Concentrations In Plant Tissues Research Articles

Phytoremediation of Mn-contaminated paddy soil by two hyperaccumulators (Phytolacca americana and Polygonum hydropiper) aided with citric acid.

The purpose of this study was to investigate the phytoremediation potential of two hyperaccumulator plants, Phytolacca americana L. and Polygonum hydropiper L., on manganese-contaminated paddy soils. The biomass growth, Mn concentrations in plant tissues, and potential Mn removal efficiency from soils of these two plants were studied with citric acid, and the mechanisms of citric acid on these two plants were analyzed by examining the root activity, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in leaves, as well as the concentrations of O2·- and H2O2 in leaves. The results showed that the biomass of these two plants were both promoted under low level of citric acid (3mmolkg-1). The concentration of Mn in the plants and the amount of Mn removed from the soil by the plants through harvesting were enhanced at low and intermediate (10mmolkg-1) citric acid application levels. The results also showed that root activity was enhanced at the low citric acid level and significantly inhibited under the intermediate and high levels (15mmolkg-1), which indicates the facilitative function of the low level of citric acid and the inhibitive function of the high level of citric acid application on plant biomass growth. Under the low and intermediate levels of citric acid application, O2·- in the plant leaves increased sharply, and the SOD, POD, and CAT activities also increased sharply, which made the level of H2O2 very similar to that of the control, ensuring the health of the plants. At the high level of citric acid application, however, the O2·- continued to rise sharply, while the activity of the three antioxidant enzymes declined sharply, causing the concentration of hydrogen peroxide to be much higher than that in the control, thus endangering the plants. The present study shows the potential of P. hydropiper for use in the phytoremediation of soil contaminated with a relatively low level of manganese.

Cadmium reduces zinc uptake but enhances its translocation in the cadmium-accumulator, Carpobrotus rossii, without affecting speciation

Interactions between Cd and Zn occur in soils and plants but are inconsistent. This study examined how Cd/Zn interactions influence the growth of Carpobrotus rossii (Haw.) and the accumulation of Cd and Zn in plants. Plants were grown in nutrient solutions containing 5–100 μM Zn and 0, 5 or 15 μM Cd. Plant growth and tissue concentrations were measured, and the speciation of Zn within the plant tissues determined using synchrotron-based X-ray absorption spectroscopy. There was an additive negative interaction between Cd and Zn on root growth. Only the highest level of Zn (100 μM) decreased Cd concentrations in root and shoot tissues (by 40–64%), whilst 100 μM Zn enhanced Cd translocation at 5 μM Cd but decreased it at 15 μM Cd. In contrast, both 5 and 15 μM Cd decreased Zn concentrations in root and shoot tissues but increased Zn translocation by 30–90%. This interaction was not associated with changes in Zn speciation within the plants, with most Zn associated with oxalate (48–87%). The presence of Zn and Cd resulted in an additive negative effect on root growth, but an antagonistic pattern in their accumulation in shoots of C. rossii.

Mineralogy and Maximum Phosphorus Adsorption Capacity in Soybean Development

The low natural fertility of tropical soils and the mineralogy almost dominated by iron and aluminum oxides limit the availability of phosphorus (P) to the plants, causing negative impacts on soybean yield. Objective was to evaluate the effect of phosphate fertilization on soils with different maximum phosphorus adsorption capacities (PAC) in soybean development. The experiment was carried out under greenhouse conditions, using Red-yellow Latosol (RYL) and a Typic Hapludalf (TH) soil as substrate. The analyses were performed by a completely randomized experimental design in a 5 × 2 factorial arrangement with three replications. The treatments consisted of 5 doses of P applied, corresponding to 0, 1, 6, 12, and 24% of PAC of each soil. In the soil, the mineralogy of the clay fraction (hematite, goethite, gibbsite and kaolinite) and crystallographic attributes were characterized. In the plant, we evaluated growth and pod production. The PAC of the soils ranged from 220 to 650 mg dm-3 with higher value in the RYL associated to clayey oxidic mineralogy and texture in relation to the TH of kaolinite origin and sandy texture, where the higher energy of adsorption observed was to TH. Phosphorus application from 16 to 21% of PAC, independently of the soil, promotes the same pattern of response with improvements in soybean development evidenced by increases in P content in plant tissue, plant height, root volume and aerial dry mass.

Multiple environmental factors influence 238U, 232Th and 226Ra bioaccumulation in arbuscular mycorrhizal-associated plants

Ecological consequences of low-dose radioactivity from natural sources or radioactive waste are important to understand but knowledge gaps still remain. In particular, the soil transfer and bioaccumulation of radionuclides into plant roots is poorly studied. Furthermore, better knowledge of arbuscular mycorrhizal (AM) fungi association may help understand the complexities of radionuclide bioaccumulation within the rhizosphere. Plant bioaccumulation of uranium, thorium and radium was demonstrated at two field sites, where plant tissue concentrations reached up to 46.93 μg g−1 238U, 0.67 μg g−1 232Th and 18.27 kBq kg−1 226Ra. High root retention of uranium was consistent in all plant species studied. In contrast, most plants showed greater bioaccumulation of thorium and radium into above-ground tissues. The influence of specific soil parameters on root radionuclide bioaccumulation was examined. Total organic carbon significantly explained the variation in root uranium concentration, while other soil factors including copper concentration, magnesium concentration and pH significantly correlated with root concentrations of uranium, radium and thorium, respectively. All four orders of Glomeromycota were associated with root samples from both sites and all plant species studied showed varying association with AM fungi, ranging from zero to >60% root colonisation by fungal arbuscules. Previous laboratory studies using single plant-fungal species association had found a positive role of AM fungi in root uranium transfer, but no significant correlation between the amount of fungal infection and root uranium content in the field samples was found here. However, there was a significant negative correlation between AM fungal infection and radium accumulation. This study is the first to examine the role of AM fungi in radionuclide soil-plant transfer at a community level within the natural environment. We conclude that biotic factors alongside various abiotic factors influence the soil-plant transfer of radionuclides and future mechanistic studies are needed to explain these interactions in more detail.

Antibiotic-induced effects on scaling relationships and on plant element contents in herbs and grasses.

Plant performance is correlated with element concentrations in plant tissue, which may be impacted by adverse chemical soil conditions. Antibiotics of veterinary origin can adversely affect plant performance. They are released to agricultural fields via grazing animals or manure, taken up by plants and may be stored, transformed or sequestered by plant metabolic processes. We studied the potential effects of three antibiotics (penicillin, sulfadiazine, and tetracycline) on plant element contents (macro‐ and microelements). Plant species included two herb species (Brassica napus and Capsella bursa‐pastoris) and two grass species (Triticum aestivum and Apera spica‐venti), representing two crop species and two noncrop species commonly found in field margins, respectively. Antibiotic concentrations were chosen as to reflect in vivo situations, that is, relatively low concentrations similar to those detected in soils. In a greenhouse experiment, plants were raised in soil spiked with antibiotics. After harvest, macro‐ and microelements in plant leaves, stems, and roots were determined (mg/g). Results indicate that antibiotics can affect element contents in plants. Penicillin exerted the greatest effect both on element contents and on scaling relationships of elements between plant organs. Roots responded strongest to antibiotics compared to stems and leaves. We conclude that antibiotics in the soil, even in low concentrations, lead to low‐element homeostasis, altering the scaling relationships between roots and other plant organs, which may affect metabolic processes and ultimately the performance of a plant.

Ameliorative Effect of Ammonium Sulfate on Salt Tolerance and Ion Homeostasis in Lemon (C. limon) Seedlings

To investigate interaction effects of salinity and nitrogen on growth, mineral composition and salinity tolerance of lemon seedlings, a greenhouse experiment with four sodium chloride concentrations (0, 250, 500 and 1000 mg kg-1 soil) and four nitrogen levels (0, 50, 100, and 200 mg kg-1 soil ammonium sulfate) was carried out. Experiment was conducted in a completely randomized design with three replications. Sodium and chloride ions in plant tissues were increased to toxic levels with increase in salinity which resulted in a significant reduction of plant dry weight. Nitrogen consumption up to 100 mg kg-1 soil increased plant dry weight. As the concentration of sodium chloride was increased, the improvement effect of nitrogen on plant growth was decreased. Although nitrogen had no considerable effect on sodium concentration in root and shoot, it made a decrease in chloride concentration in shoot and an increase in root concentration of this element. Salinity decreased essential nutrients concentration in plant shoot. Therefore, it can be concluded that adverse effect of salinity is to some extent due to reduction of required elements to suboptimal ranges in plant tissues. Nitrogen improved the adverse effects of salinity on plant nutrients by increasing their concentration in plant tissues. Therefore it can be inferred that part of the ameliorative effects of nitrogen on salinity adverse effects is related to the maintenance of essential nutrient concentrations in plant tissues. The results of the present study indicate that nitrogen can be applied in amounts higher than optimal level to reduce the harmful effects of salinity.

Biochar and lignite affect H+-ATPase and H+-PPase activities in root tonoplast and nutrient contents of mung bean under salt stress

This research was conducted to evaluate effects of biochar (50 and 100 g kg−1 soil) and lignite (50 and 100 g kg−1 soil) treatments on H+-ATPase and H+-PPase activity of root tonoplast, nutrient content, and performance of mung bean under salt stress. High saline conditions increased H+-ATPase and H+-PPase activities in root tonoplast, sodium (Na) content, reactive oxygen species (H2O2 and O2−) generation, relative electrolyte leakage (REL) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) activity in root and leaf, but decreased relative water content (RWC), chlorophyll content index, leaf area, potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn) and iron (Fe) content of plant tissues, root and shoot dry weight of mung bean. Lignite and biochar treatments decreased the H+-ATPase and H+-PPase activities of root tonoplast under salt stress. Moreover, these treatments increased the cation exchange capacity of soil and nutrient values in plant tissues. Biochar and lignite diminished the generation of reactive oxygen species and DPPH activity in root and leaf cells, and these superior effects improved chlorophyll content index, leaf area and growth of mung bean under both conditions. In general, the results of this study demonstrated that biochar and lignite decreased the entry of Na ion into the cells, enriched plant cells with nutrients, and consequently improved mung bean performance under salt toxicity.

Trace element mobilization during incipient bioweathering of four rock types

Lithogenic trace element (TE) patterns of distribution, fate, and behavior in soils are influenced by plants and microorganisms. Our controlled mesocosm experiments quantified how incipient weathering of mineral-bound TEs (Be, V, Sr, Ba, Cr, Co, Ni, Mo, Cu, Zn, As, Se, Ag, Cd, Sn, Sb, Tl, and Pb) varies across four porous mineral substrates (basalt, rhyolite, granite, and schist), in the presence of buffalo grass (Bouteloua dactyloides), associated bacteria, and arbuscular mycorrhizal fungi (AM), a common plant symbiont. Particular focus was given to the net transfer of elements between the solid and solution phases, including chemical denudation (loss of element from the rock to the solution), plant TE uptake, and total mobilization (sum of denudation loss and uptake into plant biomass).Results revealed differences in TE denudation among rocks, basalt having the highest loss and schist the lowest. TE leaching in solution was time-dependent and it was likely influenced by variations in pH and DOC that were rock- and treatment-specific. The element with the highest rock-normalized release to the solution and highest enrichment in plant biomass was Mo across all rocks. Plants decreased denudation loss compared to abiotic controls for a large number of TEs in all substrates due to plant uptake, but for some elements increase in weathering due to plant activity resulted in increased denudation. Differences in TE patterns of behavior could be related to their Goldschmidt groups. Plant uptake was controlled by TE availability in solution, as well as plant physiological requirements. Plants and associated microbiota significantly enhanced mobilization for the majority of TEs across all rocks.Mycorrhiza significantly increased above-ground plant biomass production in rhyolite and concentrations in plant tissues for a high number of TEs in basalt. TE uptake into biomass was positively correlated with percent mycorrhizal infection, particularly in basalt and rhyolite. Mycorrhizal fungi also influenced TE denudation, rock-water fractionation, and total mobilization according to the rock type. Mycorrhizal activity was associated with a significant decrease in pH and increase in DOC fluxes in schist, supporting the idea that fungi enhance production of root exudates especially in substrates that are difficult to weather.Our results highlight the importance of incipient weathering at the plant-rock interface for patterns of TE cycling. They also indicate the importance of mycorrhiza in mineral dissolution, TE denudation, plant element uptake, and biomass growth.

Improvement of Selected Soil Chemical Properties and Potassium Uptake by Mung Beans After Application of Liquid Organic Fertilizer in Ultisol

Recently, application of liquid organic fertilizer (LOF) in organic farming practices is of importance to prevent further soil degradation due to prolong and massive use of synthetic fertilizer. LOF provides faster plant nutrients than soil organic fertilizer. However, quality of LOF is substantially dependent on its sources. Animal wastes from rabbit, goat, and cattle are scarcely used as sources of LOF production. The study aimed to determine soil chemical improvement and potassium uptake by mung bean as affected by LOF in Ultisol. The experiment was conducted at the Greenhouse Faculty of Agriculture, employing Completely Randomized Design with two factors. The first factor was animal wastes, consisting of goat, rabbit, and cattle wastes. The second factor was LOF concentration, consisting of 0%, 25%, 50%, 75%, and 100% LOF. LOF was prepared by mixing altogether animal feces, urine, soil, green biomass, EM-4 and fresh water to total volume of 10 l in a plastic container. LOF was decanted to the polybag every week starting at one week after planting for four weeks to a total volume of 750 ml per polybag. Variables observed included soil pH, total organic-C, exchangeable K, soil nitrate-N, K concentration in plant tissue, K-uptake, and shoot dry weight of sweet corn The result showed that application of LOF from rabbit waste had the highest increment of soil pH as compared to the other treatment. However, exchangeable K was observed highest at the treatment of LOF from goat waste. Sources of LOF from animal wastes did not have an effect on K-uptake by mung bean. In addition, application of LOF up to 100% was able to improve soil chemical properties as indicated by the increase in soil pH and exchangeable K. So did the concentration and uptake of K, as well as shoot dry weight. Fertilization with LOF has benefit to the improvement of soil chemical properties leading to better K uptake.

Adaptive physiological response, carbon partitioning, and biomass production of Withania somnifera (L.) Dunal grown under elevated CO2 regimes.

Winter cherry or Ashwagandha (Withania somnifera) is an important medicinal plant used in traditional and herbal medicine system. Yet, there is no information available on response of this plant to changing climatic conditions particularly elevated atmospheric CO2 concentrations. Therefore, we conducted an experiment to examine the effect of elevated CO2 concentrations (ECs) on Withania somnifera. The variations in traits of physiological adaptation, net primary productivity, carbon partitioning, morphology, and biomass in response to elevated CO2 concentrations (ambient, 600 and 800µmol mol-1) during one growth cycle were investigated within the open top chamber (OTC) facility in the foothill of the Himalayas, Dehardun, India. ECs significantly increased photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, soil respiration, net primary productivity and the carbon content of plant tissues (leaf, stem, and root), and soil carbon. Furthermore, ECs significantly enhanced biomass production (root and shoot), although declined night leaf respiration. Overall, it was summarized that photosynthesis, stomatal conductance, water use efficiency, leaf, and soil carbon and biomass increased under ECs rendering the physiological adaptation to the plant. Increased net primary productivity might facilitate mitigation effects by sequestering elevated levels of carbon dioxide. We advocate further studies to investigate the effects of ECs on the accumulation of secondary metabolites and health-promoting substances of this as well as other medicinal plants.

Interactive Effects of Nutrients and Bradyrhizobium japonicum on the Growth and Root Architecture of Soybean (Glycine max L.).

Understanding the symbiotic performance of rhizobia and responses of plant root systems to mineral nutrient supply will facilitate the development of strategies to enhance effective rhizobia-legume symbioses. Interactive effect of nitrogen (N), phosphorus (P), and magnesium (Mg) on the symbiotic performance of soybean (Glycine max L.) with Bradyrhizobium japonicum, nodulation, root architecture, and the N concentration in plant tissue under hydroponic conditions were studied. Plant growth was significantly higher under a high N supply combined with Mg (HNHMg) than in combination with P (HNHP), which was attributed to the interaction between N and Mg ions. The plants grown at a low N concentration combined with either high or low P or Mg (LNHP, LNHMg, LNLP, and LNLMg) showed a higher nodule dry weight compared to those grown under a high N supply. We observed that the N content in the roots and shoots of soybean plants was significantly lower under LNHP or LNLP, but it was higher under HNHMg or LNHMg, indicating that Mg promotes N acquisition by the plant tissues. Neither root nor shoot growth responded significantly to P availability regardless of the N supply. We observed significant positive relationships between the number of nodules, the N content in plant tissues and the root system architecture of soybean plants grown with a variable supply of Mg combined with N, which highlights the importance of N and Mg availability in the growth medium in regulating root system architecture and nodule formation. The number of rhizobial cells colonizing soybean roots was highest under the HNHMg treatment (6.78 × 104 CFUs/cm of root tip), followed by the HNLMg (4.72 × 104 CFUs/cm of root tip) and LNHMg (4.10 × 104 CFU/cm of root tip) treatments, and lowest under the LNLMg (1.84 × 104 CFUs/cm of root tip) nutrient conditions. The results of this study contribute to new insights for the improvement of the root system and the symbiotic performance of rhizobia inoculated on legumes, stressing the importance of a balanced supply of nutrients.

Selection of plants for phytoremediation of barium-polluted flooded soils

The use of barite (BaSO4) in drilling fluids for oil and gas activities makes barium a potential contaminant in case of spills onto flooded soils, where low redox conditions may increase barium sulfate solubility. In order to select plants able to remove barium in such scenarios, the following species were evaluated on barium phytoextraction capacity: Brachiaria arrecta, Cyperus papyrus, Eleocharis acutangula, E. interstincta, Nephrolepsis cf. rivularis, Oryza sativa IRGA 424, O. sativa BRS Tropical, Paspalum conspersum, and Typha domingensis. Plants were grown in pots and exposed to six barium concentrations: 0, 2.5, 5.0, 10.0, 30.0, and 65.0 mg kg−1. To simulate flooding conditions, each pot was kept with a thin water film over the soil surface (∼1.0 cm). Plants were evaluated for biomass yield and barium removal. The highest amount of barium was observed in T. domingensis biomass, followed by C. papyrus. However, the latter exported most of the barium to the aerial part of the plant, especially at higher BaCl2 doses, while the former accumulated barium preferentially in the roots. Thus, barium removal with C. papyrus could be achieved by simply harvesting aerial biomass. The high amounts of barium in T. domingensis and C. papyrus resulted from the combination of high barium concentration in plant tissues with high biomass production. These results make T. domingensis and C. papyrus potential candidates for phytoremediation schemes to remove barium from flooded soils.

Ni bioavailability in oat (Avena sativa) grown in naturally aged, Ni refinery-impacted agricultural soils

ABSTRACTRisk assessments now use a tiered approach, beginning with conservative methods and moving toward site-specific or bioavailability-based methods, to understand the true risk posed by a contaminant. We examine four different estimates of bioavailable Ni that aim to describe oat (Avena sativa) toxicity: (1) total Ni in soil, (2) environmentally available Ni fraction (oxalate extractable), (3) environmentally bioavailable Ni fraction (free ion activity in pore water), and (4) toxicologically bioavailable Ni fraction (metal concentration in plant tissue). We tested three different agricultural soil types (sand, till clay, and heavy clay) from Port Colborne (Ontario, Canada) that naturally aged for decades after receiving aerial Ni deposition from the local Ni refining operations. Nickel rarely occurs in isolation of other elements and so field-based effects data are relatively rare. Port Colborne offers a unique opportunity to assess effects of Ni from a common anthropogenic source. Validation of bioavailability-based predictive models indicated that the Tissue Residue Approach (TRA) best predicted observed oat toxicity, while the Terrestrial Biotic Ligand Model (TBLM) and the Free Ion Activity Model (FIAM) fared better than the Total Metal Model (TMM). Our field-based study supports findings of laboratory-based studies which suggest that toxicity expressed as total Ni in soil can be improved upon.

Yield of Pennisetum glaucum L. Under Phosphate Source Doses

Phosphorus deficiency has been a limiting factor in crop yields due to the low availability of this nutrient in the soil. Thus, the objective of this work was to evaluate the growth and P concentrations in plant tissue of two cultivars of forage millet grown submitted at doses of phosphorus (P). The experiment was set in greenhouse conditions in a Hapludox. The experiment was carried out in a completely randomized design in a 4 × 2 factorial scheme, with four replications, where the factors were the control treatment (without fertilization with P) and three levels of P (50, 100 and 200 kg ha-1) as simple superphosphate and two cultivars of pearl millet (BN2 and ADR500). The following were evaluated: plant height, stem diameter, dry matter of the aerial part (DMAP) and roots (DRM), phosphorus content in the leaf, in the stem and in the roots. The interaction between doses of P with the cultivars did not significantly affect the studied variables. Cultivar ADR500 provided greater height, stem diameter and dry matter of the aerial part. The best doses were 166 kg ha-1, 173 kg-1, 203 kg ha-1 and 165 kg of phosphorus ha-1 to height, stem diameter, DMAP, DMR and phosphorus content in the leaf, respectively. The increase of phosphorus rate increased content of P in the dry matter of the stem and roots on evaluated cultivars.

Assessment of toxic impact of metals on proline, antioxidant enzymes, and biological characteristics of Pseudomonas aeruginosa inoculated Cicer arietinum grown in chromium and nickel-stressed sandy clay loam soils.

Considering the heavy metal risk to soil microbiota and agro-ecosystems, the study was designed to determine metal toxicity to bacteria and to find metal tolerant bacteria carrying multifarious plant growth promoting activities and to assess their impact on chickpea cultivated in stressed soils. Metal tolerant strain SFP1 recognized as Pseudomonas aeruginosa employing 16S rRNA gene sequence determination showed maximum tolerance to Cr (400μg/ml) and Ni (800μg/ml) and produced variable amounts of indole acetic acid, HCN, NH3, and ACC deaminase and could solubilize insoluble phosphates even under Cr (VI) and Ni stress. Metal tolerant P. aeruginosa reduced toxicity of Cr (VI) and Ni and concomitantly enhanced the performance of chickpea grown under stressed and conventional soils. At 144mgCrkg-1, the measured parameters of a bacterial strain was significantly enhanced, but it was lower compared to those recorded at 660mgNikg-1. The strain SFP1 demonstrated maximum increase in seed yield (81%) and grain protein (16%) at 660mgNikg-1 over uninoculated and untreated control. Stressed plants had more proline, antioxidant enzymes, and metal concentrations in plant tissues. P. aeruginosa, however, remarkably declined the level of stress markers (proline and APX, SOD, CAT, and GR), as well as with Cr (VI) and Ni uptake by chickpea. Conclusively, P. aeruginosa strain SFP1 due to its dual metal tolerant ability, capacity to secrete plant growth promoting regulators even under metal stress and potential to mitigate metal toxicity, could be developed as microbial inoculant for enhancing chickpea production in Cr and Ni contaminated soils.

Patterns of plant carbon, nitrogen, and phosphorus concentration in relation to productivity in China’s terrestrial ecosystems

Plant nitrogen (N) and phosphorus (P) content regulate productivity and carbon (C) sequestration in terrestrial ecosystems. Estimates of the allocation of N and P content in plant tissues and the relationship between nutrient content and photosynthetic capacity are critical to predicting future ecosystem C sequestration under global change. In this study, by investigating the nutrient concentrations of plant leaves, stems, and roots across China's terrestrial biomes, we document large-scale patterns of community-level concentrations of C, N, and P. We also examine the possible correlation between nutrient content and plant production as indicated by vegetation gross primary productivity (GPP). The nationally averaged community concentrations of C, N, and P were 436.8, 14.14, and 1.11 mg·g-1 for leaves; 448.3, 3.04 and 0.31 mg·g-1 for stems; and 418.2, 4.85, and 0.47 mg·g-1 for roots, respectively. The nationally averaged leaf N and P productivity was 249.5 g C GPP·g-1 N·y-1 and 3,157.9 g C GPP·g-1 P·y-1, respectively. The N and P concentrations in stems and roots were generally more sensitive to the abiotic environment than those in leaves. There were strong power-law relationships between N (or P) content in different tissues for all biomes, which were closely coupled with vegetation GPP. These findings not only provide key parameters to develop empirical models to scale the responses of plants to global change from a single tissue to the whole community but also offer large-scale evidence of biome-dependent regulation of C sequestration by nutrients.

A glimpse into the effect of sulfur supply on metabolite profiling, glutathione and phytochelatins in Panicum maximum cv. Massai exposed to cadmium

Sugar, amino and organic acid, glutathione (GSH) and phytochelatin (PC) content in plant tissues can be altered by S nutrition, and these metabolites have the potential to lower a plant’s susceptibility to cadmium (Cd) toxicity. In the current study, our aim was to analyze the effect of S nutrition on the metabolic profile and the synthesis of GSH and PCs in Panicum maximum cv. Massai (Massai grass) used for Cd phytoextraction, since this forage grass shows fast growth, high biomass production, and adaptation to soil and climatic adversities. We evaluated in a greenhouse combinations of three S (0.1, 1.9 and 3.7 mmol L−1) and two Cd concentrations (0.1 and 0.5 mmol L−1) in nutrient solution, within a single growth period. The tissues of plants exposed to Cd showed distinct responses related to the primary metabolism. Tryptophan, lysine, and histidine were more accumulated in all tissues when Massai grass was exposed to Cd and was grown with 1.9 and/or 3.7 mmol L−1 S, which indicates that these amino acids are probably involved in Cd accumulation and detoxification in this plant. Among the sugars and sugar derivatives detected, galactinol appears to be the most active in decrease Cd-induced oxidative stress. Although there was no effect of Cd/S combinations on the expression of the genes encoding GSH1 and PCS2, the levels of GSH and PCs were strongly increased by Cd, mainly in roots and samples comprising both stem and sheath material of Massai grass and independently of different metabolic changes occurring in these tissues. Synthesis of the majority of metabolites evaluated in this study was mostly induced when Cd-exposed Massai grass was supplied with 1.9 mmol L−1 S, but more studies in field conditions are necessary to define the optimal S concentration for the plants grown in soil.

Constructed soils for mitigating lead (Pb) exposure and promoting urban community gardening: The New York City Clean Soil Bank pilot study

Gardening provides a wide range of benefits to urban residents but may also increase risks of exposure to contaminants in soils. Here we evaluate the use of clean excavated glacial sediments and locally produced compost, to create soils for urban gardens in New York City, NY, USA. The objectives of this study are to examine contaminants in compost and manufactured soil, assess safety of produce, and evaluate the agronomic value of soil mixes with different ratios of sediment and compost. Methods of analysis include quantifying metal/metalloid concentrations in sediments, composts, and plant tissues, soil agronomic parameters (pH, salinity, organic matter, total nitrogen, total carbon), and crop yield. Contaminant levels in sediments from the New York City Clean Soil Bank (CSB) (<10 mg Pb kg−1) were far below background levels of soils in two selected gardens (66 and 1025 mg Pb kg−1), while available composts had highly variable levels of contamination (10–232 mg Pb kg−1). A relatively clean compost was used for this study (19 mg Pb kg−1). Metal/metalloid levels did not increase in constructed soils during the 1-year pilot study period, and crops were well below EU safety standards of 0.1 and 0.3 mg Pb kg−1 for fruits and leafy greens, even when surrounded by contaminated soils. Sediment/compost mixtures produced yields comparable to control plots. Results suggest that CSB sediments have high potential to serve as manufactured topsoil. Creating these soil mixtures diverts materials from expensive waste disposal, reduces contamination risks for urban residents, and promotes the myriad benefits of urban agriculture and community gardening.

Effects of rice hull, rice straw and saw dust application on the primary nutrients of rice plants grown under variable moisture conditions in a saline soil

The study was conducted at Kuakata of Patuakhali to evaluate the impacts of indigenous organic amendments such as rice hull, rice straw and saw dust alone and in combination under variable moisture conditions (moist and saturated) on the primary nutrients (N, P and K) of BRRI dhan64 grown in a coastal saline soil. The individual application of rice hull, rice straw and saw dust at the rate of 0, 4 and 8 t/ha and their combined effects were found to be significant (p ≤ 0.05) for N content in the rice plants. Effects of the treatments on phosphorus content alone and in combination were slightly additive but not significant. The maximum P content in the plant tissues was determined at saturated condition with the increased rate of the treatments (T27 = RH8RS8SD8), while the lowest content of P was recorded in control (T1 = RH0 RS0 SD0). The K content in plant tissues increased significantly (p ≤ 0.05) with the increased rate of application of rice hull, rice straw and saw dust. The higher K contents were found under saturated condition of soil. Under moist condition of soil, the highest contents of N, P and K were 21.3, 1.45 and 15.67 g/kg, respectively and under saturated condition, the highest contents of N, P and K were 23.4, 1.78 and 15.87 g/kg by the combined application of rice hull, rice straw and saw dust, respectively at the rate of 8 t/ha, suggested that the primary nutrition of rice had better response under saturated moisture condition in saline soil, which received rice hull, rice straw and saw dust.Bangladesh J. Sci. Res. 30(1&amp;2): 11-21, December-2017

Using Myriophyllum aquaticum (Vell.) Verdc. to remove heavy metals from contaminated water: Better dead or alive?

This study aimed to investigate the potential of the invasive macrophyte Myriophyllum aquaticum to remove heavy metals. The elements tested were Cd, Cr, Ni, and Zn, in single-metal trials, and experiments were performed with both the living and dead biomass of the plant.In respect of metal removal by living plants, the element that was removed the most was Zn, though Cd showed the highest concentration in plant shoots. The metal negative effect on plant growth was, therefore, more important than the level of metal concentration in plant tissue in determining the removal percentages. All the metals were mostly accumulated in the roots, where a considerable fraction of the element was simply adsorbed to root cell wall, except in the case of Cr. In shoots, the fraction of the adsorbed metal was extremely low in respect to roots, thereby implying a lower apoplastic binding capacity.As regards a possible use of the dead biomass for metal removal, we proposed the generation of a hybrid biosorbent enclosing the dried and grounded plant biomass in cotton bags to improve its handling and its adsorption capacity, in view of a valid alternative to reduce the problems of packed beds. Cadmium—and especially Zn—were the elements removed most efficiently with respect to the other metals.On comparing the removal percentages of the living biomass and the hybrid biosorbent, our data deposed in favour of the use of M. aquaticum as dead biomass for a possible application of this invasive macrophyte in the biological treatment of metal-contaminated water. Our findings may be beneficial to metal removal application accompanying wetland management, devising a possible use of M. aquaticum waste material after its removal from the invaded habitats.