Bioaccumulation and rhizofiltration potential of Pistia stratiotes L. for mitigating water pollution in the Egyptian wetlands

The bioaccumulation and rhizofiltration potential of P. stratiotes for heavy metals were investigated to mitigate water pollution in the Egyptian wetlands. Plant and water samples were collected monthly through nine quadrats equally distributed along three sites at Al-Sero drain in Giza Province. The annual mean of the shoot biomass was 10 times that of the root. The concentrations of shoot heavy metals fell in the order: Fe < Mn < Cr < Pb < Cu < Zn < Ni < Co < Cd, while that of the roots were: Fe < Mn < Cr < Pb < Zn < Ni < Co < Cu < Cd. The bio-concentration factor (BCF) of most investigated heavy metals, except Cr and Pb, was greater than 1000, while the translocation factor (TF) of most investigated metals, except Pb and Cu, did not exceed one. The rhizofiltration potential (RP) of heavy metals was higher than 1000 for Fe, and 100 for Cr, Pb and Cu. Significant positive correlations between Fe and Cu in water with those in plant roots and leaves, respectively were recorded, which, in addition to the high BCF and RP, indicate the potential use of P. stratiotes in mitigating these toxic metals.     

污水处理厂生物气溶胶抗生素抗性污染特征、来源及潜在风险

污水处理厂是抗生素抗性基因（antibiotic resistance genes,ARGs）和抗生素抗性细菌（antibiotic resistant bacteria,ARB）重要的源和汇,生物气溶胶是ARGs和ARB自污水处理厂向周边环境释放的关键载体。目前缺乏对污水处理厂生物气溶胶抗生素抗性污染特征、来源及潜在风险的系统性总结。本文从采样方法、检测方法、逸散特征、来源、潜在危害和风险评估等方面对污水处理厂抗生素抗性污染研究现状进行综述。惯性采样法和过滤法是常用的污水处理厂抗生素抗性生物气溶胶主要采集方法,而宏基因组测序、组装和分箱为其ARGs组成、可移动性和宿主提供了有效的检测方法,抗多药类、抗杆菌肽类、抗氨基糖苷类、抗四环素类、抗β-内酰胺类、抗磺胺类、抗大环内酯类和抗糖肽类等抗性基因在污水处理厂PM₁₀、PM_2.5和PM_1.0颗粒物中广泛检出。格栅间、生化反应池和污泥处理单元是污水处理厂PM₁₀、PM_2.5和PM_1.0负载ARGs和ARB的主要释放单元。污水处理厂不同粒径生物气溶胶中致病性ARB的存在增加了抗生素治疗的难度,而污水和污泥对ARGs和ARB的释放起到了重要的源的贡献。本文在研究内容、研究技术和控制策略等方面也提出了相关展望,以期为污水厂生物气溶胶抗生素抗性污染的监测和防护提供参考和借鉴。     

Commercially available plant growth regulators and promoters modify bulk tissue abscisic acid concentrations in spring barley, but not root growth and yield response to drought

Field and lysimeter experiments were conducted in 2002 to investigate the effects of an antigibberellin growth regulator (Moddus, active ingredient trinexapac‐ethyl, Syngenta Crop Protection UK Ltd, Whittlesford, Cambridge, UK) and an auxin‐stimulating (Route, active ingredient zinc ammonium acetate, De Sangosse Ltd, Swaffham Bulbeck, Cambridge, UK) growth promoter on root growth, soil water extraction and the drought response of spring barley. The effects on root growth and distribution were investigated in the field. The effects on the drought response were studied in 1.2‐m‐deep lysimeters packed with a loamy sand subsoil and sandy loam topsoil. Lysimeters were located under a fixed rain shelter, and drought was imposed by withholding irrigation. In both field and lysimeter experiments, growth regulator/promoters were applied to cv. Optic at early tillering according to the manufacturers’ recommendations. After withholding irrigation from lysimeters at Zadoks growth stage (GS) 21 (37 days after sowing), 50% of the profile available water had been depleted by flag leaf emergence (GS 37/39; 62 days after sowing). Drought significantly reduced stem biomass at ear emergence (GS 59; 78 days after sowing) but not leaf or ear dry weight; this was before there was any significant reduction in leaf water potential or stomatal conductance to water vapour. The reduction in stem biomass may reflect a change in partitioning between shoot and root in response to soil drying. When averaged over growth regulator/promoter treatments, drought reduced grain yield by approximately 1 t ha^?1. This was associated with a reduction in both ears per m² and grains per ear. The mean grain weight was not reduced by drought, in spite of significant reductions in stomatal conductance and canopy lifespan post‐anthesis. Route, and to a lesser extent Moddus, significantly increased abscisic acid accumulation in the stem base of droughted plants, and there was some indication of a possible delay in stomatal closure in Route‐treated plants as the soil moisture deficit developed. However, there was no significant effect on the amount of soil water extracted or grain yield under drought. Similarly, in field experiments, neither Route nor Moddus significantly altered total root length, biomass or distribution. There is little evidence from these experiments or in the literature to support the use of antigibberellin or auxin‐simulating growth regulator/promoters to modify root growth and drought avoidance of spring barley.     

Tolerance of Landoltia punctata to arsenate: an evaluation of the potential use in phytoremediation programs

Abstract

Plants used in phytoremediation should accumulate and tolerate a specific pollutant. Here, we aimed at evaluating a possible arsenic (As) accumulation and mechanisms of tolerance against As-induced damage in Landoltia punctata to explore this species for phytoremediation. Plants were subjected to increasing As levels. As absorption was higher with increasing As levels. The activity of superoxide dismutase and glutathione reductase as well as anthocyanin levels increased with As levels. Catalase and peroxidase activities increased in plants subjected to As levels up to 1.0?mg L^?1 and decreased at higher levels. Due to the antioxidant system, higher levels of reactive oxygen species were restrained in plants under low levels of As. However, the levels of superoxide anion, hydrogen peroxide, and lipid peroxidation increased in response to the impaired antioxidant system induced by the highest As levels. Biomass decreased in plants exposed to As and scanning electron microscopy revealed root structural damage in the root cap of plants under 3.0?mg L^?1?As. This work highlights that L. punctata can be considered a hyperaccumulator species and has potential for As phytoremediation when levels are lower than 1.0?mg L^?1—a concentration 100-fold higher than that recommended for drinking water.

Novelty Statement: Landoltia punctata can be considered a hyperaccumulator species and has the potential for arsenic phytoremediation when levels are lower than 1.0?mg L^?1.     

An increasing opine carbon bias in artificial exudation systems and genetically modified plant rhizospheres leads to an increasing reshaping of bacterial populations

To investigate how exudation shapes root‐associated bacterial populations, transgenic Arabidopsis thaliana plants that exuded the xenotopic compound octopine at low and high rates were grown in a nonsterile soil. Enumerations of both cultivable and octopine‐degrading bacteria demonstrated that the ratios of octopine degraders increased along with octopine concentration. An artificial exudation system was also set up in which octopine was brought at four ratios. The density of octopine‐degrading bacteria directly correlated with the input of octopine. Bacterial diversity was analysed by rrs amplicon pyrosequencing. Ensifer and Pseudomonas were significantly more frequently detected in soil amended with artificial exudates. However, the density of Pseudomonas increased as a response to carbon supplementation while that of Ensifer only correlated with octopine concentrations possibly in relation to two opposed colonization strategies of rhizosphere bacteria, that is, copiotrophy and oligotrophy.     

Assessment of plant growth attributes,bioaccumulation, enrichment,and translocation of heavy metals in water lettuce (Pistia stratiotes L.) grown in sugar mill effluent

This study was conducted to assess the pollutant uptake capability of water lettuce (Pistia stratiotes L.) in terms of bioaccumulation, enrichment, and translocation of heavy metals grown in sugar mill effluent. Results showed that the maximum fresh weight (328.48 ± 2.04 gm kg^?1), total chlorophyll content (2.13 ± 2.03 mg g^?1 fwt), and relative growth rate, RGR (11.89 gg^?1 d^?1) of P. stratiotes were observed at 75% concentration of the sugar mill effluent after 60 days of phytoremediation experiment. The bioaccumulation factor (B_F) of different heavy metals was greater than 1 with 50% and 75% concentrations of sugar mill effluent and this indicated that P. stratiotes was hyperaccumulator or phytoremediator of these metals. The enrichment factor (E_F < 2 for Cu, Fe, Cr, Pb, Zn, and Mn) and (E_F > 2 for Cd) indicated that P. stratiotes mineral enrichment deficient and it moderately enriched the different heavy metals. Moreover, translocation factor (T_F) was less than 1 which indicated the low mobility of metals in different parts (root and leaves) of P. stratiotes after phytoremediation. Therefore, P. stratiotes can be used for phytotreatment of sugar mill effluent up to 50% to 75% concentrations and considered as hyperaccumulator aquatic plant for different heavy metals and other pollutants from the contaminated effluents.     

污水处理厂中四环素和磺胺类抗生素抗性基因的分布、传播及去除

近年来,抗生素滥用造成的抗性基因(ARGs)污染问题引起了人们的关注.四环素及磺胺类抗生素由于价格低廉被广泛使用,大量残留的四环素和磺胺通过各种途径进入污水处理厂,并进一步导致ARGs的污染.为深入了解四环素和磺胺类ARGs的污染及治理现状,本研究对污水处理厂中四环素和磺胺类ARGs的分布情况及传播机制进行了综述,并重点讨论了不同污水处理工艺对ARGs的去除效果.在此基础上,从加大污水处理厂ARGs污染调查、改进污水处理工艺以及探讨ARGs传播机制等方面进行了展望.     

Palaeolimnological responses of nine North African lakes in the CASSARINA Project to recent environmental changes and human impact detected by plant macrofossil, pollen, and faunal analyses

This paper presents multi-proxy palaeolimnological analyses from recent sediments in the nine CASSARINA lakes in northernmost Africa, three from each of Morocco, Tunisia, and Egypt. The lakes are diverse, ranging from hypersaline to brackish lagoons and fresh-water lakes from high to low conductivity and pH. The macrofossils analysed include fruits, seeds, and vegetative remains of plants, lagoon and fresh-water Mollusca, a range of other aquatic animals, and from one site in each country, Ostracoda and Foraminifera. The diverse macrofossils are multi-proxy indicators of environmental change, and demonstrate changes in response to human activities in the catchments of all the lakes. The three Egyptian Nile Delta lakes have received massive inputs of fresh-water due to modifications of the flow of the R. Nile culminating in the Aswan High Dam built in 1964. Elsewhere, water withdrawal is frequently a serious threat. One lake with high biodiversity in Morocco has been drained and cultivated, and a rare acid-water lake in Tunisia is in danger of drying up. The internationally famous Garaet El Ichkeul in Tunisia, which was so important for birds, has become permanently saline with a loss of diversity. All the lakes are affected by agricultural and/or urban run-off and are experiencing changes as a result of human activities. Several are in a marginally sustainable condition, whereas others are permanently damaged.     

Population genetics and antibiotic susceptibility of invasive Haemophilus influenzae in Manitoba, Canada, from 2000 to 2006

One hundred and twenty-two isolates of Haemophilus influenzae causing invasive disease were collected in Manitoba, Canada, from 2000 to 2006 and examined for serotype, biotype, sequence type (ST) by multilocus sequence typing and antibiotic susceptibility. Nonserotypeable (NST) isolates accounted for over half of the isolates collected (69 isolates, 56.6%). There were 36 serotype a, five serotype b, two serotype c, one serotype d, four serotype e and five serotype f isolates collected. The 69 NST isolates were found to be very diverse, with isolates representing six biotypes and 45 STs. The serotypeable isolates were more clonal, with each of the serotypes showing little diversity in their biotypes and STs. Of the 122 isolates, 17% were resistant to ampicillin due to beta-lactamase production, 10.7% were resistant to trimethoprim-sulfamethoxazole, 1.6% were resistant to clarithromycin, 2.5% were resistant to amoxicillin-clavulanic acid and none was resistant to ciprofloxacin or moxifloxacin. Antibiotic resistance was more common in the NST strains, with 37.7% showing resistance to at least one antibiotic compared to 15% in the serotypeable strains. The results of this study suggest a shift in the epidemiology of invasive H. influenzae infections in the post-Hib vaccine era, and surveillance should include all serotypeable and NST isolates.     

Effects of Bacillus subtilis and antibiotic growth promoters on the growth performance,intestinal function and gut microbiota of pullets from 0 to 6 weeks

The development of digestive organs and the establishment of gut microbiota in pullets play an important role throughout life. This study was conducted to investigate the effects of Bacillus subtilis (BS) on growth performance, intestinal function and gut microbiota in pullets from 0 to 6 weeks of age. Hy-line Brown laying hens (1-day-old, n = 504) were randomly allotted into four diets with a 2 × 2 factorial design: (1) basal diet group (control); (2) antibiotics group (AGP), the basal diet supplemented with 20 mg/kg Bacitracin Zinc and 4 mg/kg Colistin Sulphate; (3) BS group, the basal diet supplemented with 500 mg/kg BS and (4) mixed group, the basal diet supplemented with both AGP and BS. As a result, when BS was considered the main effect, BS addition (1) reduced the feed conversion ratio at 4 to 6 weeks (P < 0.05); (2) decreased duodenal and jejunal crypt depth at 3 weeks; (3) increased the villus height : crypt depth (V : C) ratio in the duodenum at 3 weeks and jejunal villus height at 6 weeks and (4) increased sucrase mRNA expression in the duodenum at 3 weeks as well as the jejunum at 6 weeks, and jejunal maltase and aminopeptidase expression at 3 weeks. When AGP was considered the main effect, AGP supplementation (1) increased the V : C ratio in the ileum at 3 weeks of age; (2) increased sucrase mRNA expression in the duodenum at 3 weeks as well as the ileum at 6 weeks, and increased maltase expression in the ileum. The BS × AGP interaction was observed to affect average daily feed intake at 4 to 6 weeks, and duodenal sucrase and jejunal maltase expression at 3 weeks. Furthermore, dietary BS or AGP addition improved caecal microbial diversity at 3 weeks, and a BS × AGP interaction was observed (P < 0.05) for the Shannon and Simpson indexes. At the genus level, the relative abundance of Lactobacillus was found to be higher in the mixed group at 3 weeks and in the BS group at 6 weeks. Moreover, Anaerostipes, Dehalobacterium and Oscillospira were also found to be dominant genera in pullets with dietary BS addition. In conclusion, BS could improve intestinal morphology and change digestive enzyme relative expression and caecum microbiota, thereby increasing the efficiency of nutrient utilization. Our findings suggested that BS might have more beneficial effects than AGP in the study, which would provide theoretical evidence and new insight into BS application in layer pullets.     

Phytofiltration of As3+, As5+, and Hg by the aquatic macrophyte Potamogeton pusillus L,and its potential use in the treatment of wastewater

The aim of this paper was to investigate the capacity of the aquatic macrophyte Potamogeton pusillus to remove As³⁺, As⁵⁺, and Hg from aqueous solutions. The plants were exposed to 0 mg.L^?1, 0.1 mg.L^?1, 0.5 mg.L^?1, 1 mg.L^?1, or 2 mg.L^?1 of As³⁺, As⁵⁺, and Hg for 20 days. The results obtained for the individual removal of As³⁺, As⁵⁺, and Hg from water solutions, together with their accumulation in P. pusillus, indicate that this plant can be effectively used for the removal of Hg and of moderate concentrations of As³⁺ or As⁵⁺ (0.1 mg.L^?1) from aquatic systems. Roots and leaves accumulated the highest amount of As when the plant was exposed to As⁵⁺, but when it was exposed to As³⁺, the root accumulated the highest amount of As, and the leaves, the highest amount of Hg. When compared to other aquatic plants species, the results showed that P. pusillus demonstrated a higher Hg accumulation (2465 ± 293 µg.g^?1) when the transfer coefficient was 40,580 ± 3762 L.kg ^?1, showing the great potential of this macrophyte for phytoremediation of water contaminated with Hg. To the extent of our knowledge, this is the first report on bioaccumulation of As³⁺, As⁵⁺, and Hg by P. pusillus.     

Global warming is projected to lead to increased freshwater growth potential and changes in pace of life in Atlantic salmon Salmo salar

Global warming has been implicated in widespread demographic changes in Atlantic salmon Salmo salar populations, but projections of life-history responses to future climate change are lacking. Here, we first exploit multiple decades of climate and biological data from the Burrishoole catchment in the west of Ireland to model statistical relationships between atmospheric variables, water temperature, and freshwater growth of juvenile Atlantic salmon. We then use this information to project potential changes in juvenile growth and life-history scheduling under three shared socioeconomic pathway and representative concentration pathway scenarios from 1961 to 2100, based on an ensemble of five climate models. Historical water temperatures were well predicted with a recurrent neural network, using observation-based atmospheric forcing data. Length-at-age was in turn also well predicted by cumulative growing degree days calculated from these water temperatures. Most juveniles in the Burrishoole population migrated to sea as 2-year-old smolts, but our future projections indicate that the system should start producing a greater proportion of 1-year-old smolts, as increasingly more juveniles cross a size-based threshold in their first summer for smoltification the following spring. Those failing to cross the size-based threshold will instead become 2-year-old smolts, but at a larger length relative to 2-year-old smolts observed currently, owing to greater overall freshwater growth opportunity. These changes in age- and size-at-seaward migration could have cascading effects on age- and size-at-maturity and reproductive output. Consequently, the seemingly small changes that our results demonstrate have the potential to cause significant shifts in population dynamics over the full life cycle. This workflow is highly applicable across the range of the Atlantic salmon, as well as to other anadromous species, as it uses openly accessible climate data and a length-at-age model with minimal input requirements, fostering improved general understanding of phenotypic and demographic responses to climate change and management implications.     

Germination potential,growth patterns and reproductive effort of Juncus articulatus and Glyceria australis in temporary shallow wetlands in Australia

Juncus articulatus is an exotic aquatic species occuring over large areas of Mother of Ducks Lagoon, a shallow and temporary wetland in northern New South Wales, Australia. The other dominant perennial species at the site is the native Glyceria australis. Little is known of the ecology of either species or of the potential of J. articulatus to invade wetlands. The germination potential, growth patterns and reproductive effort of J. articulatus and G. australis were compared in response to water regime, grazing and competition. Both species have persistent seed banks from which only a small percentage of seeds germinate in repeated wetting events and from sediment stored dry. J. articulatus germinated in very high numbers from Mother of Ducks Lagoon sediment, but was rare in other lagoons in the region. G. australis germinated in comparatively lower numbers from Mother of Ducks Lagoon sediment and was rare in other lagoon sediments despite being present in the extant vegetation in several lagoons. The introduced J. articulatus has several life cycle characteristics that differ from G. australis, notably a high allocation of biomass to inflorescences under all water regimes. Clipping stimulated above ground vegetative and sexual reproduction for J. articulatus and high numbers of tillers facilitate the sexual reproductive effort. Because J. articulatus is ubiquitous in the region, our results suggest that management of this exotic species should be directed towards minimizing recruitment opportunities and that this could be achieved by increasing variation in water regimes in combination with reduced disturbance from grazing.     

Monitoring the acoustic activity of an aquatic insect population in relation to temperature,vegetation and noise

1. Acoustic population monitoring is a noninvasive method that can be deployed continuously over long periods of time and at large spatial scales. One of the newly discovered threats acting on biological diversity is anthropogenic noise. High levels of anthropogenic noise occur in aquatic environments, yet their effects on animals living in freshwater habitats have very rarely been investigated.
2. Here, we used acoustic monitoring and automatic detection to assess the acoustic activity of a population of a soniferous freshwater insect.
3. The sounds emitted by the corixid Micronecta scholtzi were recorded in a Mediterranean pond with an array of 12 hydrophones. An automatic analysis based on a measure of the amplitude found in the frequency band of M. scholtzi was developed to assess the level of acoustic activity. We used functional linear models, accounting for the periodicity of the calling behaviour, to estimate the possible effect of temperature, vegetation and a noise due to an immersed engine.
4. The automatic analysis was validated as an efficient method to measure the acoustic activity. The monitoring revealed a clear 24-hr pattern in the acoustic activity of M. scholtzi and three peaks of activity during the morning. Functional linear models revealed negative effects of both temperature and vegetation and showed that an engine noise, played back for 2 hr during the night, elicited an increase in the level of acoustic activity of the population. Moreover, a cross-correlation procedure showed that noise delayed the acoustic activity of the population.
5. Our results suggest that acoustic survey and automatic detection are efficient methods to monitor the acoustic activity of an insect population especially in response to an anthropogenic disturbance.

     

The influence of ultraviolet radiation on growth,photosynthesis and phenolic levels of green and red lettuce: potential for exploiting effects of ultraviolet radiation in a production system

Studies have shown that natural ultraviolet (UV) radiation increases secondary products such as phenolics but can significantly inhibit biomass accumulation in lettuce plants. In the work presented here, the effect of UV radiation on phenolic concentration and biomass accumulation was assessed in relation to photosynthetic performance in red and green lettuce types. Lettuce plants in polythene clad tunnels were exposed to either ambient (UV transparent film) or UV-free conditions (UV blocking film). The study tested whether growth reduction in lettuce plants exposed to natural UV radiation is because of inhibition of photosynthesis by direct damage to the photosynthetic apparatus or by internal shading by anthocyanins. Ambient levels of UV radiation did not limit the efficiency of photosynthesis suggesting that phenolic compounds may effectively protect the photosynthetic apparatus. Growth inhibition does, however, occur in red lettuce and could be explained by the high metabolic cost of phenolic compounds for UV protection. From a commercial perspective, UV transparent and UV blocking films offer opportunities because, in combination, they could increase plant quality as well as productivity. Growing plants continuously under a UV blocking film, and then 6 days before the final harvest transferring them to a UV transparent film, showed that high yields and high phytochemical content can be achieved complementarily.     

Clear water associated with biomass and nutrient variation during the growth of a Charophyte stand after a drawdown,in a tropical coastal lagoon

The community of Charophytes in the Imboassica coastal lagoon in Brazil (22° 24 S and 42° 42 W) sometimes occupies almost the entire benthic region, and presents a large variation in C:N:P ratio. The effect of drawdown on the regeneration and buildup of biomass and on the nutrient concentration of these macroalgae was studied at three different sampling sites. Drawdown results in a high level of mortality in the macroalgae stands and after the water level later rises, the process of oospore germination begins. The drawdowns occurred in November 96 and January 97, and after March 97 we took samples in order to determine biomass values and the concentration of carbon, nitrogen and phosphorus. The results indicate that the fast growth of Charophytes may absorb a great amount of the nutrients entering the lagoon. The biomass reached maximum values of between 400 and 600 g DW m^–2, and the C:N:P ratio varied from 51:7:1 to 1603:87:1, indicating that this macroalgae may grow in a wide range of nutrient concentration. The presence of this community in the Imboassica lagoon may act as one of the limiting factors controlling phytoplanktonic primary production, decreasing nutrient availability in the water column (`bottom-up' control) and keeping the water clear after drawdowns. Probably through the habitat structure produced by the great biomass reached, they provide substrate and shelter for the structuring of a community with grazing zooplankton, which acts as a `top-down' controlling mechanism on the phytoplankton.     

Comparative morphology of epicortical roots in Old and New World Loranthaceae with reference to root types, origin, patterns of longitudinal extension and potential for clonal growth

The large mistletoe family, Loranthaceae, contains 75 genera, three of which are terrestrial root parasites. The remaining 72 genera are aerial parasites. Four basic haustorial system types are found in aerial genera: epicortical roots (ERs), wood roses, clasping unions and bark strands. The focus of this report is on genera in which ERs are present. Presence of ERs is based on our worldwide collection of haustoria and from literature sources. Our collections include 78% of all aerial genera and 72% of genera with ERs. Collections were analyzed using comparative morphological methods. Of the 72 aerial genera 40 (56%) have ERs and 75% of these are Old World. ERs are the most common haustorial type for Loranthaceae on every major landmass except Africa. Three ER types are described, basal, cauline and adventitious. Basal and adventitious ERs occur in both the Old and New World, whereas cauline ERs are exclusively New World. Adventitious ERs form in a few species in response to injury or epiparasitism. Significant differences occur between basal and cauline ERs in the extent and pattern of elongation, frequency of lateral root formation, and production of haustoria and shoots. Three patterns of axis extension of ERs are recognized, the monochasial sympodium, dichasial sympodium and monopodium. Marked differences in patterns of axis elongation occur between the Old and New World genera analyzed. In Old World taxa 94% of lateral roots contributed to a monochasial sympodium, whereas in New World taxa 84% of root extension was monopodial. Two strategies of resource procurement occur in genera with ERs; the “phalanx” strategy is found in species with basal ERs only, the “guerilla” strategy in New World species with cauline ERs. Species with ERs have the potential for clonal growth through fragmentation of stems, ERs, or both, but the extent of clonal growth in nature is unknown. The large number and wide distribution of genera with ERs add support to the hypothesis that the presence of ERs is an ancestral trait for aerial Loranthaceae.     

Pathogenicity of the rice root nematode,Hirschmanniella oryzae to rice plants in relation to nematode reproduction,plant growth,grain yield and biochemical changes

Influence of different inoculum levels of 0, 10, 100, 1000 and 10,000 individuals of Hirschmanniella oryzae on nematode reproduction and plant growth of rice cv. Giza171 and biochemical changes of infected plants was studied under screen-house conditions. Rate of nematode build up (P_f/P_i) was negatively correlated with the progressive increase in nematode inoculum levels. The percentage reduction in growth parameters, rice grain yield and the amount of total and reducing sugars were markedly affected showing a negative correlation with the tested inocula. The conspicuous reductions of plant growth, yield and total and reducing sugar contents were obtained by using 1000 and 10,000 nematodes per pot. The inoculum level of 1000 nematodes per pot was identified as critical population at which control programme must be started.     

Root deformation in plantations of container-grown Scots pine trees: effects on root growth,tree stability and stem straightness

Root system deformation was studied in 23 Scots pine (Pinus sylvestris L.) stands in central Sweden. The study comprised both plantations created with container-grown plants (Paperpot) and natural stands including young (7–9 year old) and older (19–24 year old) trees. Trees were measured with regards to distribution of roots, root deformation, stability, stem straightness and wood properties in stumps. Root distribution was most uniform for naturally regenerated trees. Older trees generally showed a better root distribution than young trees. The young planted trees displayed a high frequency of severely spiralled root systems, while only a few of the older trees had spiralled root systems. No severe root deformations were observed on naturally regenerated trees. Naturally regenerated trees were more stable than those which had been planted. Differences in bending moment, when trees were pulled to an angle of 10°, were considerable between young planted and naturally regenerated trees, but less pronounced for the older trees. Young planted trees had the highest frequency of severely crooked stem bases, while naturally regenerated trees had the straightest mode of growth. Tensile strength in peripheral wood samples of the stumps was substantially lower for planted than for naturally regenerated trees. Strain values to breakage of wood samples, taken from the root collar and the central- and peripheral part of the stump were lower for planted trees. The conclusions from this study are that root distribution, tree stability and stem straightness of planted Paperpot-grown trees will improve after a certain time and approach the state of naturally regenerated trees. As trees grow older, early established crooked stem bases will be compensated by radial growth and the tree will appear straighter. Inside the stem, however, problems may still remain with abnormal fibre direction and compression wood together with inferior root strength due to fibre disturbances as a result of spiralled roots. This revised version was published online in June 2006 with corrections to the Cover Date.