促根剂及水分胁迫对Cd污染异质土壤中小麦吸收、转运Cd的影响

为了研究促根剂与水分胁迫诱导小麦根伸长及其降低小麦对异质土壤中Cd吸收转运的影响,本研究制备了不同浓度Cd污染土壤,利用根箱法设置了3种不同土层(0~6 cm、7~12 cm及13~18 cm)下的Cd污染异质土壤,研究了3种添加比例(0.1%、0.2%和0.4%)下促根剂与3种水分胁迫诱导(60%、50%和40% MWHC)下小麦根伸长对降低小麦Cd吸收、转运的影响。结果表明：不同促根剂与水分胁迫诱导处理可以明显促进小麦根系生长,表现为小麦根系总长与根表面积的显著增加,其中促根剂促使下层(13~18 cm)土壤中小麦根系总长增加了63.2%~205.9%,水分胁迫诱导增加了69.1%~91.2%。不同促根剂处理可以不同程度增加小麦分蘖数,从而增加了小麦籽粒生物量(小麦籽粒生物量增加5.6%~50.3%);与对照相比,除了40% MWHC水分处理(WS3)外,不同促根剂与水分胁迫处理可以显著降低(P<0.05)Cd污染异质土壤中小麦茎叶与籽粒中Cd的浓度,降低范围分别为24.0%~41.5%和23.0%~42.7%,其中以添加0.4%促根剂处理效果最佳,不同处理对降低小麦籽粒Cd含量效果顺序为RA3≈RA2>WS2≈RA1≈WS1>WS3。基于上述结果,RA2和WS2在Cd异质污染农田修复中具有较大的应用价值。     

Cadmium (Cd) concentration in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) grown in Cd-spiked soil varies with the doses and biochar feedstock

Biochar is considered a promising amendment for the reduction of metal concentration in plants; however, the effects of biochar in terms of dose and feedstock on metal uptake by plants remain widely unclear. In the current study, three individual biochars were prepared at 450 °C from different feedstocks (wheat straw, sukh chain (Pongamia pinnata), and cotton sticks). The main aim was to evaluate their ability to remediate cadmium (Cd)-spiked soil in terms of growth response and Cd uptake by wheat (Triticum aestivum) tissues. Biochars were separately applied at 0, 1, and 2% (w/w) in Cd-spiked soil and wheat was grown until maturity in pots and then morphological and physiological parameters and Cd concentrations in grains, roots, and shoots were determined. The post-harvest soil was analyzed for extractable Cd concentrations. Plants grown in Cd-spiked soil treated with biochars had higher seed germination, lengths of roots, shoots, and spikes, grains per spike and leaf relative water contents, chlorophyll contents, and dry weight of roots, shoots, and grains as compared to the untreated control. Biochar treatments significantly decreased the Cd concentrations in shoots, roots, and grains as well as total Cd uptake by grains. Soil extractable Cd concentrations were significantly decreased with biochar treatments. The application of 2.0% wheat straw biochar was the most efficient treatment in increasing grain yield and decreasing Cd in grains as well as soil extractable Cd than the other two biochars and doses applied.     

Phosphate amendment of metalliferous tailings, Cannington Ag–Pb–Zn mine, Australia: implications for the capping of tailings storage facilities

This study appraised the use of phosphate fertilisers in immobilising metals in mine tailings to prevent their uptake into Curly Mitchell grass (Astrebla lappacea), when grown on capped, phosphate-amended tailings. Leaching experiments showed that Pb mobility was reduced by both bone meal and superphosphate amendment. Bone meal amendment also reduced Cd mobility. By contrast, Cd, Mn and Zn mobility increased in superphosphate-amended tailings due to increased acid production and, Cu was mobilised in bone meal-amended tailings possibly through the formation of soluble metal-complexing organic compounds. Arsenic and Sb were mobilised in both treatments due to phosphate ligand exchange. Greenhouse trials used Curly Mitchell grass grown on 1-m-high columns stacked with waste materials and different amendments overlain by clean topsoil. Curly Mitchell grass showed substantial uptake of Cd, Mn, Pb and Zn from unamended tailings and waste rock, where these were penetrated by the plant’s root system. Addition of phosphate fertilisers to the surface of tailings did not result in reduced metal uptake by Curly Mitchell grass. In tailings capped with limestone, the limestone layer formed an effective physical barrier preventing root penetration into the tailings and led to substantially reduced metal uptake in grass. The study demonstrates that thorough mixing of waste materials and fertilisers as well as irrigation may be required for successful phosphate immobilisation of metals in base metal tailings. Alternatively, the placement of a thin layer of crushed limestone on top of the tailings pile prior to capping may lead to the formation of a chemical and physical barrier and prevent the transfer of environmentally significant elements into the above-ground biomass of Mitchell grasses.     

Assessment of cadmium,zinc and lead contamination in leaf and root of four various species

Heavy metals toxicity is a significant problem for ecological, evolutionary, nutritional and environmental reasons. This study was carried out to evaluate the amount of cadmium, zinc and lead absorption in leaf and root of pine, cypress, plantain and ash in Isfahan, Iran, in 2013. For this purpose, three heavy metals (Cd, Pb and Zn) and three sites (heavy traffic, moderate traffic and control) were chosen based on their effects on human health. The results indicated that the highest and lowest lead and cadmium concentrations belonged to heavy traffic site and control site, respectively. Cd in leaf versus Pb in leaf and Cd in root versus Pb in root had the highest correlation coefficient among the traits indicating positive influence of leaf and root on absorbing Cd and Pb from soil, water and air. In all the studied species, the concentration of Pb was higher than that of Cd and Zn. This was certainty due to the vehicle traffic emitting much more lead than cadmium and zinc. In all the studied species, metal concentration in leaves was higher than in roots, which may be due to high concentration of heavy metals in air than in soil. In this study, Pinus eldarica Medw. tree was found to be the best species to monitor polluted sites in Isfahan city.     

Short-time response in growth and sediment properties of Zizania latifolia to water depth

Field experiments were conducted to study the short-time response in growth and sediment properties of Zizania latifolia to four levels of water depth: 10, 50, 90, and 130 cm. The results showed that Z. latifolia was sensitive to high water depth stress in terms of the significantly decreased basal stem diameter, leaf width, root length, total biomass, and root to shoot ratio with increasing water depth. It was found suitable to grow in shallow water less than 50 cm in depth. The growth of Z. latifolia significantly increased sediment moisture content and porosity, while reduced wet bulk density in sediment and NH₄–N concentration in interstitial water. Along the water depth gradient, the growth of Z. latifolia significantly impacted sediment wet bulk weight and loss on ignition, both NH₄–N and PO₄–P concentrations in interstitial water. However, no obvious regularities were observed in the sediment vertical profiles. NH₄–N and PO₄–P concentrations in interstitial water were much higher than in overlying water, indicating that they could diffuse from sediment to overlying water. NH₄–N concentration was also higher in deep sediment. Growth properties of Z. latifolia (except for leaf length) are significantly correlated to wet bulk density, loss on ignition, NH₄–N concentration in sediment and NH₄–N, PO₄–P concentrations in interstitial water. The results indicate that water depth less than 50 cm is favorable for the growth of Z. latifolia, where it can exert its ecological function effectively. This research suggests a possibility to promote the growth of Z. latifolia and exert its ecological function by rational water depth management.     

Uptake and fixation of Zn, Pb, and Cd by Thlaspi caerulescens: application in the cases of old mines of Mibladen and Zaida (West of Morocco)

Contaminated soils and mine tailings pose major environmental and agricultural problems worldwide. These problems may be partially solved by an emerging new technology: phytoremediation. This technique uses plants to extract soil contaminants from the ground. Thlaspi caerulescens is known to accumulate in their tissues several heavy metals from soil and aerial deposition. This study was conducted to screen plants growing on a contaminated site to determine their potential for metal accumulation. Seeds of T. caerulescens metallicolous have been collected in the vicinity of F.T. Laurent le Minier in the Pb–Zn mining district of les Malines (North of Montpellier, Southern France), and seeds of T. caerulescens non-metallicolous were sampled on Larzac Plateau (North of Montpellier, Southern France). Soil substrates were collected from a mine site of Mibladen and Zaida (West, Morroco). Cultivated plant and surface soil samples were analyzed for zinc, lead, and cadmium concentrations by inductively coupled plasma mass spectrometry. A non-metallicolous (NM) ecotype of T. caerulescens and a metallicolous (M) ecotype are compared for Pb, Cd, and Zn accumulation in shoot and root in five metal-contaminated soils and one uncontaminated soil. The growth of individuals from uncontaminated soil was greater than that of individuals from metal-contaminated soils. The NM populations had markedly higher root/shoot ratio compared to M populations. The results indicate that both ecotypes of T. caerulescens are highly tolerant of zinc and Cd. Ecotype NM had constitutively higher Zn uptake capacity than the M ecotype. T. caerulescens species accumulate higher amount of Zn and Cd in their tissues in polluted soil and, in both of the two ecotypes, the root Pb concentrations were much greater than those of the shoot Pb contents. From both uncontaminated and metal-contaminated soils, we conclude that T. caerulescens are interesting material for phytoremediation of zinc and cadmium.     

Implications of chloride-enhanced cadmium uptake in saline agriculture: modeling cadmium uptake by maize and tobacco

Chloride salinity has been strongly related to enhanced cadmium (Cd) uptake by plants due to increased solubility in the soil solution, even in agricultural soil with very low levels of cadmium. This finding is relevant because the cadmium content of food crops is an important concern for human health. Therefore, the aim of this study was to predict and discuss the chlorine-enhanced uptake of cadmium by two common crops: maize and tobacco under ??non-saline?? (1?mM) and ??very strongly saline?? (200?mM) scenarios using a modified ??biotic ligand model?? and datasets from a set of soil and hydroponic experiments. Results indicated that predicted cadmium uptake rates (expressed as cadmium in plant ??mol?m^?2 root) by maize and tobacco plants were consistently higher (54 and 15%, respectively) assuming conditions of ??very strong salinity?? soil compared to the simulated ??non-saline?? soil. In the light of the results of the present research, valuable information is given on modeled cadmium phytoavailability as an indication of the potential risk due to increased cadmium uptake by crops under saline conditions, especially as the enhancement of cadmium uptake in the presence of Cl^? salinity may be a general trend that occurs in many edible crops. The biotic ligand model parameterization applied in the present study attempted to simulate conditions commonly found in natural cadmium and salt-affected soils. However, caution is needed to extrapolate results obtained from these models to real soil conditions.     

The Bloom-Forming Macroalgae, <Emphasis Type="Italic">Ulva</Emphasis>, Outcompetes the Seagrass, <Emphasis Type="Italic">Zostera marina</Emphasis>, Under High CO<Subscript>2</Subscript> Conditions

While multiple species of macroalgae and seagrass can benefit from elevated CO₂ concentrations, competition between such organisms may influence their ultimate responses. This study reports on experiments performed with a Northwest Atlantic species of the macroalgae, Ulva, and the seagrass, Zostera marina, grown under ambient and elevated levels of pCO₂, and subjected to competition with each other. When grown individually, elevated pCO₂ significantly increased growth rates and productivity of Ulva and Zostera, respectively, beyond control treatments (by threefold and 27%, respectively). For both primary producers, significant declines in tissue δ¹³C signatures suggested that increased growth and productivity were associated with a shift from use of HCO₃^? toward CO₂ use. When grown under higher pCO₂, Zostera experienced significant increases in leaf and rhizome carbon content as well as significant increases in leaf carbon-to-nitrogen ratios, while sediments within which high CO₂ Zostera were grown had a significantly higher organic carbon content. When grown in the presence of Ulva; however, above- and below-ground productivity and tissue nitrogen content of Zostera were significantly lower, revealing an antagonistic interaction between elevated CO₂ and the presence of Ulva. The presence of Zostera had no significant effect on the growth of Ulva. Collectively, this study demonstrates that while Ulva and Zostera can each individually benefit from elevated pCO₂ levels, the ability of Ulva to grow more rapidly and inhibit seagrass productivity under elevated pCO₂, coupled with accumulation of organic C in sediments, may offset the potential benefits for Zostera within high CO₂ environments.     

The effects of petroleum-contaminated soil on photosynthesis of <Emphasis Type="Italic">Amorpha fruticosa</Emphasis> seedlings

A pot experiment was conducted to monitor the dynamic response of photosynthesis of Amorpha fruticosa seedlings to different concentrations of petroleum-contaminated soils from April to September. The results showed that the photosynthetic rates, stomatal conductance and transpiration rate of seedlings significantly decreased in 5–20 g kg^?1 petroleum-contaminated soil during the three given sampling period of July 31 (early), August 30 (mid-term) and September 29 (late). However, the intercellular CO₂ concentration significantly increased in 10 g kg^?1 contaminated soil, while declined in 20 g kg^?1 contaminated soil during the early sampling period as well as in 20 g kg^?1 contaminated soil during the late sampling period. The leaf relative water content of seedlings significantly increased in 20 g kg^?1 contaminated soil during the early sampling period, while it dropped dramatically in 15–20 g kg^?1 contaminated soil during the late sampling period. The contents of chlorophyll a, chlorophyll b and the total chlorophyll of seedlings showed a sharp decline during the three sampling periods in contaminated soil. Comprehensively, considering the negative effects of petroleum on the photosynthesis, growth performance and remediation effect on petroleum of A. fruticosa seedlings, this plant was tolerant of petroleum-contaminated soil and was potentially useful for the phytoremediation of petroleum-contaminated sites in northern Shaanxi, China.     

Cadmium isotopic composition in the ocean

The oceanic cycle of cadmium is still poorly understood, despite its importance for phytoplankton growth and paleoceanographic applications. As for other elements that are biologically recycled, variations in isotopic composition may bring unique insights. This article presents (i) a protocol for the measurement of cadmium isotopic composition (Cd IC) in seawater and in phytoplankton cells; (ii) the first Cd IC data in seawater, from two full depth stations, in the northwest Pacific and the northwest Mediterranean Sea; (iii) the first Cd IC data in phytoplankton cells, cultured in vitro. The Cd IC variation range in seawater found at these stations is not greater than 1.5 ε_Cd/amu units, only slightly larger than the mean uncertainty of measurement (0.8 ε_Cd/amu). Nevertheless, systematic variations of the Cd IC and concentration in the upper 300 m of the northwest Pacific suggest the occurrence of Cd isotopic fractionation by phytoplankton uptake, with a fractionation factor of 1.6 ± 1.4 ε_Cd/amu units. This result is supported by the culture experiment data suggesting that freshwater phytoplankton (Chlamydomonas reinhardtii and Chlorella sp.) preferentially take up light Cd isotopes, with a fractionation factor of 3.4 ± 1.4 ε_Cd/amu units. Systematic variations of the Cd IC and hydrographic data between 300 and 700 m in the northwest Pacific have been tentatively attributed to the mixing of the mesothermal (temperature maximum) water (ε_Cd/amu = −0.9 ± 0.8) with the North Pacific Intermediate Water (ε_Cd/amu = 0.5 ± 0.8). In contrast, no significant Cd IC variation is found in the northwest Mediterranean Sea. This observation was attributed to the small surface Cd depletion by phytoplankton uptake and the similar Cd IC of the different water masses found at this site. Overall, these data suggest that (i) phytoplankton uptake fractionates Cd isotopic composition to a measurable degree (fractionation factors of 1.6 and 3.4 ε_Cd/amu units, for the in situ and culture experiment data, respectively), (ii) an open ocean profile of Cd IC shows upper water column variations consistent with preferential uptake and regeneration of light Cd isotopes, and (iii) different water masses may have different Cd IC. This isotopic system could therefore provide information on phytoplankton Cd uptake and on water mass trajectories and mixing in some areas of the ocean. However, the very small Cd IC variations found in this study indicate that applications of Cd isotopic composition to reveal aspects of the present or past Cd oceanic cycle will be very challenging and may require further analytical improvements. Better precision could possibly be obtained with larger seawater samples, a better chemical separation of tin and a more accurate mass bias correction through the use of the double spiking technique.     

Experimental Modeling of Cyanobacterial Bloom in a Thermokarst Lake: Fate of Organic Carbon,Trace Metal,and Carbon Sequestration Potential

Thermokarst lakes, formed during permafrost thaw in Western Siberia Plain over past tens to hundreds years, cover overall territory close to million km² and may represent significant source of CO₂ and CH₄ to the atmosphere. These acidic (3 < pH < 6) and humic [10 < dissolved organic carbon (DOC) < 50 mg/L] lakes are essentially inhabited by heterotrophic bacterioplankton with rare phytoplankton bloom occurring during warm periods. In order to understand possible effects of phytoplankton bloom on thermokarst lake hydrochemistry under climate warming scenario, we cultured pure cyanobacterium (Gloeocapsa sp.) and native cyanobacterial associate separated from the natural lake water. As substrates, sterilized thermokarst lake water and peat leachate from western Siberia were used. In these laboratory microcosm experiments which lasted 10 days, we monitored daily pH, biomass, DOC, and 40 major and trace elements. Despite significant variation of pH (4 to ~10.5) and biomass (a factor of 3–5), very few dissolved elements responded to massive cyanobacterial growth. The DOC varied within a factor of 1.2–1.5, exhibiting slow increase due to exometabolite production in thermokarst lake water and an initial decrease due to photodegradation in peat leachate. Elements appreciably affected by photosynthesis in both lake water and peat leachate substrates were P, Zn, Mn, and, in a lesser degree, Cd, K, Rb, Sr, Ba, Cr, Al, and U. While P, K (Rb), Mn, and Zn removal from solution during cell growth could be linked to biological demand by cyanobacteria, the adsorption of Cd, Sr, Ba, Al, Cr, U on the cell surface in response to the pH rise is most likely. Many other trace elements did not exhibit any significant evolution of the concentration during 10-day experiment either due to their strong complexation with allochthonous organic matter and essentially organic/organo-mineral colloidal status (Fe, Ni, Co, Cu, Pb, REEs, Ti, Zr, Hf, Th) or due to the lack of element interaction with cyanobacterial cells, via both adsorption and intracellular uptake (B, Si, V, Mo, As, Sb, Cs). Therefore, possible intensification of cyanobacterial bloom in thermokarst lakes caused by leaching of thawing peat will likely affect only few macronutrients and micronutrients such as P, K, Mn, and Zn, while the majority of trace elements bound to allochthonous DOC in the form of organic and organo-mineral colloids will not be affected by cyanobacterial biomass production and pH rise due to photosynthesis. Cyanobacterial bloom in organic-rich (20 mg DOC/L) thermokarst lakes exhibited significant potential of carbon sequestration from the atmosphere, which is more than an order of magnitude higher than the CO₂ evasion due to heterotrophic plankton respiration of allochthonous DOC.     

Variation of cadmium uptake, translocation among rice lines and detecting for potential cadmium-safe cultivars

Cadmium (Cd) pollution highly threats to rice consumption for humans. This study aims to investigate the variation of Cd uptake and translocation among rice lines and to screen cadmium-safe cultivars (CSCs). Total of 146 rice lines were grown in artificially Cd pollution hydroponics within 30 day followed by a pot culture in which 17 rice lines were planted and treated with different Cd levels until maturity. The results showed that Cd tolerance and Cd accumulation significantly (p < 0.05) varied among 146 rice lines in the hydroponics experiment as well as among the 17 rice lines in the followed pot culture. Cd contents of brown rice significantly correlated with Cd accumulations in plant and their translocation from vegetative organs to edible parts, implying that extremely attention should paid to Cd translocation and its influence factors for CSCs selection. IRBN95-90 and D26B of maintainer lines and Lu5278-I332, Lu17-T21712, Lu17-I2R60 of restorer lines were detected to be potential CSCs under 2 and 10 mg kg^?1 Cd level, which confirmed the feasibility of selection of CSCs from rice lines. Therefore, the study confirmed the variations of Cd uptake and translocation among rice lines and a combinatorial and recursive selection process is feasible and affordable to screen CSCs to reduce Cd risk for rice consumption.     

Phytoremediation potential and morphological changes of plants growing in the vicinity of lead smelter plant

With the increasing industrialization, heavy metals concentration in soils has greatly increased. Phytoremediation is a low-cost, non-intrusive and aesthetically harmonious technology that uses plants to remediate contaminated sites by heavy metals. The aim of the study was to determine Cd, Pb and Zn concentration in the biomass of plant species growing on a multi-metal-contaminated site of lead smelter processing, to assess the workability of using these plants for phytoremediation purposes and highlight possible damage in morphological leaf changes. Two plant species, i.e., Ipomoea asarifolia and Urochloa decumbens and the associated soil samples were collected and analyzed Cd, Pb and Zn concentrations and then calculating the bioconcentration factor and translocation factor parameters for each element. Leaves and roots samples were observed by light microscopy. Metal concentrations varied greatly and majorly depend on site sampled, plant species and tissue. Cd, Pb and Zn in tissue ranged from 0 to 102.48, 0 to 381.04 and 12.84 to 295.02 mg Kg^?1. However, none of the plant showed potential for hyperaccumulation. Both plants showed bioaccumulation factor more than one, where it was 7.66 and 6.82 for Pb and Zn in U. decumbens, respectively. Translocation factor was calculated below one for both plants and all metals. Morphological studies revealed development of adaptive features that strengthen the U. decumbens to grow in contaminated soil. Our study suggests that I. asarifolia and U. decumbens have potential for phytostabilization at multi-metal-contaminated site.     

C3 and C4 Biomass Allocation Responses to Elevated CO2 and Nitrogen: Contrasting Resource Capture Strategies

Plants alter biomass allocation to optimize resource capture. Plant strategy for resource capture may have important implications in intertidal marshes, where soil nitrogen (N) levels and atmospheric carbon dioxide (CO₂) are changing. We conducted a factorial manipulation of atmospheric CO₂ (ambient and ambient?+?340?ppm) and soil N (ambient and ambient?+?25?g?m^?2?year^?1) in an intertidal marsh composed of common North Atlantic C₃ and C₄ species. Estimation of C₃ stem turnover was used to adjust aboveground C₃ productivity, and fine root productivity was partitioned into C₃?CC₄ functional groups by isotopic analysis. The results suggest that the plants follow resource capture theory. The C₃ species increased aboveground productivity under the added N and elevated CO₂ treatment (P?<?0.0001), but did not under either added N or elevated CO₂ alone. C₃ fine root production decreased with added N (P?<?0.0001), but fine roots increased under elevated CO₂ (P?=?0.0481). The C₄ species increased growth under high N availability both above- and belowground, but that stimulation was diminished under elevated CO₂. The results suggest that the marsh vegetation allocates biomass according to resource capture at the individual plant level rather than for optimal ecosystem viability in regards to biomass influence over the processes that maintain soil surface elevation in equilibrium with sea level.     

Residual impact of biochar on cadmium uptake by rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) grown in Cd-contaminated soil

Cadmium (Cd) is the family member of toxic heavy metals, and its accumulation in food crops has become a global environmental constraint. Biochar potentially minimizes the metal contents in plants, but limited work has been reported on its residual effect on subsequent crops. The residual effect of various biochar levels (0, 1.5, 3.0, and 5.0% w/w) on Cd accumulation in rice has been investigated in this study. Biochar treatments enhanced the rice growth, photosynthesis, and antioxidant enzymes, whereas diminished the Cd contents and oxidative stress in rice. Cadmium concentration in shoots decreased by 24.4, 36.6, and 57.5% in 1.5, 3.0, and 5.0% biochar treatments over the control. Biochar supply enhanced the soil pH and electrical conductivity, whereas diminished the soil bioavailable Cd. Overall, the results depicted a significant residual impact of rice straw biochar on rice growth attributes and Cd uptake. However, studies are still needed to explore the long-term sustainability of biochars prepared from different feedstocks on bioavailability of toxic metals in soils and uptake by food crops under field conditions.     

Mediterranean Seagrass Growth and Demography Responses to Experimental Warming

We experimentally examined the effects of increased temperature on growth and demography of two Mediterranean seagrasses Posidonia oceanica and Cymodocea nodosa. Shoots of C. nodosa and seedlings and shoots of P. oceanica were kept in mesocosms for 3?months and exposed to temperatures between 25 and 32?°C encompassing the range of maximum summer seawater temperatures projected for the Mediterranean Sea during the twenty-first century. The response of P. oceanica seedlings to warming was evident with reduced growth rates, leaf formation rates and leaf biomass per shoot. Younger life stages of P. oceanica may therefore be particularly vulnerable to climate change and warming. Leaf formation rates in the shoots of P. oceanica declined with increasing temperature and the lowest population growth (?0.005?day^?1) was found at 32?°C. Temperature effects on C. nodosa were variable. Rhizome growth increased with warming (0.07?C0.09?cm?day^?1?°C of warming), whereas other indicators of plant performance (aboveground/belowground biomass, leaf biomass and population growth) appeared to be stimulated by increased temperature to a threshold temperature of around 29?C30?°C beyond which they declined. P. oceanica and C. nodosa are likely to be negatively impacted by the effects of global warming over the next century and climate change poses a significant challenge to seagrasses and may stress these key habitat-forming species that are already suffering losses from anthropogenic impacts.     

Joint toxic effects of heavy metals and atrazine on invasive plant species <Emphasis Type="Italic">Solidago Canadensis L</Emphasis>.

In this study, the joint effects of Cd(Ⅱ), Pb(Ⅱ) and atrazine (ATR) on Solidago Canadensis L. were investigated. The results showed that soil containing Cd, Pb and ATR could inhibit root elongation of Solidago Canadensis L., and that there was a positive linear relationship between the inhibitory rate of root elongation and the concentrations of Pb(Ⅱ). The mixture of Cd(Ⅱ) and Pb(Ⅱ)-ATR in soil showed a significant adverse effect on root and shoot biomass of Solidago Canadensis L. Acetylsalicylic acid (ASA) contents increased slightly at the lower concentrations of Cd(Ⅱ)-ATR, then decreased when Cd(Ⅱ)-ATR concentrations were higher than those of 1.0 TUmix(Cd+ATR). The toxic effect of Pb(Ⅱ)-ATR on the ASA contents of Solidago Canadensis L. was greater than that of Cd(Ⅱ)-ATR. Soluble sugar contents firstly decreased and then increased with increasing concentrations of Cd(Ⅱ)-ATR and displayed fluctuation with increasing concentrations of Pb(Ⅱ)-ATR. Total protein contents in-creased with increasing concentrations of Cd(Ⅱ) and Pb(Ⅱ)-ATR , relative to the control sample. The NP-SH con-tents showed a significant increase up to 12.2 mg/gfw of Cd(Ⅱ)-ATR, followed by a significant decline to 4.5 mg/gfw after 14 days of exposure. The effect of Pb(Ⅱ)-ATR was similar to that of Cd(Ⅱ)-ATR but the amount of NP-SH was not higher than that of Cd(Ⅱ)-ATR.     

Evaluation of the use of legumes for biodegradation of petroleum hydrocarbons in soil

The aim of this research was to evaluate the potential of six legumes: Medicago sativa L., Glycine max, Arachis hypogea, Lablab purpureus, Pheseolus vulgaris and Cajanus cajan to restore within a short period of time soil contaminated with 3% crude oil. The legumes in five replications were grown in crude oil-contaminated and crude oil-uncontaminated soil in a completely randomized design. Plants were assessed for seedling emergence, plant height and leaf number. GC–MS was used to analyze the residual crude oil from the rhizosphere of the legumes. Plant growth parameters were reduced significantly (P < 0.05) for legumes in contaminated soil compared to their controls. In the 4th week after planting (WAP), shoot height increased across the species up to the 8th WAP. However, in the 12 WAP no significant increase in the shoot of all species was observed. Two WAP legumes planted in contaminated soil had significantly (P < 0.05) higher leaf number than these planted in uncontaminated soil with the exception of M. sativa. In the 4th WAP, only A. hypogea and P. vulgaris had increased leaf number, while in the 6th WAP, only L. purpureus had increased leaf number and survived up to the 12th WAP while most of the legumes species died. Chromatographic profiles indicated 100% degradation of the oil fractions in C. cajan and L. purpureus after 90 days. For other legumes however, greater losses of crude oil fractions C₁–C₁₀ and C₁₀–C₂₀ were indicated in rhizosphere soil of P. vulgaris and G. max, respectively. The most effective removal (93.66%) of C₂₁–C₃₀ components was observed in G. max-planted soil even though vegetation was not established. The legumes especially C. cajan, L. purpureus and A. hypogea are promising candidates for phytoremediation of petroleum hydrocarbon-impacted soil.     

Element contents in shoots of sunflower (Helianthus annuus): Prediction versus measuring

Sunflower (Helianthus annuus) is cultivated as food and feed crop as well as for bioenergy production. It is also investigated towards its ability to remove contaminants from soil and accumulate them in the shoots (phytoextraction). So the reliable prediction of element contents in shoots based on soil contents would be advantageous to easily decide whether plants grown on a certain area could be either used as food and feed or for phytoremediation in combination with bioenergy production. However, it is desirable to predict element contents in plants based on only a few numbers of predictors. This would mean on the one hand a reduced effort in time and costs for analysis and on the other hand existing data on soil quality could be than used for estimations of the element uptake of plants on larger scales. Samples of sunflowers were used, that were grown in plots situated at two different sites in Germany and treated with different amendments (NPK-fertilizer, Streptomyces + Mycorrhiza, Rendzina). One site (heavy metal polluted) was the test field “Gessenwiese”, which is situated on the area of the former uranium leaching heap “Gessenhalde”. The other site (non-contaminated) was the lysimeter station Falkenberg. Shoot contents of Ca, Cd, Co, Cu, K, Ni, Pb, and Zn were correctly predicted by the mobile soil fraction extracted with 1 M NH₄NO₃ solution (simple regression), whereas for Mg, S, and U the specifically adsorbed soil fraction (extraction with 1 M NH₄OAc solution) needs to be added as predictor (PLS regression). Mn was the only element in the data set for which simple regression based on total soil contents (digestion with HF, HClO₄, and HNO₃) had to be used be used for correct prediction in the studied data set.