as a good plant growth responses, photosynthetic characteristics candidate for use in energy production, the paper industry, and antioxidant enzyme activities of A. donax under biofuels and the development of building materials (Nassi different levels of Cd stress. et al., 2010; Elhawat et al., 2014). As a C3-grass, A. donax shows high photosynthetic rates and unsaturated 2. Material and methods photosynthetic potential compared to C4 plants (Alshaal et al., 2015). Previous studies have shown that, under high 2.1. Test soil and plant levels of cadmium, arsenic, plumbum, chromium and nickel stress, A. donax can growth and remain healthy, A mixed medium of soil and water, collected from the with its photosynthetic system unharmed (Alshaal et al., garden of the Guangxi Institute of Botany, was used to 2015). This ability is based on its high antioxidant capacity, simulate the wetland environment. The basic which allows its antioxidative enzymes to catalyse the physiochemical properties of soil and water were - dismutation of highly reactive O2 into non-toxic forms, analyzed (Table 1). The test soil (5 kg) was placed in plastic such as O2 and H2O (Miao et al., 2012). These results pots (base diameter × height × outside diameter: indicate that metals, such Cd, Ni, As, Cr and Pb, are most 26 cm × 75 cm × 38.5 cm) and the volume of the likely sequestered in a very effective manner within the water was always maintained at 4 L above that of the soil A. donax plant, thus providing potent protection of the (3.9 ± 0.3 cm). Test soil in each pot was homogeneously photosynthetic machine. There are several works sprayed with aqueous solutions containing 0.00, 0.01, concerning the promising phytoremediation potential of 0.025, 0.05, 0.125 and 2.5 mg Cd per liter of water A. donax as applied to bauxite residue/red mud that were prepared by dissolving salts of CdCl2·2.5H2O. (Alshaal et al., 2013), urban wastewater and saline The soil-grown plants were obtained from young lands (Williams et al., 2008; Mirza et al., 2010; Zema et al., meristematic buds in tissue culture grown in sterile 2012; Elhawat et al., 2014), marginal lands (Nassi et al., aqueous medium. Table 1. Basic physiochemical properties of tested soil and water pH TN (g kg-1) TP (g kg-1) TK (g kg-1) AN (mg kg-1) AP (mg kg-1) Cd (mg kg-1) Soil 6.50 1.167 0.80 0.78 181.26 3.72 0.01 -1 -1 2+ -1 2+ -1 - -1 -1 pH DO (mg L ) SpC (µs cm ) Ca (mg L ) Mg (mg L ) HCO3 (mmol L ) Cd (µg L ) Water 7.38 1.56 235.00 53.00 7.63 1.70 ˂0.001 Note: TN, total nitrogen; TP, total phosphorus; TK, total potassium; AN, ammonia nitrogen; AP, available phosphorus; DO, dissolved oxygen; SpC, specific conductance (6 ml per 1.0 g of soil, v/v: 1:1:1) for 1 hour at 95 °C. The 2.2. Culture and harvest of plant plant samples were digested in nitric acid by microwave reaction system (Multiwave PRO, Austria) and the A. donax was cultivated in a greenhouse with day/night temperature control settings were as follows: 5 min, temperatures of 28/20 °C and a relative humidity of 65%. 95 °C; 10 min, 180 °C; 45 min, 200 °C. (200 mg in 3 mL During the growing period of A. donax, the volume of the conc. HNO3). Following digestion all the samples were water was always maintained at 4 L above that of the soil determined by inductively coupled plasma-mass (3.9 ± 0.3 cm). After four months of cultivation, spectrometry (ICP-MS, PerkinElmer Instruments, USA). photochemical efficiency, photosynthetic gas exchange The phytoextraction ability of A. donax L. plants was parameters and antioxidant enzymes activities were assessed using a translocation factor (TF) and a determined for each of the plants.