|Year : 2021 | Volume
| Issue : 1 | Page : 28-31
Mimosa pudica: Novel plant as arsenic hyperaccumulator
Firoz Naem Khan1, Kamal Uddin Zaidi1, Rajesh Kumar Tenguria2, Vijay Thawani3
1 Biotechnology and Pharmacology Laboratory, Centre for Scientific Research and Development, People's University, Bhopal, Madhya Pradesh, India
2 Department of Botany, Division of Microbiology, Government Motilal Vigyan Mahavidhyalaya, Bhopal, Madhya Pradesh, India
3 People's College of Medical Sciences and Research Centre, Bhopal, Madhya Pradesh, India
|Date of Submission||23-Jan-2018|
|Date of Acceptance||08-Jan-2021|
|Date of Web Publication||29-Jun-2021|
Dr. Firoz Naem Khan
Biotechnology and Pharmacology Laboratory, Centre for Scientific Research and Development, People's University, Bhanpur, Bhopal- 462 037, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: Arsenic contamination in soil and its environmental effects have been studied for its global impact around the globe. Materials and Methods: This study evaluated the role of five plant species collected from arsenic-contaminated sites in in vitro phytoremediation of arsenic and its correlation with rhizobacteria under hydroponic conditions using high-performance liquid chromatography -ICP. Results: Mimosa pudica showed the ability to uptake arsenic with/ without Rhizobium. Conclusion: It is concluded that rhizosphere microbiota helps plants to increase arsenic uptake and may be utilized as an efficient biological alternative in phytoremediation.
Keywords: High-performance liquid chromatography -ICP, phytoextraction, phytoremediation, plant–microbe interaction
|How to cite this article:|
Khan FN, Zaidi KU, Tenguria RK, Thawani V. Mimosa pudica: Novel plant as arsenic hyperaccumulator. J Mahatma Gandhi Inst Med Sci 2021;26:28-31
|How to cite this URL:|
Khan FN, Zaidi KU, Tenguria RK, Thawani V. Mimosa pudica: Novel plant as arsenic hyperaccumulator. J Mahatma Gandhi Inst Med Sci [serial online] 2021 [cited 2022 May 16];26:28-31. Available from: https://www.jmgims.co.in/text.asp?2021/26/1/28/319833
| Introduction|| |
Arsenic (As) pollution causes serious environmental problems and is a major concern throughout the world. Regions in Bangladesh, western United States, Mexico, northern Chile, Argentina, Hungary, Romania, Mongolia, Taiwan, Vietnam, Thailand, Nepal, and India contain As concentrations >50 μg/L. The World Health Organization (WHO) has set guidelines on a maximum acceptable value for As in drinking water to be 10 μg/L and 2 μg/g on a fresh weight basis in food. The standard is that the maximum concentration of As which would not cause any significant health risk to a 70 kg consumer over a lifetime water consumption of 2 l/day.
Phytoremediation is a cost-effective and environmental method of extracting pollutants from soils like As. The discovery of As-hyperaccumulating ferns and their biochemistry, ecology, and agronomy have rapidly increased their potential utility. Phytoextraction has become increasingly popular because of its low cost compared to other traditional remedies. The costs include planting, maintenance, harvesting, and disposal of plant biomass. The volume and mass of the plant disposal are lesser than the disposal of soil when excavation is required. However, because phytoextraction is dependent on the plant, conditions at the site must be able to maintain plant production, and the contaminant must be accessible to the roots for uptake. In addition, soils with very high contaminant concentrations may inhibit plant growth and/or significantly prolong the amount of time required for remediation.
This study aimed to assess the indigenous plant species efficacy as As hyperaccumulators and identify the role of rhizobacteria.
| Materials and Methods|| |
The plant samples of Lantana camara (Raimuniya), Vetiver zizanioides (Vetiver grass), Mimosa pudica (Lajwanti), Ipomoea fistulosa (Besaram), and Calotropis procera (Akaua) were collected from polluted soil of general area Mandideep, an industrial region on the outskirts of Bhopal, Madhya Pradesh. The plants were collected along with soil and kept in sterile sampling bags and maintained under greenhouse conditions as stock culture. The plant specimen was identified and authenticated by Dr. R. K Tenguria, Botanist Department of Botany, Govt. M. V. M, Bhopal with specimen no (F/R20,16) deposited at the botanical herbarium.
In vitro development of hydroponic culture system and plant propagation
Young plant samples having 2–3 leaves from stock culture were washed with sterile water and transferred to 250 ml Hoagland solution for new root formation. The plants were kept in greenhouse at the average temperature of 14°C (night) and 30°C (day) under the optimal photoperiod. They were allowed to grow for 2 weeks prior to experiments.
Characterization of plant growth performance
On acclimatization with hydroponic condition, the samples of L. camara, V. zizanioides, M. pudica, I. fistulosa and C. procera were transferred in 250 ml Hoagland nutrient solution with various concentration of As of 25, 50, and 100 ppm along with controls of each.
M. pudica (Lajwanti) was selected for further experiments because of its adaptation to in vitro culturing and survival in greenhouse conditions.
Estimation of arsenic
Digestion of samples was performed using plant leaves biomass collected from control (without As) and As supplemented Hoagland nutrient solution for estimation of As. Further, leaves were thoroughly washed in tap water followed by thrice washing with distilled water and dried at 60°C for 3 days in a hot air oven. Homogenization was performed with pulverization in mortar and pestle and their powdered dry weight was determined. In 1 g of leaf sample, 6.5 ml nitric acid and 2.5 ml hydrochloric acid were added and digested using a microwave sample preparation system (300 W for 15 min). After cooling, the sample solution was filtered through Whatman filter paper No. 42 and volume of filtrate was adjusted to 100 ml using double distilled water. The standard solution was prepared from the pure As stock (disodium arsenate) obtained from E-Merck (Cat. No: 1.70303.0100). Estimation of As was done using the high-performance liquid chromatography (HPLC).
The high-performance liquid chromatography with inductively coupled plasma mass (HPLC-ICP) analysis showed that As was accumulated in the live and dead plant biomass of M. pudica (Lajwanti). Accumulation of As was proportional to the concentration of As in the growth medium and duration of culture. After a particular duration growth, As accumulation was more under higher concentrations while less under lower concentrations of Hoagland nutrient solution.
Isolation of Rhizobium
To study the effect of Rhizobium on phytoremediation of As, the culture was obtained from M. P. Agro Industry, Bhopal, and maintained in laboratory conditions. Five gram of Rhizobium was suspended in 20 ml of 0.85% sodium chloride solution and was kept for about 30 min to allow large particles to settle down, then 1 ml of suspension was added to 50 ml of enrichment medium (8 g nutrient broth and 0.5 g yeast extract in 1000 ml distilled water). The culture was then incubated at 30°C on a rotating shaker at 200 rpm for 7 days. Then, 1 ml of the sample was transferred into 100 ml of mineral medium (0.5 g ammonium chloride, 0.25 g magnesium chloride hexahydrate, 0.5 g potassium dihydrogen phosphate, 0.5 g beef extract, and 0.3 g glucose in 1000 ml distilled water, pH 5.6) and incubated at 35°C for 48 h. The regular subculturing was done once a week to maintain the culture. The culture was centrifuged and the pellet was rinsed thrice with distilled water, and 1 ml of culture was inoculated in 250 ml flasks containing 100 ml of nutrient broth and incubated for 48 h on a shaker incubator. The pellet-containing bacterial cells were extracted using centrifugation at 5500 rpm for 7 min and were suspended in fresh nutrient broth for further use as rhizobacterial inoculums. For the selective isolation of Rhizobium, yeast extract mannitol agar (YEMA) with Congo red was used.
In vitro effect of Rhizobium on the phytoremediation
M. pudica was acclimatized to Hoagland nutrient solution for further assessment of As in the presence of Rhizobium to detect change in phytoremediation efficiency. For preparation of Rhizobium suspension, 1 ml of inoculum from nutrient broth was suspended in 5 ml of distilled water. M. pudica was dipped into 100 ml Rhizobium suspension for 30 min and was transferred to Hoagland solution with different As concentrations along with control.
Rhizobium-cultured plant biomass was detected on the basis of appearance of new leaves, coloration of leaves, and overall growth pattern of the plants and changes in morphology. For detection of As concentration, live and dead biomass of each plant leaves samples was collected after 14 days of transplantation. All the leaf samples were oven dried at 60°C for 3 days and then pulverized and homogenized to determine the dry weight. One gram each of dry plant leaf sample was taken and As estimation using the HPLC-ICP. Agilent G3288–8000, 4.6 mm × 250 mm, plus G3154–65002 Guard column was used for As determination.
| Results and Discussion|| |
On the basis of plant experiments conducted on five plant species, only one, i.e., M. pudica was selected due to its better acclimatization to greenhouse conditions. During collection, it was observed that M. pudica was abundantly prevalent in the area of sample collection. The HPLC-ICP analysis showed As uptake by M. pudica without Rhizobium to be 24 mg/kg (25 ppm), 49 mg/kg (50 ppm), and 97.9 mg/kg (100 ppm) in extraction percentage 96, 98, and 97.9, respectively [Table 1] and [Graph 1],[Graph 2],[Graph 3].
|Table 1: Extraction percentage of arsenic in Mimosa pudica without and with Rhizobium|
Click here to view
In vitro effect of Rhizobium on the phytoremediation
Rhizobium isolates on nutrient agar appeared whiteopaque, milky to waterytranslucent colonies. Nutrient agar stock culture transferred on yeast extract mannitol agar (YEMA) medium showed pure isolated colonies of Rhizobium culture as circular, light pink, convex, entire, and translucent. Microscopically, the bacteria were Gram-negative rods.
It was observed that M. pudica had an ability to accumulate As in the presence of Rhizobium. The HPLC-ICP analysis showed increased As accumalation and extraction percentage of 24.19 mg/kg (96.78%) in 25 ppm, 49.16 mg/kg (98.32%) in 50 ppm, and 98.36 mg/kg (98.36%) in 100 ppm. Total increase on addition of Rhizobium was 0.78, 0.32, and 0.46 at 25, 50, and 100 ppm, respectively [Table 1] and [Graph 4],[Graph 5],[Graph 6].
Terrestrial As hyperaccumulators have specialized mechanisms that allow them to solubilize, take up, and store As in a nontoxic form. Chinese brake ferns (Pteris vittata) have been used to extract As in the field and greenhouse experiments to assess the performance of phytoremediation from contaminated soil have been done. Recent developments in in situ bioremediation of trace metal contaminated soils along with microbial dynamics in the rhizospheres of plants growing on such soil and their significance in phytoremediation showed the natural role of plant growth promoting rhizobacteria, P-solubilizing bacteria, mycorrhizal-helping bacteria, and arbuscular mycorrhizal fungi in maintaining soil fertility. The As tolerance and accumulation were investigated in P. vittata collected from As contaminated and uncontaminated sites in China compared with Pteris semipinnata (non-As hyperaccumulator) in hydroponics exhibited higher As tolerance in hydroponic culture. A comparison study conducted for As accumulation and tolerance among four populations of P. vittata from habitats showed rise in uptake of As.
Recent findings suggest that the synergistic association of Eichhornia crassipes and various rhizobacteria is an effective strategy to enhance removal of As. E. crassipes (Mart.) Solms either alone or in association with plant growth promoting rhizobacteria. Pseudomonas and Azotobacter inoculation to E. crassipes resulted in enhanced As removal compared to uninoculated control. A study investigated the micro-distribution of As in three ecotypes after exposure to arsenite (AsIII) and arsenate (AsV). It indicated that oxidation and chelation contributed to the accumulation of As in P. vittata.
| Conclusion|| |
It was observed that M. pudica was able to accumulate the As and maintained it in nontoxic form. The plant species without Rhizobium was able to uptake arsenic. This can be interrelated as the plants were acclimatized to the higher As conditions prevailing in the industrial area of Mandideep from where the plant was collected and adapted to utilize As and survive under that stress. It also describes that rhizosphere microbiota helps plants to increase As uptake and may be utilized as an efficient biological alternative in phytoremediation.
The authors are thankful to People's University, Bhopal, for financial support to conduct this study and for providing laboratory facilities to carry out the research work.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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