Effects of weed abundance and frequency of hand weeding on the establishment of transplanted Imperata cylindrica

Imperata cylindrica is an important component of grasslands in several Asian countries. Its vigorous rhizome elongation enables the plant to quickly cover bare ground, making it a candidate for revegetation projects. In these projects, initial and subsequent management practices often differ. Initial management strategies are important for encouraging rapid cover by the target species. We tested the effects of initial hand weeding on I. cylindrica cover and weed growth over 2 years. Two types of soil (A and B) were scattered on a recently constructed river embankment at a depth of 10 cm. Both soils A and B are nutrient-poor and high (> 7.0) pH. Plots were hand-weeded once or twice a year (W₁ and W₂ treatments, respectively), or mowed but not weeded (M treatment) with four replications. Plug plants of I. cylindrica were introduced. I. cylindrica became dominant in soil A with the W₂ treatment, with 50% cover in year 2. Conversely, I. cylindrica failed to establish in soil B regardless of treatment, due to dominance of the weed Sorghum halepense. Soil B included creeping rhizomes of S. halepense, and vigorous growth from rhizomes is likely a major reason for its predominance. S. halepense seedlings germinated in both soils, but were successfully eradicated when weeded at less than 1 month of age. Thus, for successful revegetation, land managers should use soil that does not contain creeping rhizomes of S. halepense. If rhizomes are not present, hand weeding twice a year for 2 years is sufficient for establishment of I. cylindrica.

     

A Unique Feature of Iron Loss via Close Adhesion of Helicobacter pylori to Host Erythrocytes

Iron deficiency anemia is an extra-stomach disease experienced in H. pylori carriers. Individuals with type A blood are more prone to suffering from H. pylori infection than other individuals. To clarify the molecular mechanisms underlying H. pylori-associated anemia, we collected erythrocytes from A, B, O, and AB blood donors and analyzed morphology, the number of erythrocytes with H. pylori colonies attached to them, and iron contents in erythrocytes and H. pylori (NCTC11637 and SS1 strains) by means of optical microscopy, scanning electron microscopy, and synchrotron radiation soft X-ray imaging. The number of type A erythrocytes with H. pylori attached to them was significantly higher than that of other erythrocytes (P<0.05). Far more iron distribution was observed in H. pylori bacteria using dual energy analysis near the iron L2, 3 edges by soft X-ray imaging. Iron content was significantly reduced in host erythrocytes after 4 hours of exposure to H. pylori. H. pylori are able to adhere more strongly to type A erythrocytes, and this is related to iron shift from the host to the bacteria. This may explain the reasons for refractory iron deficiency anemia and elevated susceptibility to H. pylori infection in individuals with type A blood.     

Lithotrophic iron-oxidizing bacteria produce organic stalks to control mineral growth: implications for biosignature formation

Neutrophilic Fe-oxidizing bacteria (FeOB) are often identified by their distinctive morphologies, such as the extracellular twisted ribbon-like stalks formed by Gallionella ferruginea or Mariprofundus ferrooxydans. Similar filaments preserved in silica are often identified as FeOB fossils in rocks. Although it is assumed that twisted iron stalks are indicative of FeOB, the stalk''s metabolic role has not been established. To this end, we studied the marine FeOB M. ferrooxydans by light, X-ray and electron microscopy. Using time-lapse light microscopy, we observed cells excreting stalks during growth (averaging 2.2 μm h⁻¹). Scanning transmission X-ray microscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy show that stalks are Fe(III)-rich, whereas cells are low in Fe. Transmission electron microscopy reveals that stalks are composed of several fibrils, which contain few-nanometer-sized iron oxyhydroxide crystals. Lepidocrocite crystals that nucleated on the fibril surface are much larger (∼100 nm), suggesting that mineral growth within fibrils is retarded, relative to sites surrounding fibrils. C and N 1s NEXAFS spectroscopy and fluorescence probing show that stalks primarily contain carboxyl-rich polysaccharides. On the basis of these results, we suggest a physiological model for Fe oxidation in which cells excrete oxidized Fe bound to organic polymers. These organic molecules retard mineral growth, preventing cell encrustation. This model describes an essential role for stalk formation in FeOB growth. We suggest that stalk-like morphologies observed in modern and ancient samples may be correlated confidently with the Fe-oxidizing metabolism as a robust biosignature.     

EPR spectra of Photosystem I and other iron protein components in intact cells of cyanobacteria

Electron paramagnetic resonance (EPR) spectra were recorded of whole filaments of the cyanobacteria Nostoc muscorum and Anabaena cylindrica. Signals due to manganese were removed by freezing and thawing the cells in EDTA. EPR spectra were assigned on the basis of their g values, linewidths, temperature dependence and response to dithionite and light treatments. The principal components identified were: (i) rhombic Fe³⁺ (signal at g = 4.3), probably a soluble storage form of iron; (ii) iron-sulfur centers A and B of Photosystem I; (iii) the photochemical electron acceptor ‘X’ of Photosystem I; this component was also observed for the first time in isolated heterocysts; (iv) soluble ferredoxin which was present at a concentration of 1 molecule per 140 ± 20 chlorophyll molecules; (v) a membrane-bound iron-sulfur protein (g = 1.92). A signal g = 6 in the oxidized state was probably due to an unidentified heme compound. During deprivation of iron the rhombic Fe³⁺, centers A, B and X of Photosystem I, and soluble ferredoxin were all observed to decrease.     

Localization and quantification of Pb and nutrients in Typha latifolia by micro-PIXE

Typha latifolia is a plant species widely used for phytoremediation. Accumulation, localization and distribution of Pb and mineral nutrients were investigated in roots, rhizomes and leaves of Typha latifolia grown at 0, 50, 100 and 250 μM Pb concentrations in a pot experiment under controlled conditions. Bulk elemental concentrations were determined by X-ray fluorescence (XRF) spectroscopy whereas micro-proton-induced X-ray emission (micro-PIXE) was used for element localization in root and rhizome tissues. Gradual increase in bulk Pb concentrations was observed in Typha latifolia roots and rhizomes treated with increasing Pb concentrations, however in rhizomes Pb concentrations were an order of magnitude lower than in roots. In leaves Pb concentrations were around the limit of detection for XRF (~20 μg g(-1)). An increase in concentration of K and Ca in roots, rhizomes and leaves, of iron and zinc in roots and leaves, and of Mn in rhizomes was observed either at 50 and/or 100 μM Pb treatments, whereas for K and Ca in roots, rhizomes and leaves, Fe and Zn in roots and leaves and Mn in rhizomes, or at 250 μM Pb treatment the increase was seen for concentrations of Fe and Zn in rhizomes and Cu in roots. Mn concentrations decreased with Pb treatments in roots and leaves. Element localization using micro-PIXE analysis demonstrated Pb accumulation in epidermal and cortical tissues of treated roots and rhizomes, while in endodermis and vascular tissues Pb was not detected. A displacement of Ca from epidermal to cortical tissues was observed in Pb treated roots and rhizomes, pointing to cell wall immobilization of Pb as one of the tolerance mechanisms in Typha latifolia. High level of colocalization of Pb with P (r = 0.60), S (r = 0.37) and Zn (r = 0.70) was observed in Pb treated roots, while in rhizomes colocalization with the mentioned elements was still positive, but not that prominent. These results indicate that Pb may form complexes with phosphorus and sulfur compounds in roots and rhizomes, which may also represent attraction sites for binding Zn. Because of its large root and rhizome surface area acting as main sites for Pb adsorption, Typha latifolia may represent potentially efficient plant species for phytoremediation of Pb contaminated soils and waters.     

The formation of iron plaques on roots and rhizomes of the seagrass Cymodocea serrulata (R. Brown) Ascherson with implications for sulphide intrusion

Despite the fact that iron plaque formation is ubiquitous in aquatic macrophytes and has been known for several decades, there are few reports of plaque occurrence in seagrasses to date. Herein we present the first microscopical observation and chemical quantification of iron (Fe) plaques on the shoots, rhizomes and roots of the seagrass Cymodocea serrulata (R. Brown) Ascherson collected from intertidal seagrass beds in Thailand. Plaques were observed on shoot bases, rhizomes and roots with the highest concentrations of iron in the plaques from the roots, reaching an average of 509 μmol gDW⁻¹. Interestingly, the most negative stable sulphur isotope (δ³⁴S) values, indicating H₂S intrusion into the plants occurred in the sampling site with the most intense root oxidizing capacity, as indicated by a greater Fe plaque formation. These apparently contradictory findings may be attributed to oxidizing capacity of root tips and root hairs sufficient to promote Fe(III) deposition in the rhizosphere, preceding deposition of plaques on the roots. While this rhizosphere oxidation may result in a more efficient sulphide detoxification during the day photosynthetic phase, root tips and hairs may serve as vulnerable sites for sulphide intrusion at night. The presence of Fe plaque on C. serrulata roots and rhizomes reveals the complexity of seagrass–sediment interactions and deserves further attention to understand if this is a local phenomenon or a newly discovered adaptive mechanism in seagrasses.     

Eremophilane-type sesquiterpene lactones from Ligularia hodgsonii Hook

A dimeric eremophilane sesquiterpene lactone with a cyclobutane ring, biliguhodgsonolide (1) and an uncommon seco-sesquiterpene derivative, (4S,5S,6R,10R)-8,9-seco-12-hydroxyeremophil-7(11)-en-14,6;12,8-diolid-9-al (2), were isolated from the roots and rhizomes of Ligularia hodgsonii Hook. Their structures, including the absolute stereochemistry, were elucidated by spectroscopic data and CD analysis. The cyclobutane ring was confirmed by single-crystal X-ray diffraction.     

Changes in soil carbon stock after deforestation and subsequent establishment of “Imperata” grassland in the Asian humid tropics

Globally, tropical deforestation is often followed by the establishment of fire-prone grassland. In Southeast Asia, Imperata cylindrica grassland is the dominant land cover after deforestation. No quantitative data are available on the changes in soil carbon (C) stock upon such land conversion. We aimed to elucidate changes in soil C stock after deforestation followed by the occurrence and persistence of I. cylindrica grassland in the Asian humid tropics. We compared soil C stock between primary forests (n?=?20) and grasslands (n?=?14) with a wide range of soil textures in East Kalimantan (Indonesian Borneo). We also assessed the temporal change in soil C stock in the grassland sites between 1992 and 2004 by comparing identical soil pits (n?=?7). Soil C stock (0–100 cm deep) increased by 23% following transition from primary forest to grassland during about 10 years. Over 12 years at the grassland sites, however, soil C stock did not change in the 0–100 cm depth, but we observed increased blackness of soil, especially coarse-textured soils. The increase in C stock following the transition was largely attributed to the organic matter supply by grass roots, rhizomes, and charred materials from wildfires to the subsurface soils and subsoils (5–100 cm). The unchanged soil C stock (0–100 cm) over 12 years at the grassland sites suggests that the soil C stock level there has nearly reached a new equilibrium state. However, the increased blackness of the soil suggests changes in the quality of soil organic matter by higher subsoil root input and deeper bioturbation by earthworms.     

Trace element composition of Ural licorice Glycyrrhiza uralensis Fisch. (Fabaceae Family)

The trace element composition of the subsurface (roots and rhizomes), overground (leaves and stems), and reproductive (bean valves) organs of Glycyrrhiza uralensis Fisch. was determined by synchrotron radiation X-ray fluorescence analysis (SRXFA). Concentrations of Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Hg, Pb, Bi, Th, and U were measured. The data obtained were used to estimate the distribution of some elements in samples of various organs of licorice. Glycyrrhiza uralensis is an accumulator of Fe, Mn, Cu, and Co.     

Construction of a haustorium development associated SSH library in Thesium chinense and analysis of specific ESTs included by Imperata cylindrica

Thesium chinense Turcz. is a facultative hemiparasite that can invade host plants by inducing haustoria on neighboring host roots to access the water and nutrients of the host. Suppression subtractive hybridization (SSH) was performed to identify the differentially expressed genes during haustorial development. A total of 395 recombinants were randomly selected for sequencing. Two hundred seventy-six ESTs were retained after this screening procedure, and after DNA sequencing, 217 ESTs (78.6%) exhibited significant homology with previously identified genes in GenBank. Based on GO annotation, we selected 9 ESTs that may be associated with the development of haustorium and be induced by Imperata cylindrica (L.) Beauv.var.major (Nees)C．E．Hubb. for qRT-PCR. The results revealed that the relative quantities of the 4 ESTs from among the 9 ESTs that involved cell-wall modification (pectin methylesterase, TcPME), signal transduction (auxin-responsive aux/iaa gene, TcAux/IAA) and metabolism (class III peroxidase, TcPrx; phenylalanine ammonia-lyase, TcPAL) all increased simultaneously with the development of the roots of T. chinense and I. cylindrica. These results indicated that the relative quantities of TcPME, TcAux/IAA, TcPrx and TcPAL were affected by the secretions of the I. cylindrica root that T. chinense accreted and that these effects were meaningful to the development of the haustorium of T. chinense.     

NITROGEN FIXATION ASSOCIATED WITH NATURAL AND CULTIVATED STANDS OF TYPHA LATIFOLIA L. (TYPHACEAE)

Acetylene reduction by bacteria associated with Typha latifolia L. roots and rhizomes was studied in the field and in the laboratory. In situ studies indicated that the rate of acetylene reduction in a natural cattail population was ca. 4-fold higher than in a cultivated cattail stand. Nitrogenase activity was found to occur principally in the rhizosphere of roots and rhizomes with the greatest activity occurring in association with mature roots. Scanning electron and light microscopy, and 2, 3, 5 triphenyltetrazolium chloride reduction showed that bacterial associations were limited to the rhizoplane of this angiosperm. One diazotrophic bacterial genus was found to be associated with roots and rhizomes and was identified as the facultative anaerobe Bacillus. Contribution of free-living cyanobacteria to total nitrogen fixation in the natural stand was negligible. Calculations show that a natural stand of cattails may fix 18 kg nitrogen ha^−-1 yr^−-1 or ca. 8.2% of the total nitrogen present in the standing crop.     

Belowground rhizomes and roots in waterlogged paleosols: Examples from the Middle Jurassic of Beijing,China

Plant rhizomes and roots occur in terrestrial ecosystems since at least the Devonian, but the documentation of belowground plant tissues is sparse in the fossil record. In this study, fossils representing belowground rhizomes and roots are described from the top of the Upper Yaopo Formation (Middle Jurassic), at the Yuejiapo section, Mentougou District, Beijing, China. Morphological studies of the plant fossils, together with lithofacies analyses, provide new information on plant–soil interactions during the Jurassic period. Three types of rooting systems are recognized from two fossiliferous beds. The Bed-1 Flora is interpreted as representing a Cladophlebis-dominated community, where abundant foliage remains mainly of Cladophlebis cf. scariosa and Cladophlebis delicatula are associated with Type-A rooting system. The Bed-2 Flora includes Type-B and Type-C rooting systems, although the floristic composition is unknown due to the absence of identifiable foliage remains. The Type-A and Type-B rooting systems consist of abundant in situ vertical rhizomes, fine shoot-borne roots and lateral roots, and are consistent with those of some extant ferns. The Type-C rooting system shows a thick central taproot and at least three orders of lateral roots, an architecture typical of various gymnosperms. The in situ rooting systems, as well as sedimentary evidence, contribute to the recognition of stacked, reworked Entisols in a dynamic waterlogged environment.     

Vessels in Nelumbo (Nelumbonaceae)

Vessels have been previously reported in the roots (but not rhizomes) of Nelumbo on the basis of light microscopy. We have reinvestigated vessel occurrence in Nelumbo by means of scanning electron microscopy (SEM). On the basis of these studies, vessels are characteristic of root metaxylem. Pores in primary walls of pits of end walls of these vessels are various in size, but feature incomplete lysis of pit membranes, often with residual webs or threads of primary wall material, much as in vessels of primitive woody dicotyledons. In addition, we newly report occurrence of vessels in metaxylem of rhizomes; pores in these vessels are smaller and more confined than in those of roots. The present study offers not only data of possible use in determining the phylogenetic position of Nelumbonaceae, but also contributes evidence that vessel origin in Nelumbonaceae relates to habit and ecology. We conclude that organographic distribution of vessels in Nelumbo follows the patterns seen in monocotyledons, which, like Nymphaeaceae and other aquatics, have sympodial architecture.     

Nitrogen Fixation Associated with Rinsed Roots and Rhizomes of the Eelgrass Zostera marina

Nitrogen fixation was associated with the rinsed roots and rhizomes of the seagrass, Zostera marina L. Nitrogenase activity (acetylene reduction) was greater on rhizomes compared to roots, and on older roots and rhizomes relative to younger tissue. Compared to aerobic assays, anaerobic or microaerobic conditions enhanced the rate of acetylene reduction by rhizomes with attached roots, with the highest activity (100 nanomoles per gram dry weight per hour) occurring at pO₂ = 0.01 atmosphere. Addition of glucose, sucrose, or succinate also increased the rate of acetylene reduction under anaerobic conditions, with glucose providing the most stimulation. In one experiment, comparison of acetylene reduction assays with ¹⁵N₂ incorporation yielded a ratio of about 2.6:1. Seagrass communities are thought to be limited by the availability of nitrogen and, therefore, nitrogenase activity directly associated with their roots and rhizomes suggests the possibility of a N₂-fixing flora which may subsidize their nutritional demand for nitrogen.     

Different patterns of aerenchyma formation in two hygrophytic species of Paspalum (Poaceae) as response to flooding

Paspalum modestum and P. wrightii are perennial grasses growing in permanent and seasonally flooded areas, respectively. The former produces short rhizomes and floating culms, the latter forms long rhizomes and erect culms. Variations in percentage aerenchymatous space (PAS) in different organs as a response to flooding was analysed using a clone of each species. Eighteen plantlets of each clone were cultivated during 7 months under flooded vs. unflooded conditions. After this period, roots, rhizomes, culms, and leaf sheaths were collected and prepared. PAS was measured using an image analysis device, and data were analysed using ANOVA.Production of aerenchyma took place in both species within the cortical parenchyma of roots, rhizomes and culms, and the mesophyll of leaf sheaths, both in flooded and unflooded plants. Under flooding conditions PAS increased in both species, although the individual response of organs differed: whereas in P. modestum PAS increased primarily in substratum-fixed roots, in P. wrightii all organs produced additional aerenchyma uniformly. Contrasting responses are understood as adaptations to permanent and seasonal flooding, respectively.     

Colonisation pattern of nonpathogenic Fusarium oxysporum, a potential biological control agent, in roots and rhizomes of tissue cultured Musa plantlets

Under laboratory conditions, nonpathogenic, endophytic Fusarium oxysporum inflicts high mortality among banana weevils and nematodes. Following inoculation into banana (Musa spp.) tissue cultured plants, successful colonisation is necessary for efficient biological control of these pests. The pattern of root and rhizome colonisation by two nonpathogenic Ugandan F. oxysporum strains (V2w2 and III4w1) in cv. Nabusa (AAA‐EA) was investigated using light microscopy. Percentage of colonisation in the rhizomes (93%) was higher than in the roots (56%), but hyphal density in the roots (0.30 mm^?2) was higher than in the rhizomes (0.21 mm^?2). The root bases were better colonised (76%) than root midsections (53%) or tips (39%). Both the strains colonised the roots and the rhizomes, with numerous hyphae infecting the hypodermis but fewer infecting the cortex. Colonisation of vascular tissues was not recorded. Despite the presence of hyphae in intercellular and intracellular spaces of the roots and the rhizomes, normal cell structure was observed. Our report provides the first in situ observation and quantification of endophyte colonisation in banana. The study demonstrated the ability of F. oxysporum strains V2w2 and III4w1 to penetrate intact host tissues and recolonise the host internally upon inoculation, an important step for their suitability as biological control agents.     

ELEMENTAL ANALYSIS OF DEPOSITS ON THE ROOTS OF SPARTINA ALTERNIFLORA LOISEL.

Spartina alterniflora, salt marsh cordgrass, is the dominant angiosperm of a large majority of regularly flooded marshes of the Atlantic and Gulf coasts of the United States. In Louisiana, this species often occurs in two distinct zones: a more productive streamside site (adjacent to tidal creeks), and a less productive and sparsely populated inland area. Reddish-brown deposits are present on the roots of streamside Spartina and visually absent from the roots of inland plants. A study of streamside roots using scanning electron microscope and energy dispersive X-ray microanalysis demonstrated that the coatings are restricted to the outer cell wall of the epidermis and are composed primarily of iron. Roots of inland plants have minor iron deposits. Citrate-dithionite extraction of the coatings and subsequent atomic absorption spectrophotometric analysis confirmed these deposits to be iron, although some manganese was present. Approximately 50 times more iron was found on streamside roots compared to roots from inland plants. These results indicate a better developed oxidized rhizosphere associated with streamside Spartina roots than the inland and, hence, the potential for a more favorable environment in which nutrient uptake may proceed.     

空心莲子草营养器官结构与三萜皂苷动态积累的关系

采用组织化学定位、显微制片技术和三萜皂苷定量分析方法对空心莲子草营养器官结构与三萜皂苷类物质积累关系进行了研究。结果表明：空心莲子草宿根、根状茎、茎和叶中均有三萜皂苷物质的积累,叶和根状茎内含量十分丰富。在相同采收期内含量依次为：叶＞根状茎＞根＞茎,叶中主要积累于栅栏组织细胞内。空心莲子草的根和根状茎横切面均属于异常结构,具有成同心环状排列的三生维管束。在宿根和根状茎的次生韧皮部、栓内层、三生韧皮部和结合组织内均有三萜皂苷的分布,三生结构在宿根和根状茎中占有主要地位,是三萜皂苷积累的主要场所。在不同采收期内叶、根状茎和根中三萜皂苷的积累趋势基本一致,均随生长期的增加而递增。空心莲子草茎的横切面由表皮、皮层、维管束和髓腔组成,仅部分皮层细胞和初生韧皮部内有三萜皂苷分布。     

Investigation of iron-containing products from natural and laboratory cultivated Sphaerotilus-Leptothrix bacteria

Bacterial biomass collected from sheath-forming bacteria of the genera Sphaerotilus and Leptothrix was collected from a high-mountain natural stream water source. The elemental constitution and oxide phases of the products after selective cultivation of the bacteria on two different elective media using neutron activation analysis (NAA), electron microscopy (SEM, TEM), and X-ray diffraction (XRD) were studied. A high enrichment level of iron was revealed by the NAA technique in cultivated isolates as compared to the reference sample from nature. Three types of iron oxide compounds were established after cultivation in Adler’s medium: lepidocrocite (γ-FeOOH), magnetite (Fe₃O₄), and goethite (α-FeOOH). The cultivation in the Isolation medium yielded a single phase, that of goethite, excluding one sample with a distinguishable amount of lepidocrocite. XRD and EM investigations show that the biogenic oxides are nanosized. Our study exemplifies the possibilities of the biotechnology approach for obtaining, under artificial conditions, large quantities of iron-containing by-products that could be of further used in appropriate nano- and biotechnologies.     

Nitrogen fixation by Anabaena cylindrica

Hydrogen-supported nitrogenase activity was demonstrated in Anabaena cylindrica cultures limited for reductant. Nitrogen-fixing Anabaena cylindrica cultures sparged in the light with anaerobic gases in the presence of the photosynthesis inhibitor DCMU slowly lost their ability to reduce acetylene in the light under argon but exhibited near normal activities in the presence of 11% H₂ (balance argon). The hydrogen-supported nitrogenase activity was half-saturated between 2 and 3% H₂ and was strongly inhibited by oxygen (50% inhibition at about 5–6% O₂). Batch cultures of Anabaena cylindrica approaching stationary growth phase (“old” cultures) lost nitrogenase-dependent hydrogen evolution almost completely. In these old cultures hydrogen relieved the inhibitory effects of DCMU and O₂ on acetylene reduction. Our results suggest that heterocysts contain an uptake hydrogenase which supplies an electron transport chain to nitrogenase but which couples only poorly with the respiratory chain in heterocysts and does not function in CO₂ fixation by vegetative cells.