Effects of Municipal Sewage Sludge Doses on the Chlorophyll Contents and Heavy Metal Concentration of Sugar Beet (Beta vulgaris var. saccharifera)

The present study was conducted to assess the suitability of sewage sludge amendment (SSA) in soil for Beta vulgaris var. saccharifera (sugar beet) by evaluating the heavy metal accumulation and physiological responses of plants grown at a 10%, 25%, and 50% sewage sludge amendment rate. The sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently increasing accumulation in plant parts. Cd, Pb, Ni, and Cu concentrations in roots were significantly higher in plants grown at 25% as compared to 50% SSA; however, Cr and Zn concentration was higher at 50% than 25% SSA. The concentrations of heavy metal showed a trend of Zn > Ni > Cu > Cr > Pb > Cd in roots and Zn > Cu > Ni > Cr > Pb > Cd in leaves. The only instance in which the chlorophyll content did not increase after the sewage sludge treatments was 50%. There were approximately 1.12-fold differences between the control and 50% sewage sludge application for chlorophyll content. The sewage sludge amendment led to a significant increase in Pb, Cr, Cd, Cu, Zn, and Ni concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency (US EPA). The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake and the leaf and root concentrations of Ni, Zn, Cd, Cu, Cr, Pb, and Zn in plants as compared to those grown on unamended soil. More accumulation occurred in roots and leaves than in shoots for most of the heavy metals. The concentrations of Cd, Cr, and Pb were more than the permissible limits of national standards in the edible portion of sugar beet grown on different sewage sludge amendment ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet may not be a good option due to risk of contamination of Cr, Pb, and Cd.     

Taproot promoters cause tissue specific gene expression within the storage root of sugar beet

The storage root (taproot) of sugar beet (Beta vulgaris L.) originates from hypocotyl and primary root and contains many different tissues such as central xylem, primary and secondary cambium, secondary xylem and phloem, and parenchyma. It was the aim of this work to characterize the promoters of three taproot-expressed genes with respect to their tissue specificity. To investigate this, promoters for the genes Tlp, His1-r, and Mll were cloned from sugar beet, linked to reporter genes and transformed into sugar beet and tobacco. Reporter gene expression analysis in transgenic sugar beet plants revealed that all three promoters are active in the storage root. Expression in storage root tissues is either restricted to the vascular zone (Tlp, His1-r) or is observed in the whole organ (Mll). The Mll gene is highly organ specific throughout different developmental stages of the sugar beet. In tobacco, the Tlp and Mll promoters drive reporter gene expression preferentially in hypocotyl and roots. The properties of the Mll promoter may be advantageous for the modification of sucrose metabolism in storage roots.     

Use of roots transformed by Agrobacterium rhizogenes in rhizosphere research: applications in studies of cadmium assimilation from sewage sludges

The use of roots transformed by Agrobacterium rhizogenes in models for the rhizosphere is discussed. A list of species for which transformed root cultures have been obtained is provided and the example of studies of cadmium assimilation from sewage sludges is given to illustrate how transformed root cultures can be used in physiological tests under non-sterile conditions.     

施用污泥对油菜根际养分和不同种类重金属的影响

根际是控制植物养分动态的重要因素,养分动态也影响着根际土壤环境。当土壤被污水污泥改良后,根际土壤中的养分和重金属性质也会发生变化。目前很少有人研究施用污泥的土壤中植物根系对根际重金属有效性和分布的影响。采用根垫—冰冻薄层切片法对施用污泥后土壤中油菜根际的养分和重金属分布情况进行研究,以期探明污泥改良土壤中根际重金属的活化特征。当土壤施用污泥后,根际土壤中DTPA提取态Zn,Cd,Ni,Mn,有效磷,有效钾和铵态氮被显著消耗,而根际土壤中DTPA提取态Cu没有明显的消耗或积累。当土壤中施用大量污泥时,根际土壤的pH值随着离根表面距离的增加而增加。无论土壤是否用污泥处理,油菜根际土壤中可交换态Cu都显著减少。当土壤被50%污泥改良时,在距离根表面0—2 mm处的油菜根际土壤中碳酸盐结合态,铁锰氧化物结合态,有机物结合态,残渣态的Cu和Zn都被消耗较多。污泥的施用对油菜的生长有促进作用。随着污泥施用量的增加,油菜地上部分Cu和Zn的含量没有显著变化。施用污泥量小于25%的土壤中,污泥没有增加重金属的可利用性和移动性。除了Cu,油菜根际土壤中DTPA提取态Zn,Cd,Ni的减少表明施用污泥的土壤中重金属的活化是非常有限的。     

Tissue partitioning of cadmium in transgenic tobacco seedlings and field grown plants expressing the mouse metallothionein I gene

Since agricultural crops contribute >70% of human cadmium (Cd) intake, modification of crops to reduce accumulation of this pollutant metal during plant growth is desirable. Here we describe Cd accumulation characteristics of seedlings and field grown tobacco plants expressing the Cd-chelating protein, mouse metallothionein I. The objective of the transformation is to entrap Cd in roots as Cd-metallothionein and thereby reduce its accumulation in the shoot. Transformed and control seedlings were exposed for 15 days in liquid culture at a field soil-solution-like Cd concentration of 0.02 μm. Transformed seedlings ofNicotiana tabacum cultivar KY 14 contained about 24% lower Cd concentration in shoots and about 5% higher Cd concentration in roots than control seedlings. Dry weights of transformed and control tissues did not differ significantly. In the field in 1990, mature transformedN. tabacum cv. KY 14 plants exposed only to endogenous soil Cd contained about 14% lower leaf lamina Cd concentration than did controls. Differences were significant at thep≤0.1 level in 13 of 16 leaf positions. Leaf dry weight did not differ significantly but transformed field plants had 12% fewer leaves and were 9% shorter than the controls. Copper (Cu) concentration was significantly higher (ca10%) in the bottom nine leaf positions of transformed plants suggesting that reduced leaf number and plant height may be due to Cu deficiency or toxicity. Alternatively, somaclonal variation or gene position effects may be involved. No differences were found in zinc levels. WithN. tabacum cv. Petit Havana, transformed seedlings contained no less Cd in shoots but 48% higher Cd concentration in roots. However, dry weights of shoots and roots of transformed seedlings were 25% and 26%, respectively, greater than in controls. In the field, transformed and control plants of this cultivar showed little significant differences in leaf Cd content, plant height or leaf number. Although comparison of additional metallothionein-expressing tobaccos and other plants is needed, results obtained with cultivar KY 14 support the hypothesis that sequestration of Cd in roots as Cd-metallothionein may have potential for reducing Cd content of above root tissues of certain plants.     

Effect of soil pH and sewage sludge on VA mycorrhizal infection of soybeans

Summary Small plots were amended in 1976 or 1978 with four kinds of sewage sludge. The sludges represented samples considered to be relatively free of heavy metals as well as sludges highly contaminated with heavy metals. Sludges were added to a silt loam soil at rates of 224 or 448 Mgha⁻¹. The soils were maintained at a high or low pH regime. In 1984, soybeans (Glycine max L. Merril. var. ‘Clark’) were planted and grown to the R4 stage. After harvest, roots were removed from the soil, washed, and examined for VA mycorrhizal infection. It was found that the heavy metal content of the sludge alone was generally not related to determining the extent of mycorrhizal infection. A heat treated sludge, high in heavy metals, exhibited the highest degree of mycorrhizal infection when the soil was maintained at a pH of 6.2. With this treatment, 52% of the root segments examined were infected by mycorrhiza. When the same sludge was added to a soil with a slightly lower pH (5.7) none of the roots examined were infected by mycorrhiza. When soybean roots were examined from soils that received no sludge and were maintained at either a low (5.6) or high (6.2) pH, there was no significant difference in mycorrhizal infection between the pH regimes. These results therefore indicate that sewage sludge may inhibit mycorrhizal infection if the sludge contains a high concentration of heavy metals and the sludge is applied to the soil with a low pH. Scientific Article No. A-4093 and Contribution No 7078 of the Maryland Agric. Exp. Stn., Dept. of Agronomy, University of Maryland, College Park, MD 20742.     

The dynamics of hormonal status of developing red beet root (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.) in correlation with the dynamics of sugar accumulation

We studied the dynamics of phytohormone levels (indole-3-acetic acid, abscisic acid, cytokinins, and gibberellin-like substances) in red beet (Beta vulgaris L.) roots at different developmental stages in comparison with the data on the dynamics of sugar accumulation in order to test possible hormonal regulation of sugar accumulation. The obtained data suggest the involvement of cytokinins and gibberellin-like substances in the control of sugar accumulation in the roots, while indole-3-acetic acid, abscisic acid, and gibberellin-like substances can control the outflow. The data on the dynamics of phytohormone levels shed light on their specific physiological role in red beet root development.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2005, pp. 30–35.Original Russian Text Copyright © 2005 by Ozolina, Pradedova, Salyaev.     

Phytohormone changes during storage root growth in Beta species

The physiological and morphological factors necessary for efficient accumulation of sucrose in sugar beet (Beta vulgaris L.) are considered in relation to potential uses of plant growth regulators to modify the anatomy of storage roots so as to increase sucrose content and yield. The percentage of sucrose in root fresh and dry matter is closely related to root structure. Sugar beet, mangold and chard are three sub-species of Beta vulgaris that differ considerably in their anatomy, assimilate partitioning, sucrose concentration and root dry matter yield. The concentrations of indole-3-acetic acid (IAA), abscisic acid (ABA) and cytokinins were measured during the growth of the storage root in each of these cultivars. Correlations were found between the phytohormone levels and the formation of secondary cambia and their subsequent cell division and expansion activity.     

Characterization of cadmium desorption in soils and its relationship to plant uptake and cadmium leaching

Experiments on Cd desorption were conducted with a range of water-to-soil ratios to assess the desorption characteristics of Cd in soils and the availability of Cd for absorption by plant roots and leaching to groundwater, Soil samples were collected from sites contaminated by a former Pb and Zn smelter, by sewage irrigation, or with artificial additions of Cd and sewage sludge. Glasshouse pot experiments were conducted in which the yield and Cd uptake of crop plants were determined. Cadmium leached from soil columns was also studied using soil lysimeters. The soil solution Cd concentration decreased with increasing solution-to-soil ratio and followed a negative power function. Two constants obtained from logarithmic linear regression were identified. The intercept (C₁) was Cd concentration in the soil solution where the solution/soil ratio was equal to 1 and this constant was the intensity factor of the initial element supply in the soil. The slope (a) showed a decreasing trend for Cd concentration in the soil solution which was related to the soil buffering capacity. A corrected concentration (C₁/a) is proposed for expressing soil desorption ability. This combined index was significantly correlated with Cd uptake by plants and also with Cd leached from soil columns.     

EGTA对Cd胁迫下蓖麻Cd积累和营养元素吸收的影响

以‘淄蓖麻5号’蓖麻品种为材料,通过盆栽试验研究了重度Cd土壤污染（100 mg·kg^-1）条件下,不同浓度（0、0.5、1.0、2.0 mmol·kg^-1）外源螯合剂——乙二醇双(2-氨基乙基醚)四乙酸(EGTA)对蓖麻植株生长、Cd积累和营养元素吸收的影响,探讨外源螯合剂调控Cd污染土壤上植物生长和修复效应。结果显示：（1）在Cd胁迫下,土壤中外源添加0.5~2.0 mmol·kg^-1EGTA使蓖麻根系鲜、干重比不添加EGTA对照不同程度降低,但植株总干重没有受到显著影响。（2）外源EGTA能有效促进Cd从蓖麻根部向地上部的转移,2.0 mmol·kg^-1的EGTA处理使蓖麻叶片Cd 含量显著增加了41.34倍;与不添加EGTA对照相比,外源EGTA处理蓖麻叶片中Cd积累量随添加EGTA的浓度增加而显著大幅度增加14.0~45.6倍,占相应植株总积累量的36.89%~58.63%,而茎中Cd积累量增加幅度较小,根中Cd积累量则显著降低。（3）Cd胁迫条件下,外源EGTA对蓖麻各器官矿质元素含量的影响不一,EGTA促进K向蓖麻地上部的转运,同时抑制Mg向植株地上部转运;随土壤添加的EGTA浓度提高,蓖麻植株对Ca吸收表现为低促高抑,叶片Zn含量和植株Cu含量逐渐增加,叶片和根系Fe含量及植株各器官Mn含量显著增加。与无Cd胁迫对照相比,EGTA在提高植株Cd积累的同时,降低了根系对K的吸收。研究表明,Cd胁迫显著抑制了蓖麻植株的生长,适宜浓度的外源EGTA对Cd的这种抑制有显著的缓解作用;外源EGTA改变了Cd在蓖麻根、茎、叶中的积累分布情况,提高了Cd从根系向地上部,尤其是向叶片的转移能力,从而强化了蓖麻对Cd污染土壤的修复效率;在采用EGTA强化植物修复Cd污染土壤时,应适量增施K肥以保证植株的正常生理代谢。     

Enzymes Involved in the Postharvest Degradation of Sucrose in Beta vulgaris L. Root Tissue

The reducing sugar content of sugar beet (Beta vulgaris L.) roots increased during 30 days of storage at 21 C and 160 days at 5 C as a result of an increase in acid invertase activity. Sucrose synthetase and neutral invertase activities were high at harvest but declined during storage, thus showing no relationship with postharvest reducing sugar accumulation in sugar beet roots. Acid α-glucosidase activity was detected in fresh roots but showed no activity with sucrose as a substrate.     

添加污泥对尾矿砂理化性质及香樟生理特性的影响

以香樟作为指示植物,选取黄岩、临海和路桥地区污水处理厂污泥,将污泥与尾矿砂按(污泥质量比例为0%对照、25%、50%和75%)配比进行栽培试验。测定添加污泥对尾矿砂理化性质以及香樟生理特性的影响。结果表明:随着污泥比例的增加,混合基质中的有机质、全氮、全磷明显增加,pH值明显降低,离子交换量明显减少,Cu和Cd总量明显增加,而Pb总量明显减少,Zn总量没有明显变化,Cu、Cd和Zn的DTPA提取量明显增加,而Pb的DTPA提取量明显减少。黄岩和临海污泥在25%和50%比例时,香樟叶和茎的生物量和叶绿素含量明显增加,而根的生物量没有明显变化,在75%比例时,生物量和叶绿素含量均明显减少;而添加路桥污泥使香樟叶、茎和根的生物量和叶绿素含量明显减少。丙二醛含量则与生物量和叶绿素含量呈现相反的变化特征。黄岩和临海污泥在25%和50%比例时,根和叶的Cu、Cd、Pb和Zn含量明显减少,在75%比例时,Cu、Cd和Zn含量则明显增加;而添加路桥污泥使叶和根的Cu、Cd和Zn含量明显增加,Pb含量明显减少。研究表明添加污泥提高了尾矿砂的养分含量,同时改变了其重金属组成,对污泥重金属含量和有机质组成的监控可以准确地预测污泥改良后尾矿砂对植物毒性的变化。     

Phytoextraction of cadmium with Thlaspi caerulescens

The in situ phytoextraction of cadmium from soils can only be achieved using plants that are both tolerant to high Cd concentrations and able to extract sufficient amounts of the metal. However, very few plant species are capable of remediating Cd polluted soils in a reasonable time frame. This paper aims to show that the population of the hyperaccumulator Thlaspi caerulescens J. & C. Presl. from Viviez (south of France), which has a high Cd-accumulating capability, is an efficient tool to remove Cd from contaminated soils. Roots of T. caerulescensViviez proliferate in hot spots of metals in soils which is particularly advantageous because of heterogeneity of the distribution of metal in polluted soils. Isotopic techniques showed that plants from this population acquire Cd from the same pools as non-accumulating species, but that it was much more efficient than non-hyperaccumulators at removing the metal from the soil labile pool. This is due: to (i) a specific rooting strategy, and (ii) a high uptake rate resulting from the existence in this population of Cd-specific transport channels or carriers in the root membrane. Growth and overall extraction can be improved with appropriate N fertilisation, supplied either as mineral fertilisers or uncontaminated sewage sludge. Selecting bigger plants is possible from within a suitable Cd-accumulating population to improve the phytoextraction process. Growing the Cd-accumulating populations results in a reduction in the availability of Cd and Zn as shown with field and lysimeter experiments conducted for several years. As a result, on a practical aspect, Cd hyperaccumulating populations of T. caerulescens may be used as a tool to efficiently reduce the availability of Cd in soils, providing appropriate populations are used.     

Sporamin-mediated resistance to beet cyst nematodes (Heterodera schachtii Schm.) is dependent on trypsin inhibitory activity in sugar beet (Beta vulgaris L.) hairy roots

Sporamin, a sweet potato tuberous storage protein, is a Kunitz-type trypsin inhibitor. Its capability of conferring insect-resistance on transgenic tobacco and cauliflower has been confirmed. To test its potential as an anti-feedant for the beet cyst nematode (Heterodera schachtii Schm.), the sporamin gene SpTI-1 was introduced into sugar beet (Beta vulgaris L.) by Agrobacterium rhizogenes-mediated transformation. Twelve different hairy root clones expressing sporamin were selected for studying nematode development. Of these, 8 hairy root clones were found to show significant efficiency in inhibiting the growth and development of the female nematodes whereas 4 root clones did not show any inhibitory effects even though the SpTI-1 gene was regularly expressed in all of the tested hairy roots as revealed by northern and western analyses. Inhibition of nematode development correlated with trypsin inhibitor activity but not with the amount of sporamin expressed in hairy roots. These data demonstrate that the trypsin inhibitor activity is the critical factor for inhibiting growth and development of cyst nematodes in sugar beet hairy roots expressing the sporamin gene. Hence, the sweet potato sporamin can be used as a new and effective anti-feedant for controlling cyst nematodes offering an alternative strategy for establishing nematode resistance in crops.     

Selection of natural isolates of Trichoderma spp. for biocontrol of Polymyxa betae as a vector of virus causing rhizomania in sugar beet

The soil fungus Polymyxa betae, Keskin, besides being a root parasite, plays a role of a vector in dissemination of Beet necrotic yellow vein virus (BNYVV) causing rhizomania in sugar beet. An alternative to its chemical control is the application of antagonistic microorganisms suppressing proliferation of the fungal vector. In the present work, 66 Trichoderma isolates have been obtained from sugar beet plantations from diverse locations in Slovakia. The ability of the selected isolates to grow at low temperature (10 °C) and to suppress the colonization of roots with P. betae and the multiplication of BNYVV in roots under glasshouse conditions were tested. The roots of sugar beet seedlings growing in the BNYVV-infested soil were analyzed by serological ELISA test using monoclonal and polyclonal antibodies for the presence of BNYVV and checked microscopically for the occurrence of cystosori of P. betae. The efficacy of the selected strains to suppress the proliferation of BNYVV varied on the average between 21 and 68%. On the basis of these tests, candidate strains for practical application in biocontrol of sugar beet rhizomania were selected.     

The bioavailability of cadmium to lettuce and cabbage in soils previously treated with sewage sludges

The application of sewage sludges to soils may lead to increased soil-Cd levels. The bioavailability of Cd is determined by the interaction of a number of soil physico-chemical and plant variables, of which pH is the most important. Duplicate samples of sludge-treated soils were transferred to tubs in the field, one of each pair being limed to pH 7±0.5. Lettuce and cabbage were grown to maturity and analysed for Cd. Liming always reduced Cd uptake by the plants. Three soil extractants, 1 M NH₄NO₃, 0.05 M EDTA-(Na)₂ and 0.05 M CaCl₂ were used as indices of Cd bioavailability. CaCl₂ proved to be the most effective for both lettuce and cabbage. Multiple linear regression equations were derived to describe the uptake and accumulation of Cd by both crops. The relative influence of soil variables differed between the two species. Unlike those of a number of pot experiments conducted in glasshouses, the data from this experiment are comparable with those of crop samples taken from the field.     

Genetic localization of four genes for nematode (Heterodera schachtii Schm.) resistance in sugar beet (Beta vulgaris L.)

Sugar beet (Beta vulgaris L.) is highly susceptible to the beet cyst nematode (Heterodera schachtii Schm.). Three resistance genes originating from the wild beets B. procumbens (Hs1 ^pro-1) and B. webbiana (Hs1 ^web-1, Hs2 ^web-7) have been transferred to sugar beet via species hybridization. We describe the genetic localization of the nematode resistance genes in four different sugar beet lines using segregating F₂ populations and RFLP markers from our current sugar beet linkage map. The mapping studies yielded a surprising result. Although the four parental lines carrying the wild beet translocations were not related to each other, the four genes mapped to the same locus in sugar beet independent of the original translocation event. Close linkage (0–4.6 cM) was found with marker loci at one end of linkage group IV. In two populations, RFLP loci showed segregation distortion due to gametic selection. For the first time, the non-randomness of the translocation process promoting gene transfer from the wild beet to the sugar beet is demonstrated. The data suggest that the resistance genes were incorporated into the sugar beet chromosomes by non-allelic homologous recombination. The finding that the different resistance genes are allelic will have major implications on future attempts to breed sugar beet combining the different resistance genes.     

Cadmium uptake and bioaccumulation in selected cultivars of durum wheat and flax as affected by soil type

Accumulation of cadmium (Cd) in crop plants is of great concern due to the potential for food chain contamination through the soil-root interface. Although Cd uptake varies considerably with plant species, the processes which determine the accumulation of Cd in plant tissues are affected by soil factors. The influence of soil type on Cd uptake by durum wheat (Triticum turgidum var. durum L.) and flax (Linum usitatissimum L.) was studied in a pot experiment under environmentally controlled growth chamber conditions. Four cultivars/lines of durum wheat (Kyle, Sceptre, DT 627, and DT 637) and three cultivars/lines of flax (Flanders, AC Emerson, and YSED 2) were grown in two Saskatchewan soils: an Orthic Gray Luvisol (low background Cd concentration; total/ABDTPA extractable Cd: 0.12/0.03 mg kg^-1, respectively) and a Dark Brown Chernozem (relatively high background Cd concentration; total/ABDTPA Cd: 0.34/0.17 mg kg^-1 respectively). Plant roots, stems, newly developed heads, and grain/seeds were analyzed for Cd concentration at three stages of plant growth: two and seven weeks after germination, and at plant maturity. The results showed that Cd bioaccumulation and distribution within the plants were strongly affected by both soil type and plant cultivar/line. The Cd concentration in roots leaves and stems varied at different stages of plant growth. However, all cultivars of both plant species grown in the Chernozemic soil accumulated more Cd in grain/seeds than plants grown in the Orthic Gray Luvisol soil. The different Cd accumulation pattern also corresponded to the levels of ABDTPA extractable and metal-organic complex bound soil Cd found in both soils. Large differences were found in grain Cd among the durum wheat cultivars grown in the same soil type, suggesting the importance of rhizosphere processes in Cd bioaccumulation and/or Cd transport processes within the plant. Distribution of Cd in parts of mature plants showed that durum grain contained up to 21 and 36% of the total amount of Cd taken up by the plants for the Orthic Gray Luvisol and Chernozemic soils, respectively. These results indicate the importance of studying Cd speciation, bioaccumulation and cycling in the environment for the management of agricultural soils and crops.     

Cadmium inducible Fe deficiency responses observed from macro and molecular views in tobacco plants

Responses induced by Cd exposure were assessed in tobacco seedlings (Nicotiana tabacum L.) using macro and molecular indices. The 100 μM of Cd exposure reduced the total dry weight and chlorophyll index of the seedlings as much as the genuine Fe-deficiency. Concentration of Fe in the shoots decreased, whereas that in the roots increased by the Cd exposure, especially in the apoplasmic space. It is probable that Cd interferes mainly with the step of Fe-translocation from the roots to shoots and this sets the upper-part of the plant in a state of Fe-deficiency. The Cd exposure coordinately increased the expressions of the exogenous and the endogenous Fe-deficiency responsive genes, HvIDS2 _pro ::GUS, NtFRO1 and NtIRT1 in the roots. This is the first data to demonstrate the responses of Cd-inducible Fe-deficiency at a molecular level.