Tolerance of Impatiens balsamina L., and Crotalaria retusa L. to grow on soil contaminated by used lubricating oil: A comparative study.

Screening of plant species with an ability to grow on contaminated soil is the most critical step in the planning of a phytoremediation program. While flourishing growth of Impatiens balsamina L. and Crotalaria retusa L. has been observed in areas adjacent to automobile service stations in Sri Lanka, no systematic study of their tolerance to used lubricating oil (ULO) contaminated soil has been carried out. Therefore, the aim of the present study was to investigate the comparative responses of I. balsamina L. and C. retusa L. to soil contaminated with ULO. Both species exhibited 100% seed germination in soils treated with 1%-5% w/w ULO. After 120 h exposure, root lengths and biomass of germinated seedlings of both species were significantly (p < 0.05) reduced in all treatments above 3% w/w ULO. The measured growth parameters of plants following 90 d exposure to 0.5-3% w/w ULO, indicated significant (p < 0.05) negative effects on I. balsamina and C. retusa at >1% w/w and >2% w/w ULO, respectively. There were no significant effects on chlorophyll content or root anatomy of either species under any treatments. Therefore, we concluded that I. balsamina can tolerate up to 1% of ULO and C. retusa up to 2% w/w ULO without displaying any negative effects. Comparatively higher biodegradation of ULO in the rhizosphere, root nodule formation, increases in root length and root hair density are all possible strategies for the exhibited higher tolerance of C. retusa. Therefore, the overall results indicate that C. retusa has the greater potential to be used in phytoremediation of ULO contaminated soils. The findings of the present study will be beneficial in planning phytoremediation program for ULO contaminated soil.

Cadmium Uptake by Cuttings of Impatiens walleriana in Response to Different Cadmium Concentrations and Growth Periods.

Impatiens walleriana (I. walleriana), a potential cadmium (Cd) hyperaccumulator, can propagate by cuttings, which are less expensive to grow than seedlings. Different growth periods for cuttings, however, may lead to different physiological characteristics. In this study, I. walleriana cuttings were hydroponically grown in Cd-containing solutions (1.0-10.0 µM) for various growth periods (10-60 days). Experimental results showed that the Cd treatments had negative effects on growth compared to the controls that were not spiked with Cd. The extension of the growth period promoted most of the growth exhibitions of I. walleriana, except for SPAD readings for cuttings grown in the 5.0 and 10.0 µM solutions. The accumulation of Cd also increased over time, except in the roots of the cuttings grown in the 5.0 and 10.0 µM solutions. The subcellular distribution and chemical forms of Cd showed that I. walleriana developed better tolerance and detoxification capacities in the cuttings grown in the 5.0 and 10.0 µM solutions than in the cuttings grown in the other two Cd treatments.

Utilization of solar energy in sewage sludge composting: fertilizer effect and application.

Three reactors, ordinary, greenhouse, and solar, were constructed and tested to compare their impacts on the composting of municipal sewage sludge. Greenhouse and solar reactors were designed to evaluate the use of solar energy in sludge composting, including their effects on temperature and compost quality. After 40 days of composting, it was found that the solar reactor could provide more stable heat for the composting process. The average temperature of the solar reactor was higher than that of the other two systems, and only the solar reactor could maintain the temperature above 55°C for more than 3 days. Composting with the solar reactor resulted in 31.3% decrease in the total organic carbon, increased the germination index to 91%, decreased the total nitrogen loss, and produced a good effect on pot experiments.

Chelator effects on bioconcentration and translocation of cadmium by hyperaccumulators, Tagetes patula and Impatiens walleriana.

French marigold (Tagetes patula) and impatiens (Impatiens walleriana) can act as hyperaccumulator plants for removal of cadmium (Cd) from contaminated sites. In this study, an exponential decay model was used to predict the maximum removal of Cd from artificially spiked soils by impatiens. Application of a chelator, EDTA, was also assessed for effects on the bioconcentration (BCF) and translocation (TF) factors of the two species with four replicates. Exposure to Cd significantly decreased the biomass of two plant species. Impatiens and French marigold accumulated Cd at a rate of 200-1200 mg Cd kg(-1) in shoots, with BCFs and TFs of 8.5-15 and 1.7-2.6, respectively.

Hydrogen sulphide, a novel gasotransmitter involved in guard cell signalling.

Hydrogen sulphide (H(2) S) has been proposed as the third gasotransmitter. In animal cells, H(2) S has been implicated in several physiological processes. H(2) S is endogenously synthesized in both animals and plants by enzymes with l-Cys desulphydrase activity in the conversion of l-Cys to H(2) S, pyruvate and ammonia. The participation of H(2) S in both stomatal movement regulation and abscisic acid (ABA)-dependent induction of stomatal closure was studied in epidermal strips of three plant species (Vicia faba, Arabidopsis thaliana and Impatiens walleriana). The effect of H(2) S on stomatal movement was contrasted with leaf relative water content (RWC) measurements of whole plants subjected to water stress. In this work we report that exogenous H(2) S induces stomatal closure and this effect is impaired by the ATP-binding cassette (ABC) transporter inhibitor glibenclamide; scavenging H(2) S or inhibition of the enzyme responsible for endogenous H(2) S synthesis partially blocks ABA-dependent stomatal closure; and H(2) S treatment increases RWC and protects plants against drought stress. Our results indicate that H(2) S induces stomatal closure and participates in ABA-dependent signalling, possibly through the regulation of ABC transporters in guard cells.

The use of Sunpatiens (Impatiens spp.) as a bioindicator of some simulated air pollutants--using an ornamental plant as bioindicator.

Sunpatiens were exposed separately or combined to ozone gas (130 ppb), fluoranthene (10 microM) and sulphuric acid mists (pH 3) sprayed as simulated pollutants in chamber conditions for 21 d. The treatments negatively affected the gas (CO(2) and moisture) exchange, leaf chlorophyll fluorescence, and the leaf-quality expressed in chlorophyll value (SPAD). Fluoranthene and the acid individual negative effects on the measured eco-physiological variables were nearly the same on Sunpatiens; their effects became aggravated on combining the duo. The foliar symptom assessments of chlorosis, necrosis and stippling revealed severe damages in ozone containing treatments compared with other treatments. The presence of fluoranthene exuberate ozone negative effects on some of the plant eco-physiological status. Where mannitol (1mM) additions were contained in treatments, mitigation effects of the negative impact of pollutants resulted. These findings indicated that Sunpatiens can be used as an active bioindicator of singular and multiple pollutants in field conditions.

Arbuscular mycorrhizal fungi protect a native plant from allelopathic effects of an invader.

The allelopathic potential of the Eurasian invasive plant Alliaria petiolata has been well documented, with the bulk of the effects believed to be mediated by arbuscular mycorrhizal fungi (AMF). We exposed the herbaceous annual Impatiens pallida, which is native to North America, to fractionated A. petiolata extracts at four developmental stages (germination, presymbiosis growth, symbiosis formation, and symbiosis growth) by using exposure levels expected to be similar to field levels. Surprisingly, we found strong direct effects on I. pallida germination and growth, but no indirect effects on I. pallida growth mediated by AMF. We also observed strong synergistic effects with a complete A. petiolata extract that inhibited I. pallida germination and presymbiosis root growth more than either a glucosinolate or flavonoid enriched fraction alone. In fact, the flavonoid enriched fraction tended to stimulate germination and presymbiosis root growth. In contrast to these strong direct effects, I. pallida plant growth during both the symbiosis formation and symbiosis growth phases was unaffected by A. petiolata extracts. We also found no inhibition of AMF colonization of roots or soils by A. petiolata extracts. We show that AMF can actually ameliorate allelopathic effects of an invasive plant, and suggest that previously observed allelopathic effects of A. petiolata may be due to direct inhibition of plant and fungal growth before symbiosis formation.

Density-dependent phytotoxicity of impatiens pallida plants exposed to extracts of Alliaria petiolata.

Invasive plants are by definition excellent competitors, either indirectly through competition for resources or directly through allelopathic inhibition of neighboring plants. Although both forms of competition are commonly studied, attempts to explore the interactions between direct and indirect competition are rare. We monitored the effects of several doses of extracts of Alliaria petiolata, a Eurasian invader in North America, on the growth of Impatiens pallida, a North American native, at several planting densities. The density-dependent phytotoxicity model predicts that as plant density increases, individual plant size will decrease, unless a toxin is present in the soil. In this case, individual plant size is predicted to increase as plant density increases, as plants share a limited toxin dose. We tested this model using fractions of an A. petiolata extract enriched in flavonoids or glucosinolates, as well as a combined fraction. The flavonoid-enriched fraction and the combined fraction suppressed I. pallida growth but only when applied at a dose eight times higher than that expected in the field. When treated with a dose equivalent to estimated field exposure levels, I. pallida growth was not distinguishable from that of control plants that received no extract, showing that indirect competition for resources was more important for determining the growth of I. pallida than direct allelopathic inhibition by A. petiolata. This is an important reminder that, even though many plants have the demonstrated potential to exert strong allelopathic effects, those effects may not always be apparent when other forms of competition are considered as well.

Evaluation of the genotoxicity induced by the fungicide fenarimol in mammalian and plant cells by use of the single-cell gel electrophoresis assay.

Fenarimol, a systemic pyrimidine carbinol fungicide, is considered to be not genotoxic or weakly genotoxic, although the available toxicological data are controversial and incomplete. Our results obtained in vitro with leukocytes of two different rodent species (rat and mouse) show that fenarimol affects DNA, as detected by the single-cell gel electrophoresis (SCGE, Comet) assay. This fungicide is able to induce DNA damage in a dose-related manner, with significant effectiveness at 36 nM, but without significant interspecies differences. Simultaneous exposure of rat leukocytes to fenarimol (36-290 nM) and a model genotoxic compound (50 microg/ml bleomycin) produced a supra-additive cytotoxic and genotoxic effect. This supports previous findings suggesting possible co-toxic, co-mutagenic, cancer-promoting and co-carcinogenic potential of fenarimol, and modification of the effects of other xenobiotics found to be influenced by this agrotoxic chemical, with consequent different toxicological events. The potential for DNA strand breaks to act as a biomarker of genetic toxicity in plants in vivo was also considered, in view of the fact that higher plants represent reliable sensors in an ecosystem. Significant DNA breakage was observed in the nuclei of Impatiens balsamina leaves after in vivo treatment with fenarimol (145 nM, 1h). More than 50% of the cells showed such DNA damage.