Relationships between the trace-elements (TE) content of plants and associated soil have been widely investigated especially to understand the ecology of TE hyperaccumulating species to develop applications using TE phytoextraction. Many studies have focused on the possibility of quantifying the soil TE fraction available to plants, and used bioconcentration (BC) as a measure of the plants ability to absorb TE. However, BC only offers a static view of the dynamic phenomenon of TE accumulation. Accumulation kinetics are required to fully account for TE distributions in plants. They are also crucial to design applications where maximum TE concentrations in plant leaves are needed. This paper provides a review of studies of BC (i.e. soil-plant relationships) and leaf-age in relation to TE hyperaccumulation. The paper focuses of Ni and Mn accumulators and hyperaccumulators from New Caledonia who were previously overlooked until recent Ecocatalysis applications emerged for such species. Updated data on Mn hyperaccumulators and accumulators from New Caledonia are also presented and advocate further investigation of the hyperaccumulation of this element. Results show that leaf-age should be considered in the design of sample collection and allowed the reclassification of Grevillea meisneri known previously as a Mn accumulator to a Mn hyperaccumulator.

/pdf/leaf-age-and-soil-plant-relationships-key-factors-for-1rmbg6pmjl.pdf

Leaf-age and soil-plant relationships: key factors for reporting trace-elements hyperaccumulation by plants and design applications

Chenopodium ambrosioides L. can tolerate high concentrations of manganese and has potential for its use in the revegetation of manganese mine tailings. Following a hydroponic investigation, transmission electron microscopy (TEM)-energy disperse spectroscopy (EDS) was used to study microstructure changes and the possible accumulation of Mn in leaf cells of C. ambrosioides in different Mn treatments (200, 1000, 10000 μmol·L(-1)). At 200 μmol·L(-1), the ultrastructure of C. ambrosioides was clearly visible without any obvious damage. At 1000 μmol·L(-1), the root, stem and leaf cells remained intact, and the organelles were clearly visible without any obvious damage. However, when the Mn concentration exceeded 1000 μmol·L(-1) the number of mitochondria in root cells decreased and the chloroplasts in stem cells showed a decrease in grana lamellae and osmiophilic granules. Compared to controls, treatment with 1000 μmol·L(-1) or 10000 μmol·L(-1) Mn over 30 days, gave rise to black agglomerations in the cells. At 10000 μmol·L(-1), Mn was observed to form acicular structures in leaf cells and intercellular spaces, which may be a form of tolerance and accumulation of Mn in C. ambrosioides. This study has furthered the understanding of Mn tolerance mechanisms in plants, and is potential for the revegetation of Mn-polluted soils.

Effects of manganese on the microstructures of Chenopodium ambrosioides L., A manganese tolerant plant

Daucus carota is a biennial herb of the Umbelliferae family, which is a candidate plant for the phytoremediation of Mn pollution. To reveal the mechanism of this plant to adapt to Mn stress, plant growth, anatomical structure, Mn accumulation characteristic, Mn subcellular distribution, and chemical forms of D. carota under six Mn2+ concentrations by pot culture experiments were studied. The results showed that with the rising Mn concentrations, the total dry weight and leaf area of D. carota increased firstly and then decreased, while the specific leaf area increased. The thickness of the main vein, upper epidermis, and lower epidermis; the thickness of the palisade tissue; and the thickness of the spongy tissue of the leaves increased firstly and then decreased. The Mn content in the aboveground and underground parts of D. carota increased, and the values of the bioconcentration factor (BCF) and translocation factor (TF) were higher than 1. The Mn existing in the cell wall and soluble components accounted for the largest proportion, and the proportion of Mn in the cell wall increased with increasing concentrations of Mn. In addition, Mn mainly existed in ethanol extraction state, deionized water extraction state, and sodium chloride extraction state. The results showed that D. carota could alleviate the damage caused by high manganese concentration by storing most of manganese in the cell wall and vacuole and existing in the form of low-activity state.

/pdf/subcellular-distribution-and-chemical-forms-of-manganese-in-1qkcja0v.pdf

Subcellular distribution and chemical forms of manganese in Daucus carota in relation to its tolerance

Polygonum hydropiper was a new hyper-accumulated Mn plant.The experiments were carried out in order to find out subcellular distribution characteristics and chemical pattern of Mn in cell and the physiological and biochemical mechanisms of Polygonum hydropiper responding to Mn stress.The results indicated that the accumulation of Mn in the cell wall(accumulation rate as high as 36.34%)and the vacuole of the leaves(accumulation rate as high as 65.64%)might be one of the mechanisms of tolerance and hyperaccumulation of Polygonum hydropiper to Mn.Most Mn in leaves were the speciation of H2O-solubility organic salts or manganese oxalates.The content of chlorophyll a did not change under different Mn concentration treatments except that its content decreased remarkably when Mn concentration was 8 000 μmol/L in solutions.The membranes were not harmed by Mn when its concentration was less than 5 000 μmol/L in solutions;Under different Mn concentrations of Mn,the content of their soluble proteins of leaves had changed at some stage.The activity of SOD and POD were gradually improved with the increasing of Mn concentration,which could eliminate activated oxygen free radical,This might be the other physiological mechanism of tolerance and hyperaccumulation of Polygonum hydropiper responding to Mn.

Tang Shu

Papers

Physiological and Molecular Mechanisms of Mn Uptake by Hyperaccumulting Plant Polygonum hydropiper (Polygonaceae)