To characterize bacteria associated with Zn/Cd-accumulating Salix caprea regarding their potential to support heavy metal phytoextraction. Three different media allowed the isolation of 44 ...rhizosphere strains and 44 endophytes, resistant to Zn/Cd and mostly affiliated with Proteobacteria, Actinobacteria and Bacteroidetes/Chlorobi. 1-Aminocyclopropane-1-carboxylic acid deaminase (ACCD), indole acetic acid and siderophore production were detected in 41, 23 and 50% of the rhizosphere isolates and in 9, 55 and 2% of the endophytes, respectively. Fifteen rhizosphere bacteria and five endophytes were further tested for the production of metal-mobilizing metabolites by extracting contaminated soil with filtrates from liquid cultures. Four Actinobacteria mobilized Zn and/or Cd. The other strains immobilized Cd or both metals. An ACCD- and siderophore-producing, Zn/Cd-immobilizing rhizosphere isolate (Burkholderia sp.) and a Zn/Cd-mobilizing Actinobacterium endophyte were inoculated onto S. caprea. The rhizosphere isolate reduced metal uptake in roots, whereas the endophyte enhanced metal accumulation in leaves. Plant growth was not promoted. Metal mobilization experiments predicted bacterial effects on S. caprea more reliably than standard tests for plant growth-promoting activities. Bacteria, particularly Actinobacteria, associated with heavy metal-accumulating Salix have the potential to increase metal uptake, which can be predicted by mobilization experiments and may be applicable in phytoremediation.
Metal-accumulating woody species have been considered for phytoextraction of metal-contaminated sites. We investigated Zn and Cd accumulation in tissues of adult trees and associated herbaceous ...species collected from contaminated areas in Central Europe. We found considerable Cd and Zn accumulation in various willow, poplar and birch species with up to 116
mg
Cd
kg
−1 and 4680
mg
Zn
kg
−1 in leaves of
Salix caprea. Annual variation of Cd and Zn concentrations in leaves of
Salix caprea were small, indicating that data obtained in different years can be compared. Metal concentrations in leaves were not related to total (
aqua regia) or labile (1
M NH
4NO
3 extract) concentrations in soil but the accumulation factors (leaf concentration: soil concentration) for Cd and Zn followed an inverse log type function. Metal partitioning between tissues showed a minimum in the wood, with increasing concentrations of Cd and Zn towards the leaves and fine roots.
Adult field-grown Salix caprea, Populus tremula and other tree species accumulate up to 4680
mg
Zn
kg
−1 and 116
mg
Cd
kg
−1 in their leaves.
Effect of N and P fertilisation and aeration on biodegradation of crude oil in aged hydrocarbon contaminated soils Syafruddin, S.,University of Natural Resources and Applied Life Sciences, Vienna (Austria). Dept. of Forest and Soil Sciences; Wieshammer, G.,University of Natural Resources and Applied Life Sciences, Vienna (Austria). Dept. of Forest and Soil Sciences; Puschenreiter, M.,University of Natural Resources and Applied Life Sciences, Vienna (Austria). Dept. of Forest and Soil Sciences ...
Plant, soil and environment,
(Apr 2010), Letnik:
56, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We conducted two laboratory experiments to examine the effects of fertilization and agitation (aeration) on crude oil degradation in two soils with differential nutrient (nitrogen, phosphorus) ...availability. Two soils that had been spiked with crude oil two years before were mixed with nitrogen and/or phosphorus at three different levels and subsequently incubated 28 days (Exp. 1). In experiment 2 we investigated the effect of repeated agitation (manual mixing) on hydrocarbon degradation with and without fertilization. One of the soils was also freshly spiked to assess the impact of ageing. Heptane-extractable hydrocarbon concentrations were determined in both experiments and substrate-induced respiration in Exp. 2. The generally small changes of hydrocarbon concentrations during 28 days of incubation in Exp. 1 are likely attributed to low bio-accessibility of hydrocarbons as a consequence of long-term ageing. Fertilization with N or P or combination of both was ineffective in most treatments of Exp. 1, which may be explained by limited oxygen supply due to the high proportions of clay and silt. However, agitation enhanced hydrocarbon biodegradation in the sandy-loamy soil by about 15% (Exp. 2) compared to non-agitated treatments. In contrast, we observed no effect of agitation in the sandy soil.
We screened 20 different clones of willow and poplar species in hydroponic experiments for their metal resistance and accumulation properties. Plants were exposed for 4 weeks either to single ...additions of (μM) 4.45 Cd or 76.5 Zn, or a metal cocktail containing the same amounts of Cd and Zn along with 7.87 Cu and 24.1 Pb. Plant biomass, metal tolerance and metal accumulation pattern in roots and leaves varied greatly between clones. The leaf:root ratio of metal concentrations was clearly underestimated compared to soil experiments. The largest metal concentrations in leaves were detected in
Salix dasyclados (315
mg Cd
kg
−1 d.m.) and a
Salix smithiana clone (3180
mg Zn
kg
−1 d.m.) but these species showed low metal tolerance. In spite of smaller Cd and Zn concentrations, the metal-tolerant clones
Salix matsudana,
Salix fragilis-1, and
Salix purpurea-1 hold promise for phytoextraction as they produced large biomass and metal contents in leaves.
Hydroponically grown willows and poplar clones accumulate up to (mg
kg
−1 d.w.) 315 Cd and 3180 Zn in leaves.
Rhizosphere characteristics, heavy metal accumulation and growth performance of two willow (Salix x rubens) clones Vyslouzilova, M.(Vyzkumny Ustav Melioraci a Ochrany Pudy, Prague (Czech Republic)); Puschenreiter, M.(University of Natural Resources and Applied Life Sciences in Vienna (Austria). Dept. of Forest and Soil Sciences); Wieshammer, G.(University of Natural Resources and Applied Life Sciences in Vienna (Austria). Dept. of Forest and Soil Sciences) ...
Plant, soil and environment,
20/Aug , Letnik:
52, Številka:
8
Journal Article
Recenzirano
Odprti dostop
In a rhizobox experiment, two clones of Salix x rubens derived from contaminated and non-contaminated sites were tested for growth performance and metal (Cd, Pb and Zn) accumulation on a polluted ...Calcaric Cambisol. The largest metal concentrations in leaves were 66.7 mg Cd/kg, 12.8 mg Pb/kg and 1,090 mg Zn/kg. The results indicate that metal tolerance and accumulation may be a constitutive rather than an adaptive property in the studied plant. Soil pH did not differ among rhizobox compartments. However, acid neutralization capacity was decreased in rhizosphere. Dissolved organic C in rhizosphere was increased by 37% and seemed to enhance labile fraction of Pb and Zn, whereas Cd was not affected. The replenishment of labile metals from less labile soil fractions was efficient enough to almost compensate the plant uptake. S. x rubens can effectively induce chemical changes in the rhizosphere, which is very promising for a clean up of metal-polluted soils.
Nickel uptake and cellular compartmentation were investigated in three Ni hyperaccumulators: Alyssum bertolonii (Desv), Alyssum lesbiacum (Candargy) and Thlaspi goesingense (Hálácsy). The three ...species showed similar hyperaccumulation of Ni, but T. goesingense was less tolerant to Ni than the two Alyssum species. An addition of 500 mg Ni kg−1 to a nutrient‐rich growth medium significantly increased shoot biomass of all three species, suggesting that the Ni hyperaccumulators have a higher requirement for Ni than normal plants. Energy‐dispersive X‐ray microanalysis (EDXA) was performed on frozen‐hydrated tissues of leaves (all species) and stems (Alyssum only). In all species analysed, Ni was distributed preferentially in the epidermal cells, most likely in the vacuoles, of the leaves and stems. In stems, there was a second peak of Ni in the boundary cells between the cortical parenchyma and the vascular cylinder. The non‐glandular trichomes on the leaf surfaces of the two Alyssum species were highly enriched with Ca, but contained little Ni except in the base. In the leaves of T. goesingense, the large elongated epidermal cells contained more Ni than the cells of the stomatal complexes. The role of cellular compartmentation in Ni hyperaccumulation is discussed.
Lysimeters constructed of polyacrylic and fitted with either a porous nylon membrane or a porous ceramic cup were tested for their adsorption characteristics with respect to Pb, Cr, Cu, As, Cd, Co, ...Mn, Ni, and Zn. Laboratory tests were conducted at pH 4, 5, and 6 using metal concentrations that are representative of natural soil solutions. The ceramic lysimeters significantly lowered the concentrations of Cd, Co, Mn, Ni, and Zn, and almost completely removed Pb, Cr, Cu, and As from solution. The nylon lysimeters had virtually no effect on metal concentrations at pH 4 to 5, and only slightly decreased the concentrations of As, Cr, Cu, and Pb at pH 6. Based on field experience, an optimized design of the nylon lysimeter is presented using double nylon membranes to improve the mechanical resistance
Results indicate that a suite of biological assays should be used to assess soil remediation processes.
Soils polluted with heavy metals can cause phytotoxicity and exhibit impared microbial ...activities. In this paper we evaluate the responses of different biological endpoints to in situ remediation processes. Three soil amendments (red mud, beringite and lime) were applied to two soils polluted by heavy metals. Oilseed rape, wheat, pea and lettuce were grown successively in pots on the untreated and amended soils and their yield and metal uptake were determined. A suite of microbial tests (lux-marked biosensors, Biolog and soil microbial biomass) were performed to determine the effect of the soil amendments on the functionality and size of the soil microbial community. In both soils all three amendments reduced phytotoxicity of heavy metals, enhanced plant yields and decreased the metal concentrations in plants. The red mud treatment also increased soil microbial biomass significantly. The microbial biosensors responded positively to the remediation treatments in the industrially-contaminated soil used in the experiment. Red mud applied at 2% of soil weight was as effective as beringite applied at 5%. The results also showed that since the biological systems tested respond differently to the alleviation of metal toxicity, a suite of biological assays should be used to assess soil remediation processes.
Two water treatment sludges (WTS-A, WTS-B), two red muds (RM), and red gypsum (RG), all rich in iron oxy-hydroxides, were added to a soil highly polluted with As and Cu at 2% (w/w) to reduce metal ...bioavailability. Because the amendments increased soil pH to approximately 6, a lime treatment to the same pH and an unamended treatment were included for comparison. All the amendments had significant positive effects on the soil microbial biomass and growth of ryegrass (Lolium multiflorum Lam. cv. Avance), but only WTS-A improved lettuce (Lactuca sativa L. cv. Tom Thumb) growth. The mineralization of added ammonium nitrogen was not significantly affected by the treatments, while a physiologically based extraction test (PBET) showed that bioaccessibility of As was low (<5%) and decreased only in the WTS-A treatment. Concentrations of As in soil pore water and extractable As only decreased in the WTS and RG treatments. In contrast, Cu concentrations in soil pore water and extractable Cu decreased in all treatments, by more than 84% in the WTS, RM, and RG treatments. Non-isotopically exchangeable As and Cu were present in colloids in the soil pore water. Untreated soil had <4% isotopically exchangeable As and this decreased by approximately 50%, with WTS, RM, and RG. The labile Cu pool represented a large proportion (34%) of the total Cu pool, and the isotopically exchangeable and soluble Cu were strongly correlated with soil pH. Acidification of the treated soils showed that the labile As and Cu both increased in the treated soils compared with untreated soils. The significance of the treatment effects on soil fertility and potential off-site transport of As and Cu to ground water are discussed.
Available tools to study rhizosphere characteristics at a sub-mm spatial resolution suffer from a number of shortfalls, including geometrically and physiologically ill-defined root layers containing ...soil or other growth medium. Such designs may result in over-or underestimation of root-induced changes in the rhizosphere. We present a novel rhizobox design that overcomes these shortfalls. Plants are pre-grown in a soil-root compartment with an opening slit at the bottom. As plants reach the targeted physiological stage, this compartment is transferred on top of a rhizosphere soil compartment attached to a vertical root-only compartment. The latter is made up of a membrane (pore size 7 µm to restrict root hair growth into the rhizosphere compartment or 30 µm to restrict only root growth) and a transparent acrylic window which is gently pressed against the membrane and rhizosphere soil compartment using an adjustable screw. This design allows roots to penetrate from the upper soil-root compartment through the slit into the root-only compartment. Root growth and distribution can be monitored through the acrylic window using digital camera equipment. Upon termination of the experiment, the rhizosphere compartment is removed and frozen prior to separation of sub-mm soil layers using microtome techniques. In a test experiment, canola (Brassica napus L. cv. Sprinter) developed a fairly dense root monolayer within 8 days. Using measurement of soil characteristics at 0.5-1-mm increments across the rhizosphere we demonstrate that the proposed rhizobox design is yielding reproducible data. Due to exudation of LMWOC, we found a statistically significant increase of DOC towards the root plane, whereas more stable soil characteristics were not affected by root activity. Limitations and further extensions of this rhizobox design, including the use of micro suction cups and microsensors for pH and redox potential to measure spatial and temporal changes in a non-destructive manner are discussed along with potential applications such as validation of rhizosphere models.
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