Changes in Tillering, Nutritional Status, and Biomass Yield of Panicum Maximum Used for Cadmium Phytoextraction

Although several grasses have been evaluated for cadmium (Cd) phytoextraction, there are no studies assessing how Cd is accumulated and distributed in the tissues of Panicum maximum grown in mildly polluted soils. The evaluation of tillering, nutritional status and biomass yield of this grass, mainly along successive shoot regrowths, is not well studied so far. Thus, P. maximum Jacq. cv. Massai was grown for two periods in an Oxisol presenting bioavailable Cd concentrations varying from 0.04 (control) to 10.91 mg kg−1 soil. Biomass yield of leaves and stems´ growth have decreased under the highest Cd exposure, but it did not occur in the regrowth period, indicating that Cd-induced toxicity is stronger in the early stages of development of P. maximum. The tillering was not compromised even the basal node presenting Cd concentrations higher than 100 mg kg−1 DW. We identified a restriction on Cd transport upwards from basal node, which was the main local of Cd accumulation. Apparently, P, K, Mg, S and Cu are involved in processes that restrict Cd translocation and confer high tolerance to Cd in P. maximum. The Cd-induced nutritional disorders did not negatively correlate with factors used to calculate phytoextraction efficiency. However, the nutritional adjustments of P. maximum to cope with Cd stress restricted the upward Cd transport, which decreased the phytoextraction efficiency from the available Cd concentration of 5.93 mg kg−1 soil.

Nitrate Increases Cadmium Accumulation in Sweet Sorghum for Improving Phytoextraction Efficiency Rather Than Ammonium

Sweet sorghum has potential for phytoextraction of cadmium (Cd) owning to its large biomass and relatively high Cd tolerance. Nitrogen affects both growth and Cd concentrations in plants. However, different forms of nitrogen effects on Cd accumulation in sweet sorghum to improve efficiency of Cd phytoremediation is still elusive. In this study, nitrate substantially promoted both dry weight and Cd concentrations in leaves, stems + sheaths and roots of sweet sorghum when compared with ammonium. As a result, Cd accumulation in nitrate-supplied sweet sorghum was around 3.7-fold of that in ammonium-supplied plants under unbuffered pH condition, while the fold was about 2.2 under buffered pH condition. We speculated pH values and Cd species in the growth medium to some extent contributed to increased Cd accumulation as affected by nitrate. Net photosynthesis rate and Fv/Fm of nitrate-treated plants under Cd stress were higher than that of ammonium-treated plants when the pH was unbuffered. Responses of antioxidant capacity in roots to Cd stress with nitrate application were stronger than that with ammonium supplementation. Taken together, nitrate is more suitable than ammonium for Cd phytoextraction by using sweet sorghum, which is able to enhance at least double efficiency of phytoextraction.

Effect of Plant Growth Promoting Rhizobacteria on Phytoextraction of Critical Raw Materials and Potentially Toxic Elements in Soil

<p>There are several regions of the world where soils are contaminated with potentially toxic elements (PTE) and/or have critical raw materials (CRM) that cannot be extracted through conventional raw material extraction techniques because of their low amounts. Phytoextraction- a kind of phytoremediation- offers good option or method to sustainably remediate these contaminated soils and extract these CRM from soils. The successful phytoextraction of these elements of interest from soil is dependent on their bioavailability for plant uptake and biomass production which could be increased by inoculating soil with plant growth promoting rhizobacteria (PGPR) and the element acquisition characteristics of the plant species used for phytoextraction. This study investigated the effect of the PGPR Bacillus amyloliquefaciens - FZB42 also called Rhizovital produced as spore’s formulation by ABiTEP on the phytoextraction efficiency of two selected species, Zea mays and Fagopyrum esculentum grown in potted soils under artificial lighting conditions for about 8 weeks in a laboratory. Results showed that for Fagopyrum esculentum, the inoculation of soil with Rhizovital increased the uptake of As, Cu, Pb and Co, Ni, Mg, K, P, La, Ce, Y, sum of Heavy Rare Earth Elements (HREE), sum of Light Rare Earth Elements (LREE) but significantly only for Cu and Co at alpha level 0.05 and insignificantly decreased the uptake for Ge. For Zea mays, results showed that inoculating soil with Rhizovital decreased uptake for all elements investigated and significantly so for only Co but showed an insignificant increasing effect on the uptake of Cu. For the two test species, similarity in effects of inoculation of soil with Rhizovital on uptake of elements only existed for Cu (increasing effect) and Ge (decreasing effect) suggesting that the addition of Rhizovital to soil could increase the Cu phytoextraction efficiency of Zea mays and Fagopyrum esculentum and decrease the phytoextraction efficiency of Germanium in both plants. Results from this research suggest that inoculation of soil with the PGPR Bacillus amyloliquefaciens - FZB42 could increase the phytoextraction of Copper by Zea mays and Fagopyrum esculentum respectively, thus enhancing the phytoextraction efficiency of both plants in soils contaminated by copper. Also, results suggest that inoculation of soil with Rhizovital could increase the phytoextraction efficiency of Fagopyrum esculentum for most of the PTEs and CRM investigated in this experiment and that Fagopyrum esculentum is a good candidate for PGPR assisted phytoextraction of PTE and CRM</p>

New Light on Phytoremediation: The Use of Luminescent Solar Concentrators

The latest developments in photovoltaic studies focus on the best use of the solar spectrum through Luminescent Solar Concentrators (LSC). Due to their structural characteristics, LSC panels allow considerable energy savings. This significant saving can also be of great interest in the remediation of contaminated sites, which nowadays requires green interventions characterized by high environmental sustainability. This study reported the evaluation of LSC panels in phytoremediation feasibility tests. Three plant species were used at a microcosm scale on soil contaminated by arsenic and lead. The experiments were conducted by comparing plants grown under LSC panels doped with Lumogen Red F305 (BASF) with plants grown under polycarbonate panels used for greenhouse construction. The results showed a higher production of biomass by the plants grown under the LSC panels. The uptake of the two contaminants by plants was the same in both the growing conditions, thus resulting in an increased total accumulation (defined as metal concentration times produced biomass) in plants grown under LSC panels, indicating an overall higher phytoextraction efficiency. This seems to confirm the potential that LSCs have to be building-integrated on greenhouse roofs, canopies, and shelters to produce electricity while increasing plants productivity, thus reducing environmental pollution, and increasing sustainability.