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Phytoremediation of lead by a wild, non-edible Pb accumulator Coronopus didymus (L.) Brassicaceae
Abstract
Coronopus didymus was examined in terms of its ability to remediate Pb-contaminated soils. Pot experiments were conducted for 4 and 6 weeks to compare the growth, biomass, photosynthetic efficiency, lead (Pb) uptake and accumulation by C. didymus plants. The plants grew well having no visible toxic symptoms and 100% survivability, exposed to different Pb-spiked soils 100, 350, 1500 and 2500 mg kg⁻¹, supplied as lead nitrate. After 4 weeks, root and shoot concentrations reached 1652 and 502 mg Pb kg⁻¹ DW while after 6 weeks they increased upto 3091 and 527 mg Pb kg⁻¹ DW respectively, at highest Pb concentration. As compared to the 4 week experiments, the plant growth and biomass yield were higher after 6 weeks of Pb exposure. However, the chlorophyll content of leaves decreased but only a slight decline in photosynthetic efficiency was observed on exposure to Pb at both 4 and 6 weeks. The Pb accumulation was higher in roots than in the shoots. The bioconcentration factor of Pb was > 1 in all the plant samples but the translocation factor was < 1. This suggested C. didymus as a good candidate for phytoremediation of Pb-contaminated soils and can be used for future remediation purposes.
... However, in the present study, using a concentration of Pb in the range described as effective to cause significant inhibition of plants growth under hydroponic conditions (Kumar and Prassad, 2018), a significant increase in both leaf and root growth in B. auriculata was observed. Several studies have also shown the beneficial effect of Pb on plant growth, although in most cases plants were exposed to low concentrations of Pb (Sidhu et al., 2018;Batista et al., 2017;Sidhu et al., 2018). For example, in Helianthus annuus the exposure to concentrations of Pb up to 100 mg L À1 stimulated biomass production, while higher concentrations led to the opposite effect (Batista et al., 2017). ...
... However, in the present study, using a concentration of Pb in the range described as effective to cause significant inhibition of plants growth under hydroponic conditions (Kumar and Prassad, 2018), a significant increase in both leaf and root growth in B. auriculata was observed. Several studies have also shown the beneficial effect of Pb on plant growth, although in most cases plants were exposed to low concentrations of Pb (Sidhu et al., 2018;Batista et al., 2017;Sidhu et al., 2018). For example, in Helianthus annuus the exposure to concentrations of Pb up to 100 mg L À1 stimulated biomass production, while higher concentrations led to the opposite effect (Batista et al., 2017). ...
... For example, in Helianthus annuus the exposure to concentrations of Pb up to 100 mg L À1 stimulated biomass production, while higher concentrations led to the opposite effect (Batista et al., 2017). Lupinus albus did not show any toxicity symptoms when grown with 180 mM Pb (García et al., 2017) and Coronopus didymus also tolerated increasing Pb concentrations up to 2.5 mg g À1 , with a concentration-dependent enhancement of root and shoot length being observed (Sidhu et al., 2018). This positive effect was explained by the phenomenon of hormesis, the stimulatory or beneficial effect induced by low doses of metals or toxic compounds (Calabrese and Blain, 2009;Sidhu et al., 2018;Batista et al., 2017). ...
Abstrat
The uptake and distribution of Pb and the mechanisms involved in the metal tolerance have been investigated in a mine population of Biscutella auriculata. Seedlings were exposed to 125 μM Pb(NO3)2 for 15 days under semihydroponic conditions. The results showed an increase in the size of Pb-treated seedlings and symptoms of toxicity were not observed. ICP-OES analyses showed that Pb accumulation was restricted to root tissue. Imaging of Pb accumulation by dithizone histochemistry revealed the presence of the metal in vacuoles and cell wall in root cells. The accumulation of Pb in vacuoles could be stimulated by an increase in phytochelatin PC2 content. Pb did not promote oxidative damage and this is probably due the increase of antioxidative defenses. In the leaves, Pb produced a significant increase in superoxide dismutase activity, while in roots an increase in catalase and components of the Foyer– Halliwell–Asada cycle were observed. The results indicated that Biscutella auriculata has a high capacity to tolerate Pb and this is mainly due to a very efficient mechanism to sequester the metal in roots and a capacity to avoid oxidative stress. This species could therefore be very useful for phytostabilization and repopulation of areas contaminated with Pb.
... The dimension of the pots were 12 cm × 8 cm (dia x height). The pots filled with soil were kept for 7 days for maturing, and the planting was done afterward (Sidhu et al., 2018). ...
... Pot experiments were performed following a completely randomized design under greenhouse conditions (Sidhu et al., 2018). The natural soil was spiked with heavy metals salts, namely, CdCl 2 ·2.5H 2 O and Pb(NO 3 ) 2 ·H 2 O. Three replicates were setup for each of the 10 different concentration levels of the metal treatments including control. ...
Phytoremediation is gaining interest in recent years as a simple and effective strategy for heavy metal decontamination. The most straightforward strategy for successful heavy metal clean-up is searching for efficient hyperaccumulator species that grow naturally in contaminated sites. The present study, therefore, is the first detailed account of hyperaccumulator potentialities of a neglected and underutilized (NUS) species Cleome rutidosperma DC. Hydroponic screening experiment against Cadmium and Lead revealed that even at 10 mg/kg concentration, it could accumulate 42.49 mg/kg of Cd and 27.79 mg/kg of Pb in shoots while 134.71 mg/kg Cd and 491.35 mg/kg of Pb in its roots and these values were significantly higher than the control plants. This plant could efficiently accumulate as high as 639.07 mg/kg of Cd, 8726.03 mg/kg of Pb in its roots while 752.83 mg/kg Cd and 3732.64 mg/kg Pb in its shoots as evident from the pot experiments. In case of Cd, there was no significant effect of toxicity on the phytophisiological parameters. But increasing concentrations of Pb did have toxic effects on total chlorophyll content. This plant showed to have a BCF >1 in most of the tested concentrations. At the highest treatment concentration, however, both the BCF and TF was found to be greater than 1. This indicated that C. rutidosperma can accumulate as well as translocate the heavy metals to its aerial parts when the metal concentration is extremely high proving itself to be an efficient hyperaccumulator. In order to decode the chemical signals this plant may emit through the roots to cope the stress, root exudates were collected, purified and analysed through GCMS. This revealed the presence of five major compounds namely palmitic acid, linoleic acid, Oleic acid, campesterol and stigmasterol which mainly are metabolic markers for detoxification mechanisms triggered by various stresses. Therefore, based on this study, C. rutidosperma can be termed as a potent hyperaccumulator and can further be exploited for remediation of other class of environmental pollutants.
... The dimension of the pots were 12 cm × 8 cm (dia x height). The pots filled with soil were kept for 7 days for maturing, and the planting was done afterward (Sidhu et al., 2018). ...
... Pot experiments were performed following a completely randomized design under greenhouse conditions (Sidhu et al., 2018). The natural soil was spiked with heavy metals salts, namely, CdCl 2 ·2.5H 2 O and Pb(NO 3 ) 2 ·H 2 O. Three replicates were setup for each of the 10 different concentration levels of the metal treatments including control. ...
Phytoremediation is gaining interest in recent years as a simple and effective strategy for heavy metal decontamination. The most straightforward strategy for successful heavy metal clean-up is searching for efficient hyperaccumulator species that grow naturally in contaminated sites. The present study, therefore, is the first detailed account of hyperaccumulator potentialities of a neglected and underutilized (NUS) species Cleome rutidosperma DC. Hydroponic screening experiment against Cadmium and Lead revealed that even at 10 mg/kg concentration, it could accumulate 42.49 mg/kg of Cd and 27.79 mg/kg of Pb in shoots while 134.71 mg/kg Cd and 491.35 mg/kg of Pb in its roots and these values were significantly higher than the control plants. This plant could efficiently accumulate as high as 639.07 mg/kg of Cd, 8726.03 mg/kg of Pb in its roots while 752.83 mg/kg Cd and 3732.64 mg/kg Pb in its shoots as evident from the pot experiments. In case of Cd, there was no significant effect of toxicity on the phytophisiological parameters. But increasing concentrations of Pb did have toxic effects on total chlorophyll content. This plant showed to have a BCF >1 in most of the tested concentrations. At the highest treatment concentration, however, both the BCF and TF was found to be greater than 1. This indicated that C. rutidosperma can accumulate as well as translocate the heavy metals to its aerial parts when the metal concentration is extremely high proving itself to be an efficient hyperaccumulator. In order to decode the chemical signals this plant may emit through the roots to cope the stress, root exudates were collected, purified and analysed through GCMS. This revealed the presence of five major compounds namely palmitic acid, linoleic acid, Oleic acid, campesterol and stigmasterol which mainly are metabolic markers for detoxification mechanisms triggered by various stresses. Therefore, based on this study, C. rutidosperma can be termed as a potent hyperaccumulator and can further be exploited for remediation of other class of environmental pollutants.
... Measurements were taken at appropriate wavelengths. The chlorophyll a, chlorophyll b and carotenoids wavelengths used were 644 nm, 663 nm and 452 nm with spectrophotometer (Halo DB-20/DB-20S, Dynamica Company, London, UK) and final measurements were calculated by using the following formulas [17][18][19][20][21][22]. ...
... Similarly, many researchers have reported that there is a great reduction in biomass of plants, as well as the growth of plants due to metal stress in wheat, rice and Brassica napus L. [19][20][21]. In the present study, the reduction in plant agronomic characteristics with increasing concentrations of Pb was in accordance with the work done by previous researchers [20,22,23]. The inhibited agronomic traits were a prominent indication of Pb stress in plants [3,24]. ...
Lead (Pb) is one of the most toxic elements on earth. The main origins of Pb pollution are automobiles, paint and electroplating industries. Pb-induced stress has very toxic effects on plant growth and biomass. The concentration of reactive oxygen species (ROS) in plant cells significantly increases under Pb stress, which interrupts the biochemical cycles in cells and leads to cell death. Therefore, it is essential to clean up the Pb-polluted soils. Among all techniques that are used to clean soil that is metal-contaminated, the best technique is phytoremediation. The present study intends to determine the role of citric acid (CA) and glutathione (GSH) in the phytoremediation of Pb by using castor bean plants. Plant biomass was significantly reduced due to Pb stress. Lead toxicity was also harmful to the photosynthetic pigments and antioxidant enzymes activities. In reverse, the content of malondialdehyde (MDA), H2O2 concentration and electrolyte leakage (EL) were increased under Pb stress. The combined application of GSH and CA enhanced photosynthetic pigments, antioxidant enzyme activities and plant biomass and minimized MDA, H2O2 and EL under Pb stress. The amount of Pb in roots and leaves remarkably increased by the joint application of CA and GSH. The combined application of CA and GSH (5 mM + 25 mM, respectively) was proven to be beneficial compared to the control. From the present results, we can conclude that the combined application of CA and GSH promoted the phytoremediation of Pb and helped the host plant to combat Pb toxicity.
... In plant cells under heavy metal stress, it regulates high glutathione to glutathione disulphide (GSH/GSSG) ratio (Sidhu et al., 2016). Phytoremediation is a productive, nature-friendly technology adopted by plants to sequester heavy metal contaminants from polluted soils (Sidhu et al., 2018a;Sidhu et al., 2018b). Furthermore, this technology enhances the soil fertility, reinstates the wildlife and can be implemented on a wider range (Mench et al., 2009). ...
... Coronopus didymus is a promising wild plant species having the potential to withstand heavy metal contaminated soils (Sidhu et al., 2017a;2017b;2018a;.. It is autochthonous to South America and is extensively dispersed throughout the world (Yannitsaros, 1986). ...
Zinc (Zn) is a vital micronutrient for plants, but its abundance can be calamitous. In this study, a screenhouse experiment was conducted over a 6-week period to assess the effect of soil enrichment with Zn regimes (100, 250 and 500 mg kg-1) on growth, Zn accumulation, photosynthetic pigment concentration, oxidative stress markers and activities of antioxidant enzymes in Coronopus didymus. Results revealed that Zn concentration in C. didymus roots and shoots reached up to 1848 mg kg-1 DW and 1845 mg kg-1 DW at 500 mg kg-1 Zn regime, respectively. The plant growth (root-shoot length and biomass) increased, while leaf pigment concentration and soluble protein content in C. didymus tissues decreased progressively with the increased Zn regimes in the soil. At 500 mg kg-1 Zn regime, hydrogen peroxide and malondialdehyde level increased ∼219% and 111% in roots, while ∼170% and 105% in shoots, with respect to the control. Likewise, superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and glutathione reductase activities increased significantly with elevated Zn levels. Contrarily, compared to the control, CAT activity declined gradually and reached a minimum of ∼45% in roots and 12% in shoots under highest Zn regime. The results suggested that C. didymus displayed high Zn accumulation and emerged as a tolerant plant species towards Zn stress. Elevated Zn regimes provoked reactive oxygen species generation in C. didymus tissues which was effectively neutralised and scavenged by the antioxidant enzymes, thus marked its efficacy to be potentially employed in phytoremediation and reclamation of Zn-contaminated soils.
... Soil contamination by inorganic contaminants is, nowadays, a serious environmental concern with calamitous future repercussion to our ecosystem. Various anthropogenic activities like metallurgical processes, smelting, burning of fossil fuels, vehicular emissions and untreated industrial effluents have led to the release of heavy metal contaminants in soil ecosystems (Sidhu, 2016;Sidhu et al., 2018). Among the inorganic contaminants, nickel (Ni), is an indispensable micro element for plants, but high Ni concentrations in soil could prove noxious to them (Chen et al., 2009). ...
... Keeping in mind about Ni toxicity, it is obligatory to remediate Ni-contaminated soils. Various mechanical or chemical techniques have been employed to mitigate the concentration of metal contaminants present in the soils (Sidhu et al., 2018). Among all, phytoextraction is the best suitable in situ strategy used for the remediation of contaminated soils. ...
... Cd levels in T. latifolia roots were higher than those reported in T. latifolia (1230-2339 mg/Kg) [39], T. angustifolia (1213-2977 mg/Kg) [40], and T. orientalis (300-1100 mg/Kg) [41] where other culture conditions were used. Bioconcentration (BCF) and translocation (TF) factors are two indicators used to evaluate the plant's ability to accumulate heavy metals [42]. BCF refers to the metal absorbed by the plant in the roots from the substrate, while TF indicates the ability of the plant to transport the metal from roots to shoots [43]. ...
The Typha genus comprises plant species extensively studied for phytoremediation processes. Recently, Pseudomonas rhodesiae GRC140, an IAA-producing bacterium, was isolated from Typha latifolia roots. This bacterium stimulates the emergence of lateral roots of Arabidopsis thaliana in the presence and absence of cadmium. However, the bacterial influence on cadmium accumulation by the plant has not been determined. Moreover, the P. rhodesiae GRC140 effect in Cd phytoextraction by T. latifolia remains poorly understood. In this work, an axenic hydroponic culture of T. latifolia was established. The plants were used to evaluate the effects of cadmium stress in axenic plants and determine the effects of P. rhodesiae GRC140 and exogenous indole acetic acid (IAA) on Cd tolerance and Cd uptake by T. latifolia. Biomass production, total chlorophyll content, root electrolyte leakage, catalase activity, total glutathione, and Cd content were determined. The results showed that Cd reduces shoot biomass and increases total glutathione and Cd content in a dose-dependent manner in root tissues. Furthermore, P. rhodesiae GRC140 increased Cd translocation to the shoots, while IAA increased the Cd accumulation in plant roots, indicating that both treatments increase Cd removal by T. latifolia plants. These results indicate that axenic plants in hydroponic systems are adequate to evaluate the Cd effects in plants and suggest that T. latifolia phytoextraction abilities could be improved by P. rhodesiae GRC140 and exogenous IAA application.
... El factor de bioconcentración (FBC) y el factor de translocación (FT) son valores claves necesarios para estimar el potencial de una planta como fitoextractora o fitoestabilizadora (AL-Jobori y Kadhim, 2019). Según Sidhu et al. (2017), las especies de plantas con FBC > 1 y FT < 1 tienen el potencial de acumular altas concentraciones del metal en sus raíces y pueden ser utilizadas para fines de fitoestabilización. En promedio, el FBC y FT de los tratamientos (sin incluir al control) resultaron 1.69 y 0.62, respectivamente (Figuras 2 y 3). ...
El objetivo de esta investigación fue determinar la acumulación, distribución y tolerancia de cadmio (Cd) en girasol en suelos contaminados con dicho metal. La investigación consistió en dos experimentos conducidos en macetas bajo condiciones de invernadero. En el primero se probaron concentraciones de 0, 10, 15, 20 y 25 mg Cd kg-1 suelo y se evaluó la altura, producción de materia seca y concentración de Cd en raíz, tallo, hoja e inflorescencia a los 84 días. Para el segundo, la concentración fue de 20 mg Cd kg-1 suelo y se evaluó a los 35, 49, 63, 75 y 84 días la concentración de Cd en los mismos órganos. Las dosis de Cd no tuvieron efecto en la altura de planta ni en la producción de materia seca, siendo el índice de tolerancia (IT) equivalente a 1, lo que demostró su alta tolerancia por este metal. En general, se encontró que al incrementar las dosis de Cd en suelo aumentó la concentración de Cd en planta. Independiente a la época de evaluación, la raíz concentró más Cd debido a una baja translocación hacia la zona aérea. El factor de bioconcentración (FBC) fue mayor a 1 bajo las diferentes dosis de Cd. En tanto al factor de translocación (FT), este resultó menor a 1 en ambos experimentos. Según los valores del FT y FBC encontrados, el girasol se comportaría como un fitoestabilizador por debajo de 25 mg Cd kg-1 suelo.
... Increased globalization and industrialization have exposed plants to different abiotic (drought, heat, flood, cold, and metals) and biotic (bacteria, viruses, and fungi) stresses in their natural ecosystems (Nabi et al., 2019). They hamper the growth and development of plants, modulate physiological metabolism such as photosynthesis thereby disturbing global food security (Chan et al., 2016;Kudo et al., 2017;Sidhu et al., 2017Sidhu et al., , 2018Sidhu et al., , 2020 (Fig. 10.1). Among all the abiotic stresses, drought is the most complex phenomenon that limits the productivity of crops worldwide (Ullah et al., 2018). ...
Brassinosteroids (BRs) are plant steroidal hormones involved in several key physiological and biochemical processes of plants, i.e., vascular differentiation, seed germination, fertility, shoot and root growth, and flowering and also in response to environmental stresses. BRs were first identified in the pollen of Brassica napus in the early 1970s, and later during the same decade several members of the BR family were isolated from different plant species. BRs are synthesized most likely in the endoplasmic reticulum of plant cell and its synthesis is controlled by several transcription factors. External factors such as nutrient availability also influence BR biosynthesis and signaling. Moreover, BR signaling plays a crucial role in regulating diverse processes related to plant growth under normal and suboptimal growth environments. These compounds exist in free and conjugated form and their activity is highly dependent on the presence of hydroxyl group on side chain or steroid ring. Among various forms of BRs, 24-epibrassinolide (EBL) has been identified as the most active BR. During the past five decades, the BRs biosynthesis pathways have been well investigated with reverse and forward genetic techniques and nearly 60 compounds with a structure similar to that of BRs have been detected and isolated from various plant parts. These compounds were found in bryophytes (2 families), algae (6 families), pteridophytes (8 families), gymnosperms (4 families), angiosperms (35 families), and in some other plant-derivative products. This chapter discusses the initiation of research on BRs, their discovery, inhibitors, classification, and biodiversity. Moreover, it also highlights the mechanism of BR biosynthesis and signaling in plants.
... Increased globalization and industrialization have exposed plants to different abiotic (drought, heat, flood, cold, and metals) and biotic (bacteria, viruses, and fungi) stresses in their natural ecosystems (Nabi et al., 2019). They hamper the growth and development of plants, modulate physiological metabolism such as photosynthesis thereby disturbing global food security (Chan et al., 2016;Kudo et al., 2017;Sidhu et al., 2017Sidhu et al., , 2018Sidhu et al., , 2020 (Fig. 10.1). Among all the abiotic stresses, drought is the most complex phenomenon that limits the productivity of crops worldwide (Ullah et al., 2018). ...
The increase in temperature due to climate change events has increased the frequency of heat stress, resulting in severe crop yield losses globally. High temperature stress induces photosynthetic apparatus impairment leading to excessive reactive oxygen species production, which severely hampers plant growth and physiological processes. Brassinosteroids (BRs) are a group of steroid phytohormones and are known to regulate plant growth and development, and tolerance to environmental stresses such as high temperature stress. The present chapter highlights the effect of heat stress on plant growth. It further highlights the role of BR in the amelioration of heat stress–induced disruption in plant morphology, chlorophyll, and photosynthesis. It further discusses the role of BR in the regulation of the antioxidant defense system of plants. Moreover, the mechanism of BR signaling and its cross-talk with abscisic acid (ABA) in response to heat stress has also been discussed.
... Increased globalization and industrialization have exposed plants to different abiotic (drought, heat, flood, cold, and metals) and biotic (bacteria, viruses, and fungi) stresses in their natural ecosystems (Nabi et al., 2019). They hamper the growth and development of plants, modulate physiological metabolism such as photosynthesis thereby disturbing global food security (Chan et al., 2016;Kudo et al., 2017;Sidhu et al., 2017Sidhu et al., , 2018Sidhu et al., , 2020 (Fig. 10.1). Among all the abiotic stresses, drought is the most complex phenomenon that limits the productivity of crops worldwide (Ullah et al., 2018). ...
The climate change events have increased the vulnerability of plants to cold or low temperature stress, leading to reduced plant growth and productivity. Brassinosteroids (BRs) are steroid plant hormones and can enhance cold stress tolerance in plants. BRs are involved in a number of growth and developmental processes of plants including, germination, reproductive development, photosynthesis, hormonal regulation, and gene expression. BRs pretreatment prior to cold stress exposure helps in cold acclimation in plants through physiological and molecular alteration. Likewise, exogenous application to cold stressed plants protects the photosynthetic apparatus and regulates the hormone synthesis and redox homeostasis through inhibiting ROS production in intercellular organelles. Moreover, BR treatment upregulates the enzymatic and nonenzymatic antioxidant activities and triggers the cellular signaling pathways and enhances the expression of genes related to cold stress tolerance. This chapter highlights the role of BRs in the mediation of cold stress–induced damage on plant morphology, physiology, and biochemical traits. It further highlights the interaction of BR with reactive oxygen species (ROS) and the role of BRs in redox homeostasis. Moreover, the molecular basis of BR-induced cold stress tolerance has also been elucidated.
... The contamination of our environment by heavy metals has become a serious and very important worldwide problem. Industrial and anthropogenic activities such as galvanization, smelting, mining, excessive use of fertilizers, traffic have caused the release of significant amounts of metals into the environment [1]. In contrast to organic substances, heavy metals are essentially non-biodegradable and therefore they accumulate in the environment. ...
Soil pollution by heavy metals has become a global problem, as soil contamination by pollutants of mineral origin poses many risks to the environment and human health. To cope with this problem, researchers have developed many treatment techniques, and among these techniques is a botanical treatment which depends on the use of plants called heavy metal bioaccumulating plants to clean up contaminated soils, this technique has several processes such as phytoaccumulation, phytovolatilization, phytoextraction, phytodegradation etc. this review deals with the different mechanisms involved in phytoremediation, their advantages/limitations, the factors influencing bioaccumulation and mobility of metals in soil, and the different families of heavy metal bioaccumulating plants.
... The conventional physicochemical technologies are expensive and threaten soil microbiota and soil properties (Fasenko and Edwards 2014;Singh and Santal 2015). In contrast, phytoremediation is considered cost-effective, environmentally friendly, and easy to adopt with good public perception (Ali, Khan, and Sajad 2013;Dhaliwal et al. 2020;Saifullah et al. 2016;Sidhu et al. 2018aSidhu et al. , 2020Ullah et al. 2020). In phytostabilization, metals are stabilized and being immobile in the soil using green plants (Hou et al. 2020). ...
This work aims to assess growth, physiology, and metal uptake response of Brachiaria mutica and Leptochloa fusca under different contamination levels of Cd (10 and 50 mg kg⁻¹) and Pb (50 and 250 mg kg⁻¹) stress. Results of pot trial showed increasing metal concentration affected B. mutica more as compared to L. fusca. In B. mutica metal stress substantially reduced shoot dry biomass, root dry biomass, total chlorophylls, and carotenoids contents by 89%, 85%, 65%, and 61%, respectively, while enhanced the SOD activity up to 62 U min⁻¹ g⁻¹ FW. L. fusca showed better growth, chlorophylls and carotenoid contents, SOD activity (up to 79 U min⁻¹ g⁻¹ FW), shoot metal uptake potential (Cd 110 µg pot⁻¹, Pb 91.57 µg pot⁻¹), and root metal concentration (Cd 126 mg kg⁻¹ dm, Pb 117 mg kg⁻¹ dm) compared to B. mutica under Pb and Cd stress. While both grass species showed metal translocation factor less than unity under all levels of metal stress. Keeping in view the above results, it is concluded that L. fusca having better growth and physiology with TF < 1 could be used for phytostabilization of Pb and Cd to reclaim the soil having moderate to lower levels of contamination.
... Reducing and controlling the pollution of heavy metals in soils is to find out the sources of contamination [10,11]. On local scale, agricultural soils are being polluted by addition of heavy metals through natural and human activities [12][13][14]. Heavy metals in agricultural soils are mainly derived from weathering of parent materials, industrial emissions, disposal of high metal wastes, fertilizers, agrochemicals, irrigation water, atmospheric accumulation and pesticides [15,16]. Each conclusion concerning the function of any assessment in soil quality and organization should be established on authentic data on the degree and causes of heavy metal contamination in a region [17]. ...
Soil contamination by heavy metals is very important for environmental scientists due to the greater mobilization of metals and the possibility of contamination of groundwater. One of the most effective tools for evaluating the risk is the combination of experimentation with computer modeling. Modeling techniques are important in assessing the potential risks associated with heavy metals in the environment. Determination of models that can precisely evaluate the heavy metals in soils is an important need of agricultural researches, which could eradicate the weaknesses in the measurement of heavy metals in soils. The purpose of the present study is to test and compare different models according to their suitability for describing the estimation of heavy metals. The models used in this study were multilayer perceptron neural network (MLP), M5 model tree (M5) and bagging approach (BM5P). The data from 164 sampling sites from Neyshabur and Mashhad plains were taken in this study. The inputs combination according to feature selection-based correlation was used to feed the models. To model soil heavy metals, soil attributes, namely sand, silt, clay (as texture fractions), organic carbon, pH and available phosphorus, were entered in some models. To evaluate the performance of various techniques used in this study, several statistical indexes, including the correlation coefficient, root-mean-square error, Nash–Sutcliffe coefficient, Willmott’s index (d) and mean absolute error, were assessed. Comparison of different models for Fe, Cu, Mn and Zn indicated that MLP is the most suitable method for estimations of Fe and Mn, whereas BM5P and M5P are the most suitable models for determinations of Cu and Zn, respectively. This study concluded that machine learning models can be successfully applied to the rapid prediction of soil heavy metals using soil variables.
... Cadmium exposure causes acute toxicity to lungs and liver, and damage to kidneys (Wang et al., 2015a;Meng et al., 2018). Lead influences intelligence development in children and causes learning disabilities, cardiovascular disorders, hypertension, and nephropathy (Sidhu et al., 2018). These harmful heavy metals enter soils through geogenic processes and/or anthropogenic activities like smelting, mining and fertilization (Pan et al., 2016). ...
... Several physical and chemical methods were applied for soil remediation and reclamation in the past years, but these techniques have high maintenance costs and may cause secondary pollution (Haque et al., 2008). Phytoremediation is an affordable and sustainable technology for soil remediation (Adesodun et al., 2010), which is achieved by growing hyperaccumulating plants to extract the heavy metals from the rhizosphere region and sequester them to the above ground harvestable parts (Sidhu et al., 2017(Sidhu et al., , 2018, extensively studied because of its high efficiency, low cost and redundant to secondary pollution. ...
... Cadmium exposure causes acute toxicity to lungs and liver, and damage to kidneys (Wang et al., 2015a;Meng et al., 2018). Lead influences intelligence development in children and causes learning disabilities, cardiovascular disorders, hypertension, and nephropathy (Sidhu et al., 2018). These harmful heavy metals enter soils through geogenic processes and/or anthropogenic activities like smelting, mining and fertilization (Pan et al., 2016). ...
... Several physical and chemical methods were applied for soil remediation and reclamation in the past years, but these techniques have high maintenance costs and may cause secondary pollution (Haque et al., 2008). Phytoremediation is an affordable and sustainable technology for soil remediation (Adesodun et al., 2010), which is achieved by growing hyperaccumulating plants to extract the heavy metals from the rhizosphere region and sequester them to the above ground harvestable parts (Sidhu et al., 2017(Sidhu et al., , 2018, extensively studied because of its high efficiency, low cost and redundant to secondary pollution. ...
Comparative impact of CO2 application and endophyte inoculation was investigated on the growth, rhizosphere characteristics, and cadmium (Cd) absorption of two ecotypes of Sedum alfredii Hance in response to Cd stress under hydroponic or rhizo-box culture conditions. The results showed that both CO2 application and endophyte inoculation significantly (P < 0.05) promoted plant growth (fresh weight and dry weight), improved
root morphological properties (SRL, SRA, SRV, ARD and RTN) and exudation (pH, TOC, TN, soluble sugar and organic acids), changed Cd uptake and distribution of both ecotypes of S. alfredii. Meanwhile soil total and DTPA extractable Cd in rhizo-box decreased by biofortification treatments. Superposition biofortification exhibits utmost improvement
for the above mentioned parameters, and has potential for enhancing phytoremediation efficiency of hyperaccumulator and sustaining regular growth of non-hyperaccumulator in Cd contaminated soils.
... The utility of these conventional approaches for treatment of contaminated sites has limitations and may involve serious risks. Phytoremediation is an in situ, non-conventional strategy in which plants are employed to extract or inactivate heavy metals that are present individually or collectively in multimetal-contaminated soils (Sidhu et al., 2018(Sidhu et al., , 2017bSidhu, 2016;Sung et al., 2013). Moreover, it is an aesthetically pleasing, cost-effective, and affordable approach. ...
... The results of Table 2 show that the BCF was not greater than 1 in the root and shoots of Ocimum basilicum at none of the studied lead concentrations, but the TF was more than 1 in the examined samples, with the exception of the control. Therefore, this species is unsuitable for lead phytostabilization due to a root BCF < 1 and TF > 1 (Sidhu et al., 2017b). The maximum lead TF is in C 3 Pb 100 , which is consistent with the findings of Chorom et al. (2009) who found the highest lead TF for canola in treatment with high concentration of the compost. ...
Among the chemical pollutants, lead is one of great importance ecologically and hygienically, because it threatens the health of the communities by penetrating into the food cycle. Phytoremediation is required along with modifying chelates to improve the efficiency of metal remediation. The aim of this study was to investigate the effect of vermicompost and EDTA on the absorption of various Pb concentrations from the soil and determine their accumulation level in the roots and shoots of Ocimum basilicum in the form of pot experiment in a completely randomized design with three replications. We applied vermicompost 3 mg/kg soil, EDTA 8 mg/kg soil, and lead nitrate at the concentrations of 50 and 100 mg/kg soil. AAS was employed to read the amount of Pb in the extracts. The results showed that the use of amendment materials increases significantly the Pb accumulation in the plant shoots. The results of calculating bioconcentration factor and transfer factor showed that this plant is unsuitable for the phytostabilization and phytoextraction of Pb.
... pigments was observed in response to Pb exposure (John et al. 2012), which was the main cause of biomass reduction (Rai et al. 2016). A similar effect was reported for two other Pb accumulator species, Coronopus didymus (Sidhu et al. 2017) and Chrysanthemum indicum (Mani et al. 2015). In contrast, in our present study, neither population of T. minuta exhibited this toxic effect, while enhanced pigments and consistently enhanced biomass production were observed. ...
Tagetes minuta L. is a plant which accumulates Pb under certain conditions, making it a candidate for phytoextraction projects because it also produces marketable essential oils without detectable Pb levels. Although extraction efficiency has been shown to significantly vary between individuals, these results have been obtained using only historically exposed populations, which leads to the questions: Is the ability to tolerate and accumulate Pb a property of the species? Or is it a characteristic of some individuals from a historically exposed population? In this context, a greenhouse experiment was performed to analyse the intrapopulation and interpopulation variability in response to Pb among individuals from historically unexposed and exposed populations. In addition, we also attempted to identify relationships between certain capabilities (toleration and accumulation of Pb) and the physiological parameters related to oxidative stress or the volatile compounds of the essential oils. The Pb concentration was determined by total reflection X-ray fluorescence, physiological parameters were obtained by spectrophotometry, and essential oils were analysed by gas chromatography. The results demonstrated that adequate tolerance and accumulation capabilities are present in T. minuta, irrespective of the exposure history. These findings may be associated to a hormesis response, which includes enhancement of pigments, biomass production and the uptake of other heavy metals such as micronutrients. Nevertheless, the historically exposed population had a better tolerance to Pb, since it presented defence characteristics reflected in the essential oil composition and in the avoidance of damage at the lipid peroxidation level after Pb uptake.
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... To lessen the environmental risks of Pb contamination, suitable strategies are indispensable to remediate Pb-contaminated sites. Of different conventional technologies including chemical or mechanical techniques, phytoremediation is a promising, green technology to restore metal contaminated soils due to its cost effectiveness and environmentally friendliness (Sidhu, 2016;Sidhu et al., 2017d). Besides, the inception of green cover on the polluted soils lemmatises the risk of heavy metal movement through water percolation and wind erosion. ...
Identification and screening of wild, wasteland plants for the remediation of heavy metal contaminated soils is a crucial phytotechnological approach. In a pot experiment, Chenopodium murale was tested for the phytoextraction of lead (Pb) from the contaminated soils. The experiment was conducted for 8 weeks to appraise the effect of varied Pb regimes (300, 400, 500mgkg-1) on the bioaccumulation and physiological responses of C. murale plants. At 500mgkg-1 Pb regime, the concentration of Pb in roots and shoots reached a maximum of 2513 and 2301mgkg-1 DW, respectively. The plants highlighted a very high tolerance with 100% survival towards Pb toxicity, although exhibited a slight decrease in biomass yield, chlorophyll content and protein levels. However, a dramatic mount in H2O2 content, MDA level and bio-activities of antioxidant enzymes (SOD, CAT and POD) was noticed. BCF and TF values were more than unity at all the Pb regimes. Results were scrutinized, accentuating the profit of raising C. murale in Pb-contaminated soils as this plant species can be a promising candidate for soil remediation and their restoration purposes.
The present study pertains to the evaluation of the effects of nickel on bioaccumulation, growth parameters, contents of protein, and antioxidant enzymes in root and shoots of Solanum lycopersicum as well as ameliorating effects of [S, S]-ethylenediamine-N–N’-disuccinic acid (EDDS). Nickel treatment at different concentrations (5, 10, 15, 20, 25, 30, 40, 50, 60, 100, and 250 µM) enhanced activities of all antioxidative enzymes in roots and shoots of S. lycopersicum when compared to the control. Dose-dependent increase was observed for dehydroascorbate (DHAR) and peroxidase (POD) up to 40 µM Ni while an increase was observed for ascorbate peroxidase (APX), catalase (CAT), and glutathione S-transferase (GST) up to 50 µM Ni. Activity of glutathione reductase (GR) was maximum at 5 µM Ni for roots and at 50 µM Ni for shoots. In the presence of EDDS, both roots and shoots have shown increased activity of POD at 40, 50, and 60 µM of Ni, and CAT at 60 µM of Ni whereas reduced activity of APX was shown at 40, 50, and 60 µM of Ni for shoots and at 40 and 50 µM of Ni for roots. GR exhibited increased activity in roots while reduced activity in shoots except at 60 µM of nickel treatment. No change was observed for translocation factor, protein, DHAR, and GST activities while bioaccumulation factor was enhanced at 50 and 60 µM of Ni in the presence of EDDS. Further, this present study clearly revealed that EDDS could combat nickel-induced stress in S. lycopersicum by enhancing activities of CAT, GR, and POD, resulting into ameliorated growth parameters.
Lead (Pb) is known as a toxic metal and a non-essential element for plant metabolism and growth. This work investigated the phytotoxicity of Pb induced stress and assessed the accumulation potential of Pb in two Asteraceae plants; Limbarda crithmoides and Helianthus annuus. The experiments were performed for 45 days using different concentrations of Pb (0, 100, 200, 300 and 500 µmol.L–1). The dry biomass production in shoots and roots of Limbarda crithmoides were significantly enhanced with the increase of Pb doses in the growth medium, Helianthus annuus plants showed a modest variation in shoot and root dry weights, but without any significant difference as compared to the untreated plants. In addition, metal tolerance index values determined in the shoots and roots of these two species followed a similar trend as the dry weight contents. Both phenolic compounds and flavonoids were significantly increased in the two Pb treated species in comparison to the untreated plants (except flavonoid content of Limbarda crithmoides roots). Total inorganic nitrogen and macronutrient uptake were also assessed, and the two species showed different behaviour when varying Pb concentrations. Moreover, the two species accumulated Pb in their roots more than in the shoots (less than 1000 µg.g–1 DW) with a low translocation from roots into shoots (translocation factor < 1). Our findings demonstrated that both Limbarda crithmoides and Helianthus annuus were tolerant to Pb stress; nonetheless, the two species could not be classified as Pb hyperaccumulators.
Dissolved organic matter (DOM) or iron/manganese (hydro)oxides were important factors in the migration of Cd in sediments of wetlands. DOM and Fe oxides simultaneously affect the longitudinal and transverse migration of Cd in wetlands sediments of plants was still unclear. In this study, a 14-day rhizobox experiment was conducted and the result showed that the rhizosphere effect of Cd migration was only limited to the upper layer of sediments (-2 to -4 cm). Fe with fulvic acid (FA) simultaneously existed can precipitate Cd(II) from supernatant to sediments downward. Fe oxides at sediment concentration could effectively prevent Cd(II) from migrating to root surface (0.21 vs 0.02 At%). While Fe oxides with FA together at sediment concentration could effectively promoted the migration of Cd(II) to root surface (0.07 vs 0.08 At%). The formation of organo-metallic complexes of Fe in the presence of FA profoundly proved this finding (increased by ~33.0%). And the polysaccharides and aromatics in organic matter were the chief functional groups participating in the incorporation of Cd and Fe oxides. The findings reveal the migration rules of Cd(II) in sediments by FA and Fe oxides and give an insight into the mechanisms of Cd(II) migration to the root surface around wetland plants.
Brassinosteroids constitute naturally occurring plant hormones that are involved in the regulation of various metabolic functions associated with morphological, physiological, and developmental processes in plants. The polyhydroxylated steroidal hormones occur widely in the plant kingdom and exhibit structural variations. The recent advancement in different molecular approaches has led to the understanding of various processes involving BR synthesis, signaling, and pathways in plants. BRs not only play an important role in the growth and development of plants but also in providing tolerance against various abiotic and biotic stresses. Current trends indicate a myriad role of BRs in the amelioration of drought stress in plants that results in systematic stress management under fluctuating environmental conditions. This chapter provides insights into drought stress and its effect on the growth of plants. Further, the chapter focuses on the role of BRs in mitigating the negative effect of drought stress that critically hampers the growth and metabolism of plants.
Phytoremediation has been proposed as a cost-effective method for removing potentially toxic elements (PTEs) from the soil. In this regard, biodegradable chelating agents can be used without harming the environment to increase the efficiency of phytoremediation. In the present work, a greenhouse experiment was conducted to investigate the effect of nitrilotriacetic acid (NTA; 0, 15, and 30 mmol L−1 per pot) on the uptake, chemical forms, and subcellular distribution of Cd in maize (Zea mays L.) grown in Cd-spiked soils (0, 25, and 50 mg Cd kg−1 soil) under leaching conditions. NTA application decreased biomass production (18–33%) yet enhanced Cd concentrations in shoots and roots of maize by more than 50%. Subcellular fractionation of NTA-applied Cd-containing leaves indicated that 41–53% of the Cd was localized in cell walls (FCW), 33–39% in soluble fraction (FS), and 13–19% in cellular organelles (FO). Moreover, NTA enhanced inorganic (FE), water-soluble (FW), and pectates and proteins-integrated Cd (FNaCl) forms, but reduced the insoluble forms (FHAc and FHCl). The increase of FNaCl may possibly help the plant to adapt to Cd stress. Also, NTA decreased soil DTPA-extractable Cd significantly, due to the increase in Cd leached and Cd absorbed by plants. The use of NTA can significantly increase the phytoremediation potential of maize, but it may also increase Cd toxicity in plants exposed to high amounts of Cd. Therefore, it is important to determine the optimal amount of chelator for enhancing phytoremediation.
Heavy metals pollution represents a serious issue for cultivable lands and ultimately threatens the worldwide food security. Lead (Pb) is a menacing metal which induces toxicity in plants and humans. Lead toxicity reduces the photosynthesis in plants, resulting in the reduction of plant growth and biomass. The excessive concentration of Pb in soil accumulates in plants body and enters into food chain, resulting in health hazards in humans. The phytoremediation is eco-friendly and cost-efficient technique to clean up the polluted soils. However, to the best of our Knowledge, there are very few reports addressing the enhancement of the phytoremediation potential of castor bean plants. Therefore, the present study aimed to investigate the potential role of glutathione (GSH), as a promising plant growth regulator, in enhancing the lead stress tolerance and phytoremediation potential of castor bean plants grown under lead stress conditions. The results indicated that Pb stress reduced the growth, biomass, chlorophyll pigments and gas exchange attributes of castor bean plants, causing oxidative damage in plants. Pb stress induced the oxidative stress markers and activities of antioxidant enzymes. On the other hand, the application of GSH reduced oxidative stress markers, but enhanced the growth, biomass, photosynthetic pigments, gas exchange attributes, Pb accumulation and antioxidant enzymes activities of lead-stressed castor bean plants. Both Pb uptake and Pb accumulation were increased by increasing concentrations of Pb in a dose-additive manner. However, at high dose of exogenous GSH (25 mg L-1) further enhancements were recorded in the Pb uptake in shoot by 48% and in root by 46%; Pb accumulation was further enhanced in shoot by 98% and in root by 101% in comparison with the respective control where no GSH was applied. Taken together, the findings revealed the promising role of GSH in enhancing the lead stress tolerance and phytoremediation potential of castor bean (Ricinus communis) plants cultivated in Pb-polluted soils through regulating leaf gas exchange, antioxidants machinery, and metal uptake.
The aim of this study was to assess the potential of the woody nickel hyperaccumulator species Blepharidium guatemalense (Standl.) Standl. for agromining in southeastern Mexico. Pot trials consisting of nickel dosing (0, 20, 50, 100 and 250 mg Ni kg-1), and synthetic and organic fertilization were conducted. Field trials were also undertaken with different harvesting regimes of B. guatemalense. Foliar nickel concentrations increased significantly with rising nickel additions, with a 300-fold increase at 250 mg Ni kg-1 treatment relative to the control. Synthetic fertilization strongly increased nickel uptake without any change in plant growth or biomass, whereas organic fertilization enhanced plant shoot biomass with a negligible effect on foliar nickel concentrations. A 5-year-old stand which was subsequently harvested twice per year produced the maximum nickel yield tree-1 yr-1, with an estimated total nickel yield of 142 kg ha-1 yr-1. Blepharidium guatemalense is a prime candidate for nickel agromining on account of its high foliar Ni concentrations, high bioconcentration (180) and translocation factors (3.3), fast growth rate and high shoot biomass production. Future studies are needed to test the outcomes of the pot trials in the field. Extensive geochemical studies are needed to identify potential viable agromining locations.
Keywords: agronomy, fertilization, hyperaccumulation, neotropics, Ni yield, phytomining.
Heavy metal-contaminated soils present an imminent threat to agriculture, biodiversity, and ecosystem stability. The soils which are polluted with heavy metals are not suitable for cultivation of crops because the polluted medium adversely affects their growth, development, physiology, and production outputs. In addition, heavy metals accumulated in plants’ tissues may flow through the food chain and can lead to toxic consequences in the ecosystem. Remediation and reclamation of such soil is a challenging task which requires substantial intellectual, economic, and scientific inputs. Physical and chemical methods currently employed for heavy metal stress management in soils pose economic, environmental, and labor difficulties and they must, therefore, be substituted with easy, eco-friendly, and cost-effective measures to ensure agricultural sustainability. Phytoremediation is an attractive approach which employs the use of plants for removal of heavy metals from soil. Weeds, in particular, may serve as ideal agents because they are not directly used by human beings and animals and thus reduce the chances of food chain toxicity. In this chapter, the potential roles of different weed species in phytoremediation of heavy metal-polluted soils are discussed.
In this study, cadmium (Cd) solution spraying and Cd-contaminated soil pot experiments were conducted to investigate the influence of Cd from atmospheric deposition and soil on the growth, cumulative distribution, chemical morphology, physiological, and biochemical responses of Amaranthus tricolor L. The results indicated that Cd in plants mainly came from soil (92–98%) and was stored in the roots in large quantities while the portion from atmospheric deposition could also effectively increase Cd content in stems and leaves (2–3%). Cd was mainly stored in plant cell walls and would transfer to the soluble part under high-concentration soil stress Cd from atmospheric deposition alone promoted the growth of plants, but high Cd concentrations from soil had the negative influence. The contents of H2O2 and MDA in plants increased under soil and atmospheric Cd stress, indicating that the plant cells were damaged by oxidative stress. The content of antioxidant enzymes such as POD, CAT, SOD, and antioxidants like AsA and GSH increased under low-concentration Cd stress but decreased under elevated stress, suggesting that high Cd-contaminated soil poses severe toxicity on the antioxidant system of the plants. Hence, the accumulation and physiological response of plants under multi-source Cd contamination were mainly affected by high soil Cd concentrations. Though the effect of atmospheric deposition is relatively less, it cannot be ignored.
Cadmium (Cd) is one of the most toxic contaminants, causing a lot of harm to environment and the human health. An outdoor pot experiment for 60 days was conducted to study the Cd(II) effects on growth, biomass, physiological properties, Cd uptake, and accumulation in Youngia japonica plants but also to evaluate the effect of Y. japonica growth on enzyme activity of Cd-contamination soils. Generally, the application of Cd(II) less than 120 mg kg⁻¹ stimulated the growth of the plants, whereas at 160 mg kg⁻¹ or higher levels, a significant reduction was observed. For all treatments > 10 mg kg⁻¹ Cd(II) in soil, values of Cd in roots and aboveground parts were more than the critical value of 100 mg kg⁻¹ and reached highest values of 252.51 and 314.29 mg kg⁻¹, respectively. The bioconcentration factors (BCF) and translation factors (TF) for all Cd treatments were more than 1.0, with the former ranging from 1.03 to 5.46 and the later from 1.04 to 1.33. The activities of peroxidase (POD) and superoxide dismutase (SOD), as well as the levels of glutathione (GSH) and proline in Y. japonica plants after exposure to 10–200 mg kg⁻¹ Cd(II) were stimulated, implying that they were defensive guards to the oxidative stress produced by Cd. The urease, dehydrogenase, and alkaline phosphatase activities under low Cd concentrations can be enhanced by planting Y. japonica species but inhibited under high Cd concentrations. Our data provide comprehensive evidence that Y. japonica has the typical properties of a Cd hyperaccumulator and thus may be practically employed to alleviate Cd from contaminated soils.
Plants used in phytoremediation should accumulate and tolerate a specific pollutant. Here, we aimed at evaluating a possible arsenic (As) accumulation and mechanisms of tolerance against As-induced damage in Landoltia punctata to explore this species for phytoremediation. Plants were subjected to increasing As levels. As absorption was higher with increasing As levels. The activity of superoxide dismutase and glutathione reductase as well as anthocyanin levels increased with As levels. Catalase and peroxidase activities increased in plants subjected to As levels up to 1.0 mg L⁻¹ and decreased at higher levels. Due to the antioxidant system, higher levels of reactive oxygen species were restrained in plants under low levels of As. However, the levels of superoxide anion, hydrogen peroxide, and lipid peroxidation increased in response to the impaired antioxidant system induced by the highest As levels. Biomass decreased in plants exposed to As and scanning electron microscopy revealed root structural damage in the root cap of plants under 3.0 mg L−1 As. This work highlights that L. punctata can be considered a hyperaccumulator species and has potential for As phytoremediation when levels are lower than 1.0 mg L⁻¹—a concentration 100-fold higher than that recommended for drinking water.
Novelty Statement: Landoltia punctata can be considered a hyperaccumulator species and has the potential for arsenic phytoremediation when levels are lower than 1.0 mg L⁻¹.
Phytoremediation is an emerging technology that employs the use of higher plants for the clean upt he contaminated environment, a cost-effective, environment-friendly. In this study, the role of puring( Codiaeumvarigatum ) plants as a potential phytoremediator to soils contaminated with lead (Pb) was investigated. A pot experiment was conducted for four and eight weeks to compare the biomass andlead content in root, stem and leaf by puring. The plant grew well exposed Plants that grow well are exposed to Pb with as much as 250 mg.kg ⁻¹ and 375 mg.kg ⁻¹ soil. The result presented here showed that root, stem and leaf biomassdecrease with increasing concentration and exposure time. Pb accumulation increases with increasing concentration and time of exposure. Pb accumulation in roots> stems> leaves. Bioaccumulation of factors is less than 1 while factor translocation is more than one. Metal tolerance index values range 95.545%to103.406%. This suggests that Codiaeumvarigatum was a candidate for phytoremediation of lead
Information is needed for comparative assessment and agronomic practices for phytoavoidation in multi-pollutant field. A field study was conducted to explore 97 Brassica pekinensis L. genotypes with permissible limit of contaminants growing in a severely Cd, moderately nitrate and slightly Pb multi-polluted field. Thirteen genotypes, i.e. KGZY, CXQW, CAIB, JINL, JQIN, JFEN, WMQF, XLSH, TAIK, BJXS, JUKA, XYJQ and GQBW, were identified with permissible limit for nitrate, Cd and Pb based on their resistance to heavy metal and nitrate accumulation in leaves when grown in co-contaminated soils. Furthermore, the correlation between essential and toxic elements concentrations in plant of B. pekinensis were inconsistent. Generally speaking, application of increasing Ca, K and S fertilizers in appropriate forms and dosages tended to increase the yield and quality of B. pekinensis cultivated in multi-pollutant field.
To determine whether grafting increases cadmium (Cd) accumulation in the post-grafting generation of hyperaccumulator plants, the effects of grafting on Cd accumulation characteristics of post-grafting generations of a potential Cd-hyperaccumulator Solanum photeinocarpum were evaluated in pot and field experiments. The following four grafting combinations were examined: ungrafted (UG), self-rooted grafting involving one S. photeinocarpum seedling (SG), self-rooted grafting involving two S. photeinocarpum seedling developmental stages (DG), and grafting on wild potato rootstock (PG). Grafting did not induce genetic changes in S. photeinocarpum, and increased the shoot biomass and the amount of Cd extracted by the shoots of the first, second, and third generations of S. photeinocarpum (PG > DG > SG > UG). Additionally, enhanced superoxide dismutase, peroxidase, and catalase activities and increased soluble protein contents of the first post-grafting generation were observed for the DG and PG, whereas only enhanced superoxide dismutase and peroxidase activities were observed for the SG. Grafting increased the DNA methylation levels by inducing hypermethylation in the first post-grafting generation (PG > DG > SG > UG). Therefore, grafting can enhance the Cd accumulation (phytoremediation) ability of post-grafting generations of S. photeinocarpum by enhancing DNA methylation levels, especially when wild potato rootstock is used.
Selecting (inter-varietal) Brassica juncea for tolerance to metal-contamination has been proposed as a strategy to develop superior genotypes for phytoextraction of lead (Pb) through selection and breeding techniques. To understand the differences among accessions of a single species to Pb accumulation, a pot experiment was conducted with three B. juncea accessions under levels of Pb added to the soil (0, 90, 180, and 540 mg kg-1). The duration of the growth period was 100 d. Pb concentration levels did not affect the flowering of B. juncea accessions. Plant height, shoot dry matter, and root dry matter were reduced linearly when soil Pb concentration increased to 540 mg kg-1. A significant interaction between Pb concentration levels and accessions was observed for Pb concentration in shoots and roots, indicating genotypic variation in Pb absorption. The concentration of Pb in shoots in accession PI 180266 was 51% higher compared to
accessions PI 649105 and PI 432379 when soil Pb concentration increased to 540 mg kg-1. It can be concluded that the B. juncea accessions differed significantly in Pb uptake, and the selection of tolerant cultivars might be helpful for Pb phytoremediation of contaminated soils.
Heavy metals are among the most critical environmental pollutants close to industrial areas. One example is the cultivated fields in the south of Alborz industrial city in Iran, which is irrigated by treated industrial wastewater. It is contaminated by heavy metals and irrigation with wastewater treatment plants effluent, which made it salty. In this study, the application of 2 amendments, biosolids and cow manure, in improving the heavy metal accumulation in the ornamental sunflower from these types of soils was investigated. A greenhouse experiment using a completely randomized design with 4 replications and applying cow manure and biosolids in 3 weight ratios (6%, 12%, 25%) was conducted to evaluate the efficiency of sunflower in removing Pb, Ni, and Zn from the soil. Adding the amendments increased the rate of germination by 50% to 176%. Although the simultaneous utilization of cow manure in high ratios with biosolids and cow manure with low biosolids decreased the sunflower survival, nonetheless, the simultaneous addition of these organic amendments could increase the survival rate in other treatments. Moreover, the plants’ biomass was increased by adding modifiers such as cow manure and biosolids. The results showed that in treatments with 2 modifiers, the remediation factor of Pb, Zn, and Ni has increased 83.7 to 95.5, 78.4 to 87.5, and 74.9 to 94.9, respectively, in comparison to the control one. Therefore, we conclude that adding biosolids and cow manure simultaneously could improve the ornamental sunflower ability to accumulate heavy metals.
Indoleacetic acid (IAA) is a plant growth regulator that plays an important role in plant growth and development, and participates in the regulation of abiotic stress. To explore the effect of IAA on cadmium toxicity in Cinnamomum camphora, an indoor potted experiment was conducted with one-year-old C. camphora seedlings. The influence of IAA on cadmium accumulation, net photosynthetic rates, respiration, photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll and carotenoids), osmoregulatory substances (proline, soluble sugar and soluble protein) and the malondialdehyde content in C. camphora leaves treated with 30 mg kg-1 cadmium was analysed with or without the addition of 10 mg kg-1 IAA. Cadmium accumulation in the leaves of C. camphora with the addition of exogenous IAA was significantly higher than accumulation during cadmium stress without additional IAA (ca 69.10% after 60 days' incubation). During the culture period, the net photosynthetic rate in C. camphora leaves subjected to cadmium stress without the addition of IAA was up to 24.31% lower than that of control plants. The net photosynthetic rate in C. camphora leaves subjected to cadmium stress and addition of IAA was up to 30.31% higher than that of leaves subjected to cadmium stress without the addition of IAA. Chlorophyll a, total chlorophyll and carotenoid contents in the cadmium-stressed leaves without the addition of IAA were lower than those in the control treatment. The presence of IAA increased the chlorophyll a, total chlorophyll and carotenoid contents relative to the cadmium stress without the addition of IAA. The respiration rate and concentrations of proline, soluble sugar, soluble protein and malondialdehyde in C. camphora leaves subjected to cadmium stress without the addition of IAA were higher than those in the control. The addition of IAA reduced the respiration rate, and the concentrations of proline, soluble sugar, soluble protein and malondialdehyde in C. camphora leaves when compared with the cadmium stress without the addition of IAA. These results indicate that exogenous IAA improves photosynthetic performance and the growth environment of C. camphora by enhancing the net photosynthetic rate, increasing concentrations of osmoregulatory substances, removing reactive oxygen radicals and eliminating potential damage, thereby reducing the toxic effects of cadmium on C. camphora.
The evaluation of plants occurring naturally at contaminated environments are essential for applying this species in remediation techniques. In this context, the Sagittaria montevidensis with potential for phytoremediation was studied at an anthropogenic polluted stream in southern Brazil. The nutrients and heavy metal content were determined in the phytomass. The phytoremediation indexes were evaluated such as bioconcentration factor (BCF), translocation factor (TF), plant effective number (PEN), and potential phytoremoval (mg m⁻²). The S. montevidensis was then detected as presenting natural phytoextraction ability for potassium and calcium elements and also demonstrated rhizofiltration potential for phosphorus, manganese, aluminum, vanadium, sulfur, iron, arsenic, copper, magnesium, zinc, sodium, lead, cadmium, nickel, chromium, considering its ability of bioaccumulating these contaminants and retain high levels in the roots. The highest potential for bioremoval (mg m⁻²) of the S. montevidensis was detected for potassium and calcium (recommending thus the use for phytoextraction) and for aluminum, phosphorus, iron, magnesium, sulfur, and sodium, along with heavy metals (recommended for rhizofiltration). The S. montevidensis decontamination ability, along with its biomass production and its adaptability represents a great advance in order to the recovery of this degraded area and possible application in other contaminated watercourses in Brazil.
This study assessed the effects of Pb (0, 200, 500, 1000 mg kg⁻¹) and Cd (0, 5, 15, 30, 50 mg kg⁻¹) on photosynthesis in Amaranthus spinosus (A. spinosus), as well as the potential for phytoremediation by pot-culture experiment. Exposure to Pb/Cd produced a concentration-dependent decrease in biomass and all photosynthesis parameters, except for non-photochemical quenching, which increased with the metal concentration. The metals accumulated more in roots compared to shoots. The bioconcentration factor (BCF) of Pb was <1 in shoots at all Pb levels, whereas the BCF was <1 in roots at all but the lowest concentration of Pb. Roots extracted Cd from soil at all treatments. The translocation factor of Cd was larger than that of Pb suggesting that Cd is more mobile than Pb in A. spinosus. Amaranthus spinosus displays a high tolerance for both Pb and Cd with regards to growth and photochemical efficiency, but it is more sensitive to Cd than Pb. Amaranthus spinosus accumulates Pb and Cd primarily in the roots and Cd is more bioconcentrated and translocated in comparison to Pb. This investigation shows that A. spinosus has good potential for phytoremediation of soils contaminated by low levels of Cd and Pb.
A three-crop repeated phytoextraction experiment was conducted using four soils (S1–S4) highly polluted with cadmium (Cd) and two enhanced phytoextraction pot experiments using the most polluted soil (S4) to investigate the feasibility of Cd removal from highly polluted soils using the Cd/zinc (Zn)-hyperaccumulator Sedum plumbizincicola. Shoot biomass showed no significant difference during the repeated phytoextraction experiment on the four test soils and shoot Cd content showed a decreasing trend with the three consecutive crops in soils S1, S2, and S3 but not in soil S4. The Cd removal rates in soils S1, S2, S3, and S4 were 84.5, 81.6, 45.3, and 32.4%, respectively. Rice straw application increased Cd extraction efficiency by 42.6% but the addition of ethylenediaminedisuccinic acid, biochar or nitrogen had no effect on Cd remediation. Shoot Cd content increased significantly (1.57 and 1.71 times, respectively) at low (S0-1) and high (S0-2) sulfur addition rates. Soil extractable-Cd in S0-1 after the experiment showed no significant difference from the control but was 2.43 times higher in S0-2 than in the control. These results indicate that S. plumbizincicola shows good prospects for the phytoextraction of Cd from highly polluted soils and that the process can be enhanced by adding straw and/or sulfur to the soil.
Dalbergia sissoo DC, a leguminous tropical timber tree has been investigated against the Pb toxicity; under the Pb-stress, plant’s morphology, biochemical parameters and genomic template stability (GTS) screened in vitro. At the optimum Pb tolerance level (150 mg L⁻¹), plant’s defense mechanism—superoxide dismutase, catalase, ascorbate peroxidases and proline could trigger to achieve optimum vegetative growth with minimum fluctuations of the GTS. Further, D. sissoo roots could accumulate 2399.8 ± 16 mg kg⁻¹ Pb. Scanning electron microscopy and energy dispersive X-ray spectrometer analysis also revealed the deposition of Pb in root tissues. In a 1 year pot experiment with Pb-contaminated soil, the plants exhibited normal growth, and Pb accumulation significantly enhanced by the amalgamation of citric acid in the soil. Thus, the tree may prove as a potential candidate for Pb phytostabilization.
The picturesque limestone karsts across the Sino-Vietnamese border are renowned biodiversity hotspot, distinguished for extremely high endemism of calciphilous plants restricted to caves and cave-like microhabitats that have functioned as biological refugia on the otherwise harsh habitats. To understand evolutionary mechanisms underlying the splendid limestone flora, dated phylogeny is reconstructed for Asian Begonia, a species-rich genus on limestone substrates represented by no less than 60 species in southern China, using DNA sequences of nrITS and chloroplast rpL16 intron. The sampling includes 94 Begonia species encompassing most major Asian clades with a special emphasized on Chinese species.
Except for two tuberous deciduous species and a species with upright stems, a majority of Sino-Vietnamese limestone Begonia (SVLB), including sect. Coelocentrum (19 species sampled) and five species of sect. Diploclinium, Leprosae, and Petermannia, are rhizomatous and grouped in a strongly supported and yet internally poorly resolved clade (Clade SVLB), suggesting a single evolutionary origin of the adaptation to limestone substrates by rhizomatous species, subsequent species radiation, and a strong tendency to retain their ancestral niche. Divergence-time estimates indicate a late Miocene diversification of Clade SVLB, coinciding with the onset of the East Asian monsoon and the period of extensive karstification in the area.
Based on our phylogenetic study, Begonia sect. Coelocentrum is recircumscribed and expanded to include other members of the Clade SVLB (sect. Diploclinium: B. cavaleriei, B. pulvinifera, and B. wangii; sect. Leprosae: B. cylindrica and B. leprosa; sect. Petermannia: B. sinofloribunda). Because species of Clade SVLB have strong niche conservatism to retain in their ancestral habitats in cave-like microhabitats and Begonia are generally poor dispersers prone to diversify allopatrically, we propose that extensive and continuous karstification of the Sino-Vietnamese limestone region facilitated by the onset of East Asian monsoon since the late Miocene has been the major driving force for species accumulation via geographic isolation in Clade SVLB. Morphologically species of Clade SVLB differ mainly in vegetative traits without apparent adaptive value, suggesting that limestone Begonia radiation is better characterized as non-adaptive, an underappreciated speciation mode crucial for rapid species accumulations in organisms of low vagility and strong niche conservatism.
Lead (Pb) contamination in soils is a serious concern because it can be taken up by crops and then transferred through the food chain, posing a potential risk to human health. Indian mustard (Brassica juncea) and wheat (Triticum aestivum) are important crop species known to accumulate heavy metals in their tissues. This study aimed at understanding the transport and accumulation of Pb in these two species and the risk associated with consumption of these foods, which would help us in mitigating accumulation of Pb in edible tissues. The plants were grown at different Pb concentrations for the entire life cycle, and the partitioning of the metal to different tissues was examined. The results showed that plant species differ widely in their ability to transport and accumulate Pb in different tissues. In B. juncea, there was significant accumulation of Pb in both siliques and seeds, whereas most of the Pb in wheat was concentrated in the vegetative tissues and less to the flag leaf and reproductive tissues. In both species, although seed Pb concentrations exceeded acceptable limits, dietary intake did not exceed acceptable limits in most treatments, indicating that more studies on Pb transport and redistribution in crop species is necessary.
Background
Lead (Pb) heavy metal pollution in water bodies is one of the serious problems across the world. This study was designed to find out the effect of Pb toxicity on physiological and biochemical changes in Eichhornia crassipes (water hyacinth) seedlings.
Results
The plant growth was significantly inhibited (50%) at 1000 mg/L Pb concentration. Accumulation of Pb was higher in root than in shoot tissues. The maximum level of Pb accumulation was noticed in roots (5.45%) followed by petiole (2.72%) and leaf tissues (0.66%). Increasing the Pb concentration gradually decreased the chlorophyll content. Intracellular distribution of Pb was also studied using SEM-EDX, where the Pb deposition was observed in both root and leaf tissues. MDA content increased in both the leaf and root tissues up to the 400 mg/L Pb treatment and slightly decreased at higher concentrations. The activity of antioxidative enzymes, such as APX and POX, positively correlated with Pb treatment, while in the case of SOD and CAT enzymes increased up to 800 mg/L treatment and then slightly decreased at higher concentration in both leaf and root tissues.
Conclusions
These results suggest that water hyacinth plants have efficient mechanism to tolerate Pb toxicity, as evidenced by an increased level of antioxidative enzymes. Results clearly indicate that water hyacinth is a feasible plant for hyperaccumulation of heavy metals from polluted wetlands.
Pot and field experiments were conducted to elucidate the phytostabilization potential of two grass species (Thysanolaena maxima and Vetiveria zizanioides) with respect to lead (Pb) tailing soil. Three fertilizers (Osmocote® fertilizer, cow manure, and organic fertilizer) were used to improve the physicochemical properties of tailing soil. V. zizanioides treated with organic fertilizer and cow manure showed the highest biomass (14.0 ± 2.6 and 10.5 ± 2.6 g per plant, respectively) and the highest Pb uptake in the organic fertilizer treatment (T. maxima, 413.3 μg per plant; V. zizanioides, 519.5 μg per plant) in the pot study, whereas in field trials, T. maxima attained the best performances of dry biomass production (217.0 ± 57.9 g per plant) and Pb uptake (32.1 mg per plant) in the Osmocote® treatment. In addition, both grasses showed low translocation factor (1). During a 1-year field trial, T. maxima also produced the longest shoot (103.9 ± 29.7 cm), followed by V. zizanioides (70.6 ± 16.8 cm), in Osmocote® treatment. Both grass species showed potential as excluder plants suitable for phytostabilization applications in Pb-contaminated areas.
Referee: Professor Alan J.M. Baker, School of Botany, The University of Melbourne, VIC 3010, Australia A relatively small yet diverse group of plants are capable of sequestering metals in their shoot tissues at remarkably high concentrations that would be toxic to most organisms. This process, known as metal hyperaccumulation, is of interest for several reasons, including its relevance to the phytoremediation of metalpolluted soils. Most research on hyperaccumulators has focused on the physiological mechanisms of metal uptake, transport, and sequestration, but relatively little is known regarding the genetic basis of hyperaccumulation. There are no known cases of major genetic polymorphisms in which some members of a species are capable of hyperaccumulation and others are not. This is in contrast to the related phenomenon of metal tolerance, in which most species that possess any metal tolerance are polymorphic, evolving tolerance only in local populations on metalliferous soil. However, although some degree of hyperaccumulation occurs in all members of the species that can hyperaccumulate, there is evidence of quantitative genetic variation in ability to hyperaccumulate, both between and within populations. Such variation does not appear to correlate positively with either the metal concentration in the soil or the degree of metal tolerance in the plant. Studies using controlled crosses, interspecific hybrids, and molecular markers are beginning to shed light on the genetic control of this variation. As molecular physiology provides greater insights into the specific genes that control metal accumulation, we may learn more about the genetic and regulatory factors that influence variable expression of the hyperaccumulation phenotype.
Contamination of soils by heavy metals is of widespread occurrence as a result of human, agricultural and industrial activities. Among heavy metals, lead is a potential pollutant that readily accumulates in soils and sediments. Although lead is not an essential element for plants, it gets easily absorbed and accumulated in different plant parts. Uptake of Pb in plants is regulated by pH, particle size and cation exchange capacity of the soils as well as by root exudation and other physico-chemical parameters. Excess Pb causes a number of toxicity symptoms in plants e.g. stunted growth, chlorosis and blackening of root system. Pb inhibits photosynthesis, upsets mineral nutrition and water balance, changes hormonal status and affects membrane structure and permeability. This review addresses various morphological, physiological and biochemical effects of Pb toxicity and also strategies adopted by plants for Pb-detoxification and developing tolerance to Pb. Mechanisms of Pb-detoxification include sequestration of Pb in the vacuole, phytochelatin synthesis and binding to glutathione and aminoacids etc. Pb tolerance is associated with the capacity of plants to restrict Pb to the cell walls, synthesis of osmolytes and activation of antioxidant defense system. Remediation of soils contaminated with Pb using phytoremediation and rhizofiltration technologies appear to have great potential for cleaning of Pb-contaminated soils.
Phytoremediation is a technology to clean the environment from heavy metals contamination. The objectives of this study are to threat Pb contaminated wastewater by using phytoremediation technology and to determine if the plant can be mention as hyperaccumulator. Fifty plants of Scirpus grossus were grown in sand medium and 600 L spiked water in various Pb concentration (10, 30 and 50 mg/L) was exposed. The experiment was conducted with single exposure method, sampling time on day-1, day-14, day-28, day-42, day-70, and day-98. The analysis of Pb concentration in water, sand medium and inside the plant tissue was conducted by ICP-OES. Water samples were filtered and Pb concentration were directly analyzed, Pb in sand samples were extracted by EDTA method before analyzed, and Pb in plant tissues were extracted by wet digestion method and analyzed. The results showed that on day-28, Pb concentration in water decreased 100%, 99.9%, 99.7%, and the highest Pb uptake by plant were 1343, 4909, 3236 mg/kg for the treatment of 10, 30, and 50 mg/L respectively. The highest BC and TF were 485,261 on day-42 and 2.5295 on day-70 of treatment 30 mg/L, it can be mentioned that Scirpus grossus is a hyperaccumulator.
Lead is a heavy metal of particular concern with respect to environmental quality and health. The lack of plant species that accumulate and tolerate Pb is a limiting factor to understand the molecular mechanisms involved in Pb tolerance. In this study we identified Hirschfeldia incana, a Brassicaceae collected from metalliferous mine spoils in Morocco, as a Pb accumulator plant. H. incana exhibited high Pb accumulation in mine soils and in hydroponic cultures. Major Pb accumulation occurred in the roots and a part of Pb translocated from the roots to the shoots, even to the siliques. These findings demonstrated that H. incana is a Pb accumulator species. The expression of several candidate genes after Pb-exposure was measured by quantitative PCR and two of them, HiHMA4 and HiMT2a, coding respectively for a P1B-type ATPase and a metallothionein, were particularly induced by Pb-exposure in both roots and leaves. The functional characterization of HiHMA4 and HiMT2a was achieved using Arabidopsis T-DNA insertional mutants. Pb content and primary root growth analysis confirmed the role of these two genes in Pb tolerance and accumulation. H. incana could be considered as a good experimental model to identify genes involved in lead tolerance and accumulation in plants.
Suitable plant species are able to accumulate heavy metals and to produce biomass useful for non-food purposes. In this study, three endemic Mediterranean plant species, Atriplex halimus, Portulaca oleracea and Medicago lupulina were grown hydroponically to assess their potential use in phytoremediation and biomass production. The experiment was carried out in a growth chamber using half strength Hoagland's solutions separately spiked with 5 concentrations of Pb and Zn (5, 10, 25, 50, and 100 mg L(-1)), and 3 concentrations of Ni (1, 2 and 5 mg L(-1)). Shoot and root biomass were determined and analyzed for their metals contents. A. halimus and M. lupulina gave high shoot biomass with relatively low metal translocation to the above ground parts. Metals uptake was a function of both metals and plant species. It is worth noting that M. lupulina was the only tested plant able to grow in treatment Pb50 and to accumulate significant amount of metal in roots. Plant metal uptake efficiency ranked as follows: A. halimus > M. lupulina > P. oleracea. Due to its high biomass production and the relatively high roots metal contents, A. halimus and M. lupulina could be successfully used in phytoremediation, and in phytostabilization, in particular.
The mobilization of heavy metals by man through extraction from ores and processing for different applications has led to the release of these elements into the environment. Since heavy metals are nonbiodegradable, they accumulate in the environment and subsequently contaminate the food chain. This contamination poses a risk to environmental and human health. Some heavy metals are carcinogenic, mutagenic, teratogenic and endocrine disruptors while others cause neurological and behavioral changes especially in children. Thus remediation of heavy metal pollution deserves due attention. Different physical and chemical methods used for this purpose suffer from serious limitations like high cost, intensive labor, alteration of soil properties and disturbance of soil native microflora. In contrast, phytoremediation is a better solution to the problem. Phytoremediation is the use of plants and associated soil microbes to reduce the concentrations or toxic effects of contaminants in the environments. It is a relatively recent technology and is perceived as cost-effective, efficient, novel, eco-friendly, and solar-driven technology with good public acceptance. Phytoremediation is an area of active current research. New efficient metal hyperaccumulators are being explored for applications in phytoremediation and phytomining. Molecular tools are being used to better understand the mechanisms of metal uptake, translocation, sequestration and tolerance in plants. This review article comprehensively discusses the background, concepts and future trends in phytoremediation of heavy metals.
The potential of 6 tree species (Leucaena leucocephala, Acacia mangium, Peltophorum pterocarpum, Pterocarpus macrocarpus, Lagerstroemia floribunda, Eucalyptus camaldulensis) for phytoremediation of Pb in sand tailings (total Pb >9850 mg kg(-1)) from KEMCO Pb mine in Kanchanaburi province, Thailand, were investigated employing a pot experiment (3 months) and field trial experiment (12 months). In pot study E. camaldulensis treated with Osmocote fertilizer attained the highest total biomass (15.3 g plant(-1)) followed by P. pterocarpum (12.6 g plant(-1)) and A. mangium (10.8 g plant(-1)) both treated with cow manure. Cow manure application resulted in the highest root Pb accumulation (>10000 mg kg(-1)) in L. floribunda and P. macrocarpus. These two species also exhibited the highest Pb uptake (85-88 mg plant(-1)). Results from field trial also showed that Osmocote promoted the best growth performance in E. camaldulensis (biomass 385.7 g plant(-1), height 141.7 cm) followed by A. mangium (biomass 215.9 g plant(-1), height 102.7 cm), and they also exhibited the highest Pb uptake (600-800 microg plant(-1)). A. mangium with the addition of organic fertilizer was the best option for phytostabilization of Pb-contaminated mine tailing because it retained higher Pb concentration in the roots.
Plants of Indian mustard (Brassica juncea) were treated with either 50 µM Cd, 250 µM Zn, or 25 µM Cd+125 µM Zn and the progression of chlorosis in the mature leaves
monitored. As relative chlorophyll (Chl) contents in the mature leaves decreased to 75, 50, and 25 % relative to controls,
both mature and young leaves were harvested and the Chl pools extracted. The metal treatments caused a greater loss of Chl
b than Chl a. As mature leaves underwent progressive chlorosis, the young leaves displayed a characteristic over-greening, due largely
to increased content of Chl b. However, as the young leaves began to experience chlorosis, a greater loss of Chl b was also observed. Thus during metal induced chlorosis, there is a preferential turnover of the Chl b pool in mature and young leaves.
Cuttings and seedlings of Jatropha curcas L. were exposed to different regimes of lead (Pb) stress as Pb(NO₃)₂ at 0 (CK), 0.5, 1, 2, 3, and 4 mM kg⁻¹ soil.
The effect of Pb treatment on the root length, tolerance index, photosynthetic pigments, photosynthetic activity, lipid peroxidation, and antioxidant enzyme was studied in a greenhouse pot experiment.
The results showed that root lengths and tolerance index decreased with increase of Pb concentration, but tolerance index of cuttings was always lower than those of the seedlings. For cuttings, Pb treatment had a stimulating effect on chlorophyll content, carotenoid content, and superoxide dismutase (SOD) activity at low concentration and an inhibitory effect at higher concentration. For seedlings, SOD activity increased with increasing Pb concentration. In both seedlings and cuttings, Pb caused inhibition of leaf growth and photosynthesis, and induced the membrane damage which was more obvious in the cuttings. In comparison with the control, the dynamic tendency of catalase and perxidase activities in the leaves of Pb-stressed plants all ascended, and then declined.
The increase in enzyme activities demonstrated that seedlings were more tolerant to Pb stress than cuttings. These results also indicate that the antioxidant system may play an important role in eliminating or alleviating the toxicity of Pb in J. curcas seedlings and cuttings. The accumulation of Pb increased in a concentration-dependent manner; however, its translocation from root to shoot was low. The cuttings accumulated significantly higher Pb in roots than seedlings.
Glasshouse and field studies showed that Vetiver grass can produce high biomass (>100t/ tha(-1) year(-1)) and highly tolerate extreme climatic variation such as prolonged drought, flood, submergence and temperatures (-15 degrees - 55 degrees C), soils high in acidity and alkalinity (pH 3.3-9.5), high levels of Al (85% saturation percentage), Mn (578 mg kg(-1)), soil salinity (ECse 47.5 dS m(-1)), sodicity (ESP 48%), anda wide range of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn). Vetiver can accumulate heavy metals, particularly lead (shoot 0.4% and root 1%) and zinc (shoot and root 1%). The majority of heavy metals are accumulated in roots thus suitable for phytostabilization, and for phytoextraction with addition of chelating agents. Vetiver can also absorb and promote biodegradation of organic wastes (2,4,6-trinitroluene, phenol, ethidium bromide, benzo[a]pyrene, atrazine). Although Vetiver is not as effective as some other species in heavy metal accumulation, very few plants in the literature have a wide range of tolerance to extremely adverse conditions of climate and growing medium (soil, sand, and railings) combined into one plant as vetiver. All these special characteristics make vetiver a choice plant for phytoremediation of heavy metals and organic wastes.
Elevated lead (Pb) concentrations in residential houseyards around house walls painted with Pb-based pigments pose serious human health risks, especially to children. Vetiver grass (Vetiveria zizanioides L.) has shown promise for use in in situ Pb phytoremediation efforts. However, little is known about the biochemical mechanisms responsible for the observed high Pb tolerance by vetiver. We hypothesized that vetiver exposure to Pb induced the synthesis of phytochelatins (PC(n)) and the formation of Pb-PC(n) complexes, alleviating the phytotoxic effects of free Pb ions. Our main objective was to identify PC(n) and Pb-PC(n) complexes in root and shoot compartments of vetiver grass using high-performance liquid chromatography coupled to electrospray mass spectrometry (HPLC-ES-MS). After 7 d of exposure to Pb, vetiver accumulated up to 3000 mg Pb kg(-1) in shoot tissues, but much higher Pb concentrations were measured in root ( approximately 20,000 mg kg(-1)), without phytotoxic symptoms. Scanning electron micrographs showed Pb deposition in the vascular tissues of root and shoot, suggesting Pb translocation to shoot. Collision-induced dissociation analyses in MS/ MS mode during HPLC-ES-MS analysis allowed for the confirmation of four unique PC(n) (n = 1-4) based on their respective amino acid sequence. The high tolerance of vetiver grass to Pb was attributed to the formation of PC(n) and Pb-PC(n) complexes within the plant tissues, using ES-MS and Pb mass isotopic patterns. These data illustrate the mechanism of high Pb tolerance by vetiver grass, suggesting its potential usefulness for the remediation of Pb-contaminated residential sites.
Stabilization of metals with amendments and red fescue (Festuca rubra, cv. Keszthelyi 2) growth was studied on an acidic and phytotoxic mine spoil (pH(KCl) 3.20-3.26; Cd 7.1 mg kg(-1), Cu 120 mg kg(-1), Pb 2154 mg kg(-1) and Zn 605 mg kg(-1)) from Gyöngyösoroszi, Hungary in a pot experiment. Raising the pH above 5.0 by lime (CaCO(3)), and supplementing with 40 mg kg(-1)nitrogen (NH(4)NO(3)) made this material suitable for plant growth. All cultures were limed with 0.5% (m/m) CaCO(3) (treatment 1), which was combined with 5% (m/m) municipal sewage sludge compost (treatment 2), 5% (m/m) peat (treatment 3), 7.5% (m/m) natural zeolite (clinoptilolite) (treatment 4), and 0.5 (m/m) KH(2)PO(4) (treatment 5). Treatments 1-5 were combined with each other (treatment 6). After 60 days of red fescue growth, pH of the limed mine spoil decreased in all cultures units. Application of peat caused the highest pH decrease (1.15), while decrease of pH was less than 0.23 in treatments 2, 5 or 6. Application of lime significantly reduced concentrations of metals in the 'plant available' fraction of mine spoil compared to non-limed mine spoil. Amendments added to limed mine spoil changed variously the ratio of Cd, Cu, Pb and Zn in exchangeable or 'plant available' fractions, differently influencing the phytoavailability of these metals. Most of the metals were captured in the roots of test plants. Treatment 2 caused the appearance of less Cd in shoots (<0.1 microg g(-1)) or roots (3.11 microg g(-1)), while treatment 5 resulted in the highest Cd concentration (2.13 microg g(-1)) in shoots. Treatments did not influence significantly the Cu accumulation in shoots. The Pb accumulation of roots (44.7 microg g(-1)) was most effectively inhibited by combined treatment, while the highest value (136 microg g(-1)) was found in the culture treated with potassium phosphate. Pb concentration in shoots was below the detection limit, except for treatments 5 and 6. Peat application resulted in higher Zn concentration (448 microg g(-1)) in shoots than other amendments, where these values were around 100 microg g(-1). All amendments influenced positively the dry matter yield of red fescue grown in limed mine spoil, however the application of 0.5 phosphate was less favourable. Liming, application of amendments and growth of red fescue can stabilize metals in acidic and phytotoxic mine spoil, and by phytostabilization they can reduce the risk of metal contamination of the food chain.
Coontail (Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1-100microM) for 1-7days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748mugPbg(-1) dw after 7d which reflected its metal accumulation ability, however most of the metal (1222microgg(-1) dw, 70%) was accumulated after 1d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC(2) and PC(3)) were synthesized to significant levels at 10 and 50microM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.
Coronopus didymus has been emerged as a promising wild, unpalatable plant species to alleviate lead (Pb) from the contaminated soils. This work investigated the hypothesis regarding various metabolic adaptations of C. didymus under lead (Pb) stress. In pot experiments, we assessed the effect of Pb at varied concentrations (500–2900 mg kg−1) on growth, photosynthetic pigments, alteration of macromolecular (protein and carbohydrate) content, and activities of enzymes like protease, α-and β-amylase, peroxidase (POX), and polyphenol oxidase (PPO) in C. didymus for 6 weeks. Results revealed that Pb exposure enhanced the growth, protein, and carbohydrate level, but decreased the leaf pigment concentration and activities of hydrolytic enzymes. The activities of POX and PPO in roots increased progressively by ~337 and 675%, respectively, over the control, at 2900 mg kg−1 Pb treatment. Likewise, contemporaneous findings were noticed in shoots of C. didymus, strongly indicating its inherent potential to cope Pb-induced stress. Furthermore, the altered plant biochemical status and upregulated metabolic activities of POX and PPO indulged in polyphenol peroxidation elucidate their role in allocating protection and conferring resistance against Pb instigated stress. The current work suggests that stress induced by Pb in C. didymus stimulated the POX and PPO activities which impart a decisive role in detoxification of peaked Pb levels, perhaps, by forming physical barrier or lignifications.
In a screenhouse experiment, we investigated the role of two environment friendly chelants, Ammonium molybdate and EDDS for Pb mobilisation and its extraction by Coronopus didymus under completely randomized controlled conditions. Seedlings of C. didymus were grown in pots having Pb-contaminated soil (1200 and 2200 mg kg⁻¹) for 6 weeks. Plants were harvested, 1 week after the addition of A. molybdate and EDDS. Results revealed that A. molybdate and EDDS enhanced the uptake and accumulation of Pb in roots and shoots of C. didymus. At 2200 mg kg⁻¹ Pb level, compared to Pb-alone treatment, the maximal concentration of Pb was increased upto ∼10% and ∼19%, in roots whereas ∼8% and ∼18%, respectively, in shoots on addition of 2 mmol kg⁻¹ A. molybdate and EDDS. Additionally, Pb + EDDS treatments enhanced the plant biomass and triggered strong antioxidative response, more efficaciously than Pb + A. molybdate and Pb-alone treated plants. In this study, EDDS relative to A. molybdate was more efficient in mobilising and extracting Pb from soil. Although, EDDS followed by A. molybdate had good efficacy in mitigating Pb from contaminated soils but C. didymus itself has the inherent affinity to tolerate and accumulate Pb from contaminated soils and hence in future, can be used either alone or with some other eco-friendly amendments for soil remediation purposes.
New findings are recorded and a dot map with all localities in Greece is included.-from Author
We studied chelate effects on castor bean (Ricinus communis L.) growth. These effects included Cd and Pb accumulation in plant tissues and the chemical behavior of Cd and Pb in the plant rhizosphere and non-rhizosphere. Tests were conducted in a glasshouse using the rhizobag method. Two castor bean cultivars (Zibo-3 and Zibo-9) were grown in soil contaminated with 3.53mg/kg Cd and 274mg/kg Pb. The soil was treated with citric acid (CA), ethylenediamine disuccinic acid (EDDS) or ethylenediamine tetraacetic acid (EDTA) (5mmol/kg). EDDS-treated soil produced 28.8% and 59.4% greater biomass for Zibo-3 and Zibo-9 respectively. In contrast, CA and EDTA inhibited the growth of the two cultivars. Zibo-9 had greater tolerance than Zibo-3 to chelate toxicity. Based on Cd and Pb plant uptake, EDDS could substitute for EDTA for phytoremediation of Cd in soil. EDTA was the most effective of the three chelates for Pb phytoremediation but it is less suitable for field use due to toxicology environmental persistence. Acid extractable Cd and Pb in the rhizosphere or reducible Cd and Pb in the non-rhizosphere of soil were the main influences on Cd and Pb accumulation in castor bean.
A screenhouse experiment was conducted to assay the effect of Lead (Pb) on oxidative status, antioxidative response and metal accumulation in Coronopus didymus after 6 weeks. Results revealed a good Pb tolerance and accumulation potential of C. didymus towards the increasing Pb concentrations (500, 900, 1800, 2900 mg kg−1) in soil. The content of Pb in roots and shoots elevated with higher Pb levels and reached a maximum of 3684.3 mg kg−1 and 862.8 mg kg−1 Pb dry weight, respectively, at 2900 mg kg−1 treatment. Pb exposure stimulated electrolyte leakage, H2O2 level, MDA content and the activities of antioxidant machinery (SOD, CAT, APX, GPX and GR). However, at the highest Pb concentration, the activities of SOD and CAT declined. The H2O2 level and MDA content in roots increased significantly up to ∼500% and 213%, respectively, over the control, at 2900 mg kg−1 Pb treatment. Likewise, concurrent findings were noticed in shoots of C. didymus, with the increasing Pb concentration. The present work suggests that C. didymus exhibited a good accumulation potential for Pb and can tolerate Pb-induced oxidative stress by an effective antioxidant defense mechanism.
A simple, rapid method requiring few manipulations for the extraction of chlorophylls from fragmented leaf tissue of angiosperms and gymnosperms is compared with the widely used acetone method. Unlike the acetone method where grinding and subsequent centrifugation are essential, this method makes use of incubation at 65 °C of leaf tissue immersed in dimethyl sulphoxide. The new method was found to be as efficient as acetone for chlorophyll extraction and superior in terms of chlorophyll stability.
Phytoextraction is an environmentally friendly and a cost-effective strategy for remediation of heavy metal contaminated soils. However, lower bioavailability of some of the metals in polluted environments e.g. lead (Pb) is a major constraint of phytoextraction process that could be overcome by applying organic chelators. We conducted a glasshouse experiment to evaluate the role of citric acid (CA) in enhancing Pb phytoextraction. Brassica napus L. seedlings were grown in hydroponic media and exposed to various treatments of Pb (50 and 100 μM) as alone or in combination with CA (2.5 mM) for six weeks. Pb-induced damage in B. napus toxicity was evident from elevated levels of malondialdehyde (MDA) and H2O2 that significantly inhibited plant growth, biomass accumulation, leaf chlorophyll contents and gas exchange parameters. Alternatively, CA application to Pb-stressed B. napus plants arrested lipid membrane damage by limiting MDA and H2O2 production and by improving antioxidant enzyme activities. In addition, CA significantly increased the Pb accumulation in B. napus plants. The study concludes that CA has a potential to improve Pb phytoextraction without damaging plant growth.
Phytoremediation is a promising option for reclaiming soils contaminated with toxic metals, using plants with high potentials for extraction, stabilization and hyperaccumulation. This study was conducted in Cameroon, at the Bassa Industrial Zone of Douala in 2011, to assess the total content of 19 heavy metals and 5 other elements in soils and phytoremediation potential of 12 weeds. Partial extraction was carried out in soil, plant root and shoot samples. Phytoremediation potential was evaluated in terms of the Biological Concentration Factor, Translocation Factor and Biological Accumulation Coefficient. The detectable content of the heavy metals in soils was Cu:70–179, Pb:8–130, Zn:200–971, Ni:74–296, Co:31–90, Mn:1983–4139, V:165–383, Cr:42–1054, Ba:26–239, Sc:21–56, Al:6.11–9.84, Th:7–22, Sr:30–190, La:52–115, Zr:111–341, Y:10–49, Nb:90–172 in mg kg−1, and Ti:2.73–4.09 and Fe:12–16.24 in wt%. The contamination index revealed that the soils were slightly to heavily contaminated while the geoaccumulation index showed that the soils ranged from unpolluted to highly polluted. The concentration of heavy metals was ranked as Zn > Ni > Cu > V > Mn > Sc > Co > Pb and Cr in the roots and Mn > Zn > Ni > Cu > Sc >Co > V > Pb > Cr > Fe in the shoots. Dissotis rotundifolia and Kyllinga erecta had phytoextraction potentials for Pb and Paspalum orbiculare for Fe. Eleusine indica and K. erecta had phytostabilisation potential for soils contaminated with Cu and Pb, respectively.
Dianthus carthusianorum is one of the dominant plant species colonising the Zn-Pb waste deposits in Bolesław, Southern Poland. It differs in terms of morphology and genetics from ecotypes inhabiting non-metal-polluted areas. The response of waste-heap (metallicolous, M) and reference (nonmetallicolous, NM) ecotypes of D. carthusianorum to Pb in hydroponics was investigated and compared in this study. The plants of the M ecotype were more tolerant to Pb than these of the NM ecotype in spite of accumulation of higher concentrations of Pb. In both ecotypes, about 70-78% of Pb was retained in roots. In non Pb-treated plants, a higher glutathione (GSH) level was found in the M ecotype. After the Pb exposure, the GSH level decreased and was similar in both ecotypes. Lead treatment induced synthesis of phytochelatins (PCs) only in the plant roots, with significantly higher concentrations thereof detected in the NM ecotype. Malate and citrate concentrations were higher in the M ecotype; however, they did not change significantly upon any Pb treatment in either ecotype. The results indicated that neither PCs nor organic acids were responsible for the enhanced Pb tolerance of the waste-heap plants.
A DTPA soil test was developed to identify near‐neutral and calcareous soils with insufficient available Zn, Fe, Mn, or Cu for maximum yields of crops. The extractant consists of 0.005 M DTPA (diethylenetriaminepentaacetic acid), 0.1 M triethanolamine, and 0.01 M CaCl 2 , with a pH of 7.3. The soil test consists of shaking 10 g of air‐dry soil with 20 ml of extractant for 2 hours. The leachate is filtered, and Zn, Fe, Mn, and Cu are measured in the filtrate by atomic absorption spectrophotometry.
The soil test successfully separated 77 Colorado soils on the basis of crop response to Zn, Fe, and Mn fertilizers. Critical nutrient levels must be determined separately for each crop using standardized procedures for soil preparation, grinding, and extraction. The critical levels for corn using the procedures reported herein were: 0.8 ppm for Zn, 4.5 ppm for Fe, and tentatively 1.0 ppm for Mn, and 0.2 ppm for Cu.
Development of the soil test was based, in part, on theoretical considerations. The extractant is buffered at pH 7.30 and contains CaCl 2 so that equilibrium with CaCO 3 is established at a CO 2 level about 10 times that of the atmosphere. Thus, the extractant precludes dissolution of CaCO 3 and the release of occluded nutrients which are normally not available to plants. DTPA was selected as the chelating agent because it can effectively extract all four micronutrient metals. Factors such as pH, concentration of chelating agent, time of shaking, and temperature of extraction affect the amount of micronutrients extracted and were adjusted for maximum overall effectiveness.