Stephen D. Ebbs

Southern Illinois University Carbondale | SIU · Department of Plant Biology

In order to clarify how cadmium (Cd) chemical forms in planta relate to the genotype difference in Cd accumulation of spinach (Spinacia oleracea L.), two low-Cd and two high-Cd cultivars were compared under a hydroponic experiment with two concentrations of Cd (8.98 or 44.71 μmol Cd L−1). The concentrations of phosphorus in the hydroponic system we...

The unique redox chemistry on the surface of cerium oxide nanoparticles (CeO2NPs) and their broad applications in society have caused many concerns over the release and accumulation of these materials in the environment. Many investigations have been conducted with regard to the environmental health and safety effect of CeO2NPs, including their imp...

The potential release of metallic oxide engineered nanoparticles (ENP) into agricultural systems has created the need to evaluate the impact of these materials on crop yield and food safety. The study here grew sweet potato (Ipomoea batatas) to maturity in field microcosms using substrate amended with three concentrations (100, 500 or 1,000 mg kg D...

The expanding production and use of engineered nanomaterials have raised concerns about the potential risk of those materials to food safety and human health. In a prior study, the accumulation of Zn and Cu from ZnO, CuO, or CeO2, respectively, was examined in carrot (Daucus carota L.) grown in sand culture in comparison to accumulation from exposu...

Sustainable food production for a rapidly growing global population is a major challenge of this century. In order to meet the demand for food production, an additional land area of 2.7–4.9 Mha year−1 will be required for agriculture. However, one-third of arable lands are already contaminated; therefore, the use of polluted lands will have to feat...

Cerium oxide nanoparticles (CeO2 NP) are a common component of many commercial products. Due to the general concerns over the potential toxicity of engineered nanoparticles (ENPs), the phytotoxicity and in planta accumulation of CeO2 NPs have been broadly investigated. However, most previous studies were conducted in hydroponic systems and with gra...

The release of engineered nanoparticles (ENPs) into the environment has raised concerns about the potential risks to food safety and human health. There is a particular need to determine the extent of ENP uptake into plant foods. Belowground vegetables growing in direct contact with the growth substrate are likely to accumulate the highest concentr...

The Canadian oil sands industry is actively engaged in the revegetation and reclamation of sites associated with bitumen mining. One current reclamation research effort sponsored by Syncrude Canada Ltd., referred to as the Sandhill Fen Research Watershed (SFRW) project, is taking place on a former open pit mine in northern Alberta. One aspect of th...

The potential toxicity and accumulation of engineered nanomaterials (ENMs) in agricultural crops has become an area of great concern and intense investigation. Interestingly, while below ground vegetables are most likely to accumulate the highest concentrations of ENMs, little work has been done to investigate the potential uptake and accumulation...

Cyanide occurs naturally in soils, arising from biological cyanogenesis and also in some cases from anthropogenic contamination. Plant utilization of cyanide at non-toxic concentrations as a supplemental source of nitrogen has been a topic of recent scientific interest and it was investigated here using sorghum (Sorghum bicolor L.) and wheat (Triti...

Lead (Pb) contamination in soils is a serious concern because it can be taken up by crops and then transferred through the food chain, posing a potential risk to human health. Indian mustard (Brassica juncea) and wheat (Triticum aestivum) are important crop species known to accumulate heavy metals in their tissues. This study aimed at understanding...

Brakes from motor vehicles release brake pad wear debris (BPWD) with increased concentrations of heavy metals. Germination and root-elongation assays with lettuce, wheat, and soybean were used to provide an initial evaluation of the phytotoxicity of either a water extract of BPWD or BPWD particulates. In terms of germination, the only effect observ...

Premise of research. The beta beta-cyanoalanine pathway is the primary mechanism for detoxification and assimilation of excess cyanide in higher plants. Two genes (AtCysA1 and AtCysC1) mediate the first step of the pathway, and a single gene (AtNit4) mediates the second step. The potential functional redundancy between the enzymes encoded by AtCysA...

The Zn/Cd hyperaccumulator, Noccaea caerulescens, has been studied extensively for its ability to accumulate high levels of Zn and Cd in its leaves. Previous studies have indicated that the Zn and Cd hyperaccumulation trait exhibited by this species involves different transport and tolerance mechanisms. It has also been well documented that certain...

Cerium oxide nanoparticles (CeO2-NPs) are increasingly used in polishing, engine enhancement agents and many other products. Even though the acute toxicity of CeO2-NPs to plants has been investigated, the long-term effects of CeO2-NPs in the environment are still unknown. The main objective of this study was to investigate whether the treatment of...

The contribution of green roofs to urban water quality is a subject of increasing interest. This study examined heavy metals in runoff from simulated green roof systems after 22-32 months in the field to assess source or sink behavior. The green roof systems were not sources of metals, except for one instance of elevated Cu in runoff. On some dates...

The β-cyanoalanine pathway is primarily responsible for detoxification of excess cyanide produced by plants. Recent evidence suggests that cyanide detoxification via this pathway may be involved in the response and tolerance to water deficit in plants. The aim of this study was to explore this role in Arabidopsis thaliana in greater detail. The fir...

The contribution of green roofs to urban water quality, either as sinks or sources of pollutants, is an open question. This study examined leaching of Cd, Fe, Ni, Pb, and Zn from simulated green roof systems that had been deployed under field conditions and naturally leached for 22 months. The objectives were to determine if Arkalyte (an expanded c...

Gold extraction and gold phytomining involve the use of adjuvants such as cyanide, thiocyanate, or thiosulfate to facilitate the dissolution of gold and its subsequent recovery. The adjuvants can be applied at high rates, in excess of 1 kg t-1 for some ores. At these concentrations, concerns have been expressed about adjuvants persistence and assoc...

Weed competition is detrimental to crops. A 2-year field study was conducted with soybean cultivars (Glycine max L. Merr.) grown in the presence of mixed weed competition to determine whether foliar parameters and micronutrient concentrations served as predictors of seed yield and quality. Relative water content, chlorophyll fluorescence, and folia...

Cadmium (Cd) is a highly toxic heavy metal for plants, but several unique Cd-hyperaccumulating plant species are able to accumulate this metal to extraordinary concentrations in the aboveground tissues without showing any toxic symptoms. However, the molecular mechanisms underlying this hypertolerance to Cd are poorly understood. Here we have isola...

The β-cyanoalanine pathway in plants detoxifies cyanide by assimilating this metabolic poison. Given the possibility that cyanide in soil could serve as an alternate source of nitrogen for plant nutrition, this study investigated whether nitrogen deprivation of wheat seedlings altered the activity of the first enzyme of the pathway (β-cyanoalanine...

The role of glutathione and dithiothreitol as reductants supporting arsenate reductase activity in root extract from the arsenic hyperaccumulator Pteris vittata was examined. The two reductants in combination enhanced arsenate reduction in vitro more than glutathione alone. The implications of these results for in vivo arsenate reduction are discus...

Adjuvants such as cyanide, thiocyanate, and thiosulfate are applied to gold-bearing ores to increase gold solubility and plant uptake of gold during phytomining. The influence of these three adjuvants, added at rates comparable to field application (1 g kg DW-1 ore), on the leaching of heavy metals from gold ore from the Davis stockpile at the Staw...

Batch extraction and leaching studies were conducted with potential green roof substrates (e.g., Axis, Arklayte, coal bottom ash, Haydite, Lassenite, lava rock, and composted pine bark). The results indicated that these materials would not likely be sources of Cr, Cu, Fe, Ni, or Zn and that Lassenite would be considered a source of Mn if the leacha...

Cyanide assimilation by the beta-cyanoalanine pathway produces asparagine, aspartate and ammonium, allowing cyanide to serve as alternate or supplemental source of nitrogen. Experiments with wheat and sorghum examined the enrichment of (15)N from cyanide as a function of external cyanide concentration in the presence or absence of nitrate and/or am...

Arsenic (As) hyperaccumulating ferns are used to phytoremediate As-contaminated soils, including soils in residential areas. This use may pose a health risk if children were to ingest these plants. Spider brake (Pteris cretica L.) plants were grown in sand spiked with arsenate, to produce tissue As concentrations (2000-4500 mg kg DW(-1)) typical of...

Differential sorption and transport characteristics of the leaf mesophyll layer of the Prayon and Ganges ecotypes of the hyperaccumulator Thlaspi caerulescens were examined. (109)Cd influx and efflux experiments were conducted with leaf sections, and X-ray absorption near edge structure (XANES) data were collected from leaves as a general compariso...

The wastes from some industrial processes and the tailings from gold mining contain elevated concentrations of cyanide, which reacts with iron in the media to form iron cyanide complexes. This research examined the transport and possible metabolism of ferrocyanide by two native Australian trees, blue mallee and sugar gum, and by sorghum. Hydroponic...

Plants of Indian mustard (Brassica juncea) were treated with either 50 µM Cd, 250 µM Zn, or 25 µM Cd+125 µM Zn and the progression of chlorosis in the mature leaves monitored. As relative chlorophyll (Chl) contents in the mature leaves decreased to 75, 50, and 25 % relative to controls, both mature and young leaves were harvested and the Chl pools...

The accumulation of excess Cd in the seeds of cereal and other crops compromises their commercial value and presents a potential risk to human health. Indian mustard [Brassica juncea (L.) Czern.] is a moderate accumulator of heavy metals such as Cd and Zn, and the seeds are consumed throughout the world, particularly in the Indian subcontinent. The...

The phytoextraction of gold is an exciting new area of research involving the use of plants to extract gold from a low grade ore and waste products. The aim of this study was to screen some Australian native plant species and exotic agricultural species for their potential use in cyanide-induced phytoextraction of gold from a crushed ore body. Plan...

Site 36 at the Crab Orchard National Wildlife Refuge includes a Cd-contaminated soil dominated by deer tongue grass (Panicum clandestinum L.). Analysis of deer tongue grass from this site indicated that biomass and leaf surface area were reduced and that there was a linear relationship between both plant bioavailable soil Cd and total soil Zn and t...

The capacity of silver (Ag +) to inhibit the transport of arsenite by the arsenic (As) hyperaccumulating fern Pteris vittata was investigated. The hydroponic growth medium was supplemented with 200 µ µ µ µ µM arsenite and 1, 10, or 100 µ µ µ µ µM Ag + , with roots and pinnae harvested intermittently following treatment. Treatment with Ag + signific...

This case study was conducted to evaluate the use of reclaimed lake sediment as a growth media for vegetable production and to estimate whether accumulation of micronutrients and heavy metals in the vegetables would impact human nutrition or health, respectively. Five plant species, bean (Phaseolus vulgaris L.), broccoli (Brassica oleracea L.), car...

A model for cyanide species uptake by willow (Salix eriocephala L. var. Michaux) was developed to interpret data from hydroponic experiments quantitatively. While the potential for cyanide phytoremediation has been demonstrated modeling will aid in determining plant processes that contribute to cyanide transport and metabolism in willow and will ta...

A plant uptake model is applied to describe free cyanide and ferrocyanide transport and fate in willow (Salix eriocephala var. Michaux) grown in hydroponics. The model is applied to experimental data to determine best-fit parameter values, their associated uncertainty, and their relative importance to field-scale phytoremediation applications. The...

American ginseng root (Panax quinquefolius) has a number of purported therapeutic effects, including inhibition of cancer cell proliferation. The ability of environmentally relevant heavy metals to alter ginseng effects on cancer cell growth was the subject of this study. A water extract of American ginseng root was applied alone or in combination...

Competition is a major density-dependent factor structuring plant populations and communities in both natural and agricultural systems. Seedlings of the model plant species Arabidopsis thaliana cv. Columbia, and the Columbia-derived stomatal mutants sdd1 and tmm1, were grown under controlled conditions at increasing densities of 1, 10, 20, and 50 p...

Four methods were tested for extraction and recovery of six major ginsenosides (Rb1, Rb2, Rc, Rd, Re, and Rg1) found in roots of American ginseng (Panax quinquefolius): method A, sonication in 100% methanol (MeOH) at room temperature (rt); method B, sonication in 70% aqueous MeOH at rt; method C, water extraction (90 degrees C) with gentle agitatio...

Cyanide has long held a prominent position amongst metabolic inhibitors, best known as an inhibitor of aerobic respiration [1]. However, given the ubiquity of cyanide and cyanogenic (cyanide-containing) compounds in nature, it is not surprising that these compounds can be biologically transformed or utilized. The metabolic capacity to transform cya...

Chapters 1, 3, and 4 describe the production of cyanide via natural and anthropogenic sources. A range of plants and organisms produce cyanide (Chapter 3). Natural or anthropogenic cyanide deposited or discharged to soil or surface waters can be transported by water (Chapters 9 and 10), and be subject to biodegradation, adsorption, or volatilizatio...

The four most common atoms that make up life on earth are carbon, hydrogen, nitrogen, and oxygen, and hydrogen cyanide (HCN) is comprised of three of these essential macronutrients. Cyanide played a pivotal role in the prebiotic development of amino acids, peptides, nucleotides, lipids, and membranes, and continues to be an integral part of nature...

The presence of elevated concentrations of heavy metals limits the usage of sewage sludge as a fertilizer and soil amendment. Experiments were carried out to examine the extent to which seven plant species phytoextracted Zn and Cu from dewatered sludge. The hyperaccumulators Thlaspi caerulescens and Sedum alfredii showed the greatest removal of Zn,...

A method for free cyanide and strongly-complexed cyanide measurement within plant tissue was developed to study uptake and movement of cyanide species separately from cyanide metabolism and metabolite movement by a willow plant (Salix eriocephala var. Michaux). Spike recoveries from solutions with and without plant tissue, using various solvent com...

Cyanide compounds are produced as waste products of a number of industrial processes and several routes for their removal from the environment are under investigation, including the use of biodegradation. The most recent developments in this area have come from studies of the hydrolytic and oxidative pathways for biodegradation and the conditions t...

Yellow foxtail (Setaria glauca L. P. Beauv) growing on a cadmium-contaminated site was sampled to determine the extent of cadmium bioaccumulation in aerial tissues and the impact of cadmium on growth and development. Water-extractable Cd concentrations in the soil ranged from 5.0 to 18.0 mg L -1 . Aerial tissues contained elevated concentrations of...

Barley (Hordeum vulgare L.), oat (Avena sativa L.), and wild cane (Sorghum bicolor L.), were exposed to 15N-labeled ferrocyanide to determine whether these plant species can transport this iron cyanide complex. Plants were treated with ferrocyanide in a nutrient solution that simulated iron cyanide contaminated groundwater and soil solutions. This...

Phytoextraction field experiments were conducted on soil contaminated with 0.39 to 8.7 Bq/g of 137Cs to determine the capacity of five plant species to accumulate 137Cs and the effects of three soil treatments on uptake. The plants tested were redroot pigweed (Amaranthus retroflexus L. var. aureus); a mixture of redroot pigweed and spreading pigwee...

Cyanide compounds are contaminants of growing importance that could be remediated biologically via phytoremediation, provided the plants possess suitable mechanisms for managing these pollutants without toxicity. The transport and metabolism of two cyanide compounds, potassium cyanide and potassium ferrocyanide, by willow (Salix eriocephala L. var....

A field test was conducted to determine the ability of three plant species to extract 137Cs and 90Sr from contaminated soil. Redroot pigweed (Amaranthus retroflexus L.), Indian mustard [Brassica juncea (L.) Czern.], and tepary bean (Phaseolus acutifolius A. Gray) were planted in a series of spatially randomized cells in soil that was contaminated i...

minerals can significantly reduce bioavailablity of 137 Cs for plant uptake, the relatively simple mineralogy (most- A field test was conducted to determine the ability of three plant ly quartz with only a trace of micaceous minerals) of species to extract 137 Cs and 90 Sr from contaminated soil. Redroot pig- weed (Amaranthus retroflexus L.), India...

Thlaspi caerulescens (J. & C. Presl, "Prayon") is a heavy-metal hyperaccumulator that accumulates Zn and Cd to high concentrations (40,000 and 4,000 mg kg DW-1 respectively) without phytotoxicity. The mechanism of Cd tolerance has not been characterized but reportedly involves vacuolar sequestration. The role of phytochelatins (PCs) in metal tolera...

A hydroponic uptake study with willow (Salix eriocephala) was conducted to demonstrate the efficacy of cyanide phytoremediation. The uptake of 15N-labeled free cyanide and ferrocyanide from solution was examined under conditions that maintained cyanide availability in solution. Cyanide speciation and concentration in the hydroponic solution were mo...

The investigation of interaction between arsenic and selenium indicated that effects on both selenate transport and Se metabolism were involved. Barley (Hordeum vulgare L.) seedlings were exposed to selenate in the presence of arsenate (0, 0.01, and 1.0 mg L-1), with Se uptake, translocation, and volatilization measured. Selenium uptake and translo...

Phytoremediation of uranium (U) contaminated soil has been hampered by a lack of information relating U speciation to plant uptake. The goals of the present study are to (1) provide fundamental information regarding uptake of U by plants; and (2) improve the phytoextraction of U from contaminated soil. The first was achieved through speciation mode...

An integrated molecular and physiological investigation of the fundamental mechanisms of heavy metal accumulation was conducted in Thlaspi caerulescens, a Zn/Cd-hyperaccumulating plant species. A heavy metal transporter cDNA, ZNT1, was cloned from T. caerulescens through functional complementation in yeast and was shown to mediate high-affinity Zn(...

In this manuscript, recent research from this laboratory into physiological and molecular aspects of heavy metal (Zn) transport in the hyperaccumulating plant species, Thlaspi caerulescens is reviewed. This research is aimed at elucidating the processes that underlie the accumulation of extraordinarily high levels of Zn in the T. caerulescens shoot...

The role of acidification and chelating agents in the solubilization of uranium (U) from contaminated soil was examined in a series of experiments. Soil acidification and the addition of chelating agents were the two methods compared initially. The results indicated that the addition of citric acid solubilized more U than acidification or the other...

Uranium (U) uptake and translocation by plants was characterized using a computer speciation model to develop a nutrient culture system that provided U as a single predominant species in solution. A hydroponic uptake study determined that at pH 5.0, the uranyl (UO2(2+)) cation was more readily taken up and translocated by peas (Pisum sativum) than...

The success of phytoremediation hinges on the selection of plant species and soil amendments that maximize contaminant removal. Indian mustard (Brassica juncea) has been shown to be effective in phytoextracting Zn, particularly after the synthetic chelate EDTA has been applied to the soil. However, the effectiveness of grass species for phytoremedi...

A field study was conducted to investigate the potential of three plant species for phytoremediation of a 137Cs-contaminated site. Approximately 40-fold more 137Cs was removed from the contaminated soil in shoots of red root pigweed (Amaranthus retroflexus L.) than in those of Indian mustard [Brassica juncea (L.) Czern] and tepary bean (Phaseolus a...

The toxicity of Zn and Cu in three species from the genus Brassica was examined to determine if these plants showed sufficient tolerance and metal accumulation to be used to phytoremediate a site contaminated with these two heavy metals. Hydroponically grown 12 d-old plants of Brassica juncea, B. rapa, and B. napus were grown for an additional 14 d...

To identify populations with the ability to accumulate heavy metals, approximately 300 accessions pertaining to 30 plant species were grown for 4 wk in a hydroponic media that approximated the nutrient and heavy metal composition of a soil contaminated with moderate levels of cadmium (Cd), copper (Cur, and zinc (Zn). The results indicated that seve...