bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of different nutrient regimes on the regulation of carbon metabolism in Norway spruce[Picea abies(L.) Karst.] seedlings
Authors: WINGLER ASTRID , EINIG WERNER , SCHAEFFER CHRISTOPH , WALLENDA THOMAS , HAMPP RÜDIGER , WALLANDER HÅKAN , NYLUND JAN‐ERIK 
Published: April 2006

summaryPhosphoenolpyruvate carboxylase (PEPC) activity, fructose 2, 6‐bisphosphate (F26BP), starch and soluble sugar contents were determined m needles and roots of Norway spruce seedlings grown in a semi‐hydroponic cultivation system under different nutrient regimes, tn needles, a surplus of nitrogen caused an increase in specific PEPC activity (up to six times control activity) and F26BP content (up to three times control level) while starch content was reduced. Sucrose contents were not affected. Basically, the responses in root samples were similar. Here, PEPC was highest at an imbalance in nutrition (+ N/ ‐P) F26BP, with root contents being 3‐ to 11 ‐times higher than those in needles, significantly exceeded control values at + N/+ P. The results show that alteration of nitrogen supply leads to marked changes in allocation of carbon between pathways, which is also influenced by P‐nutrition. Pool sizes of F26BP and activity of PEPC are indicators for these changes in leaf as well as in root tissues of Norway spruce.
Leaf age‐structure effects on plant water use and photosynthesis of two wheat cultivars
Authors: VENEKLAAS ERIK , VAN DEN BOOGAARD RIKI 
Published: April 2006

summaryThe wheat cultivars ‘Katya Al’ and ‘Mexipak 65’, grown in pots under field conditions in a Mediterranean climate, differed only slightly in growth and water use on a whole‐plant basis, although Mexipak had a smaller leaf area. When expressed on a leaf area basis, plant biomass increase and transpiration were significantly greater in Mexipak. However, previous gas exchange measurements on the youngest fully expanded leaf showed only minor differences between the two cultivars. The hypothesis that different patterns of leaf ageing contributed to the differences in plant growth and water use was tested by combining leaf demography and gas exchange measurements. Plants were subjected to two moisture treatments: ‘well‐watered’ (frequent, watering to initial soil water content) and ‘intermittent drought’ (five drying‐rewatering cycles). Mexipak had, on average, older leaves than Katya in both treatments because of fast early growth, which in turn was clue to a larger area of individual leaves rather than a faster leaf appearance rate. Stomatal conductance and net photosynthetic rate were nearly the same for the two cultivars, but were considerably reduced by drought and did not fully recover after rewatering. Stomatal conductance and photosynthesis tended to decrease with ape, but effects of age or treatment or their interactions were not significant and could not explain the discrepancy between whole plant and leaf observations. One possible explanation is that age effects‐do exist in leaves older than those investigated. Another explanation may be that changes in microclimatological conditions caused photosynthesis and transpiration to differ from rates measured under standard conditions.
The keel colour polymorphism in Lotus corniculatus L.: differences in internal flower temperatures
Authors: JEWELL JENNIFER , McKEE JUNO , RICHARDS A. J. 
Published: April 2006

summaryIn bright sunshine, temperatures within the apex of the keel of flowers of Lotus corniculatus were consistently higher in dark‐keeled than in light‐keeled individuals. Temperature differences may increase With higher ambient temperatures and averaged 5.7°C at 23.2°C ambient, In overcast conditions, no significant temperature differences between dark‐keeled and light‐keeled flowers Were observed, or light keel temperatures were slightly greater. In general, temperatures within keels were lower than ambient.Within sites, dark‐keeled plants showed a tendency to inhabit colder microsites than did light‐keeled plants. Contrary to some earlier reports, we believe that most clinal variation for keel colour is temperature related.We suggest that there may be an optimum Temperature far pollen germination and pollen rube growth. In cold microsites. dark‐keeled plants would be more fecund, but in warm microsites tight‐keeled plants would set. more seed, thus maintaining the polymorphism found in most sites.
Contribution of ectomycorrhiza to the potential nutrient‐absorbing surface of pine
Authors: ROUSSEAU J. V. D. , SYLVIA D. M. , FOX A. J. 
Published: April 2006

summaryThe increase in potential nutrient‐absorbing surface area of loblolly pine (Pinus taeda L.) seedlings as a result of ectomycorrhizal development was quantified. In one experimental. In one experiment, loblolly pine seedlings were inoculated with Pisolithus tinctorius Pers. Coker (Pt) after having first been grown from seed for 8 wk under a low phosphorus (P) nutrient regime. Eight weeks following inoculation, seedlings were harvested and ail components of the nutrient absorbing system (including the fungal mycelium) were quantified. External mycelium accounted for only 5% of the potential absorbing‐system dry weight, but this mycelium comprised 75% of the potential absorbing system area and over 99% of the absorbing length. In a second experiment, the P uptake and contribution to potential absorbing surface of Pt was compared to Cenococcum geophilum Fr. (Cg). Seedlings inoculated with Pt differed from those inoculated with Cg in that they (i) absorbed almost twice the P. (ii) had a higher frequency of fine‐root branching, (iii) developed an extensive network of rhizomorphs, and (iv) had over 1.5 times the mycelial absorbing surface area and over 3 times the mycelial length of Cg. We conclude that for both Pt and Cg inoculated plants, external mycelium made by far the greatest contribution to the overall potential absorbing surface area of the pine seedling. Differences in total mycelial surface area and mycelial length may account for differences in P uptake between seedlings inoculated with Pt and those inoculated with Cg.
The effects of slightly elevated ozone concentrations and mild drought stress on the physiology and growth of Norway spruce, Picea abies (L.) Karst. and beech, Fagus sylvatica L., in open‐top chambers
Authors: LE THIEC DIDIER , DIXON MARTIN , PIERRE GARREC JEAN 
Published: April 2006

summaryTwo clones of eight‐year old trees of Norway spruce and beech, planted directly into the soil and in open‐top chambers, were exposed to elevated ozone concentrations and subjected to mild soil drought. When ambient ozone was increased by 50 ppb, the shoot extension of both Norway spruce clones was significantly reduced. The mild drought stress was begun in July 1993 and following a soil‐drying associated with a spell of fine weather, the drought remained relatively constant for over a month. During this period, gas exchange parameters were regularly monitored between 7.00 and 9.00 GMT and on two occasions followed throughout the day. Both clones responded to the mild drought by reducing stomatal conductance and photosynthesis. There were no apparent interactions between drought and ozone. The reaction of beech was more complicated. Ozone caused a significant decrease in stomatal conductance and photosynthesis in well‐watered treatments. All the ozone‐drought stress treated trees had greater stomatal conductance than the non‐drought stressed equivalents in the morning, but the situation was reversed as the day went on. As peak ozone concentrations occur in the afternoon, it is hypothesized that over a period of time the drought stressed trees are less affected by ozone as they receive a lower cumulative dose. Coupled with the low values of vapour pressure deficit occurring in the morning, the ozone‐treated, drought‐stressed trees can support relatively higher rates of photosynthesis than the well‐watered equivalents. The chlorophyll contents of beech lent support to this hypothesis, as ozone associated reductions were less marked in drought stressed trees.
Interactions between exposure to O3 and nutrient status of trees: effects on nutrient content and uptake, growth, mycorrhiza and needle ultrastructure
Authors: RANTANEN L. , PALOMÄKI V. , HOLOPAINEN T. 
Published: April 2006

summaryThe responses of Norway spruce and Scots pine to the effects of increased O3 and Ca or Mg deficiency stress, singly and in combination, for two growing seasons, were investigated in this study. The combination of open‐air exposure to O3 concentrations of 1.3–1.6 times higher than ambient, and an inadequate supply of Ca or My, did not affect root uptake and leaching of minerals from the needles of 3‐yr‐old seedlings, indicating that the had not developed severe nutrient deficiency. However, concentration of N decreased in the 1‐yr‐old needles of seedlings exposed O3. The height of the new shoots was promoted without an increase in shoot dry weight, which together with stimulated mycorrhiza development and decreased shoot‐to‐root radio indicated allocation of carbon from shoots to roots as an early effect of level O3 exposure. Although the ultrastructural study did not reveal clear O3 related injuries in cells, starch accumulated in chloroplasts of the fumigated seedlings prown with adequate, but not with deficient nutrients. The outcome of this study suggests that in medium‐term exposure of conifer seedlings to low concentrations of O3 and nutrient deficiency, stress can be tolerated by activated defence metabolism and compensation reactions, but adverse effects may be apparent in long‐term continuous exposure.
Interactions between combined exposure to SO2 and NO2 and nutrient status of trees: effects on nutrient content and uptake, growth, needle ultrastructure and pigments
Authors: RANTANEN L. , PALOMÄKI V. , HARRISON A. F. , LUCAS P. W. , MANSFIELD T. A. 
Published: April 2006

summaryTwo‐year‐old seedlings of Norway spruce were exposed for 110 or 158 d in outdoor chambers to a combination of 30 nl 1−1 sulphur dioxide and 30 nl 1−1 nitrogen dioxide, and limited availability of K, Ca or Mg. Growth, nutrient content and changes in needle ultrastructure and pigments were determined, and nutrient demand for P, K and N was examined using root uptake methods. Exposure to pollutants did not clearly enhance any nutrient deficiencies. However, distinct ultrastructural effects of fumigation and Me and K deficiency stress, especially when applied together, were observed. Slight changes in total carotenoid concentration and the ratio of chlorophyll a/chlorophyll b contents were detected at 110 d but these disappeared as the experiment proceeded. Delayed growth of fumigated seedlings at 110 d was observed. The demand for P and N was almost unaffected by the treatments, but the demand for K increased in seedlings receiving both K deficient nutrient solution and exposure to pollutants. The results suggest that effects of simultaneous exposure to air pollutants and limited availability of nutrients were injuring cell ultrastructure and delaying growth, bur root responses and overall nutrient demand were unaffected by 158 d.
Physiological integration among tillers of Holcus lanatus: age‐dependence and responses to clipping and competition
Authors: BULLOCK J. M. , MORTIMER A. M. , BEGON M. 
Published: April 2006

summaryThe ecological consequences of physiological integration among tillers were examined in a glasshouse experiment on the clonal grass Holcus lanatus L. We measured the effects of severing the internode connection between a tiller and its parent on the growth and survival of this marked tiller. The effects of three factors on the response to Severing were determined using this procedure: competition with the parent plant, by comparing tillers repotted in isolation with tillers remaining in the neighborhood of the parent; dipping treatment, comprising no clipping, clipping only the marked tiller and its daughter tillers or clipping the whole parent plant, including the marked tiller; and the change in the response with tiller age at severing, using four tiller ages (1, 2, 4 and 8 wk). These age, clipping and severing treatments wt‐re applied factorially.After 8 wk of growth the responses to severing of the marked tillers, were dependent on the age and clipping treatments. Severing always decreased survival and growth (tiller production, biomass and tiller extension) of the youngest tillers (ages 1 and 2wk), indicating that they were dependent on the parent to support their early growth. Age 4 tillers were able to support their own growth and grew hest in isolation; but when grown in the parent's neighbourhood competition with the parent reduced growth, although parental support ameliorated these effects. Some of the oldest tillers (age 8 wk) showed decreased growth when unsevered. This indicated an outflow of resources to the parent and suggested that integration allowed the control and coordination of tiller growth.The pattern of the severing effects was similar in all clipping treatments, varying only in degree. There was little evidence of increased support for clipped tillers or for a change in the pattern of integration when the whole plant was clipped, except that age 8 tillers showed a continued benefit of the connection, in contrast to the positive effect of severing in the other two clipping treatments. The extension rate of the marked tiller showed complex responses to clipping and severing treatments, including effects of integration on regrowth after clipping. This experiment has shown that the growth of tillers in H. lanatus is highly integrated but that this integration is extremely plastic in response to tiller age and, to a lesser extent, clipping treatment.
Vegetation history of Orkney, Scotland; pollen records from two small basins in west Mainland
Authors: BUNTING M. J. 
Published: April 2006

summaryPollen analysis was carried cut on sediment sequences from two small basins situated 6 km apart in the hills of west Mainland, Orkney, At both sites, vegetation development from the late glacial until after the arrival of Neolithic people is recorded. An initial late glacial heath, interrupted by a herbaceous phase indicating the Younger Dryas, was replaced by tallherb and grassland vegetation. The Saksunarvatn ash layer was recorded, coinciding with the arrival ofCorylus avellanain the islands at around 9.2 ka BP. Extensive woodland developed at about 8000 yr BP, predominantlyBetula–CoryhuswithSalix, alnus glutinosa. QuercusandPinus sylvestrisoccasionally present. The woodland was locally affected by Mesolithic human activity and finally lost at around 5kaBP, partly as a consequence of Neolithic human activity. Mire development was actively proceeding in both basins after the woodland decline. The records illustrate the importance of human activity in the development of the treeless, varied landscape seen in Orkney today.
Molecular markers in plant ecology
Authors: BACHMANN KONRAD 
Published: April 2006

SUMMARYVarious methods from molecular biology reveal sequence polymorphisms in organelle and nuclear DNA that can be used as highly informative markers for the structure and dynamics of genomes at the level of populations and individuals. Molecular markers that can be determined without regard to the phenotype permit an unbiased comparison of the adaptation of organisms to their environment, its genetic basis and its effect on evolution. Several marker types used in ecological research and their uses and limitations arc briefly discussed. PCR‐based methods, especially arnitrary‐primer‐based RAPDs, are likely to be most widely used and receive most attention. The limited use of DNA markers for overall quantitative (phenetic) comparisons of ‘genetic variability’ and ‘generic distance’ is stressed and fheir power as qualitative markers for any and all relevant regions in the genome is emphasized. Specific applications relevant to plant ecology are illustrated. These are: identification of organism and genotype even where morphology is of little help, as in mycorrhiza; identification of clones in asexually‐reproducing species, even when they are widespread and intermingled; determining if genetic variation in elonal populations comes from mutations within elonal lines or from independent origins of clonal lines; reconstructing the genotype phylogeny and fruit dispersal of elonal (apomicuc) and inbred selling organisms, measuring the degree of outcrossing by offspring exclusion analysis; detecting and analyzing introgression and characterizing reeombinant genotypes in hybrid zones relative to differential adaptive responses: tracing the phylogenetic origin and extent of ecologically differentiated races or species; characterizing the genetic basis, mapping and isolating the genes responsible for special adaptive responses. In a final outlook, 1 speculate about unconventional sources of genetic variation affecting the ecological characteristics of plants that will become accessible to experimental analysis with the new molecular methods.ContentsSummary403I.Introduction404II.Most ecological applications concern markers in the nuclear geonome404III.DNA polymorphisms differ from allozyme pohmorphisms404IV.Types of molecular marker405V.The application of markers in ecology409VI.From marker to character413VII.Outlook414References414
Gene expression during leaf senescence
Authors: SMART CATHERINE M. 
Published: April 2006

SUMMARYLeaf senescence is a hiphly‐controlled sequence of events comprising the final stage of development. Cells remain viable during the process and new gene expression is required. There is some similarity between senescence in plants and programmed cell death in animals. In this review, different classes of senescence‐related genes are defined and progress towards isolating such genes is reported. A range of internal and external factors which appear to cause leaf senescence is considered and various models for the mechanism of senescence‐ initiation are described. The current understanding of senescence at the wrganelle and molecular levels is presented. Finally, same ideas are mooted as to why senescence occurs and why it should be studied further.ContentsSummary419I.Introduction420II.Internal factors that cause senescence423III.External factors that cause senescence427IV.What is the mechanism of senescence initiation?428V.Progress in the understanding of organelle senescence431VI.Progress in the understanding of senescence at the molecular level434VII.The control of senescence in animals and plants440VIII.Why is senescence necessary?441IX.Why study senescence?441References442
Chlorophyll development in mature lysigenous and schizogenous root aerenchymas provides evidence of continuing cortical cell viability
Authors: ARMSTRONG JEAN , ARMSTRONG WILLIAM 
Published: April 2006

SUMMARYThe‘greening’of mature aerenchymatous adventitious roots of Phragmrtes auttralis (Cav.) Trin. ex Steudel, rice, maize, Atorm calamus L., and Epilobium hirsutum L., when exposed to light was found to be due to chloroplast development in the cortex. In Phragmites, maize and rice, which are characterized by lysigenous cortical aerenchymos, chlomplasts developed not only in normally intact cortical cell layers adjacent to the exodermis/hypodermis and endodermis, but also in isolated radial cellular strands (and isolated cells) between the lacunae, cells which had failed to collapse during the active phase of aerenchyma development. The observation provides conclusive evidence for the continuing viability and the potential for active metabolism of the non‐lysed cells of lysigenous aerenchymas.In Acortis and Epitobium, chloroplast development occurred in the cells of the schisogettmts cortical aerenchymas. In Phragmites, chloroplasts also developed in the non‐aerenchymatous cortex of illuminated fine basal lateral roots.
Experimental evidence for the autonomy of ray differentiation in Ficus sycomorus L.
Authors: LEV‐YADUN SIMCHA 
Published: April 2006

SUMMARYWounding or partial girdling leaving only a narrow cambial bridge resulted in changes in the xylem structure in stems and branches of Ficus sycomorus. Wounding inhihiitd the formation of fibre bands, induced tyiosis and differentiation of narrow vessels, and resulted in partially differentiated tissues. Partial girdling of mature trunks resulted in the formation of either a strip of traumatic xylem or a parenchymal strip in which all axial components failed to differentiate but the radial system was not affected and the rays continued to form. The differentiation of rays without an axial system is indicative of the autonomy of the radial signal system that participates in the regulation of ray formation.
Mechanisms of deposition of epicuticular wax in leaves of broccoli, Brassica oleracea var. capitata L.
Authors: ANTON L. , EWERS F. W. , HAMMERSCHMIDT R. , KLOMPARENS K. L. 
Published: April 2006

SUMMARYBroceeli (Brassika oleraceo L. var. capitata L.) leaf waxes were labelled with [2‐14Cjacetate and examined during synthesis and deposition using microautoradiography. Waxes were viewed with light microscopy and scanning electron microscopy (SEM), including cryo‐SEM. In microautoradiography, silver grains resulting from radioactive decay of labelled waxes seemed to be distributed randomly throughout the cuticle. This random distribution supports the hypothesis of diffusion or complex anastomosing pores as the mechanism of epicuriculur wax position. The hypothesis of wax‐depositing pores running perpendicular to the leaf surface is not supported.
Identification of the ectomycorrhizal basidiomycete Tylospora fibrillosa Donk by RFLP analysis of the PCR‐amplified ITS and IGS regions of ribosomal DNA
Authors: ERLAND S. , HENRION B. , MARTIN F. , GLOVER L. A. , ALEXANDERS I. J. 
Published: April 2006

SUMMARYSitka spruce mycorrhizas, macroscopically identified as being formed by Tylospora fibritiosa Donk, were sampled from a young and on old plantation and the mycobionts were isolated into pure culture. DNA was extracted and fragments of the ribosomal DNA (rDNA) were amplified using the polymerase chain reaction (PCR). The primers were directed to conserved regions of fungal rDXA and hybridize to a wide range of fungi. One amplified region includes the internal spacer (ITS) region which has a low degree of conservation. The JTS amplification products, which were approximately 600 base pairs (bp), were digested with a variety of restriction endonucleases in order to detect restriction fragment length polymorphisms (RFLPs). The RFLPs clearly separated T. fibrillosa from other ectomycorrhizal species but there were only minor differences between the T. fibrillosa isolates. PCR amplification of the ITS region, digestion with the endonudeasc HinfI and examination of the RFLPs produced proved to be a rapid method by which to distinguish T. fibriHosa from a large number of other basidiomyictes. The method was also applied to DNA extracted, from single mycotrhizal root tips. The imergenic spacer region (1GS) of the rDNA is more variable than the ITS region in several fungal species. The 5’end of the 25S and the intergenic region between the 25S and the 5S genes were amplified and analyzed as above. Polymorphisms between T. fibritiosa isolates within this region were limited and RFLPs were not useful m discriminating between isolates, suggesting a low genetic variability in this species.