bluuebunny/crossref_metadata_2025 huggingface dataset:
Biosynthesis and root exudation of citric and malic acids in phosphate‐starved rape plants
Authors: HOFFLAND ELLIS , VAN DEN BOOGAARD RIKI , NELEMANS JAAP , FINDENEGG GÜNTER
Published: September 2010

summary

Rape (Brassica napus L.) plants are efficient users of rock phosphates. This has been ascribed to the excretion of malic and citric acids from the roots during phosphorus deficiency, resulting in a decrease of the pH in the rhizosphere and a consequent solubilization of the rock phosphate. In this paper the biosynthesis and excretion of organic acids were investigated, partly by comparing physiological reactions to P deficiency of rape with those of an inefficient user of rock phosphate from the same family, hedge mustard (Sisymbrium officinale Scop.). In the leaves of both species, both citrate levels and phosphoenolypyruvate carboxylase were nearly doubled in P–deficient plants, and the citrate/sugar ratio in the phloem exudate into EDTA solution was doubled as well.

After exposure of the shoots of rape plants to 14CO2 in the light, the specific activities of citrate in the root and in the nutrient solution were ten times higher than those of malate, and also much higher than the respective activities of citrate in P–sufficient controls. It is suggested that citrate produced in the leaf is exported to the roots, where it is accumulated in the excretion region. Malic acid which is prevailing in the exudate is probably newly–synthesized within the excreting root segment. When no phosphate is supplied, this excretion zone is located 1–2 cm behind the root tips. However, when rock phosphate is applied locally this zone shifts along the root to that part which is in direct contact with the rock phosphate particles. No accumulation and excretion of organic acids could be observed with the roots of P–deficient Sisymbrium.
Evidence against a role for phytochelatins in naturally selected increased cadmium tolerance in Silene vulgaris (Moench) Garcke
Authors: DE KNECHT JOOP A. , KOEVOETS PAUL L. M. , VERKLEIJ JOS A. C. , ERNST WILFRIED H. O.
Published: September 2010

summary

The production of phytochelatins in roots of both cadmium–sensitive and cadmium–tolerant plants of Silene vulgaris (Moench) Garcke in response to Cd supply was recorded over a 7–day growth period. At the same level of Cd, sensitive plants produced more phytochelatins than tolerant ones. In sensitive roots this higher production of PCs was associated with a higher Cd content within one day. From the third day, however, Cd contents were similar, but the difference in PC production persisted. Exposure to buthionine sulphoximine strongly inhibited the production of phytochelatins in roots during cadmium treatment in both sensitive and tolerant plants, but only affected root growth of sensitive plants. Sensitive plants exhibited a higher Cd uptake, which was manifested in a higher Cd accumulation in the shoot. It is concluded that differential cadmium tolerance mechanism in Silene vulgaris is not due to differential production of phytochelatins.
Carnivory in pitcher plants of the genus Heliamphora (Sarraceniaceae)
Authors: JAFFE KLAUS , MICHELANGELI FABIÁN , GONZALEZ JORGE M. , MIRAS BEATRIZ , CHRISTINE RUIZ MARIE
Published: September 2010

summary

Field studies of Heliamphora nutans Benth., H. heterodoxa Steyerm., H. minor Gleason, H. ionasii maguire and H. tatei Gleason in the Guayana Highlands of Venezuela, show that the last named species is a true carnivore, possessing all of the following traits: attraction of prey through special visual and chemical signals, trapping and killing of prey, digestion of prey through secreted enzymes, presence of commensals, presence of wax scales aiding in the capture of prey, and absorption of nutrients. The other species possess all traits except they seem neither to secrete proteolytic enzymes nor produce wax scales. The pattern of the carnivorous syndrome among Heliamphora species suggests that the carnivorous habit has evolved in nutrient–poor habitats to improve the absorption of nutrients by capturing mainly ants and only H. tatei further evolved mechanisms for rapid assimilation of organic nutrients and for capturing a variety of flying insects. The carnivorous traits are lost in low light conditions, indicating that nutrient supply is limiting only under fast growth.
Vegetational succession, acidification and allogenic events as recorded in F landrian peat deposits from an isolated Fenland embayment
Authors: WHEELER A. J.
Published: September 2010

summary

Palaeoecological investigations have been carried out at Wood Fen including pollen and macrofossil analysis. The vegetational history is related to other Fenland sites and is dated by radiocarbon. The base of the vegetational record is dominated by Quercus, Tilia, Corylus/Myrica, Taxus and Ulmus pollen, envisaged as components of the pre‐fen woodland. A rise in the water table resulted in the accumulation of peat which has been correlated with the deposition of a marine/brackish clay (‘fen clay’) in the west of the basin dated at between 4150 BP and 3800 BP. A rise in the acidophilous flora occurred at 3615 BP represented by a change from monocotyledonous to Sphagnum peat and subsequent colonisation by Pinus. Loss–on–ignition data suggests that the colonization by pine was interrupted by a brief flooding episode and subsequently terminated by a major rise in the regional water level with an inferred date of between 3300 BP and 3000 BP, based on comparison with other sites. The high water table probably prevented development to raised bog although an acidophilous flora persisted until a return to eutrophic alder carr at the top of the profile.

The nature of the autogenic succession and acidification is discussed and the chronostratigraphic relationships of allogenic influences are considered.
Holocene vegetation history of Flinders Island
Authors: LADD P. G. , ORCHISTON D. W. , JOYCE E. B.
Published: September 2010

summary

Two swamp sites on Flinders Island in Bass Strait provide evidence of vegetation cover for the period 10000 BP to present. Steppe vegetation in which Compositae Liguliflorae taxa and chenopods were important was present on the Flinders Island part of the Bassian Isthmus during the earliest part of the record. However, it was replaced by eucalypt forest or woodland with a grassy understorey and some shrubs as sea level rose to form the present island by 6000 BP. The eucalypt dominated vegetation became less important about 940 BP when Callitris became prominent until very recently. This change may be related to a drier climate.

Flinders Island is one of the few sites in Australia where humans were absent for an extended time (c. 4700 to 200 BP) during the Holocene. There is no particular indication of pollen or charcoal changes which can be related to the disappearance of humans from the island. However, at Killiecrankie Swamp the arrival of Europeans 200 yr ago probably caused the increased charcoal input to the swamp sediments and the vegetation change observed. Likewise Middle Patriarch Swamp records changes due to clearing and swamp drainage in the most recent times. The fact that the swamp deposits contain charcoal and pollen, together with the density of swamps on the eastern side of the island means the area is very favourably placed to provide detailed information on firing regimes unaffected by humans, in a sclerophyll vegetation very similar to that in large areas of southeastern Australia.

In the light of the pollen evidence from this study and that from other southeastern mainland and Tasmanian sites it is suggested that the apparent prominence of Casuarina in the southwest of Victoria and southeast of South Australia during the early Holocene was due to local soil factors and drier climate. Later changes in soil and climate led to a decrease in Casuarina and increase in Eucalyptus.
Evolutionary origins and natural functions of fructans – a climatological, biogeographic and mechanistic appraisal
Authors: HENDRY GEORGE A. F.
Published: September 2010

Genes for fructan synthesis arose in plants on several occasions ranging from the Cambrian (in Dasycladales‐like algae), the late Devonian (in Jungermannialian liverworts) through to the Tertiary (six orders of angiosperms, including the evolutionarily advanced Poales and Asterales). The widespread occurrence of fructan processing in eubacteria may hove been in response to the rapidly increasing availability of fructan in the angiosperms and the expansion of grass‐eating mammals in the mid‐Tertiary. The origin mid evolution of the majority of fractan‐rich angiosperm families, from fossil evidence, occurs in a relatively narrow window from the Oligocene to the mid‐Miocene (30–15 Ma ago). These epochs coincide with the development in several regions, in most continents, of seasonal rainfall and more prolonged periods of water shortage. The replacement of tropical and temperate forests by a fructan flora in drylands and semi‐arid to arid regions was world‐wide and accounts for tile rapid expansion of fructan‐rich families in the mid‐Tertiary and again in drier phases of the early Holocene. The natural distribution of the contemporary fructan Mora confirms the association of fructan‐rich families with temperate through to sub‐tropical regions with seasonal or more sporadic rainfall and not with regions of low temperatures. It is argued that the natural function of fructan is in maintaining growth during periods of limited water availability. The function of fructan as a vacuolar and soluble carbohydrate in osmoregulation and in Growth by cell inflation rather than temperature‐dependent cell division is given as the most likely explanation for the global success of the 15% of the angiosperm flora which store fructan as a principal reserve carbohydrate.
Purification and properties of an invertase with sucrose: sucrose fructosyltransferase (SST) activity from the roots of Cichorium intybus L.
Authors: VAN DEN ENDE WIM , VAN LAERE ANDRÉ
Published: September 2010

An invertase was purified From Cichorium intyhbus L. roots by a combination of ammonium sulphate precipitation. Concanavalimn A affinity chromatography, anion exchange chromatography and gel filtration. A 230–fold purification and a final specific activity of 2.7U per mg protein was obtained. The enzyme has a M, of 93000 as estimated by gel filtration ans after SDS‐PAGE a single bannd with a M, of 50000 was found. Optima activity was found between pH 5 and pH 5.5.At low substrate concentrations equal amounts of fructose and glucose were produced (apperant Kw 55 mm). At higher sucrose concentrations progressively more isokestose was produced and fructose synthesis was inhibited. The high sucrose concentrations needed for isokestose systhesis do not support a physiological role for the enzyme in fructan biosynthesis.
Growth dynamics and associated mycorrhizal fungi of little bluestem grass [Schizachyrium scoparium (Michx.) Nash] on burned and unburned sand prairies
Authors: DHILHON SHIVCHARN S. , ANDERSON ROGER C.
Published: September 2010

WP examined the influence of burning on little bluestem grass productivity and its vesicular‐arbuscular mycorrhizal (VAM) fungal associates in a sand prairie community over (bar growing seasons (1586‐4). Above‐and below‐ground productivity was higher on the burned sites than on the unhurried sites. Percent VAM funga1 colonization levels were significantly burned sites than on the unburned sites. In contrast, early in the growing season, colonized and specific rout lengths were longer on the burned site than on the unburned sites but differences were not always significant. Roots of plants on the burned sites supported more fungal biomass than roots on the unburned sites especially during the early growing season. However, colonization d:it;i suggest that the fungi were unable to keep up with the greater below‐ground production of plants on the burned prairies. Mycorrhizal inoculum potential levels of little bluestem rooi zone and randomly collected soil and VAM fungal spore densities were lower on the burned sites than the unburned sites during the year of the burn. Above‐ and below‐ground tissue samples showed significantly higher concentrations and accumulations of several inorganic, nutrients on the burned site early and later in the growing season.However, in contrast, plants on the unburned sites had greater nutrient‐use efficiencies for several nutrients than plants on the burned sites. Lower nutrient‐use efficiencies of plants on burned sites may in pan be due to the onset of harsher environmental conditions during the growing season and/or to associated VAM fungi‐ VAM fungi associated with plants on the burned sites are likely a carbon drain on these plants, supporting greater fungal biomass, and hence, plants on burned sand prairie sites may not benefit from their VAM fungal association especially early in the growing season.
Antifungal compounds from the roots of mycotrophic and non‐mycotrophic plant species
Authors: PAUL SCHREINER R. , KOIDE ROGER T.
Published: September 2010

The roots of twelve plant spades From bath mycotrophic (hosts of YAM fungi) and non‐mycotropic (non‐hosts) families were examined for their ability to produce antifungal compounds. A TLC bioassay was used with the fungus Cladosporium cucumerimun Ellis & Arch. Of the non‐mycotrophic species, five species from the Brassicaceae [Brassica kaber (DC.) Wheeler, Brassica napus L., Brassica campestris L.,Thlaspi arvense L., Rhaphanus raphasnistrum L.] had detectable antifungal compounds in extracts from roots, while two species from the Chenopodiaceae (Spinacea oleracea L., Beta vulgaris L.) and one species from the Amaranthaceae (Amaranthus retroflexus L.) did not. One mycotrophic species (Daucus carota L.) also had a detectable antifungal compound in root extracts, while three other mycotrophic species (Lactuca sativa LK., Abutilon theophrasti Medic., sorghum bicolor L.) did not. Chloroform extracts of B. kaber roots appeared to have the greatest quantity of extractable antifungal compounds as detarmined by the TLC bioassay. In a separate experiment, chloroform extracts from B. kaber roots greatly inhibited the germination of spores of Glomus etunicatum Becker and Gerd., while extracts from a number of other mycotrophic and non‐mycotrophic plant roots were only marginally inhibitory. Three antifungal compounds in chloroform extracts from B. kaber roots were shown to be derived from glucosinolates. The predominant antifungal compound was identified as +‐hydroxybenzyl isothiocyanate, the isothiocyanate produced by the action of myrosinase on glucosinalbin. The data provide evidence of a possible role for glucosinolates in determining the non‐mycotrophic status in B. kaber.
Factors affecting appressorium development in the vesicular–arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe
Authors: GIOVANNETTI MANUELA , AYIO LUCIANO , SBRANA CRISTIANA , SILVIA CITERNESI ANNA
Published: September 2010

Investigations on the luck of appressorium formation in the roots of the non‐host plant Lupinus albus L. showed that root exudates do not inhibit mycelial growth of the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, but that they hinder hyphal attachment and fungal recognition of roots. Exudates do not stimulate hyphal proliferation in the rhizosphere. G. mosseae hyphae were able to recognize and attach to excised root of both lupin and host plants, forming swellings resembling apressoria. No growth of G. mosseae hyphae was observed around simulated roots consisting of nylon, silk, polyamide and glass threads, whereas appressoria were formed on heterologous hyphae of VAM fungal species. The hypothesis that a purely thigmotropic stimulate could trigger hyphal attachment and the further differentiation of appressoria was excluded.
Photosynthetic activity of Scots pine (Pinus sylvestris L.) needles during winter is affected by exposure to SO2 and NO2 during summer
Authors: STRAND MARTIN
Published: September 2010

A 50‐year‐old stand of Scots pine (Pinus sylvestris L. with a mean height of 12 m. located 60 km northwest of Umeå in northern Sweden, was furnigated with SO2 and NO2 from June to September in 1998 and 1989. SO2 and NO2 were released from vertical vent‐pipes arranged ina circle with a diameter of 60m. During fumigation, the average concentrations of both SO2 and NO2 in the centre of the circle were 10–15 nl l‐1. Measurements of CO2 evolution and chlorophyll a fluorescence of needles were made under laboratory conditions. For samples collected in January of 1989 and 1990, the light‐ and CO2‐saturated rate of O2 evolution at 20°C in needles of trees exposed to SO2+ NO2 was lower than in needles of trees exposed to ambient clean air. Furthermore, the photochemical efficiency of photosystem II, as indicated by the ratio of variable to maximum fluorescence was lower for needles of fumigated trees, in samples collected in December 1989 and January 1990. These results suggest that low concentrations of SO2+ NO2 may have significant long‐term effects n the photosynthetic apparatus in needles of Scots pine. The observed responses may be triggered by unfavourable environmental conditions during autumn and winter. However, no evidence for a greater sensitivity to prolonged freezing stress at –19°C was found in needles of trees exposed to SO2+ NO2 when measured in December or January.
Response of radish to multiple stresses
Authors: PELL E. J. , SINN J. P. , ECKARDT R , VINTEN JOHANSEN C. , WINNER W. E. , MOONEY H. A.
Published: September 2010

Experiments were conducted 10 determine what impact ozone (O3) and/or soil moisture deficit had on tile growth and development of radish plums. Plants of Raphanus sativus L. Cherry Belle and Raphanus sativus × raphanistrum (wild type) grown in modified open‐top chambers, were treated with O3 and/or subjected to reduced soil moisture throughout growth and development. Experiments were performed in the spring and autumn of 1989. Plants nr both genotypes exhibited a more adverse response to soil moisture deficit in the spring experiment and in O3, in the autumn experiment. The higher light intensity and temperature prevailing in the spring, in contrast to those during the autumn, were thought to favour a negative impact of reduced soil moisture. The spring conditions fostered high relative growth rate and more rapid water loss by the shoot on both a relative and absolute basis. These same conditions may have placed the plants in a physiological state which minimized toxicity by O3. Carbon partitioning in the spring favoured reproduction while the autumn carbon was preferentially partitioned to the hypocotyl and foliage for Cherry Belle and Wild Type, respectively. The importance of these partitioning differences between genotype was explored as it related to injurious and compensatory responses to the two Stresses. Since the plants were not equally sensitive to reduced soil moisture and O3, in the same experiments, interactions were frequently absent. When interactions occurred, O3 injury was reduced in plants also grown in soil with reduced moisture content.
Pollination‐dependent female reproductive success in a self‐compatible outcrosser, Asphodelus aestivus Brot.
Authors: SCHUSTER AYELET , NOY‐MEIR IMANUEL , HEYN C. CLARA , DAFNI AMOTS
Published: September 2010

Experiments were carried out, during three years (1986‐8), on a population of Asphodelus aestivus Brot. (Liliaceae) in n semi‐arid environment, to test whether seed production of plants was limited by quantity and/or quality of pollen supply. The natural pollinator are mainly solitary bees.

The fraction pf flower setting MM varied from 8 to 40% between years. Fruit set of plants caged to exclude inserts was less than 3%. Fruit set was increased by artificial pollination of flowers with their own pollen to 43‐64%, This indicates that the plant is self‐compatible, but due to the position of the anthers and stigma, insect visits are required for effective pollination. Cross‐pollinated caged flowers set yet more fruits (59–82%) and much more (2‐4 times) full seeds per fruit than self‐pollinated flowers.

The artificial addition of cross‐pollen to flowers, in the natural environment, increased the moan number of full seeds per flower on the whole plant. Thus, natural reproduction was limited by insect pollination.

A quantitative Biffed was indicated by a strong positive association between the number of pollen grains on a stigma and the probabilities of the flower maturing a fruit and of its ovules setting seeds. Furthermore, in 20‐60% of [lowers in the population, stigma loads were less than 13 pollen grains, which indicated very low probability of fruit maturation.

A qualitative response was shown by the positive effect of artificially added cross‐pollen on the number of full vs. empty seeds, an effect similar to that of cross‐ vs. self‐pollination in caged plants.

The proportion of full seeds developing in a clone of Asphodelus in the natural population was inversely related to the proportion of inflorescences in its neighbourhood that belonged to the same clone, which suggests that fertility is limited by an excess of pollen from the same clone being supplied by insects.

It is concluded that female reproductive success of Asphodelus aestivus in its natural environment depended on both the amount and origin of the pollen supplied by us pollinators.
Variation within white clover (Trifolium repens L.) for phenotypic plasticity of morphological and yield related characters, induced by phosphorus supply
Authors: CARADUS J. R. , HAY M. J. M. , MACKAY A. D. , THOMAS V. J. , DUNLOP J. , LAMBERT M. G. , HART A. L. , VAN DEN BOSCH J. , WEWALA S.
Published: September 2010

The range of variation for phenotypic plasticity for morphological and yield related characters caused by varying the level of phosphorus (P) supply, was determined both across and within cultivars of white clover [Trifolium repens L.). Analysis of variance was used as a quolitative measure of phenotypic plasticity (i.e. significance of P effect) and to determine differential phenotypic plasticity (i.e. significance of genotype × P interaction). Quadratic P response curves were calculated and plasticity measured quantitively as maximum slope.

While all plant characters measured exhibited plasticity, yield related characters were generally more plastic titan characters associated with plant morphology when compared using a scale independent test based on F‐ratios. Internode length and leaf size were the must plastic morphological characters and it is suggested that they are chiefly responsible for the resultant yield response of white clover to increased phosphate fertiliser supply. There was highly significance of variation for plasticity among genotypes for all plant characters measured, although within cultivars, significance of variation for plasticity among genotypes varied with cultivar. Magnitude of plasticity of genotype was not closely related to origin of cultivar. plant type, growth or breeding history. Many characteristics varied independently for an increase or decrease in plasticity of characters is an achievable option.
Genecological studies of groundsel (Senecio vulgaris L.). IV. Rate of development in plants from different habitat types
Authors: THEAKER A. J. , BRIGGS D.
Published: September 2010

In order to test the hypothesis that precocious variants might be at a selective advantage in well‐weeded sites, ripen pollinated achenes of Senecio vulgaris L. were collected in eastern Britain from three populations representative of each of live habitat types (botanic gardens, field margins, inland and coastal sandy areas and shingle beaches) Some subject to weeding and cithers not. Progenies of a number of seed‐parents (families) were grown in a garden trial, and life‐history and reproductive characteristics were recorded, in particular the rate of development from sowing, with synchronous germination, to first fruiting. Populations from botanic gardens were characterized by families exhibiting precocious reproduction, a finding which supports oru initial hypothesis. However, a degree of variation was detected in samples from all three botanic gardens ‐ Orford, Kew and Cambridge ‐ confirming the results of an earlier study of groundsel in the University Botanic Garden, Cambridge. In contrast, samples from maritime shingle beaches had a slower rate of development. There was no evidence of population variation, suggesting that genetic drift or founder effects might be important or that there may be selection for a narrow range of phenotypes, in such areas. Furthermore, at Shingle Street, Suffolk, there was evidence of sharp local differentation between plants from the single beach and from an arable field margin, 50m away, located behind sea defence. The characteristics of plants from other habitat types are discussed in relation to the apparent selection pressures imposed by different land use. Our results provide evidence of trade‐offs in life‐history evolution, e.g. the precocious variants were comparatively dwarf at first fruiting and shorter‐lived.
Taphonomy of plant remains on floodplains of tundra rivers, present and Pleistocene
Authors: WEST R. G. , ANDREW R. , PETTIT M.
Published: September 2010

Plant remains in fine sediments on the floodplains of the Sagavanirklok and Atigun Rivers on the North Slope of Alaska have been analysed and related to sedimentary processes. The pollen spectra are very different from those from pool or surface samples from the wider regional vegetation. The difference is explained by rapidity and time of deposition. The macroscopic remains include elements of the floodplain and moist tundra communities, and include shrubs, heath taxa and herbs. The relation between the macroscopic remains and pollen spectra is examined. The results are compared with pollen spectra from Pleistocene cold‐stage fluviatile sequences in East Anglia, where similar differences have been found between the pollen spectra and macroscopic remains from sediments of floodplains and pools. The importance of a knowledge of taphonomy in interpreting pollen and macroscopic assemblages is stressed.
Varying the ratio of 15N‐labelled ammonium and nitrate‐N supplied to perennial ryegrass: effects on nitrogen absorption and assimilation, and plant growth
Authors: BAILEY J. S.
Published: September 2010

A detailed study was carried out to obtain information on the relative rates of NH4+ and NO3−‐N uptake and assimilation by perennial ryegrass (Lolium perenne L.), when grown in soil and supplied with different ratios of NH4+ and NO3−‐N. Following two preliminary defoliations, plants were supplied with 15N‐(differentially) labelled NH4+ and NO3−‐N in three different ratios (20∶80, 50∶50 and 80∶20), followed by sequential destructive harvests of shoots and roots taken at four points during a 35‐d regrowth period. When supplied with equimolar concentrations of NH4+ and NO3−‐N, perennial ryegrass absorbed both forms of nitrogen at almost identical rates; and even when the two N forms were supplied in widely disproportionate concentrations, both forms appear to have been absorbed at equal rates, at least until the supply of the minor nitrogen component in each treatment was almost exhausted, i.e. by day 3 of regrowth. It is suggested that this matching of NH4+ and NO3−‐N absorption rates by plants maximizes the advantages and minimizes the disadvantages associated with the exclusive use of either form of nitrogen, and thereby optimizes the potential for vegetative and reproductive regeneration. Fifteen days after the application of 15N‐labelled fertilizer, shoot and root yields differed little between treatments. However, plants grown with NH4+ and NO3−‐N at a ratio of 50∶50 had accumulated significantly more root (soluble) carbohydrate than those in the other two treatments. Consequently, when subjected to defoliation at day 15, these former plants were clearly in the best position to re‐mobilize root carbohydrate and initiate shoot regeneration. However, further work is needed in order to determine whether or not this finding holds true for plants subjected to a multiple (bi‐ to tri‐weekly) defoliation regime, e.g. in a grazing situation.
Aerobic nitrogen fixation is confined to a subset of cells in the non‐heterocystous cyanobacterium Symploca PCC 8002
Authors: FREDRIKSSON CHARLOTTA , MALIN GILLIAN , SIDDIQUI PIRZADA J. A. , BERGMAN BIRGITTA
Published: September 2010

Symploca PCC 8002 Kützing is a filamentous cyanobacterium that lacks the specialized cells, known as heterocysts, that protect nitrogenase from O2 in most aerobic N2‐fixing cyanobacteria. Nevertheless, Symploca is able to carry out N2 fixation in the light under aerobic conditions. When cultures were grown under light/dark cycles, nitrogenase activity commenced and increased in the light phase and declined towards zero in the dark. Immunolocalization of dinitrogenase reductase in sectioned Symploca trichomes showed that the enzyme was present only in 9% of the cells. These cells lacked any obvious mechanical protection against atmospheric O2 and their ultrastructural characteristics were similar to those of cells that did not contain any dinitrogenase reductase. The nitrogenase‐containing cells possessed carboxysomes that were rich in ribulose‐1,5‐bisphosphate carboxylase/oxygenase and phycoerythrin, a light harvesting pigment of PS II. This indicates that these cells had a capacity for both N2 fixation and photosynthesis. The significance of the localization pattern for dinitrogenase reductase is discussed in the context of N2 fixation in Symploca PCC 8002.
Metabolic responses of Norway spruce (Picea abies) trees to long‐term forest management practices and acute (NH4)2SO4 fertilization: transport of soluble non‐protein nitrogen compounds in xylem and phloem
Authors: WEBER PAUL , STOERMER HEIKE , GEßLER ARTHUR , SCHNEIDER STEPHAN , VON SENGBUSCH DOMINIK , HANEMANN ULRIKE , RENNENBERG HEINZ
Published: September 2010

From laboratory experiments with seedlings and young trees of Norway spruce (Picea abies L. Karst.), a cycling pool of soluble non‐protein N compounds is thought to be indicative of the N‐nutritional status of trees. In order to test whether this assumption can be transferred to mature trees grown in the field, xylem sap and phloem exudate were collected from spruce trees in two remote forest stands: (1) a N‐limited stand (Villingen site), and (2) a stand where trees are sufficiently supplied with N from the soil (Schluchsee site). Trees at these sites were c. 80–100 (Villingen site) and c. 40–60 (Schluchsee site) yr old. In addition to untreated control areas, one entire watershed area at both sites was subjected to (NH2)2SO4 fertilization to the soil.

In the xylem sap of the spruce roots at both sites Gln, Asp and Arg were the dominant total soluble non‐protein nitrogen (TSNN) compounds. In the xylem sap of the trunk and the twigs Arg was virtually absent and Gln plus Asp dominated TSNN. On average, TSNN in the xylem sap of trees at the Schluchsee site was 1·5–2‐fold higher than those at Villengen. Highest TSNN contents in the xylem sap were found during growth and development of current year tissues, while the lowest TSNN contents were found in summer. At the Villingen site (NH4)2SO4 fertilization caused an increase in the Gln content in the xylem sap of all tree sections analysed as well as an increase in the Arg content in the xylem sap of the roots. At the Schluchsee site only a small increase in TSNN contents of the xylem was observed, mostly in the xylem sap of the roots. In phloem exudates TSNN contents were much higher in trees on the Schluchsee than on the Villingen site. The seasonal pattern of TSNN in phloem exudates was similar to the seasonal pattern found in the xylem sap. During spring and early summer Gln was the predominant TSNN compound in phloem exudates, but during late summer and autumn Arg became predominant. At the Villingen site (NH4)2SO4 fertilization caused a significant increase in TSNN contents in phloem exudates of twigs and roots, but at Schluchsee an increase in TSNN was found only in phloem exudates of the roots. At both field sites Arg that was not transported to the shoot by xylem transport, was allocated from the leaves to the roots by phloem transport and was cycled within the root system by both xylem and phloem transport. From these results it is calculated that shoot‐to‐root signalling by long‐distance transport of amino compounds can also contribute to the regulation of N‐nutrition of mature spruce trees. Apparently, the internal cycling of individual N compounds within spruce trees differs considerably.
Relationships between atmospheric nitrogen inputs and the vertical nitrogen and phosphorus concentration gradients in the lichen Cladonia portentosa
Authors: HYVÄRINEN M. , CRITTENDEN P. D.
Published: September 2010

The relationship between precipitation chemistry and the concentrations of nitrogen ([N]) and phosphorus ([P]) in the cushion‐forming lichen Cladonia portentosa (Dufour) Coem. (=C. impexa (Harm)) was investigated. Samples of C. portentosa were collected from heathlands and upland moorlands close to 31 rural sampling stations in the UK Acid Deposition Monitoring Network, which provides data on wet deposition and NO2 concentrations in air. The [N] and [P] were measured in the top 5 mm of lichen thalli (thallus apices) and also in a horizontal stratum between 40–50 mm from the apices (thallus base). The [N] (per unit dry mass) was 0·08–1·82% and [P] was 0·04–0·17%, depending on collection site and lichen fraction analysed. Concentrations of both elements were c. 2–5 times greater in the apices than in the basal strata, and [N] and [P] values in each stratum were strongly positively correlated. Lichen [N] was positively correlated with N deposition: this relationship was stronger when using [N] values for thallus bases than for the apices. By contrast, thallus [N] was poorly correlated with [N] values in precipitation. When [NO2] in air was included together with NO3− deposition in a linear regression model explaining thallus base N, the model fit was significantly improved, whereas modelled values of NH3 deposition rate for the heathland sites did not correlate with lichen [N]. It is suggested that the proportionately greater enrichment of [N] in the thallus base might reflect a perturbation of internal recycling of thallus N at polluted sites. Thallus [P] was generally weakly linked to wet N deposition but positively correlated with [NO2] in air. It is not known whether the trend for increasing thallus [P] values indicates decreasing lichen growth rate and reduced growth dilution of P in polluted areas, or is due to regional variation in P deposition rate.
Development of the leafy shoot in Sphagnum (Bryophyta) involves the activity of both apical and subapical meristems
Authors: LIGRONE ROBERTO , DUCKETT JEFFREY G.
Published: September 2010

This light‐ and electron‐microscope study of four species of Sphagnum reveals that stem elongation involves meristematic activities unique to the group and hitherto unrecognized. The internal tissue of the mature stem arises by the concerted activity of an apical (primary) and a subapical (secondary) meristem. The primary meristem comprises the immediate derivatives of the single apical cell. Following a small number of divisions, the primary derivatives differentiate into highly vacuolate parenchymatous cells with a storied arrangement. Subsequently, the large vacuoles are replaced by numerous small vacuoles and the cells then divide repeatedly, by transverse septa, producing files of about nine short cells. Finally, ninefold elongation of these secondary cells is responsible for extension growth of the main stem below the mature capitulum. An early step in primary differentiation is the confinement of pre‐existing plasmodesmata to distinct pitted areas. Further enlargement of the cells during primary and secondary differentiation involves the thickening of non‐pitted wall areas, followed by expansion and thinning out, while the pitted areas remain virtually unchanged. A cortical array of microtubules is regularly found in association with non‐pitted wall areas, while the unexpanded pitted areas are associated with smooth endoplasmic reticulum showing continuity with desmotubules. Though sharing much the same cytology as the conducting cells in bryoid mosses, in terms of their development the central stem cells in Sphagnum are not homologous with those of other mosses. The unique mode of stem development may be an important factor in the ecological success of Sphagnum.
The leafy stems of Sphagnum (Bryophyta) contain highly differentiated polarized cells with axial arrays of endoplasmic microtubules
Authors: LIGRONE ROBERTO , DUCKETT JEFFREY G.
Published: September 2010

Contrary to the long‐held belief that, internal to the cortical sterome, the central region of Sphagnum stems comprises unspecialized parenchyma, the present light‐ and electron‐microscope study has revealed that these cells in fact have a highly specialized cytoplasmic organization. Their key features are: (a) the absence of large central vacuoles; (b) a spindle‐shaped nucleus positioned internally; (c) a prominent axial system of endoplasmic microtubules associated with the nucleus, mitochondria, pleomorphic vacuoles, and membrane‐bounded tubules and vesicles; (d) a distinct cytoplasmic polarization, with the cellular region near the capitulum being richer in organelles than the basal region; and (e) a high frequency of plasmodesmata in the cross walls with an enlarged median region containing no discernible desmotubule. Such a distinctive combination of cytological features has been hitherto only described for putative food‐conducting cells in bryoid mosses. The results introduce a major new character common to Sphagnum and bryoid mosses and strongly suggest that this cytological organization underlines cellular specialization in symplasmic transport.
Seed dormancy and the control of germination
Authors: Finch‐Savage William E. , Leubner‐Metzger Gerhard
Published: September 2010

Seed dormancy is an innate seed property that defines the environmental conditions in which the seed is able to germinate. It is determined by genetics with a substantial environmental influence which is mediated, at least in part, by the plant hormones abscisic acid and gibberellins. Not only is the dormancy status influenced by the seed maturation environment, it is also continuously changing with time following shedding in a manner determined by the ambient environment. As dormancy is present throughout the higher plants in all major climatic regions, adaptation has resulted in divergent responses to the environment. Through this adaptation, germination is timed to avoid unfavourable weather for subsequent plant establishment and reproductive growth. In this review, we present an integrated view of the evolution, molecular genetics, physiology, biochemistry, ecology and modelling of seed dormancy mechanisms and their control of germination. We argue that adaptation has taken place on a theme rather than via fundamentally different paths and identify similarities underlying the extensive diversity in the dormancy response to the environment that controls germination.

Contents

Summary
501

I.
Introduction
502

II.
What is dormancy and how is it related to germination?
502

III.
How is nondeep physiological dormancy regulated within the seed at the molecular level?
509

IV.
How is nondeep physiological seed dormancy regulated by the  environment? Ecophysiology and modelling
514

V.
Conclusions and perspectives
518

Acknowledgements
519

References
519

Supplementary material
523
The small RNA world of plants
Authors: Bonnet Eric , Van de Peer Yves , Rouzé Pierre
Published: September 2010

RNA has many functions in addition to being a simple messenger between the genome and the proteome. Over two decades, several classes of small noncoding RNAs c. 21 nucleotides (nt) long have been uncovered in eukaryotic genomes, which appear to play a central role in diverse and fundamental processes. In plants, small RNA‐based mechanisms are involved in genome stability, gene expression and defense. Many of the discoveries in this new ‘small RNA world’ were made by plant biologists. Here, we discuss the three major classes of small RNAs that are found in the plant kingdom, namely small interfering RNAs, microRNAs, and the recently discovered trans‐acting small interfering RNAs. Recent results shed light on the identification, integration and specialization of the different components (Dicer‐like, Argonaute, and others) involved in the biogenesis of the different classes of small RNAs in plants. Owing to the development of better experimental and computational methods, an ever increasing number of small noncoding RNAs are uncovered in different plant genomes. In particular the well‐studied microRNAs seem to act as key regulators in several different developmental pathways, with a marked preference for transcription factors as targets. In addition, an increasing amount of data suggest that they also play an important role in other mechanisms, such as response to stress or environmental changes.

Contents

Summary
451

I.
Introduction
452

II.
Small interfering RNAs
453

III.
MicroRNAs
455

IV.
Trans‐acting siRNAs
462

V.
Conclusion and perspectives
462

Acknowledgements
463

References
463
Jasmonate signalling network in Arabidopsis thaliana: crucial regulatory nodes and new physiological scenarios
Authors: Balbi Virginia , Devoto Alessandra
Published: September 2010

Plant development and stress responses are regulated by complex signalling networks that mediate specific and dynamic plant responses upon activation by various types of exogenous and endogenous signal. In this review, we focus on the latest published work on jasmonate (JA) signalling components and new regulatory nodes in the transcriptional network that regulates a number of diverse plant responses to developmental and environmental cues. Not surprisingly, the majority of the key revelations in the field have been made in Arabidopsis thaliana. However, for comparative reasons, we integrate information on Arabidopsis with recent reports for other plant species (when available). Recent findings on the regulation of plant responses to pathogens by JAs, as well as new evidence implicating JAs in the regulation of senescence, suggest a common mechanism of JA action in these responses via distinct groups of transcription factors. Moreover, a significant increase in the amount of evidence has allowed placing of specific mitogen‐activated protein kinases (MAPKs) as crucial regulatory nodes in the defence signalling network. In addition, we report on new physiological scenarios for JA signalling, such as organogenesis of nitrogen‐fixing nodules and anticancer therapy.

Contents

Summary
1

I.
Introduction
2

II.
Key players in the jasmonate biosynthetic and signalling pathways
2

III.
High‐throughput studies add new elements to stress‐activated signalling networks
6

IV.
Novel contribution of kinase cascades to cross‐talk between jasmonate and other defence‐signalling pathways
8

V.
Jasmonates and senescence
10

VI.
New physiological scenarios for jasmonates
11

VII.
Conclusions and perspectives
13

Acknowledgements
13

References
13
Comparison of quality characteristics of full fat and low fat paneer developed from yak milk
Authors: KANDEEPAN GURUNATHAN , SANGMA SUDHIR
Published: September 2010

Growing health concerns of consuming high fat products offer scope to develop low fat foods. Therefore, a study was undertaken to compare quality attributes of full fat and low fat paneer prepared from yak milk. Optimisation of fat to 1% level significantly increased density in yak milk. Moisture and ash significantly increased but yield and fat decreased in low fat yak milk paneer. No significant difference in microbial load was observed between full fat and low fat paneer. An acceptable low fat paneer with improved body and texture can be prepared with 1% fat in yak milk.
Plantations, Resistance and the Greening of the Agrarian Question in Coastal Ecuador
Authors: GERBER JULIEN‐FRANÇOIS , VEUTHEY SANDRA
Published: September 2010

Worldwide, industrial tree plantations are at the origin of a growing number of conflicts between local populations and commercial planters. Such conflicts – which often turn out to be ‘environmental’– have largely remained understudied. By focusing on the establishment of an industrial eucalypt monoculture in a coastal Ecuadorian canton, this paper investigates the effects of the penetration of capital into the rural sphere, emphasizing the resulting resistance campaign of a local NGO originating from a peasant organization. We analyse the evolution of land conflicts in the region – historically as well as operationally during the latest eucalypt campaign. We find that displacement of local peasants is a recurrent theme, while environmental issues have recently been incorporated into the resistance to landowners. We thus argue that the agrarian question also includes – now perhaps more than ever – an environmental dimension, thereby providing space for a fruitful dialogue between political ecologists and students of agrarian conflicts.
Documentation of diabetes care in home nursing service in a Swedish municipality: a cross‐sectional study on nurses’ documentation
Authors: Annersten Gershater Magdalena , Pilhammar Ewa , Alm Roijer Carin
Published: September 2010

Scand J Caring Sci; 2011; 25; 220–226
 
Documentation of diabetes care in home nursing service in a Swedish municipality: a cross‐sectional study on nurses’ documentation

Objectives:  To assess what was documented by Registered Nurses regarding diabetes care in a Swedish municipality’s home nursing service; to what extent diabetes‐related nursing actions were planned for, performed and evaluated according to the goals of metabolic control, treatment and prevention of complications.

Design:  Cross‐sectional study.

Subjects:  Registered Nurses’ documentation of patients with diabetes mellitus (n = 172).

Main outcome measurers:  Number of recorded different nursing actions planned, performed and evaluated.

Result:  The overall standard of records was insufficient. Evaluation of blood glucose levels and metabolic control was documented in 61% of the records; weight was documented in 4% of the records. Blood pressure was recorded in 10%. Ongoing foot ulcers were documented in 21%. Patient education or actions to prevent foot ulcers was not recorded. Tablet and insulin administration were well recorded. The nursing process was not followed.

Study limitation:  Updated medicine lists were missing in many files, this might have resulted in an underestimation of the number of included records.

Conclusion:  The Registered Nurses are responsible for a vulnerable patient group suffering from multi‐organ disease unable to maintain their own diabetes self‐care. Insufficient documentation may lead to impaired quality of care. We suggest that improved documentation routines include a structure of planning, performing and evaluation of metabolic control (blood glucose measurements, Hba1c, weight and nutrition status), complications (regular blood pressure measurements, protective foot care) and education of health care assistants in assisted diabetes self‐care.