Root structural changes of two remediator plants as the first defective barrier against industrial pollution, and their hyperaccumulation ability.

In the present day, plants are increasingly being utilized to safeguard the environment. In this study, we used Salsola crassa M. B. and Suaeda maritima L. Dumort for phytoremediation of water contaminated with heavy metals and simultaneous examination of the effect of industrial pollution on their root structures. After irrigation of a treatment group with wastewater and a control group with fresh water for 3 months, we fixed the root parts in the FAA fixator for developmental study, and measured the concentrations of Co, Ni, Zn, As, Cu, and Pb in the roots, shoots, soil, and irrigating water. The plants irrigated with wastewater showed significant accumulation of heavy metals in the roots and some translocation of heavy metals from the roots to the shoots. We also performed an experiment with two 0.3 m3 pools to more closely study the feasibility of these plants for filtering water of contaminants, including mineral compounds, and altering its chemical characteristics. In our anatomical studies, the cells of the treatment roots showed irregularities and abnormal appearances in all tissue layers. The diameter and area of the xylem and the size of the cortical parenchyma have increased in the treatment plants of both species, confirmed by Stereolite software. Phytoremediation studies indicated that S. crassa accumulated As, Cu, Zn, Pb, Co, and Ni, and S. maritima accumulated As, Co, Zn, and Cu. S. crassa accumulated more heavy metals in its roots, whereas S. maritima accumulated more in its shoots. The biological oxygen demand and chemical oxygen demand were also significantly reduced in the wastewater passed through pools with S. crassa. Our results indicate that both genera are hyperaccumulators of heavy metals and therefore hold promise for industrial wastewater treatment, especially the absorption of As.

C3 cotyledons are followed by C4 leaves: intra-individual transcriptome analysis of Salsola soda (Chenopodiaceae).

Some species of Salsoleae (Chenopodiaceae) convert from C3 photosynthesis during the seedling stage to the C4 pathway in adult leaves. This unique developmental transition of photosynthetic pathways offers the exceptional opportunity to follow the development of the derived C4 syndrome from the C3 condition within individual plants, avoiding phylogenetic noise. Here we investigate Salsola soda, a little-studied species from tribe Salsoleae, using an ontogenetic approach. Anatomical sections, carbon isotope (δ13C) values, transcriptome analysis by means of mRNA sequencing, and protein levels of the key C4 enzyme phosphoenolpyruvate carboxylase (PEPC) were examined from seed to adult plant stages. Despite a previous report, our results based on δ13C values, anatomy and transcriptomics clearly indicate a C3 phase during the cotyledon stage. During this stage, the entire transcriptional repertoire of the C4 NADP-malic enzyme type is detected at low levels compared to a significant increase in true leaves. In contrast, abundance of transcripts encoding most of the major photorespiratory enzymes is not significantly decreased in leaves compared to cotyledons. PEPC polypeptide was detected only in leaves, correlating with increased PEPC transcript abundance from the cotyledon to leaf stage.

Physiological responses and tolerance mechanisms to Pb in two xerophils: Salsola passerina Bunge and Chenopodium album L.

Lead (Pb) has great toxicity to human beings and other livings. Although there are varied ways to rehabilitate the Pb contaminated area, phytoremediation of Pb pollution in arid lands is still a difficult task, it is therefore urgent to find and identify Pb tolerant plants in arid areas. The physiological responses and tolerance mechanisms to Pb stress (expressed as the Pb concentration, e.g., 0, 50, 150, 300, 600, 800, 1000 mg/L) were investigated for the xerophils Salsola passerina Bunge and Chenopodium album L. Results indicated that S. passerina exhibited higher Pb tolerance than Ch. album in terms of the seed germination rate, bio-activities of SOD and POD, and lower MDA production. There were two ways for S. passerina to reduce Pb toxicity in organism level, e.g., cell wall precipitation and state transfer of free Pb into anchorage. These findings demonstrate that S. passerina is a Pb tolerant species and may have potential application in phytoremediation of Pb contaminated arid lands.

[Dynamics of plant community species diversity in the process of ecological rehabilitation in north Shaanxi loess area].

Based on the vegetation survey on 18 sampling plots in Wuqi County of Shaanxi Province, and by using the methods of substituting space series for time series and of contrastive analysis, the dynamics of plant community species diversity in the process of ecological rehabilitation in the County was analyzed from the aspects of succession time, rehabilitation mode, and slope direction. The results showed that in the 25 years natural succession series, the natural restoration community on previous cropland experienced the sequence of Salsola collina, Artemisia scoparia, Lespedeza davurica, Artemisia sacrorum, and Bothriochloa ischcemum, with the dominant species tended to be changed from annual to perennial and from low-class to high-class. The variations of species number, Margalef index, Simpson index, Shannon-Wiener index, and Pielou index in the succession process could all be described by a quadratic function y = at2 + bt + c, suggesting that after the outside pressure removed, the degraded ecosystem in loess area could naturally restore to an advanced and steady state, but the restoration rate would be very slow. With the same site factors and restoration periods, the Margalef index, Shannon-Wiener index and Pielou index of herb layer decreased in the order of naturally restoring on previous cropland (I) > converting cropland to grassland (II) > converting cropland to forestland (III) > afforestation on barren hills (IV), while Simpson index changed in adverse. Comparing with natural restoration, the community types of herb layer in II and III were at the more advanced stage of natural succession series though the species diversity index was lower, indicating that artificial planting would accelerate the succession process. In the same period of rehabilitation, the Margalef index, Shannon-Wiener index and Pielou index of natural restoration community were obviously higher on shady slope than on sunny slope, and the community type was at the more advanced stage of natural succession series, suggesting that the basic ecological rehabilitation condition on sunny slope was worse, and the succession rate was slower.

Role of ethylenediaminetetraacetic acid on lead uptake and translocation by tumbleweed (salsola kali L.).

Tumbleweed plants (Salsola kali L.) grown in agar and liquid media demonstrated a high capacity to accumulate Pb in their different parts without affecting biomass. Whereas shoot elongation and biomass were not significantly affected by high tissue concentrations of Pb, root growth was significantly affected relative to controls. Roots, stems, and leaves demonstrated Pb concentrations of 31,000, 5,500, and 2,100 mg/kg dry weight, respectively, when plants were grown in the agar medium containing 80 mg Pb/L. Application of ethylenediaminetetraacetic acid (EDTA) to Pb-contaminated media dramatically reduced the total acquisition of Pb from both types of media. However, EDTA significantly increased the translocation of Pb from roots to the aerial parts, as evidenced by a multifold increase (23- and 155-fold for agar and liquid media, respectively) in the translocation concentration factor. The concentration of the antioxidant thiol compounds significantly increased (p < 0.05) in plants grown with uncomplexed Pb treatments relative to control plants. Scanning-electron microscopy and electron dispersive x-ray spectroscopic evaluation of leaf samples demonstrated an interesting pattern of Pb translocation in the presence or absence of EDTA. Large Pb crystals were found across the leaf tissues (palisade, spongy parenchyma, and conducting tissues) in the absence of EDTA. Lead nanoparticles also were seen when plants were grown in Pb-EDTA solution. Ultramicroscopic features of tumbleweed provide clear evidence for the unrestricted conduction of Pb from the root to the aerial parts, and this property makes the plant a good candidate for phytoremediation.

Spectroscopic study of the impact of arsenic speciation on arsenic/phosphorus uptake and plant growth in tumbleweed (Salsola kali).

This manuscript reports the toxic effects of As2O3 (arsenic trioxide) and As2O5 (arsenic pentoxide) on S. kali as well as the arsenic and phosphate uptake and arsenic coordination within plant tissues. Plants were germinated and grown for 15 days on a Hoagland-modified medium containing either As(III) (arsenic trioxide) or As(V) (arsenic pentoxide). Subsequently, the seedlings were measured and analyzed using inductively coupled plasma optical emission spectroscopy and X-ray absorption spectroscopy techniques. Plants stressed with 2 mg L(-1) of whichever As(III) or As(V) concentrated 245 +/- 19, 30 +/- 1, and 60 +/- 3 mg As kg(-1) dry weight or 70 +/- 6, 10 +/- 0.3, and 27 +/- 3 mg As kg(-1) dry weight in roots, stems, and leaves, respectively. Arsenate was less toxic, and more As translocation occurred from the roots to the leaves. All treatments reduced P concentration at root level; however, only As(V) at 2 and 4 mg L(-1) reduced P concentration at leaf level. Regardless the arsenic species supplied to the plants, arsenic was found in plant tissues as As(III) coordinated to three sulfur ligands with an interatomic distance of approximately 2.25 angstroms.

Differential uptake and transport of trivalent and hexavalent chromium by tumbleweed (Salsola kali).

Experiments were conducted to determine the differential absorption of Cr species by tumbleweed (Salsola kali) as well as the effect of this heavy metal on plant growth and nutrient uptake. Tumbleweed seeds were grown in an agar-based media containing different concentrations of either Cr(III) or Cr(VI). The results demonstrated that the uptake of Cr was influenced by the Cr concentration in the growth medium and the speciation of this heavy metal. When supplied in the hexavalent form, the concentration of Cr in the different plant parts (2900, 790, and 600 mg kg(-1) for roots, stems, and leaves, respectively) was between 10 and 20 times higher than the amounts found when Cr was supplied in the trivalent form. In addition, it was found that in most of the experiments, Cr(III) exhibited more toxic effects on tumbleweed plants than Cr(VI). The size of roots of plants grown in 20 mg L(-1) Cr(III) were significantly smaller (p < 0.05) than those grown in 20 mg L(-1) Cr(VI). Plants exposed to 20 mg L(-1) Cr(III) produced shoots significantly shorter (p < 0.05) compared with the size of control plants and with those grown in 20 mg L(-1) Cr(VI). In addition, the absorption of macronutrients and microelements was in general lower when the plants were grown in the medium containing Cr(III). The amounts of Cr concentrated in the aerial plant parts under experimental conditions may indicate tumbleweed as a new option for the phytoremediation of Cr-contaminated soil.

Assessment of hydraulic restoration of San Pablo Marsh, California.

Inter-tidal marshes are dynamic diverse ecosystems at the transition zone between terrestrial and ocean environments. Geomorphologically, inter-tidal salt marshes are vegetated land-forms at elevations slightly greater than mean tidal levels that have distributed channels formed under ebb (drainage) tidal flows that widen and deepen in the seaward direction. The drainage channels enable tidal flows to circulate sediments and nutrients through the marsh system during normal tidal events, while depositing sediments during storm or seismic events. This dynamic system encourages considerable biodiversity while simultaneously providing water quality enhancement features that service marsh terrestrial life and marine life in the estuary. Reservoir creation limiting sediment transport, anticipated large increases in sea levels as well as agricultural and urban development have resulted in significant loss of inter-tidal marshes and subsequent adverse impacts on waterfowl, infauna and fisheries. The complex and continuously changing marsh channel hydraulics and sedimentary processes have severely constrained quantitative modeling of these marsh systems such that restoration/creation efforts remain something of an empirical science and further assessments are needed. The purpose of this paper is to outline current understanding of salt marsh hydrodynamics, sediment accretion processes and subsequent response of marsh vegetation to set the stage for assessment of a marsh restoration effort along San Pablo Bay near San Francisco, California. Several kilometers of drainage channels were constructed in a 624 ha disturbed salt marsh to restore tidal circulation and vegetation so as to enhance habitat for threatened species (e.g. clapper rail, harvest mouse, delta smelt and potentially anadromous fish species). Two distinct drainage channel systems ('east' and 'west') were installed having similar channel dimensions common to salt marshes in the region, but having design bankfull tidal prism volumes differing by a factor of two. Following channel excavation, main channel tidal flows and sediment loads as well as marsh sediment accretion rates were monitored to assess the relative success of the excavation in restoring tidal circulation and vegetation (Salicornia spp.) to the marsh. Annual aerial surveys corroborated with ground-truthing indicated that marsh vegetation rapidly expanded, from 40 to 85% coverage several years following excavation. The 'east' channel intake was nearly completely silted in within three years. However, channel surveys and flow measurements indicated that the 'east' channel system tidal prism was only about 1200 m3, more than an order of magnitude less than that of the stable 'west' channel system. Marsh sediment accretion rates were on the order of 7-8 mm yr(-1), a rate common to the Pacific coast region that exceeds estimated sea level rise rates of approximately 2 mm yr(-1). East channel network siltation resulted in storm and spring tidal flood ponding such that marsh vegetation coverage decreased to 51% of the marsh area and related habitat expansion decreased. These results are considered in terms of the primary inter-tidal marsh factors affecting possible restoration/creation strategies.

Cadmium uptake and translocation in tumbleweed (Salsola kali), a potential Cd-hyperaccumulator desert plant species: ICP/OES and XAS studies.

Cadmium is a heavy metal, which, even at low concentrations, can be highly toxic to the growth and development of both plants and animals. Plant species vary extensively in their tolerance to excess cadmium in a growth medium and very few cadmium-tolerant species have been identified. In this study, tumbleweed plants (Salsola kali) grown in an agar-based medium with 20 mgl(-1) of Cd(II) did not show phytotoxicity, and their roots had the most biomass (4.5 mg) (P < 0.05) compared to the control plants (2.7 mg) as well as other treated plants. These plants accumulated 2696, 2075, and 2016 mg Cd kg(-1) of dry roots, stems, and leaves, respectively. The results suggest that there is no restricted cadmium movement in tumbleweed plants. In addition, the amount of Cd found in the dry leaf tissue suggests that tumbleweed could be considered as potential cadmium hyperaccumulating species. X-ray absorption spectroscopy studies demonstrated that in roots, cadmium was bound to oxygen while in stems and leaves, the metal was attached to oxygen and sulfur groups. This might imply that some small organic acids are responsible for Cd transport from roots to stems and leaves. In addition, it might be possible that the plant synthesizes phytochelatins in the stems, later coordinating the absorbed cadmium for transport and storage in cell structures. Thus, it is possible that in the leaves, Cd either exists as a Cd-phytochelatin complex or bound to cell wall structures. Current studies are being performed in order to elucidate the proposed hypothesis.