bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population variation in Spartina anglica C. E. Hubbard
Authors: THOMPSON J. D. , McNEILLY T. , GRAY A. J. 
Published: April 2006

summaryThe response of clonal replicates of nine populations of Spartina anglica C. E. Hubbard to environmental variation was examined in three pot environments, designed to test for differences between the populations in their response to environmental variation. ANOVA showed that the effect of environment was highly significant for all morphological and yield characters, and that the populations were also significantly different for several characters. For above and below ground vegetative biomass, there was a significant population x environment interaction, indicative of differences in plasticity between the populations. Linear regression of the population mean value in each environment on the mean value of all populations in each environment was performed for these two traits. This showed that the response to environmental change was not significantly due to a linear relationship in some populations, hence, the method could not be used to compare the response of each population. Nevertheless, norms of reaction plots for each population showed that the three populations collected from successionally mature sites showed less response to more favourable conditions. The three mature populations also had significantly lower tiller numbers per plant in all environments. These results substantiate previous results which suggest a decline in vigour and plasticity in successionally mature populations. Morphological characters, except third leaf width and culm diameter, all proved to be significantly correlated in pairwise comparisons. This is further evidence for the occurrence in S. anglica of ‘graceful’ and ‘stocky’ variants which contrast with the highly plastic ‘anglica’ growth form.
Precociously developing individuals in populations of chickweed [Stellaria media (L.) Vill.] from different habitat types, with special reference to the effects of weed control measures
Authors: BRIGGS D. , HODKINSON H. , BLOCK M. 
Published: April 2006

summaryLong‐term weed control in gardens and arable areas is likely to be a potent selective force favouring precocious development of annual weed species. In an experiment with Stellaria media (L.) Vill., we grew progenies from open‐pollinated seed of a number of seed‐parents collected from 12 British populations of five habitat types. We raised plants in a temperate glasshouse and a garden plot, to see if plants from areas subject to weed control ‐gardens and arable fields – had a quicker rate of development from germination to flowering and fruiting than plants from habitats subject to less weed control (waysides) or no weeding pressure (seasonally exposed river sediments and bird colonies).Comparison of the behaviour of plants in the glasshouse and out‐of‐doors revealed a broadly similar pattern of behaviour. However, for some, but not all seed‐parents, rate of development was different in the two sets of conditions.In conformity with hypothesis, plants from one of the gardens were quick to reproduce, but plants from Ness Botanic Garden and arable fields were more variable than expected. Plants from less well weeded and non‐weeded sites did not conform to expectation. Plants from waysides were quick to reproduce, so too was much of the material from a bird colony on the island of Skomer. While some late‐developing plants were detected from a second bird colony (Fame) and from exposed river sediments by the Tweed and Manifold, we found a small number of precocious and some intermediate individuals in the progeny of some seed‐parents.It is possible that bird colonies and exposed river sediments are heterogeneous habitats, in which there are niches where ‘native’ variants with different rates of development are at a selective advantage.However, there is another explanation of our results. First, we discovered that, while some of the seed‐parents were probably behaving as homogeneous lines for rate of development, others show ed segregation, providing evidence that a degree of outcrossing is possible in populations of Stellaria. Secondly, there is evidence that human activities have led to habitat disturbance in and around the bird colonies and riverside vegetation we have studied. Our findings are consistent with the hypothesis that, gene flow by pollen and/or seed of precocious weedy plants has occurred in these man‐disturbed sites, leading to different patterns of variation involving hybridization between ‘introduced’ precocious plants and ‘native’ slow‐developing variants.
Studies in the vegetational history of the Northern Pennines
Authors: TURNER JUDITH , HODGSON JOYCE 
Published: April 2006

summaryTree pollen data in the form of mean frequencies for the late Flandrian were collected from 46 sites in the Northern Pennines. They indicate that as in the early and mid‐Flandrian spatial variation in the species composition of the woodlands is related to local geology, topography and climate.A sub‐set of the data was compared with published mid‐ and early Flandrian data from the same sites. Temporal variation in Betula, Pinus and Alnus is related to changes in climate, in Ulmus and Corylus to Dutch elm disease and in Fraxinus to human disturbance. Spatial diversity is at least as strong as temporal.
Accumulation of phenolic compounds in the necrotic areas of Austrian and red pine needles after spraying with sulphuric acid: a possible bioindicator of air pollution
Authors: ZOBEL ALICJA , NIGHSWANDER JAMES E. 
Published: April 2006

summaryAustrian pine (Pinus nigra Arn.) and red pine (P. resinosa Ait.) were tested for needle damage caused by sulphuric acid spray. Morphology and histology of newly grown needles were compared in 3‐ and 6‐yr‐old plants growing in the greenhouse under controlled conditions. Potted plants covered with plastic bags were sprayed daily either with distilled H2O or sulphuric acid of pH 2.5, 3.5 and 4.5. Needle tips, mid‐parts and bases were fixed after 1, 3 and 24 h, and 3, 7 and 30 d in glutaraldehyde + 0.1% caffeine for intracellular precipitation of phenolics. Histochemical reactions and electron microscopic observations showed that the morphological damage is linked to increased deposition of phenolic compounds in mesophylla cells, beginning directly under the stomata. Disorganization of membranes leads to death of the mesophyll cells, even before morphological damage is recognizable as brown spots on the needle surface. Thus the histochemical reactions and observations of cell structure revealed damage earlier than macroscopic observations.
Effect of a vesicular–arbuscular mycorrhizal fungus and rhizosphere micro‐organisms on manganese reduction in the rhizosphere and manganese concentrations in maize (Zea maysL.)
Authors: KOTHARI S. K. , MARSCHNER H. , RÖMHELD V. 
Published: April 2006

summaryMaize (Zea maysL. ev. Tau) plants were grown in a calcareous soil for six weeks in pots having separate compartments for growth of roots and vesicular‐arbuscular (VA) mycorrhizal fungal hyphae. Soil was sterilized and either left non‐inoculated (sterile treatment), or was inoculated with rhizosphere micro‐organisms only (MO–VA) or with rhizosphere micro‐organisms together with a VA mycorrhizal fungus [Glomus mosseae(Nicol & Gerd.) Gerdemann & Trappe (MO +VA)]. Concentrations of Mn in roots and shoots, as well as exchangeable Mn in rhizosphere soil, decreased in the order MO–VA < MO + VA < sterile treatment. In all treatments, the concentration of exchangeable Mn was lower in the rhizosphere soil (0–5 mm distance from the root surface) than in the bulk soil (5–15 or 15–25 mm distance from the root surface). In the rhizosphere soil, the total microbial population was similar in mycorrhizal (MO + VA) and non‐mycorrhizal (MO–VA) treatments, but the proportion of Fe‐ or Mn‐reducers was 20‐ to 30‐fold higher in the non‐mycorrhizal treatment, suggesting substantial qualitative changes in rhizosphere microbial populations upon root infection with the mycorrhizal fungi. The Mn+Iv‐reducing potential (net balance between reduction and oxidation) in the rhizosphere soil was also distinctly lower in mycorrhizal treatment compared to non‐mycorrhizal treatment.In the sterile treatment, low Mn+IV‐reducing potential and correspondingly low concentration of exchangeable Mn in soil, compared to the other treatments, indicates the importance of micro‐organisms in Mn reduction in soil and acquisition of Mn by plants. Therefore, the lower Mn concentrations in mycorrhizal plants are most probably caused by a shift in composition and activity of rhizosphere micro‐organisms. As a side effect of the treatments, improved soil aggregation, as indicated by soil adhering to the nylon net (facing hyphal compartments) after plant harvest, occurred in non‐mycorrhizal and sterile treatments but not in the mycorrhizal treatment.
A light and electron microscope study of rhizoid–ascomycete associations and flagelliform axes in British hepatics with observations on the effects of the fungi on host morphology
Authors: DUCKETT J. G. , RENZAGLIA K. S. , PELL K. 
Published: April 2006

summaryAscomycetous fungi, identified by the presence of simple septa and Woronin bodies, form a range of highly specialized associations with the unicellular rhizoids of 46 (16.2%) of the 284 species of British liverworts. The majority of these are in the two jungermannialian suborders Lepidoziineae and Cephaloziineae. Thirty three species (11.6%) also possess flagelliform axes. These extend to depths of 20–30 cm in peaty substrata and in most species bear abundant fungus‐infected rhizoids. When grown in sand or water culture, isolated from their natural substrata (sandstone rocks, peat, Sphagnum, rotten wood), the hepatics are free from rhizoid infections. On returning the plants to their native substrata, the rhizoid‐fungus associations are re‐established.Each rhizoid or fascicle of rhizoids is infected independently and a continuous strand of fungus‐containing cells is absent. Internally the flagelliform axes contain elongate parenchyma cells with abundant plasmodesmata in their transverse end walls. The apices of the axes are invested by mucilage and subapical amyloplasts appear to act as graviperceptive particles.The morphology of the flagelliform axes and the ultrastructure of the rhizoid‐fungus association varies greatly between taxa. The Lepidoziaceae and Calypogeiaceae produce fascicles of rhizoids from the bases of rudimentary leaves whereas the flagelliform axes in the Cephaloziaceae are leafless. In Cladopodiella the fungus forms a pseudoparenchymatous sheath around the rips of swollen rhizoids. Development of swollen rhizoids precedes fungal infection in Lepidozia, Kurzia and Telaranea but not in other genera. Hyphae penetrating the basal walls of the rhizoids in Cephalosia, Nowellia, Calypogeia and Odantoschisma are ensheathed by host Wall material. These diverse patterns of fungal infection suggest independent, and probably relatively recent, evolution in the various genera.The flagelliform axes in hepatics appear to be major organs of assimilation and perennation structurally and functionally analogous in the former capacity to vascular plant mycorrhizas and particularly the hairs roots in Ericaceae.
An alternative nitrogenase is not expressed in molybdenum‐deficient legume root nodules
Authors: DILWORTH M. J. , LONERAGAN J. F. 
Published: April 2006

summaryThree legume root nodule bacteria systems (Medicago polymorpha L. ‐Rhizobium meliloti, Ornithopus sativus Brot. ‐Bradyrhizobium lupini and Trifolium subterraneum L.‐ Rhizobium leguminosarum by. trifolii) were grown in solution culture under conditions likely to lead to the production of alternative nitrogenases (molybdenum‐deficient, or molybdenum‐deficient but supplemented with vanadium). Addition of 1 μM molybdenum produced significant responses in both nodule and top weights while 2 μM vanadium did not. Ethane, which is produced as well as ethylene when acetylene is reduced by vanadium nitrogenase or nitrogenase‐3 from Azotobacter, was not found in significant amounts during assays of acetylene reduction in either molybdenum‐deficient or molybdenum‐deficient, vanadium‐supplemented treatments, suggesting that no non‐molybdenum nitrogenase was produced by these root nodule bacteria.
Low temperature‐enhanced inhibition of photosynthesis by oxides of nitrogen in lettuce (Lactuca sativa L.)
Authors: CAPORN S. J. M. , MANSFIELD T. A. , HAND D. W. 
Published: April 2006

summaryThe response of photosynthetic gas exchange to oxides of nitrogen (NOx) was studied in leaves of lettuce (Lactuca sativa L.) at different temperatures. Exposure to > high concentrations (e.g. 13 μmol NOx mol−1), similar to those often found in commercial glasshouses, caused a rapid inhibition of the net assimilation of CO2. This appeared to be by a direct effect on photosynthesis rather than by a change in the stomatal conductance. In ambient CO2, (345 μmol mol−1), the percentage inhibition at 10 and 5°C was approximately 3× and 5×, respectively, that measured at 20°C. This effect of temperature also occurred when measured in CO2, enriched air (1050 μmol mol−1), which would normally accompany NOx in a glasshouse. The extent of photosynthetic inhibition caused by NOx was, however, always less in high than in low CO2.The results suggest that when burning fuel to raise the CO2, concentration and heat the glasshouse air, growers should avoid generating high concentrations of NOx, in conditions of low temperature.
Root and soil respiration responses to ozone inPinus taedaL. seedlings*†
Authors: EDWARDS NELSON T. 
Published: April 2006

summaryRespiration rates of roots of loblolly pine (Pinus taedaL.) seedlings decreased in response to elevated ozone (O3) concentrations. Estimated annual root respiration rates were 12% less in seedlings exposed to twice‐ambient O3(7 h mean = 70.110 nl 1−1) than in seedlings exposed to sub‐ambient O3(7 h mean = 20.40 nl 1−1). Measurements taken during periods of relatively rapid and of negligible root growth suggest that the reduced root respiration may be due to both reduced maintenance respiration and reduced growth respiration. Respiration rates of the soil substrate of the O3‐exposed seedlings were also below those of the substrate of seedlings exposed to sub‐ambient O3. The study supports the theory that there is a reduced supply of photosynthates to the roots of plants exposed to elevated O3. It is hypothesized that a reduced supply of photosynthates to the roots may affect soil respiration rates by reducing root exudation rates and, consequently, reducing rhizosphere microbial populations.
Seasonal changes in antioxidants in red spruce (Picea rubensSarg.) from three field sites in the northeastern United States
Authors: MADAMANCHI NAGESWARA R. , HAUSLADEN A. , ALSCHER RUTH G. , AMUNDSON R. G. , FELLOWS S. 
Published: April 2006

summaryChanges in antioxidant levels were investigated in red spruce (Picea rubensSarg.) from three field sites in the northeastern United States. Whiteface Mountain, NY at an elevation of 1090 m, represents a red spruce population in decline, while Millinocket and Howland, Maine are at 518 and 105 m above sea level, respectively, and have red spruce stands that show no symptoms of decline. The Millinocket site with saplings that are 15–20 yr old was compared with the Howland site with 60‐yr‐old trees to test the effect of age on antioxidant levels. The Howland site was compared with the Whiteface Mountain site, which has trees more than 100 yr old, to test the effects of air quality and elevation. Foliage developed in 1987 (87 needles) and in 1988 (88 needles) was sampled from May to November and from July to November, 1988, respectively. Quadratic polynomial and linear regressions were used to model the relationships through time of each variable measured. Regression coefficients were obtained by one‐way analysis of variance. The means for total glutathione and oxidized glutathione were higher at Whiteface Mountain in 87 needles, and needles of both age classes sampled in November had significantly higher oxidized glutathione at Whiteface Mountain compared to those at Howland. No significant difference was observed in the mean ascorbate content of either needle class at all the three sites. The activity of superoxide dismutase declined with time in 87 needles at Whiteface Mountain and the mean activity was lower at Whiteface Mountain than at Howland. The effects of ozone concentration, site elevation and other environmental factors on seasonal changes in antioxidant levels and superoxide dismutase activity are discussed.
Changes in germinability, ABA content and ABA embryonic sensitivity in developing seeds of Sorghum bicolor (L.) Moench. induced by water stress during grain filling
Authors: BENECH ARNOLD R. L. , FENNER M. , EDWARDS P. J. 
Published: April 2006

summaryThe effect of intermittent water stress during grain filling on the germinability of developing seeds of S. bicolor was investigated. The drought treatment was imposed in cycles within the maturation period by withholding water for 5–6 days, rewatering at the end of each drought cycle and withholding water again. Changes in abscisic acid (ABA) content and embryonic sensitivity to ABA in the maturing seeds were also monitored in order to find out if there were any parallel changes with seed germinability resulting from drought conditions. Seeds developing in plants subjected to drought showed a high level of germinability earlier in the maturation period than did control seeds; consequently, they were less resistant to pre‐harvest sprouting as shown when panicles were exposed to high humidity conditions. Very high levels of ABA accumulated in the early stages of development in seeds maturing on water‐stressed mother plants; however. ABA content fell markedly when the seeds stopped growing, and remained significantly below those recorded in control seeds until the end of the maturation period. Development under drought conditions decreased the sensitivity of the isolated embryo to exogenous ABA by about 10‐fold. The good agreement found between germinability, endogenous ABA concentrations and embryo sensitivity to ABA at different stages of development, suggests a key role for ABA as a major inhibitor of precocious germination and shows that changes in germinability caused by water stress during grain filling are likely to be related to changes in ABA pool size in the developing seed.
Studies on the localization of a protein, immunologically similar to a 62‐kilodalton sucrose‐binding protein isolated from developing soybean cotyledons, in the shoot and root of spinach
Authors: WARMBRODT ROBERT D. , VANDERWOUDE WILLIAM J. , HITZ WILLIAM D. 
Published: April 2006

summaryPrevious work, using antisera developed against a 62 kDa sucrose‐binding protein isolated from developing Soybean cotyledons, resulted in the identification of an immunologically similar protein on the sieve‐tube plasma membranes of the small minor veins of spinach (Spinacia oleracea L. var. Bloomsdale Dark Green). These studies have been expanded to determine the extent of the immunologically similar protein throughout the shoot and root of the mature spinach plant. lndirect immunogold labelling of resin‐embedded leaf and stem tissues resulted in the specific localization of colloidal gold on the plasma membrane of mature sieve tubes in the major veins and large minor veins of the lamina as well as sieve tubes of the petiole and stem. The amount of label associated with the petiole and stem sieve tubes was less than in the sieve tubes of the lamina. In all cases, the label was evenly distributed along the plasma membrane and, except for a small amount of background label on the cell walls, was not associated with any other cellular component including organelles, membranes or membrane systems. Other cell types of the vascular and ground tissues were also essentially free of label. Control sections treated with non‐immune rabbit IgG were free of label. Sections of root tissue treated with the 62 kDa antisera contained immunolabel on the plasma membrane of the sieve tubes and, in addition, the plasma membrane of various parenchymatic elements including companion cells and vascular parenchyma cells. In both root and shoot tissues, the plasma membrane of sieve tubes considered to be structurally and physiologically immature did not contain label. These results are discussed in relation to the apoplastic and symplastic transport of solutes in source and sink tissues.
Development of the ovular structures in peach [Prunus persica (L.) Batsch]
Authors: ARBELOA ARANCHA , HERRERO MARIA 
Published: April 2006

summaryChanges in the ovular tissues of peach (Prunus persica (L.) Batsch) were studied from anthesis to fertilization or degeneration in pollinated and unpollinated flowers. During this time the ovule undergoes a continuous developmental process. At anthesis the megagametophyte is immature and is not fully developed until 12 days later. During the first three weeks following anthesis the ovule increases in length from 400 to 1200μUm, and the nucellus and integuments undergo various changes particularly in the distribution of starch and cutin. These appear to be connected with early embryo sac nutrition and protection. As the ovule matures, starch accumulates mainly in the embryo sac, integuments and at the nucellar tip. This starch disappears during early embryo sac elongation. Concomitant with starch depletion, the cutin that separated the integuments from the nucellus vanishes. Other cutin accumulates between cells in the nucellar tip, thus protecting and isolating the embryo sac. Most of these changes appear to be a fixed feature of ovule development since they were also observed in a few long lived ovules in unpollinated flowers. However, in unpollinated flowers development of most of the ovules is soon interrupted: callose accumulates af the chalaza, starch disappears and the ovules degenerate.
The branch roots of Zea. II. Developmental loss of the apical meristem in field‐grown roots
Authors: VARNEY G. T. , McCULLY M. E. 
Published: April 2006

summaryMost of the first‐order branches of field‐grown maize roots are short (around 10 mm). An anatomical and morphological survey of the tips of branches from nodal roots showed that almost all branches lacked a normal apex. Most tips were broken off (e.g. 74% in the mid‐regions of roots from node 1, 95% in the same region of node 3 roots), with living, mature tissues right to their end. The remaining tips were of 3 types: (a) Determinate tips with rounded off ends, no root cap, and mature tissues right at the tip;(b) Normal tips which were miniaturized versions of main root apices with a meristem, root cap and long zone of elongation; (c) Intermediate tips in which cap loss, meristem outgrowth and differentiation were incomplete. Normal tips were mainly on branches of the youngest roots and determinate tips were the predominant intact tips of old roots. This distribution, together with anatomical features of the three tip types indicates that Determinate tips form from Normal tips by a controlled pattern of cell enlargement, differentiation and possibly, cell division. Many tips must be broken accidentally by excavation, or earlier by browsers or pathogens. There was some evidence, however, that some broken tips are formed by developmentally controlled abscission both before and after the formation of determinate tips.