bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of ozone and nutrient supply on stomatal response in birch (Betula pendula) leaves as determined by digital image‐analysis and X‐ray microanalysis
Authors: FREY BEAT , SCHEIDEGGER CHRISTOPH , GÜNTHARDT‐GOERG MADELEINE S. , MATYSSEK RAINER 
Published: April 2006

SUMMARYCuttings of Betula pendula Roth were grown in field fumigation chambers throughout one growing season in filtered air with < 3 nl l−1 O3 (control; C) or day/night = 90/40 nl 1−1 O3 (ozone fumigation: O3). Plants were watered with either low (0·005 %: LF) or high‐concentrated (0·05%: HF) fertilizer solution. Discs between second‐order veins in the central portion of the leaves were excised and immediately cryofixed in liquid nitrogen for low‐temperature scanning electron‐microscopy (LTSEM) at 1000 hours and 1400 hours. Stomatal width, area and density were measured by digital image‐analysis. X‐ray counts of potassium (K) and calcium (Ca) ions were determined by means of energy‐dispersive X‐ray microanalysis in guard and subsidiary cells. Accurate and fast measurements of stomatal apertures by image analysis were possible in birch leaves, because the darkness of the stomatal pore contrasts with the brightness of the guard cells and the cuticular ledges. Regression analysis showed a close relationship between the stomatal width and the pore area (r= 0·938, P < 0·01). At all harvest times, the stomatal pores were significantly narrowed in the high fertilization control treatment (O3/HF vs. O3/LF), and in the ozone treatment at 1400 hours (O3/HF vs. C/LF). In addition to this fertilization effect, ozone had also narrowed the stomatal pores (O3/HF vs. C/HF at 1400 hours, O3/LF vs. C/LF at all harvest times). In addition to these functional effects, morphological effects (individual leaf area, stomatal density) were determined. Single‐leaf area was increased by high fertilization, with a tendency to decrease with O3 fumigation. The stomatal density in intercostal fields was increased by O3 but decreased by high fertilisation. Stomatal widening was accompanied by increased K count rates in the guard cells, in contrast to constant K values in the subsidiary cells, irrespective of the fumigation or fertilization regimes. Calcium counts in the guard cells were similar to those in the subsidiary cells, and were independent of the aperture width. In samples with established ozone injury, the K/Ca ratio in collapsed guard cells increased compared with turgid guard cells irrespective of the pore aperture. Collapsed subsidiary cells only differed from turgid subsidiary cells when the guard cells had also collapsed and thus closed the pore.
Late Quaternary vegetation history of the Western Isles of Scotland
Authors: FOSSITT J. A. 
Published: April 2006

SUMMARYPalacoecoiocical investigations of two lake sediment sequences are used to reconstruct the vegetation history of the Western Isles. Pollen records begin in the late glacial and show a clear progression From herb‐rich grassland with abundant Salix, Rumex and Poly‐podium to widespread Empetrum nigrum heath. Woodland developed widely in the early Holocene, and regional vegetation patterns emerged. Western Lewis supported extensive areas of birch woodland with Corylus avellana, Salix, Populus and Sorbus aucuparia. Open birch‐hazel woodland dominated other lowland regions. Regional variation was accentuated when woodland underwent a sudden decline in western Lewis at about 7900 BP. Trees were replaced by blanket peat and woodland failed to recover on a regional scale after the decline‐ Woodland continued to diversify in central and eastern regions and, by 6000 BP, Quercus, Ulmus, Pinus sylvestris, Alnus glutinosa and Fraxinus excelsior had become established. Open mixed woodland persisted until the second major decline began between 5200 and 4000 UP. Woodland contracted gradually as blanket peat expanded. The Western Isles were predominantly treeless at 2500 BP. Blanket peat started to form in localized areas on the Western Isles between 9000 and 8000 BP; two main expansion phases are associated with periods of woodland decline. Sublossil wood or macrofossils are reported from a total of 40 sites. Radiocarbon ages are presented for 13 samples of these.
Fructan metabolism in expanding leaves, mature leaf sheaths and mature leaf blades of Lolium perenne. Fructan synthesis, fructosyltransferase and invertase activities
Authors: GUERRAND DAVID , PRUD'HOMME MARIE‐PASCALE , BOUCAUD JEAN 
Published: April 2006

summaryAccumulation of water‐soluble carbohydrates was studied in leaf tissues of 8‐wk‐old plants of perennial ryegrass (Lolium perenne L. var. Bravo). The roots and leaf bases were cooled to low temperatures to reduce sink activity while source activity was enhanced by continuous illumination of the shoots. This resulted in accumulation of fructans, first in sheaths, subsequently in expanding leaves, and finally in blades. Fructan concentration increased from 6 to 23 mg g−1f. wt in sheaths, from 8 to 30 mg g−1f. wt in expanding leaves and from 6 to only 17 mg g−1f. wt in mature leaf blades. Increase in concentration of low‐DP fructans preceded accumulation of high‐DP fructans. Expanding leaves accumulated significantly more glucose and fructose than did mature leaf tissue. Leaf blades contained a higher concentration of sucrose than either leaf sheaths or expanding leaves. Expanding leaves exhibited the greatest activity of SST (0.77 nkat g−1f. wt), the mature leaf blades the least (0.09 nkat g−1f. wt), whilst that of mature leaf sheaths was intermediate (0.27 nkat g−1f. wt). In each leaf tissue, invertase activity was higher than SST activity. Under conditions of fructan accumulation, SST activity increased threefold in mature leaf sheaths and 1.2‐fold in expanding leaves. In mature leaf blades, however, the activity remained constant at a low level. Invertase activity never increased. Inhibitors of protein synthesis (cycloheximide) and of RNA metabolism (actinomycin D) prevented any increase of SST activity in leaf sheaths. The results are discussed in relation to fructan metabolism in leaf tissues of Lolium perenne.
Physiological and biochemical changes in shoots of coconut palms affected by lethal yellowing
Authors: LEÓN RUBÉN , SANTAMARÍA JORGE M. , ALPIZAR LUCELY , ESCAMILLA JOSÉ A. , OROPEZA CARLOS 
Published: April 2006

summaryNoon stomatal conductance of lethal‐yellowing (LY) affected coconut palms (Cocos nucifera L. Atlantic Tall ecotype) decreased progressively as the disease developed. In the early stages of the disease and before leaf yellowing started, stomatal conductance decreased to a minimum in leaves at both the top, the middle and the base of the crown. Since altered stomatal behaviour might affect gas exchange and related processes in the plant, such as water movement and photosynthesis, these results support the hypothesis that LY‐induced stomatal closure is central to the development of LY symptoms in coconut palms, and therefore to the mode of pathogenicity of the LY mycoplasma‐like organism. Leaf yellowing occurred simultaneously with a decrease in photosynthetic rates and a decrease in protein, chlorophyll and carotenoid contents. Based on these biochemical changes a second hypothesis is proposed, that LY‐associated leaf yellowing is part of a leaf senescence process. The concentration of abscisic acid in the leaves and the capacity of leaf tissue to form ethylene increased in diseased palms, suggesting that a hormonal imbalance occurs in LY‐affected palms. Furthermore, treatment of symptomless palms with an ethylene‐releasing agent (ethephon) resulted in symptoms that mimicked some of the LY symptoms. A third hypothesis is therefore proposed, that a hormonal imbalance might be related to LY symptom development, at least with respect to nutfall and leaf senescence.
Interactive effects of ozone and soil volume on Plantago major
Authors: WHITFIELD C. P. , DAVISON A. W. , ASHENDEN T. W. 
Published: April 2006

summary Plantago major L. ssp. major usually grows on trampled paths, tracks and gateways, and its root system is often restricted by compaction or by a limited volume of soil. In this heterogeneous environment, individuals close to each other will experience variable degrees of root restriction. As some populations of P. major have been demonstrated to be sensitive to ozone, the aim of this study was to investigate the effect of root restriction on the response of P. major to ozone.It was hypothesized that root restriction should reduce the effects of ozone. If this is true it would have implications for evolution of ozone resistance. A single population of P. major was grown in controlled‐environment chambers and exposed to either charcoal/Purafil‐filtered air or to ozone (70 nl O3 l−1for 7 h d−1). Plants were grown in pots of four different volumes: 0.175 1; 0.3651; 2.2801; and 5.8301. Four harvests were performed, at 21, 37, 51 and 91 d from germination. At the final harvest, the total nitrogen content of leaf tissue was analysed and compared with that of plants collected from the field. Stomatal conductance (gs) and net carbon assimilation (A) rate were also recorded during development.Plants grown in the smallest pots exhibited severely impaired growth, lower gs and lower A than non‐restricted plants. Root growth was less impaired than shoot growth. However, only plants in the smallest pots resembled those found in the field, which implies that realistic assessment of ozone effects on this species should involve a degree of root restriction. Appearance and leaf nitrogen content of leaves suggested that root restriction may have caused nitrogen deficiency. Contrary to the initial hypothesis, exposure to ozone reduced the growth of plants in all sizes of pot. Stomatal conductance was consistently lower in plants exposed to O3, but there was no effect of ozone on A.
Effects of leaf age, basal meristem and infection with powdery mildew on photosynthesis in barley grown in 700 μmol mol−1CO2
Authors: HIBBERD J. M. , RICHARDSON P. , WHITBREAD R. , FARRAR J. F. 
Published: April 2006

summaryThe rate of net photosynthesis in the second leaf of barley was higher in 700 than 350 μmol mol−1CO2, when measured in the CO2 concentration in which the plants were grown, but the magnitude of this difference decreased as the leaf aged. Infection by powdery mildew accelerated the decline in net photosynthesis of leaves grown in either 350 or 700 μmol mol−1CO2. A/Ci curves allowed the reduction in net photosynthesis of plants exposed to 700 μmol mol−1CO2 or after infection by powdery mildew to be related to changes in the carboxylation efficiency or in the regeneration of ribulose 1,5‐bisphosphate. The carboxylation efficiency declined in plants exposed to 700 μmol mol−1CO2. In plants infected with powdery mildew, the reduction in net photosynthesis was associated with both reduced carboxylation efficiency and reduced ability to regenerate ribulose 1,5‐bisphosphate. Reduced carboxylation efficiency of the second leaf of plants grown in 700 μmol mol−1CO2, was not associated with a reduction in the concentration of rubisco within the leaf. In contrast to the presence of a close exogenous sink, leaf age had large effects on the acclimation of photosynthesis to 700 μmol mol−1CO2.
Superoxide dismutase activity in arbuscular mycorrhizal Lactuca sativa plants subjected to drought stress
Authors: RUIZ‐LOZANO J. M. , AZCÓN R. , PALMA J. M. 
Published: April 2006

summaryTotal superoxide dismutase (SOD; EC 1.15.1.1) activity, SOD specific activity and changes in the SOD isoenzymatic pattern were determined in roots and shoots of plants of Lactuca sativa L. cv. Romana colonized by the arbuscular mycorrhiza (AM) fungi Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe or Glomus deserticola (Trappe, Bloss & Menge), and in non‐mycorrhizal phosphorus‐fertilized controls. Lettuce plants were grown under well watered or drought conditions and were harvested 5 wk or 8 wk after planting. Previous studies have reported that mechanisms that decrease oxidative stress can play an important role in drought tolerance of plants. However, there is little information on either the role of superoxide dismutase in the symbiosis between AM fungi and plants, or about the response at biochemical level of the mycorrhizal symbiosis to drought stress. In our experimental conditions the protein concentration in shoots decreased in all plants as a result of drought stress (except in plants colonized by Glomus mosseae after 8 wk of growth). In general, shoots of mycorrhizal plants had more protein than did shoots of P‐fertilized plants, G. deserticola being the treatment with the highest protein concentration. However, in roots the protein concentrations did not vary as clearly as in shoots. The SOD specific activity of 5‐wk‐old plants under stress conditions was considerably higher in shoots and roots of mycorrhizal than in those of P‐fertilized plants, showing increases which ranged from 99% in G. mosseae‐mycorrhizas to 150% in G. deserticola‐mycorrhizas. Under well watered conditions shoots showed no significant differences in SOD specific activity between treatments, whereas in roots mycorrhizal colonization increased it by 16–18 %. Drought stress increased SOD activity of shoots of control plants by 17%, and that of shoots of plants colonized by G. mosseae and G. deserticola by 93 % and 128 %, respectively. Similar results were also found for roots, regardless of the plant age. The increased SOD activity in mycorrhizal plants was not related to the nutritional status of the plants. Instead, it could be ascribed to a direct mechanism of AM association in response to drought exposure. However, no changes in the SOD isozyme pattern as a consequence of mycorrhizal association or water treatment were observed.
Effect of arbuscular mycorrhizal fungi on growth, mineral nutrition and nitrogen fixation of three varieties of common beans (Phaseolus vulgaris)
Authors: IBIJBIJEN J. , URQUIAGA S. , ISMAILI M. , ALVES B. J. R. , BODDEY R. M. 
Published: April 2006

summaryA pot experiment was conducted under glasshouse conditions to investigate the effect of inoculation with four arbuscular mycorrhizal (AM) fungi (Glomus clarum, G. etunicatum, G. manihotis, Gigaspora margarita), either individually or in a mixture, and withRhizobium leguminosarumbiovarphaseoli, on the growth, mineral nutrition, and contribution of biologically fixed N2, to three nodulating bean (Phaseolus vulgaris) varieties (Carioca, Negro Argel and Rio Tibagi). The15N isotope dilution technique and three control crops (non‐nodulating bean,Panicum maximumand sorghum) were used to quantify the contribution of N2fixation. There were significant differences between the capacity of the different AM fungi to infect and colonize the roots of the different bean varieties. Inoculation with AM fungi significantly increased production of dry matter by 8–23 % and the concentration of P in plants by 160–335%. A strongly positive correlation of % root colonization by AM fungi and plant P concentration and accumulation was observed which suggests that the observed inoculation responses were a result of improved P acquisition by the mycorrhizal roots. N derived from the atmosphere increased significantly with AM fungi inoculation, with Carioca showing the best response, followed by Negro Argel and Rio Tibagi, thereby showing the indirect and positive effect of AM fungi inoculation on the N2‐fixing association betweenRhizobiumandPhaseolus vulgaris.
Effect of a genetically modified Rhizobium meliloti inoculant on the development of arbuscular mycorrhizas, root morphology, nutrient uptake and biomass accumulation in Medicago sativa
Authors: BAREA J. M. , TOBAR R. M. , AZCÓN‐AGUILAR C. 
Published: April 2006

summaryA soil microcosm system was used to evaluate the impact of a genetically modified (GM) Rhizobium meliloti strain on development and function of arbuscular mycorrhiza in alfalfa plants (Medicago sativa L.). There was no indication that this GM Rhizobium strain, which had an enhanced nodulation competitiveness ability, interfered with mycorrhiza formation by Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe. Indeed, inoculation with the GM Rhizobium strain greatly increased the number of mycorrhizal entry points in the alfalfa root system in comparison to the wild‐type strain. Mycorrhizal development and quality of nodulation increased with time and coincided with increased biomass of and nutrient (N, P) uptake by the host plant. The establishment of the symbiotic interactions also induced changes in root morphology; in particular, the degree of branching increased and the number of lateral roots was greater in plants inoculated with the GM Rhizobium strain. These results demonstrate that the GM Rhizobium strain does affect adversely the performance of arbuscular mycorrhizal symbiosis, a biosafety model system based on a functional rhizosphere.
Atomic force microscopy study of isolated ivy leaf cuticles observed directly and after embedding in Epon®
Authors: CANET D. , ROHR R. , CHAMEL A. , GUILLAIN F. 
Published: April 2006

summaryThe first results obtained by atomic force microscopy (AFM) of the fine structure of isolated ivy leaf cuticles are reported. Observations of transverse sections embedded in Epon® allow easy recognition of the general shape of cuticles as viewed by light microscopy. The surface profile shows irregularities not revealed by transmission electron microscopy (TEM). The lamellate and reticulate zones, distinguishable by TEM, were also located by AFM. The outer zone appears as an irregularly thick (c. 4 μm) homogeneous region; lamellae can be visualized only after image‐processing to subtract relief defects produced by sectioning. The second region or internal zone represents the largest part of the cuticle thickness; it appears heterogeneous and disordered. The cuticle internal surface images show imprints of the epidermal cells. At high magnification, the cell imprint central regions appear to be made up of a network of fibres of c. 50 nm diameter. Some images show that these fibres have a preferential orientation. They disappear after acid‐hydrolysis is used to eliminate polysaccharides. This study shows that AFM can produce reproducible images of isolated plant cuticles at a subcellular scale leading to new high‐resolution representations of cuticle substructure.
Infectivity of arbuscular mycorrhizal fungi after wetting and drying
Authors: BRAUNBERGER PETER G. , ABBOTT L. K. , ROBSON A. D. 
Published: April 2006

summaryIn a mediterranean environment, a hot and dry summer is followed by a cool and rainy winter, the growing season. Arbuscular mycorrhizal (AM) fungi survive in dry soil in the summer and are able to colonize newly emerged plants in winter. However, late summer and autumn rains are frequently followed by periods of drought, resulting in the wetting and drying of the soil before the onset of regular winter rains. The results of three experiments investigating the effect of wetting and drying of soil on the subsequent infectivity of different AM fungi and their individual propagules are presented.In a first experiment, pot‐culture inoculum of Acaulospora laevis Gerd. & Trappe, Glomus invermaium Hall, or fine endophytes, each containing a mixture of propagule forms, was mixed into pots of steam‐sterilized soil with low phosphorus content. Pots were treated with a wetting and drying cycle where the soil was watered to field capacity for three consecutive days and then left to dry to a water content of less than 1.5% g g−1. Infectivity was assessed in a subsequent growth cycle planted with clover. In a second experiment, the infectivity of spores of A. laevis, Glomus monosporum Gerd. & Trappe or Scutellospora calospora (Nicol & Gerd.) Walkers & Sanders, and of dried mycorrhizal root fragments of G. invermaium or S. calospora was assessed after a wetting and drying cycle in which the soil was watered to field capacity for seven consecutive days before drying. In a third experiment, the infectivity of the extraradical hyphae of G. invermaium after wetting and drying was assessed.AM fungi and their individual propagules responded differently to wetting and drying. The infectivity of pot‐culture inoculum of A. laevis, G. invermaium and fine endophytes was increased, decreased and unaffected, respectively, by wetting and drying. The infectivity of spores of A. laevis and G. monosporum was increased by wetting and drying but the infectivity of spores of 5. calospora was not affected. Infectivity of mycorrhizal root fragments of G. invermaium and S. calospora was decreased and increased, respectively, by wetting and drying. Finally, the infectivity of the extraradical hyphae of G. invermaium was eliminated by a wetting and drying cycle.These results indicate that the development and function of mycorrhizas after late summer and early autumn rains may be limited by the occurrence and predominance of propagules of different AM fungi.
Evidence for an up‐regulation of the host and a down‐regulation of the fungal phosphofructokinase activity in ectomycorrhizas of Norway spruce and fly agaric
Authors: SCHAEFFER CHRISTOPH , JOHANN PATRIK , NEHLS UWE , HAMPP RÜDIGER 
Published: April 2006

summaryFor an understanding of metabolic interactions in ectomycorrhizal associations it is essential to distinguish enzyme activities of the symbionts. For the ATP‐dependent phosphofructokinase (PFK) from ectomycorrhizas of fly agaric (Amanita muscaria (L. ex Fr.) Hooker) on Norway spruce (Picea abies (L.) Karst.) we were able to achieve a symbiont‐specific differentiation by special assay conditions. Substrate concentrations, Mg2+: ATP ratio and pH values which were optimum for the fly agaric PFK completely suppressed the PFK activity of spruce roots. On the other hand, under the optimum assay conditions for the spruce root PFK, the fungal PFK activity was reduced by more than 90%. The most pronounced difference between the enzymes of both organisms was the response towards fructose‐2,6‐bisphosphate (F26BP); whereas F26BP had no influence on the spruce PFK activity, the fly agaric PFK activity was strongly enhanced by very low levels of F26BP.The distinction of the partner‐specific PFK activities illustrated that mycorrhiza formation exerted partner‐specific effects. On the basis of host d. wt of the mycorrhizas, the host‐specific PFK activity was more than doubled compared with that of the non‐mycorrhizal short roots. By contrast, the fungal PFK activity, on a fungal d.wt basis, was reduced in the mycorrhizas to less than 1/4 of the activity of the free‐living mycelium.
Effects of jasmonic acid on mycorrhizal Allium sativum
Authors: REGVAR MARJANA , GOGALA NADA , ZALAR POLONA 
Published: April 2006

summaryIn experiments on spruce we have shown that jasmonic acid (JA), a cyclopentanone fatty acid, influences the ectomycorrhizal formation: we therefore also applied it to an endomycorrhizal symbiosis.Garlic (Allium sativum (L.)) bulbs were potted into substrates inoculated or not with arbuscular mycorrhizal fungi (AMF), and one half of the plants was foliar‐treated with 5 μm JA. A synergistic effect of JA treatment and AMF inoculation on shoot length was found. Root growth of inoculated plants was accelerated especially when JA was applied. Either JA or AMF inoculation significantly enhanced bulb development. Mycorrhizal colonization was promoted and the development of arbuscules and vesicles was enhanced upon JA application.