Response of photosynthetic and growth characteristic of Mosla chinensis and congenerous weed M. scabra to soil water content

Heterogeneity of precipitation could influence various physiological and ecological processes of plants. We present a comparative study on the ecophysiological responses of two congenerous species, Mosla chinensis (an endemic species) and M. scabra (a weedy species), to four soil water content (20%, 40%, 60% and 90% of water holding capacity (WHC), referred to as W20, W40, W60 and W90, respectively) to understand their ecophysiological responses and ecological differentiation. Results showed that both species grew well from W40 to W90, as they showed higher photosynthetic rate and biomass and bigger plants under these soil water content. However, biomass, chlorophyll a to b ratio (Chl _a/b) and root to shoot ratio (R/S) of M. scabra but not M. chinensis were significantly reduced under W20, indicating M. chinensis showed stronger capacity of sun-acclimation under severe drought than M. scabra. M. chinensis showed priority in adapting severe drought in comparison with M. scabra. We hypothesize that the different adaptive abilities to soil water content are partly responsible for their ecological differentiation observed in the field and may affect their fate in their native habitat.     

Growth and potential reproduction of <Emphasis Type="Italic">Poa crymophila</Emphasis> in response to season precipitation shortage in the Eastern Tibetan Plateau,China

The growing season in 2006 existed a quite less precipitation than previous years in the eastern of Tibetan Plateau, China. In order to explore the response strategies of the grass to drought year, the variations of growth and potential reproduction of Poa crymophila between rich (2005) and poor rainfall year (2006) were studied. Reproductive shoot biomass, above- and below-ground biomass pronounced decreased in the poor rainfall year, but the ratio of above-/below-ground biomass and vegetative shoot biomass increased. Carbon content in inflorescence increased significantly in 2006, but decreased significantly in root. Nitrogen contents and the C/N ratios in plant components were not significantly different. Sexual reproduction in 2005 and 2006 was not different. Season precipitation shortage could result in the higher mortality of vernal budding shoots or tillers. The results suggested that P. crymophila response to poor rainfall year (drought) by a smaller plant body, allocating more proportional biomass to above-ground, altering more carbon to inflorescence, and altering its reproductive way to sexual.     

Species-specific effects of P-solubilizing and N<Subscript>2</Subscript>-fixing bacteria on seedling growth of three salt-tolerant trees

Coastal afforestation suffers from low survival and slow growth due to harsh conditions and lack of robust seedlings. Inoculation of P-solubilizing bacteria (PSB) or N₂-fixing bacteria (NFB) are effective in promoting plant growth and thus potentially helpful for coastal afforestation. However, it remains unclear about the generality and specificity of these plant-growth-promoting-bacteria (PGPB) on the growth of salttolerant trees. We inoculated seedlings of two mangrove trees and one terrestrial salt-tolerant tree with pure cultures of PSB or mixed cultures of PSB and NFB. Plant biomass, height, base diameter and N and P concentrations were determined six months after bacterial inoculation. We found that inoculation of PGPB had an overall promoting effect on the seedling growth of three tree species, but the effects differed greatly (3–280% increase) among plant species and bacterial isolates or bacterial combinations. Only in the terrestrial tree, co-inoculations of PSB and NFB showed greater promoting effects than monocultures of PSB. Root: shoot ratios of seedlings were not changed by bacterial inoculation. Inoculation treatments moderately elevated N concentrations in shoots and roots and P concentrations only in roots of seedlings. Our results suggest that PGPB might have a general promoting effect on the seedling growth of salt-tolerant trees. Nevertheless, the magnitude of promoting effects and the comparative advantage of dual inoculation over single inoculation are species-specific. The generality and specificity of the plant-PGPB relationship are similar to the plantmycorrhizal symbiosis. In addition, tissue nutrient improvement might not be the main mechanism of the promoting effects by PGPB.     

Morphophysiological adaptation aspects of different Haloxylon aphyllum (Chenopodiaceae) genotypes along a salinity gradient

The seedlings of Haloxylon aphyllum from seeds with different genetic characteristics, which were collected in three natural subpopulations along a soil salinity gradient, were investigated. The plants grown under various levels of NaCl (0–300 mM) differed in the shoot length, the relative growth rate (calculated for fresh and dry biomass), as well as ions and proline contents. The heterozygous genotypes of xerohalophytic H. aphyllum have shown significant advantages in their productivity and sustainability under moderate and high salinity.     

挺水植物水田芥对镉的积累特性研究

通过前期的初步研究发现,挺水植物水田芥(Nasturtium officinale R.Br.)地上部分镉含量超过了超富集植物的临界值(100mg/kg),可能是镉超富集植物。为进一步了解水田芥在不同镉浓度梯度条件下的镉积累特性,通过盆栽试验研究了不同土壤镉浓度(0、25、50、75、100mg/kg)对水田芥生长特性、镉耐性和镉积累特性的影响。结果表明:随土壤镉浓度的增加,水田芥根系和地上部分镉含量增大,分枝数量、根系生物量、地上部分生物量、抗性系数及叶绿素SPAD值均呈降低的趋势。当土壤镉浓度大于0mg/kg时,随着土壤镉浓度的增加,水田芥的根冠比呈增加的趋势。土壤镉浓度为50~100mg/kg时,水田芥地上部分镉含量均大于100mg/kg,最大值为214.84mg/kg(土壤镉浓度为100mg/kg),地上部分富集系数(BCF)大于1,但转运系数(TF)小于1。在土壤镉浓度为50mg/kg时,水田芥地上部分镉积累量达到最大值,为192.233μg/株。因此,水田芥是一种镉富集植物,适合用于土壤镉污染浓度在50mg/kg以内的水田修复。     

Effect of elemental sulphur on solubility of soil heavy metals and their uptake by maize

A pot experiment was conducted to study the influence of elemental sulphur (S) on solubility of soil Pb, Zn and Cd and uptake by maize (Zea mays L.). Two rates of elemental sulphur (S) applied at 0 (S0) and 200 (S200) mmol kg(-1) soil with three rates of each heavy metal at Pb, 0 (Pb0), 200 (Pb200), 400 (Pb400) mg kg(-1) soil, Zn, 0 (Zn0), 100 (Zn100), 200 (Zn200) mg kg(-1) soil and Cd, 0 (Cd0), 50 (Cd50), 100 (Cd100) mg kg(-1) soil, respectively. The result showed that with S application at 200 mmol S kg(-1), soil pH decreased about 0.3 unit and the solubility of the Zn and Cd was significantly increased, but the solubility of Pb had no significant influence. The concentration of Pb, Zn and Cd in maize shoots and roots were increased with increasing rates of heavy metals. However, the concentration of Zn and Cd in shoots and roots were higher with application of S rather than without S but no significant difference was found for Pb. The highest concentration of Zn in the shoots was 2.3 times higher with application of S rather than without at the same rate of Zn, 200 mg kg(-1). Plant biomass was also significantly affected by the application of S and of heavy metals. With heavy metal addition, the shoot and root biomass were decreased with the rates of those of heavy metals increased either with or without application of S. However, the shoot biomass was significantly decreased with S application at the same rate of heavy metals except that with Zn addition. The removal of Cd and Pb by maize uptake and accumulation with application of S had no significant increase compared to that without, but the removal Zn by maize uptake from the soil increased by application of S, 90.9 microg plant(-1) contrast to 25.7 microg plant(-1) at Zn200 within a growth period of only 40 days.     

2003~2009年鄱阳湖流域土壤水分时空变化特征及影响因素

鄱阳湖流域水文过程是区域研究的热点问题,但相对于其它水文要素而言,土壤水分的时空分布特征及其影响因素尚缺乏系统研究,成为流域水文过程研究不确定性的主要来源之一。采用AMSR E土壤水分数据,从流域、子流域及地表覆被等不同的空间尺度,阐明了鄱阳湖流域2003～2009年土壤水分的年际与年内变化特征,并分析其影响因素。研究表明：在流域尺度上,土壤水分总体呈现中心低、周边高的“漏斗式”空间分布形态,但夏、秋季节空间差异性减弱,年际土壤水分呈现较强的下降趋势,其中以湖区下降速度最大;在地表覆被尺度上,林地土壤水分最高、年际下降速度最低,表明其在年际尺度上对干旱具有较强的调节作用,不同地表覆被类型的土壤水分年内差异较明显,但在6、7及10月差异较小,地表覆被对土壤水分的调节作用减弱;在影响因素方面,降水是土壤水分的主要影响因素,气温、灌溉等则一定程度上影响了土壤水分的变化特征。研究结果不仅有利于加强对流域水文过程的理解与认识,同时可为水资源管理及防旱抗旱等提供科学的辅助依据     

不同龄级南川木波罗幼苗生物量及分配格局

以不同龄级（1~5年生）南川木波罗幼苗为研究对象,研究其生物量及分配,并利用苗高（H）、基径（D）及HD2估测单株木及其器官生物量的适合模型。结果表明：（1）随着苗龄的增加,单株生物量及各器官生物量随之增加,其中枝生物量增加幅度最大;（2）地上部分各器官生物量分配率表现为：干生物量>叶生物量>枝生物量;（3）地下部分各龄级根系生物量分配以主根和粗根为主,表现为：主根>粗根>细根,地上部分生物量分配率高于地下部分,并最后趋于稳定;（4）以基径(D)作为自变量优于利用株高(H)和HD2建立生物量预测模型,并且多以幂函数为最佳,建立的生物量预测模型中,除细根生物量预测模型较差外,其它预测模型效果都较好,相关系数均达到极显著水平,表明利用本文建立的估测南川木波罗各器官生物量模型是可行的     

模拟及河道实验浮床水芹根系生长及生物量分配对比研究

为了对比研究浮床植物水芹菜在模拟及野外河道实验中根系生长及生物量分配的差异性,探索水芹浮床模拟实验与实际应用中的差异性,我们在实验河道边放置水箱,通过抽取河水到水箱中设置水芹浮床水箱模拟实验,并且与河道中水芹浮床实验作对比。结果发现:河道和水箱中植物根系指标除了平均根直径外其他指标随着水芹的生长以指数方式增长,平均根直径随着水芹的生长以指数方式下降;在根系总长度、根系总表面积、根系分叉数、根系交叠数方面,水箱中的水芹显著大于河道中的水芹(p0.05);水箱浮床水芹根系指标的增长速度大于地上部分的增长速度,河道中水芹地上部分增长速度要大于地下部分;水芹冠根比随时间的变化呈现出先下降后上升趋势,水箱中水芹冠根比的变化速率更小。水箱中的水芹受到了营养条件的限制,用模拟水芹浮床来研究其净化效率时,在一定程度上(与实际应用相比)高估了河道水芹浮床根系部分的作用。     

氮素形态及浓度对互花米草生长的影响

近年来，由于人类生产生活的影响，以化肥农药使用为主的面源污染和以工业排放为主的点源污染日益加剧，全球尤其是海岸带氮含量逐渐升高，对滨海植被的生长产生了巨大的影响。在这个背景下，通过温室模拟实验研究不同供氮水平对互花米草的影响，对研究氮对入侵植物的影响作用机制有重大意义。互花米草在两种氮肥不同氮水平处理下，株高、叶面积、生物量等生长指标以及根冠比、根长/株高等指标的变化情况不同。结果表明：随着氮量增加，米草株高、叶面积、总生物量和地上部分生物量呈先上升后下降的趋势，地下部分生物量、根冠比和根长/株高比则呈下降趋势；各项指标在无机氮肥不同氮水平处理之间存在显著差异，但在有机氮肥的各处理间差异无显著性。这说明适当的供氮水平有利于互花米草的生长，而高氮则抑制其生长     

Effect of Earthworm(Pheretima sp.) Density on Revegetation of Lead/zinc Metal Mine Tailings Amended with Soil

Abstract

The objective of this study was to investigate the effects of earthworm density on the availability of nutrients and heavy metals in metal contaminated soils. Pb/Zn mine tailings were mixed throughly with a red yellow podzolic soil at the ratio (w/w) of 75:25. Earthworms (Pheretima sp.) were introduced to the mixture at four different densities, zero, three, six and nine individuals per pot planted with ryegrass (Loliun multiflorum). The results indicated that earthworm activity significantly enhanced ryegrass shoot biomass. However, as denser earthworm population was introduced, shoot biomass tended to decrease. Earthworm activity significantly increased soil pH and availability of N, P and K in the tailings and soil mixture. There was a general tendency that uptake of Zn by ryegrass increased after earthworm inoculation, although the increase in extractable Zn in tailings and soil mixture was not significant. On the contrary, there seemed to be a lower uptake of Pb by ryegrass under earthworm inoclation, despite the fact that higher extractable Pb concentrations were observed. The present project indicated that the improved growth of ryegrass was due to improved nutrient availability and other soil conditions, by inoculation of earthworms at an appropriate rate. Further studies are needed to illustrate the relationship between metal availability and earthworm activity in the field.     

Effect of Earthworm（Pheretima sp.） Density on Revegetation of Lead/zinc Metal Mine Tailings Amended with Soil

The objective of this study was to investigate the effects of earthworm density on the availability of nutrients and heavy metals in metal contaminated soils. Pb/Zn mine tailings were mixed throughly with a red yellow podzolic soil at the ratio （w/w） of 75：25. Earthworms （Pheretima sp.） were introduced to the mixture at four different densities, zero, three, six and nine individuals per pot planted with ryegrass （Loliun multiflorum）. The results indicated that earthworm activity significantly enhanced ryegrass shoot biomass. However, as denser earthworm population was introduced, shoot biomass tended to decrease. Earthworm activity significantly increased soil pH and availability of N, P and K in the tailings and soil mixture. There was a general tendency that uptake of Zn by ryegrass increased after earthworm inoculation, although the increase in extractable Zn in tailings and soil mixture was not significant. On the contrary, there seemed to be a lower uptake of Pb by ryegrass under earthworm inoclation, despite the fact that higher extractable Pb concentrations were observed. The present project indicated that the improved growth of ryegrass was due to improved nutrient availability and other soil conditions, by inoculation of earthworms at an appropriate rate. Further studies are needed to illustrate the relationship between metal availability and earthworm activity in the field.     

Incorporating soil structure and root distribution into plant uptake models for radionuclides: toward a more physically based transfer model

Most biosphere and contamination assessment models are based on uniform soil conditions, since single coefficients are used to describe the transfer of contaminants to the plant. Indeed, physical and chemical characteristics and root distribution are highly variable in the soil profile. These parameters have to be considered in the formulation of a more realistic soil-plant transfer model for naturally structured soils. The impact of monolith soil structure (repacked and structured) on Zn and Mn uptake by wheat was studied in a controlled tracer application (dye and radioactive) experiment. We used Brilliant Blue and Sulforhodamine B to dye flow lines and 65Zn and 54Mn to trace soil distribution and plant uptake of surface-applied particle-reactive contaminants. Spatial variation of the soil water content during irrigation and plant growth informs indirectly about tracer and root location in the soil profile. In the structured monolith, a till pan at a depth of 30 cm limited vertical water flow and root penetration into deeper soil layers and restricted tracers to the upper third of the monolith. In the repacked monolith, roots were observed at all depths and fingering flow allowed for the fast appearance of all tracers in the outflow. These differences between the two monoliths are reflected by significantly higher 54Mn and 65Zn uptake in wheat grown on the structured monolith. The higher uptake of Mn can be modelled on the basis of radionuclide and root distribution as a function of depth and using a combination of preferential flow and rooting. The considerably higher uptake of Zn requires transfer factors which account for variable biochemical uptake as a function of location.     

Yield and arsenate uptake of arbuscular mycorrhizal tomato colonized by Glomus mosseae BEG167 in As spiked soil under glasshouse conditions

A glasshouse pot experiment was conducted to study the effect of arbuscular mycorrhizal (AM) colonization by Glomus mosseae BEG167 on the yield and arsenate uptake of tomato plants in soil experimentally contaminated with five As levels (0, 25, 50, 75 and 150 mg kg(-1)). Mycorrhizal colonization (50-70% of root length) was little affected by As application and declined only in soil amended with 150 mg As kg(-1). Mycorrhizal colonization increased plant biomass at As application rates of 25, 50 and 75 mg kg(-1). Shoot As concentration increased with increasing As addition up to 50 mg kg(-1) but decreased with mycorrhizal colonization at As addition rates of 75 and 150 mg kg(-1). Shoot As uptake increased with mycorrhizal colonization at most As addition levels studied, but tended to decrease with addition of 150 mg As kg(-1). Total P uptake by mycorrhizal plants was elevated at As rates of 25, 50 and 75 mg kg(-1), and more P was allocated to the roots of mycorrhizal plants. Mycorrhizal plants had higher shoot and root P/As ratios at higher As application rates than did non-mycorrhizal controls. The soil of inoculated treatments had higher available As than uninoculated controls, and higher pH values at As addition levels of 25, 50 and 75 mg kg(-1). Mycorrhizal colonization may have increased plant resistance to potential As toxicity at the highest level of As contamination studied. Mycorrhizal tomato plants may have potential for phytoextraction of As from moderately contaminated soils or phytostabilization of more highly polluted sites.     

The influence of the development of temperate fruit tree species on the potential for their uptake of radionuclides

This paper reviews the published literature that describes the phenological development of above and below ground organs of temperate fruit trees (top fruit), particularly with respect to apple (Malus domestica). Critical information is presented which is considered appropriate in developing an understanding of the potential for top fruit species to take up radionuclide contaminants from the atmosphere and the soil. Information is cited on how climatic and edaphic factors influence the growth and development of temperate fruit trees, the phenological production of their leaf area and the development and growth of their fruit and hence the potential for foliar and fruit uptake of radionuclides from the atmosphere. The study also reports on the importance of the distribution and phenological development of roots in the soil and the potential for their uptake of radionuclides from the soil. The effects of above and below ground management procedures, within temperate fruit orchards, on potential radionuclide uptake are also considered. It is concluded that the potential for the uptake of radionuclides by temperate fruit tree species will depend on a number of phenological and physiological factors. For uptake from the soil these factors include; root distribution and density in the soil profile, seasonal changes in the production and distribution of roots, and the presence and amount of water in the soil. These factors are themselves influenced by rootstock type and its growth vigour, scion type and its growth vigour, tree age, spacing of trees in the orchard, orchard management practices (presence or absence of weeds or grass under the trees) and soil type and depth. Direct uptake by the shoot, however, will be influenced by the climatic conditions at the time of exposure and the presence of foliage. Deposition and uptake are likely to change with leaf area development and the ability of radionuclides to penetrate the cuticle of the leaf changes with seasonal development. Transport of radionuclides to the fruit may also depend on the time of season, as the importance of the xylem and phloem transport routes can change with the growth and development of the fruit.     

Selenium bioavailability and uptake as affected by four different plants in a loamy clay soil with particular attention to mycorrhizae inoculated ryegrass

The aim of this study was to investigate the influence of plant species, especially of their rhizosphere soil, and of inoculation with an arbuscular mycorrhizal (AM) fungus on the bioavailability of selenium and its transfer in soil-plant systems. A pot experiment was performed with a loamy clay soil and four plant species: maize, lettuce, radish and ryegrass, the last one being inoculated or not with an arbuscular mycorrhizal fungus (Glomus mosseae). Plant biomass and Se concentration in shoots and roots were estimated at harvest. Se bioavailability in rhizosphere and unplanted soil was evaluated using sequential extractions. Plant biomass and selenium uptake varied with plant species. The quantity of rhizosphere soil also differed between plants and was not proportional to plant biomass. The highest plant biomass, Se concentration in plants, and soil to plant transfer factor were obtained with radish. The lowest Se transfer factors were obtained with ryegrass. For the latter, mycorrhizal inoculation did not significantly affect plant growth, but reduced selenium transfer from soil to plant by 30%. In unplanted soil after 65 days aging, more than 90% of added Se was water-extractable. On the contrary, Se concentration in water extracts of rhizosphere soil represented less than 1% and 20% of added Se for ryegrass and maize, respectively. No correlation was found between the water-extractable fraction and Se concentration in plants. The speciation of selenium in the water extracts indicated that selenate was reduced, may be under organic forms, in the rhizosphere soil.     

Drought Stress in Four Subalpine Species: Gas Exchange Response and Survivorship

An assessment of adaptability of saplings of four evergreen species (Picea abies Karst., Pinus mugo Turra, Pinus peuce Grisb. and Pinus heldreichii H. Christ.), native for Bulgarian treeline zone, was made on the basis of leaf gas exchange and survivability in artificially induced drought stress. The established low sensitivity of gas exchange to summer drought and the highest mortality of P. abies may be regarded as an evidence for a narrow zone of tolerance. P. peuce and P. heldreichii have low survivorship under drought conditions, regardless of the variable effect of soil moisture on the gas exchange parameters. The better survivability and significant reduction of gas exchange in response to soil water deficit of P. mugo probably will give him an advantage in future adaptation to climate change and in competition with other subalpine species. We conclude that the expected trends in climate change will most likely lead to a further narrowing of the ecological and physiological comfortable zone for two investigated endemic species.     

The combined effect of uranium and gamma radiation on biological responses and oxidative stress induced in Arabidopsis thaliana

Uranium never occurs as a single pollutant in the environment, but always in combination with other stressors such as ionizing radiation. As effects induced by multiple contaminants can differ markedly from the effects induced by the individual stressors, this multiple pollution context should not be neglected. In this study, effects on growth, nutrient uptake and oxidative stress induced by the single stressors uranium and gamma radiation are compared with the effects induced by the combination of both stressors. By doing this, we aim to better understand the effects induced by the combined stressors but also to get more insight in stressor-specific response mechanisms. Eighteen-day-old Arabidopsis thaliana seedlings were exposed for 3 days to 10 μM uranium and 3.5 Gy gamma radiation. Gamma radiation interfered with uranium uptake, resulting in decreased uranium concentrations in the roots, but with higher transport to the leaves. This resulted in a better root growth but increased leaf lipid peroxidation. For the other endpoints studied, effects under combined exposure were mostly determined by uranium presence and only limited influenced by gamma presence. Furthermore, an important role is suggested for CAT1/2/3 gene expression under uranium and mixed stressor conditions in the leaves.     

崇明东滩围垦芦苇生长、繁殖和生物量分配对大气温度升高的响应

应用开顶式生长室(OTCs)模拟增温试验，研究了上海市崇明岛东滩湿地围垦区芦苇的生长、繁殖和生物量分配对温度升高的响应。结果表明：温度升高使株高显著增加，但对茎粗的影响不明显。与对照相比，升温显著增加了叶长、叶宽、叶面积；但却显著减少了叶面积比率(LAR)和比叶面积(SLA)，对叶长/叶宽，叶质比(LMR)无显著影响。研究发现，升温使开花个体数、开花率、花序高、花颈长、花数以及种子数量均显著减少，对芦苇的繁殖起到抑制作用。此外，升温时地上部分各层生物量显著增加，而且从下到上增加程度逐渐增大；根、茎、叶的生物量显著增加；花的生物量显著减少。升温对根各层生物量影响不同，上层生物量显著增加，中层显著减少，下层变化不明显。进一步研究表明，升温使根和花生物量占总生物量的比例显著下降，茎和叶生物量所占比例显著升高。     

Arbuscular mycorrhizas contribute to phytostabilization of uranium in uranium mining tailings

Uranium (U) tailings pose environmental risks and call for proper remediation. In this paper medic and ryegrass plants were used as host plants to examine whether inoculation with an AM fungus, Glomus intraradices, would help phytostabilization of U tailings. The need of amending with uncontaminated soil for supporting plant survival was also examined by mixing soil with U tailing at different mixing ratios. Soil amendment increased plant growth and P uptake. Ryegrass produced a more extensive root system and a greater biomass than medic plants at all mixing ratios. Medic roots were extensively colonized by G. intraradices whereas ryegrass were more sparsely colonized. Plant growth was not improved by mycorrhizas, which, however, improved P nutrition of medic plants. Medic plants contained higher U concentrations and showed higher specific U uptake efficiency compared to ryegrass. In the presence of U tailing, most U had been retained in plant roots, and this distribution pattern was further enhanced by mycorrhizal colonization. The results suggest a role for AM fungi in phytostabilization of U tailings.