Removing Arsenic and Antimony by Phragmites australis: Rhizofiltration Technology

Can Environmental Stressors Determine the Condition of Ecological Plant Groups?

There is still a need to investigate the relationships between glycophytes and halophytes and the many biotic and abiotic factors in their natural environments. Therefore, we study the effects of the type of environment on the ecophysiological responses and condition of the glycophyte Elder Sambucus nigra L., the macrophyte Common Reed Phragmites australis (Cav.) Trin. ex Steud., the facultative halophyte Weeping Alkaligrass Puccinellia distans (Jacq.) Parl, and the obligate halophyte Common Glasswort Salicornia europaea L. in a saline-disturbed anthropogenic region of central Poland. We analyzed the effects of salinity, acidity, and soil organic matter on shoot length, lipoperoxidation, and proline in roots and green parts, and evaluated plant responses to environmental disturbance, which allowed for the comparison of adaptation strategies. The studies were carried out in (1) "sodium production" (near sodium factories), (2) "anthropogenic environments" (waste dumps, agroecosystems, calcium deposits, post-production tanks), (3) "wetland environments" (near river channels and riparian areas), and (4) "control" (natural, unpolluted environments). Green parts of plants are better suited to indicate environmental stress than roots. Their higher structural MDA membrane damage is related to the transport of toxic ions to the shoots by a rapid transpiration stream in the xylem. We found high salinity to be the main factor inducing growth and found it to be correlated with the high pH effect on proline increase in glycophytes (Elder, Reed) and Weeping Alkaligrass, in contrast to Common Glasswort. We suggest that proline accumulation allows osmotic adjustment in the green parts of reeds and alkaligrasses, but may have another function (in Elder). Common Glasswort accumulates large amounts of Na+, which is energetically more effective than proline accumulation for osmotic adjustment. Organic matter affects plant growth and proline levels, but soil salinity and pH alter nutrient availability. Plant distribution along the salinity gradient indicates that Elder is the most salt-sensitive species compared to Reed, Alkaligrass, and Glasswort. Salinity and the lack of control of thick reeds, which compete with other plant groups, affect the distribution of halophytes in saline environments.

Microbial Spectra, Physiological Response and Bioremediation Potential of Phragmites australis for Agricultural Production

Common reed (Phragmites australis) can invade and dominate in its natural habitat which is mainly wetlands. It can tolerate harsh environments as well as remediate polluted and environmental degraded sites such as mine dumps and other polluted wastelands. For this reason, this can be a very critical reed to reclaim wastelands for agricultural use to ensure sustainability. The present review manuscript examined the microbial spectra of P. australis as recorded in various recent studies, its physiological response when growing under stress as well as complementation between rhizosphere microbes and physiological responses which result in plant growth promotion in the process of phytoremediation. Microbes associated with P. australis include Proteobacteria, Bacteriodetes, and Firmicutes, Fusobacteria, Actinobacteria, and Planctomycetes families of bacteria among others. Some of these microbes and arbuscular mycorrhizal fungi have facilitated plant growth and phytoremediation by P. australis. This is worthwhile considering that there are vast areas of polluted and wasted land which require reclamation for agricultural use. Common reed with its associated rhizosphere microbes can be utilized in these land reclamation efforts. This present study suggests further work to identify microbes which when administered to P. australis can stimulate its growth in polluted environments and help in land reclamation efforts for agricultural use.

Metal Accumulation and Tolerance in Artemisia indica var. maximowiczii (Nakai) H. Hara. and Fallopia sachalinensis (F.Schmidt) Ronse Decr., a Naturally Growing Plant Species at Mine Site

For growing plants at mine sites, plant species that accumulate metals in tissues and are tolerant to high metal concentrations should be selected from the perspective of phytostabilization. However, the eco-chemical or elemental information of the plant species at the mine sites is limited. The purpose of this study was to identify plants that can adapt to natural growth at mine sites, via: (1) vegetation survey, (2) elemental analysis in soil and plants, and (3) detoxicant detection in plant cells. Our vegetation survey indicated that plants growing at our study site are consistent with plant species confirmed at other mine sites in previous reports. A. indica var. maximowiczii and F. sachalinensis, present at the mine site, highly accumulated Fe, Al, and Cu in the roots, indicating their metal tolerance. Furthermore, A. indica var. maximowiczii produced detoxicants such as chlorogenic acid and 3,5-dicaffeoylquinic acid in the roots, which exhibited high antioxidative activity that would play an important role in metal tolerance in A. indica var. maximowiczii. This study will be effective in providing fundamental information on phytostabilization at mine sites.

Feasibility Study of Phragmites karka and Christella dentata Grown in West Bengal as Arsenic Accumulator

A survey was undertaken, in arsenic (As) contaminated area of the Nadia district, West Bengal, India, to find native As accumulator plants. As was determined both in soil and plant parts. The results showed that the mean translocation factor of Pteris vittata L, Phragmites karka (Cav.) Trin. Ex. Steud and Christella dentata Forssk were higher than 1. It thus appeared that these plants can be efficient accumulators of As. Phytoremediation ability of C. dentata and P. karka was evaluated and compared with known As-hyperaccumulators -P. vittata and Adiantum capillus veneris L. Plants were grown in the As spiked soil (25, 50, 75 and 100 mg kg(-1)). As accumulation was found to be highest in P. vittata, 117.18 mg kg(-1) in leaf at 100 mg kg(-1) As treatment, followed by A. capillus veneris, P. karka and C. dentata being 74, 83.87 and 40.36 mg kg(-1), respectively. Lipid peroxidation increased after As exposure in all plants. However, the antioxidant enzyme activity and molecules concentration also increased which helped the plants to overcome As-induced oxidative stress. The study indicates that P. karka and C. dentata could be considered as As-accumulators and find application for As-phytoextraction in field conditions.

An overview of heavy metal challenge in plants: from roots to shoots

Heavy metals are often present naturally in soils, but many human activities (e.g. mining, agriculture, sewage processing, the metal industry and automobiles) increase their prevalence in the environment resulting in concentrations that are toxic to animals and plants. Excess heavy metals affect plant physiology by inducing stress symptoms, but many plants have adapted to avoid the damaging effects of metal toxicity, using strategies such as metal chelation, transport and compartmentalization. Understanding the molecular basis of heavy metal tolerance in plants will facilitate the development of new strategies to create metal-tolerant crops, biofortified foods and plants suitable for the phytoremediation of contaminated sites.

Phytoprotective influence of bacteria on growth and cadmium accumulation in the aquatic plant Lemna minor

Certain plants are known to accumulate heavy metals, and can be used in remediation of polluted soil or water. Plant-associated bacteria, especially those that are metal tolerant, may enhance the total amount of metal accumulated by the plant, but this process is still unclear. In this study, we investigated metal enhancement vs. exclusion by plants, and the phytoprotective role plant-associated bacteria might provide to plants exposed to heavy metal. We isolated cadmium-tolerant bacteria from the roots of the aquatic plant Lemna minor grown in heavy metal-polluted waters, and tested these isolates for tolerance to cadmium. The efficiency of plants to accumulate heavy metal from their surrounding environment was then tested by comparing L. minor plants grown with added metal tolerant bacteria to plants grown axenically to determine, whether bacteria associated with these plants increase metal accumulation in the plant. Unexpectedly, cadmium tolerance was not seen in all bacterial isolates that had been exposed to cadmium. Axenic plants accumulated slightly more cadmium than plants inoculated with bacterial isolates. Certain isolates promoted root growth, but overall, addition of bacterial strains did not enhance plant cadmium uptake, and in some cases, inhibited cadmium accumulation by plants. This suggests that bacteria serve a phytoprotective role in their relationship with Lemna minor, preventing toxic cadmium from entering plants.

Biotechnological potential of aquatic plant-microbe interactions

The rhizosphere in terrestrial systems is the region of soil surrounding plant roots where there is increased microbial activity; in aquatic plants, this definition may be less clear because of diffusion of nutrients in water, but there is still a zone of influence by plant roots in this environment [1]. Within that zone chemical conditions differ from those of the surrounding environment as a consequence of a range of processes that were induced either directly by the activity of plant roots or by the activity of rhizosphere microflora. Recently, there are a number of new studies related to rhizospheres of aquatic plants and specifically their increased potential for remediation of contaminants, especially remediation of metals through aquatic plant-microbial interaction.