bluuebunny/crossref_metadata_2025_split huggingface dataset:
DIRECT FOLIAR EFFECTS OF SIMULATED ACID RAIN
Authors: NEUFELD H. S. , JERNSTEDT J. A. , HAINES B. L. 
Published: May 2006

SummaryThe effects of foliar applications of simulated acid rain (pH 5–6, 4.0, 3.0 and 2.0) were observed for seedlings of four deciduous tree species native to the eastern United States, Liriodendron tulipifera L., Platanus occidentalis L., Liquidambar styracifiua L., and Robinia pseudo‐acacia L. Damage occurred only at pH 2.0. Liriodendron was least damaged, Platanus the most. For Liriodendron and Platanus, older leaves showed more damage than younger ones, whereas for Robinia the opposite was true. No age effect was noted for Liquidambar. Height growth was reduced at pH 20 in Platanus and Robinia, and less so in Liquidambar. Total biomass was significantly reduced at pH 2.0 for Platanus and Liquidambar, resulting mainly from reduction in stem and root biomass. Leaf biomass was not greatly affected in any of the species. Photosynthetic rates in Platanus were reduced after exposure to rain of pH 20, and were the result of changes in mesophyll conductance to CO2, as stomata! conductances were not affected. In Liquidambar, stomatal conductances to water vapour were lowered after exposure to rain of pH 2.0. Results show that under greenhouse conditions only rain of extremely low pH causes foliar damage and growth reductions. Lowered rates of photosynthesis in Platanus may have contributed to the observed reductions in growth.
HYPHAL PENETRATION OF BRASSICA (CRUCIFERAE) ROOTS BY A VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS
Authors: GLENN M. G. , CHEW F. S. , WILLIAMS P. H. 
Published: May 2006

Summary In situ observations of a vesicular‐arbuscular mycorrhizai fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe with roots of Brassica cultivars containing low and normal levels of glucosinolates (7 to 524 mg g−1fresh weight) revealed differences between fungal penetrations of all Brassica roots compared to compatible hosts. Hyphae penetrated older, thicker Brassica roots, failed to form arbuscules, and exhibited no post‐penetration stimulation of hyphal branching either internal or external to the roots. Some internal hyphae formed vesicles. Ultrastructural examination revealed that fungal hyphae penetrated Brassica roots intercellularly between dead cortical cells. Internal hyphae found near the healthy stele of the root lacked cytoplasm and had not penetrated the stele. Hyphae did not penetrate Brassica roots with healthy cortical cells; hyphae which contacted the surface of these cells became vacuolated and retracted their cytoplasm within a day. These observations indicate that functional mycorrhizas were not formed with Brassica roots, and that the level of glucosinolates in roots was not correlated with failure to establish symbiosis.
WOUND OCCLUSION AND DISCOLOURATION COLUMNS IN RED MAPLE
Authors: LEBEN CURT 
Published: May 2006

SummaryRed maple (Acer rubrum L.) stems (15–25 cm diam. at breast height) were wounded in the autumn or spring with horizontal, 1‐cm wide chain‐saw cuts 4 to 6 cm deep and 10 to 16 cm long. Wound occlusion (VO, vertical occlusion, at the wound side), bark dieback (BD, failure of horizontal occlusion above and below the wound), and the length of discoloured wood columns (DWC) were recorded after two growing seasons. For 93 trees (one wound each), correlations between lengths of BD and DWC were not significantly different above and below the wound (r= 0.58 and 0.56, respectively), with DWC being 2 to 3 times the length of BD. Corresponding correlations between the VO rating and the length of DWC were 0.41 and 0.38 (no significant difference). Compared with wounds made in the autumn, wounds made in spring caused less BD, greater VO, and shorter DWC. It is suggested that hydrostatic pressure in the wood, which is positive in the spring and negative in the autumn, is a major determinant of the volume of DWC and hence of wood that is susceptible to decay.
LIGHT AND DRY STORAGE INFLUENCES ON THE RESPIRATION OF GERMINATING SEEDS OF FIVE SPECIES
Authors: HILTON J. R. , OWEN P. D. 
Published: May 2006

SummaryIn an attempt to study the influence of light on early metabolic events in seed germination, the rates of oxygen uptake of germinating seeds of five species were measured in relation to their germination response to light and to their loss of primary dormancy during dry storage. No significant effects of light on oxygen uptake prior to germination (i.e. prior to radicle protrusion) were detected. A difference m the initial rates of oxygen uptake prior to germination was observed when seeds were stored at low (8%) moisture contents suggesting that significant changes in their respiratory capacity occurred under these conditions.
EFFECTS OF PRETREATMENT WITH PHOSPHATE IN NATURAL POPULATIONS OF AGROSTIS CAPILLARIS L.
Authors: MCCAIN S. , DAVIES M. S. 
Published: May 2006

SummaryClones of six populations of Agrostis capillaris L., collected from contrasting soils, were grown for one year in sand culture supplied with either 1 or 40 mg P dm−3 in weekly applied solutions (low and high P‐pretreatments). The pretreatments resulted in considerable phenotypic variation, measured as the fresh weight and chemical composition of tillers. The tillers were subsequently rooted in nutrient solutions containing aluminium (05 to 30 mg Al dm−3). Tillers of most phenotypes established successfully in control (0.5 mg Al dm−1) solutions while increasing Al concentration increased the number of tillers which failed to initiate roots. Therefore, when the length of the longest root on each tiller was measured after 18 d, unrooted tillers were recorded as zero values.Tillers of low P‐pretreated plants produced longer roots than those of high P‐pretreated plants in control (0.5 mg Al dm−3) solutions but their root extension was more inhibited by increasing concentration of Al than that of the high P‐tillers. However, neither phenomenon could be directly related to the initial concentration of P in the shoots of the individual clones nor to any other measure of initial phenotype.The responses of the populations to Al were not related to the chemical composition of their native soils. The findings are discussed in relation to the common practice of using vegetative tillers, propagated in conditions of high nutrient supply, in comparative ecological experiments.
DISTRIBUTION OF LIGNIN DERIVATIVES IN PLANTS
Authors: LOGAN KAREN J. , THOMAS BARRY A. 
Published: May 2006

SummaryAcetovanillone, p‐hydroxybenzaldehyde, syringic aldehyde and vanillin were prepared from a range of gymnosperm, angiosperm, pteridophyte and bryophyte lignins by alkaline oxidation. The major lignin oxidation product of gymnosperms is vanillin; that of angiosperms is syringic aldehyde. The latter is more widespread than previously thought. Its identification seems to be linked in most cases to the presence of fibres in the plant tissues analyzed. The differentiation of gymnosperm and angiosperm plant groups on these oxidation products is discussed. It is proposed that the lignin of fibre walls is the reason for these differences.
FLANDRIAN ENVIRONMENTAL HISTORY OF THE ISLE OF MULL, SCOTLAND.
Authors: WALKER M. J. C. , LOWE J. J. 
Published: May 2006

SummaryPollen–stratigraphic evidence is presented from three sites in Glen More on the Isle of Mull, Inner Hebrides, Scotland, which spans the time interval from the wastage of the Loch Lomond Advance glaciers to the virtual disappearance of woodland from the island in the Late Flandrian period. Radiocarbon dates suggest that the Isle of Mull was deglaciated by about 10000 B.P., and palynological evidence from the base of the profiles implies time‐transgressive deglacial retreat of the ice that occupied Glen More. Wastage of the last glaciers on the island was followed by the expansion of Empetrum heath and juniper scrub, the latter being widespread by about 9600 to 9500 B.p. At that time birch woodland may have been present in the lowlands and in sheltered localities along the coastal fringes, but the spread of Betula into the hills of central Mull appears to have occurred some 200 to 300 years later. Coryhis avellana became widely established around 8800 B.p. and was followed by mixed woodland genera including Quercus, Ulmus, Pinus and Alms. The relatively low representation of arboreal pollen in all three profiles suggests, however, that woodland was never widespread on Mull during the Flandrian due principally, it would seem, to exposure to strong westerly winds. The expansion of grassland and CaWuna‐dominated heaths during the Late Flandrian reflects a change to wetter climatic conditions, but may also be partly a consequence of anthropogenic activity, particularly in lowland areas.
REGULATION OF ABSCISIC ACID CONCENTRATION IN LEAVES OF FIELD‐GROWN PEARL MILLET (PENNISETUM AMERICANUM [L.] LEEKE): THE ROLE OF ABSCISIC ACID EXPORT *
Authors: HENSON I. E. , MAHALAKSHMI V. , ALAGARSWAMY G. , BIDINGER F. R. 
Published: May 2006

SUMMARYDiurnal changes in the concentration of abscisic acid (ABA) which occur in leaves of droughted, field‐grown plants of pearl millet (Pennisetum americanum [L.] Leeke) are not always correlated with changes in bulk leaf water potential (Φ). A rapid decline in ABA content of the leaves following its rise to a peak level in mid‐morning, was observed in several time‐course studies despite continued water stress.The possibility that the reduction in ABA in leaves was due to an elevated rate of its export was examined in two ways: (i) by measuring ABA concentrations in developing panicles (possible sinks for leaf‐produced ABA) and in leaves, and (ii) by comparing the amounts of ABA in ungirdled leaves and in leaves heat‐girdled at the base of the lamina to block export. ABA concentrations in panicles generally paralleled those in leaves, though the peak level of ABA in the morning in panicles occurred later than in the leaves in some samplings. Although girdling initially increased ABA concentration, it did not prevent a subsequent fall which generally paralleled the decline observed in untreated leaves. The decrease in ABA that occurred despite the block to export and despite continuing stress was, therefore, attributed to changes in the synthesis or metabolism of ABA within the leaf.The probable rate of export of ABA from leaves, calculated from the changes in its concentration due to girdling, was highest at the time of most rapid ABA accumulation and declined thereafter. The percentage export of recently assimilated carbon declined similarly. However, the probable absolute rate of export of photosynthate, computed from stomatal conductance and [14C]‐export measurements, was not uniquely related to that of ABA.
AN ESTIMATE OF THE ‘COST’ OF NUTRIENT LEACHING FROM FOREST CANOPIES BY RAIN
Authors: AMTHOR JEFFREY S. 
Published: May 2006

SUMMARYInorganic and organic substances are leached from forest canopies by rain. Estimates have been made of the percentage of net carbon assimilation associated with providing energy for both uptake and assimilation of substances leached from the canopy by rain. While leaching of nutrients from the canopy is a very significant component of nutrient cycles in forest ecosystems, it appears from the present calculations that it is generally only a minor factor in the energy (C) cycle. Energy losses associated with increased leaching as a result of rain acidification will probably cause only small reductions in forest productivity, unless they are the result of specific nutrient deficiencies.
ADVENTITIOUS ROOT FORMATION IN RELATION TO THE UPTAKE AND DISTRIBUTION OF SUPPLIED AUXIN
Authors: JARVIS B. C. , SHAHEED A. I. 
Published: May 2006

SUMMARYTriiodobenzoic acid (TIBA) or morphactin (chlorfluorenol), applied to the base of the epicotyl of mung bean cuttings, inhibit root formation in the hypocotyl. Such inhibition occurs even when cuttings are supplied with auxin at the same time. Both treatments reduce the accumulation of radioactivity in the hypocotyl when [14C]IAA is supplied to the primary leaves. Morphactin does not influence the uptake of [14C]IAA supplied basally to cuttings, nor does it have any apparent influence on the distribution of radioactivity within the cutting. However, the extent to which [14C]IAA moves from leaves to hypocotyl is influenced by the basal supply of auxin in which cuttings are placed. These observations are discussed in terms of the role of the leaves in auxin‐induced adventitious root formation.
THE POTENTIAL IMPORTANCE OF AN INCREASED ATMOSPHERIC NITROGEN SUPPLY TO THE GROWTH OF OMBROTROPHIC SPHAGNUM SPECIES
Authors: PRESS M. C. , WOODIN S. J. , LEE J. A. 
Published: May 2006

SUMMARYAtmospheric nitrate deposition varies across Northern Britain, and has increased approximately fourfold since the last century in the Manchester Region. Ombrotrophic mires depend on an atmospheric supply of elements, and some components of nitrogen deposition at two mire sites in northern Britain were investigated. The sites differed in proximity to major pollution sources. Growth of Sphagnum cuspidatum Hoffm, in bog pools was less in the polluted site and this was associated with a marked increase in tissue nitrogen concentration. Field experiments in which S. cuspidatum plants from unpolluted sites were exposed solely to atmospheric deposition in artificial bog pools showed that much of this large increase in nitrogen concentration could have resulted from atmospheric deposition alone. Concentrations of nitrate and ammonium within the range observed in bulk deposition at the polluted site reduced the growth of S. cuspidatum in a laboratory experiment. The results are discussed in relation to a general increase in atmospheric nitrogen deposition, and its potential importance to plant growth.
MUTAGENESIS AND ISOLATION OF MORPHOLOGICAL MUTANTS IMPAIRED IN NITROGEN‐FIXING CAPACITY FROM A CYNAOBACTERIUM GLOEOTRICHIA GHOSEI
Authors: MISHRA A. K. , TIWARI D. N. 
Published: May 2006

SUMMARYUltraviolet (u.v.) irradiation and treatment with nitrosoguanidine (NTG) were used to produce mutants of the cyanobacterium Gloeotrichia ghosei. Three non‐nitrogen fixing (nif−) mutants, which were also altered in their morphological characteristics, were isolated. They were designated as fil1 het+, fil1 het++ and pol− her−. The first two mutants formed heterocysts and exhibited polarity while the third (i.e. pol− het−) had neither heterocysts nor polarity. The fil1 het+strain had a developmental pattern similar to that of the parent alga, but with longer filaments, while the fil1 het++ strain formed chains of intercalary heterocysts and the long filaments showed evidence of intercalary polarity. The isolation of these mutants demonstrates the feasibility of using Gloeotrichia to relate developmental morphology to nitrogen fixation and heterocyst differentiation in a filamentous cyanobacterium.
GREATER LEAF CONDUCTANCE OF WELL‐WATERED VA MYCORRHIZAL ROSE PLANTS IS NOT RELATED TO PHOSPHORUS NUTRITION*
Authors: AUGÉ ROBERT M. , SCHEKEL KURT A. , WAMPLE ROBERT L. 
Published: May 2006

SUMMARYPlants of Rosa hybrida L. cv. ‘Samantha’, grown with high or low phosphorus (P) fertilization, were inoculated with Glomus intraradices Schenck & Smith, G. deserticola Trappe, Bloss & Menge, or left non‐mycorrhizal. All plants except the low‐P non‐mycorrhizal group had similar tissue dry weights, leaf and root surface areas, growth ratios, stomatal characteristics and P contents. The higher rate of P fertilization increased plant dry weight three‐fold and leaf area four‐fold in non‐mycorrhizal plants, but had no effect on growth characteristics of mycorrhizal plants except for a depression of colonization levels. Under well‐watered conditions (75–90% and 45–50% relative soil water content, θ), low‐P mycorrhizal plants displayed greater leaf conductance (g) than both high‐P mycorrhizal and non‐mycorrhizal plants. Leaf water potential (Ψ) was similar in colonized and uncolonized roses. Fungal species did not differ significantly in their influence on Ψ or g.
THE STRUCTURE AND FUNCTION OF THE VEGETATIVE MYCELIUM OF ECTOMYCORRHIZAL PLANTS
Authors: FINLAY R. D. , READ D. J. 
Published: May 2006

SUMMARYUsing perspex observation chambers, the uptake, translocation and distribution of 32P‐labelled phosphorus was studied in ectomycorrhizal mycelial networks of Suillus bovinus (Fr.) O. Kuntze interconnecting plants of Pinus contorta Dougl. ex Loud and Pinus sylvestris L. Label was fed either directly to the cut ends of individual mycelial strands, to plant roots, or to the unsterile peat in the vicinity of advancing mycelial fans. Where 32P was fed to individual strands or mycelial fans it was taken up and translocated through the mycelium, over distances exceeding 40 cm, to all host plants connected to the mycelial network. Ectomycorrhizal roots acted as major sinks for phosphate but the label did not move exclusively towards the plant and was distributed throughout the mycelial system. Calculated translocation rates and flux rates suggest that transport is primarily by symplastic flow rather than turgor driven bulk flow. The amount of label accumulated by each plant was significantly related both to the size of the plant shoot and to the number of mycorrhizal root tips but did not appear to be influenced by the transpiration rates of individual plants. Phosphorus supplied directly to plant roots did not move to other plants via the mycelial connections suggesting that movement of phosphorus between the fungus and host is unidirectional.
A RE‐ASSESSMENT OF THE FORM OF REPRODUCTION IN DANTHONIA SPICATA (L.) BEAUV.
Authors: PHILIPSON MELVA N. 
Published: May 2006

SUMMARYDespite early reports of cleistogamy in Danthonia spicata (L.) Beauv., recent authors have based their work on the incorrect assumption that aerial panicles are entirely chasmogamous and that cleistogamy is confined to axillary spikelets (cleistogenes). Of the florets contained in 122 panicles, 48% were chasmogamous and 52% cleistogamous. Only one panicle was entirely chasmogamous, whereas 58 were entirely cleistogamous. Chasmogamy was most prevalent in the lower parts of the spikelets and in the lower spikelets of the panicles. In addition to self‐fertilizing cleistogamous florets, an unknown but small proportion of non‐opening florets was sufficiently aberrant in their megasporogenesis to suggest that apomixis occurred. The possibility of the presence of apomixis should be considered within a typical cleistogamous system.
LATE PLEISTOCENE ZELKOVA EXTINCTION IN CENTRAL ITALY
Authors: FOLLIERI MARIA , MAGRI DONATELLA , SADORI LAURA 
Published: May 2006

SUMMARYThe genus Zelkova contains species which are nowadays distributed in an extremely fragmentary, mainly Asiatic, area. The Island of Crete retains geographically the species nearest to Italy. Fossil leaves and pollen discovered in some sites of Central Italy furnish evidence of the distribution of these trees before and during the Last (Eemian) Interglacial and of their persistence during part of the Last (Wurmian) Glaciation. The evidence is seen in two pollen diagrams from boreholes at Castiglione and Fucino which have stratigraphic continuity; at the base of the series Zelkova reaches conspicuous peaks in a phase which can be correlated with the Eemian Interglacial. During the climatic fluctuations of the last glacial Zelkova disappears in steppe periods and spreads again in favourable times up to the time of extinction, which seems to occur in both series somewhat before the latest glacial acme.
POLARIZED DNA SYNTHESIS AND CELL DIVISION IN CELL CLUSTERS DURING SOMATIC EMBRYOGENESIS FROM SINGLE CARROT CELLS
Authors: NOMURA K. , KOMAMINE A. 
Published: May 2006

SUMMARYEmbryogenic cell clusters derived from single cells of carrot (Daucus carota L. cv. ‘Kurodagosun’) showed polarized cell division during the initial stages of embryogenesis. Morphological and biochemical polarity during early embryogenesis were examined. Using an experimental system in which single cells differentiate to form embryos at high frequency, [3H]thymidine incorporation into cells and cell clusters was followed during the initial stage of somatic embryogenesis using autoradiography. Polarized incorporation of [3H]thymidine was observed after cell clusters passed the four‐cell‐stage. This polarity was preserved under conditions inducing embryogenesis, but was cancelled under conditions inducing non‐embryogenic growth. This indicates that the polarity of activity of DNA synthesis may be correlated with the expression of totipotency in embryogenesis.
THE ROLE OF ABSCISIC ACID AND CALCIUM IN DETERMINING THE BEHAVIOUR OF ADAXIAL AND ABAXIAL STOMATA
Authors: DE SILVA D. L. R. , COX R. C. , HETHERINGTON A. M. , MANSFIELD T. A. 
Published: May 2006

SUMMARYExperiments are described which attempted to clarify the reasons for differences in stomatal opening on adaxial and abaxial epidemics. Previous studies had suggested that endogenous auxin levels might be responsible. It was found that adaxial stomata were more sensitive than abaxial stomata to externally supplied abscisic acid (ABA). It is suggested that differing endogenous concentrations of calcium ions in the upper and lower epidermes may contribute to the observed differences in sensitivity to ABA. It is further suggested that studies of stomata on isolated epidermis may represent a useful model system for examining the role of cell or tissue sensitivity in determining the responses to ABA and other hormones.Data are presented which lend support to the suggestion that calcium ions play an important part. Treatment with lanthanum ions, which block calcium channels in cell membranes, had little effect on abaxial stomata, but caused the apertures of adaxial stomata to increase considerably. The chelating agent EGTA eliminated the differential behaviour of adaxial and abaxial stomata, which clearly suggests that calcium ions have a dominant role.Experiments in which EGTA and fusicoccin were presented separately and in combination indicated that their effects were independent and additive. It is suggested that they operate at different locations, or on different processes in the guard cells.
EVIDENCE ON THE PATHWAYS OF PHOSPHORUS TRANSFER BETWEEN VESICULAR – ARBUSCULAR MYCORRHIZAL PLANTS
Authors: NEWMAN E. I. , RITZ K. 
Published: May 2006

SUMMARYMycorrhizal hyphae can link one root to another, and it is possible that phosphorus passes from plant to plant by these links. We present evidence on whether this ‘direct transfer pathway’ is the major route between mycorrhizal plants, or whether most phosphorus passes from the roots of one plant to the soil before being taken up by the other plant's roots or its associated mycorrhizal hyphae (the ‘soil pool pathway’).The time‐course of loss of 32P from Lolium perenne L. roots to solution was measured after 32P had been fed to leaves. Another experiment indicated that the amount of 32P lost to soil was not influenced by mycorrhizal infection. 32P was applied to soil in which Plantago lanceolata L., mycorrhizal or non‐mycorrhizal, was growing and the time‐course of uptake determined. Using these results, two alternative models, the ‘direct transfer model’ and the ‘soil pool model’, were used to predict the time‐course and amount of 32P transfer from L. perenne to P. lanceolata. The predictions were then compared with measured transfers between these two species presented here and in a previous paper. The soil pool model's predictions of both amount and time‐course of transfer gave the better fit to observation.The evidence thus suggests that direct hyphal links between roots are not important in phosphorus transfer between these plants.