bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pollination density ‐ effects on pollen germination and pollen tube growth in Betula pubescens Ehrh. in northern Sweden
Authors: HOLM S. O. 
Published: April 2006

SUMMARYThe aim of this study was to test the hypothesis that increased pollination enhances the probability of‘pollen competition’in Betula pubescent. In an in vitro test, the germination of pollen from three B. pubescens trees, increased with increasing pollen density (r2= 0·82, 0·81 and 0·82, respectively). Pollen tubes grew at different rates in styles when testing different paternal/maternal combinations. Evidence was obtained to suggest that these differences might be attributed to both maternal and paternal effects. Further, increasing the number of tubes per style tended to increase the length of the longest tube per style, but had no significant effect on the mean length of the tubes. The r values, for the correlations of lengths with numbers of pollen tubes per style, were lower in two natural B pubescens populations than in the data from a controlled pollination experiment, is concluded that selection among male gametes may occur after supplementary pollination in B. pubescens, but in natural situations, pollen deposition is usually too low for pollen Selection to be a common occurrence.
A one‐year study on carbon, water and nutrient relationships in a tropical C3‐CAM hemi‐epiphyte, Clusia uvitana Pittier
Authors: ZOTZ GERHARD , WINTER KLAUS 
Published: April 2006

SUMMARYDiel (24 h) courses of CO2 and water‐vapour exchange of leaves of hemi‐epiphytic plants of Clusia uvitana Pittier (Clusiaceae) were measured under natural tropical conditions in the semi‐evergreen moist forest of Barro Colorado Island, Panama, from January 1991 until January 1992. Plants were studied at two sites, in the crown of a 47‐m tall tree (Ceiba pentandra) and on the shore of Lake Gatun, at a height of about 2–4 m. The following results were obtained: (1) Diel carbon gain was mainly a function of photosynthetic photon fluence rate (PPFR) on individual days. PPFR also strongly affected CAM activity. A leafless period of the host tree Ceiba pentandra resulted in higher incident PPFRs and slightly lower nighttime temperatures in the canopy of C uvitana; this led to increases in both daytime and nighttime CO2 fixation. (2) In fully mature sun leaves from the two sites, nocturnal net uptake of atmospheric CO2 occurred on almost all of the 71 days measured and nocturnal carbon gain was enhanced during the dry season. (3) In C. uvitana at the Lake site, 24‐h carbon gain during the wet and dry season was similar to C. uvitana at the Ceiba site during the leafless period of the host tree. Overall CAM activity was lower at the Lake site. (4) Recycling of respiratory CO2 was a major route for nocturnal acid synthesis. Nocturnal net uptake of atmospheric CO2 was closely correlated with changes in titratable acidity, but accounted for only about 30% of the nocturnal increase in organic acids. (5) Mature shade leaves performed CAM only during the dry season, whereas in the wet season they showed atmospheric CO2 uptake exclusively in the light. (6) Independent of exposure or season, leaves less than about 12 wk old showed a C3 pattern of diel gas exchange and the level of titratable acidity was high day and night. (7) The annual carbon budget of outer canopy leaves of C uvitana in the Ceiba site was 1780 g CO2 m‐2 a‐1 and the average long‐term water‐use efficiency was 23 × 10‐3 g CO2 g‐1 H2O. (8) Vegetative growth was strongly seasonal. Branch length increment and leaf area development was much higher in the wet season. Mineral element contents in these evergreen plants showed no age‐related changes, but a significant proportion of elements was retrieved before abscission.
Transfer of phosphate from fungus to plant in VA mycorrhizas: calculation of the area of symbiotic interface and of fluxes of P from two different fungi to A Allium porrum L.
Authors: SMITH S. E. , DICKSON S. , MORRIS C. , SMITH F. A. 
Published: April 2006

SUMMARYThe aim of the work described in this paper was to calculate the fluxes of phosphate (P) across the intraradical interfaces between two vesicular‐arbuscular mycorrhizal fungi [Glomus mosseae (Nicol. & Gerd.) Gerdemann and Trappe and Glomus sp.‘ City Beach’(WL'M 16)] and Allium porrum L. The inflows of P into roots via the fungi were calculated from inflows into mycorrhizal and non‐mycorrhizal plants for four harvest periods up to 84 d. The areas of interface between intercellular hyphae and roots, and arbuscules and roots were calculated for the same harvest periods using image analysis of sections in which the fungus was stained with nitroblue tetrazolium. The imagination of the arbuscular interface was calculated using methods based on previously published data. The fungi colonized the roots to approximately the same extent (% infection), but G. mosseae produced more intercellular hyphae and arbuscules, and hence larger interfacial areas than Glomus sp. City Beach (WUM 16).Hyphal inflows were higher for Glomus sp. City Beach (WUM 16) than G. mosseae for all except the last harvest period, but because of the lower interfacial areas, fluxes via this fungus were higher (3‐7‐12‐8 nmol m‐2 s‐1) than for G, mosseae (0‐8‐3‐2 nmol nmol m‐2 s‐1. These fluxes are in the same range as values for P influx into plant cells and considerably larger than efflux from the fungal hyphae of ecto and ericoid mycorrhizal fungi measured in cultured mycelia. We conclude that enhanced efflux from the fungus must be essential for symbiotic phosphorus uptake by plants via VA mycorrhizal fungi.
Phosphorus, soluble carbohydrates and the competition between two arbuscular mycorrhizal fungi colonizing subterranean clover
Authors: PEARSON J. N. , ABBOTT L. K. , JASPER D. A. 
Published: April 2006

SUMMARYWe investigated the competition between two arbuscular mycorrhizal fungi, Glomus sp. [isolate WUM 10(1)] and Scutellospora calospora [isolate WUM 12(3)] during the colonization of subterranean clover at four concentrations of soil phosphorus (P). When the clover seedlings were 4 wks old we collected data for plant growth, P uptake, mycorrhizal colonization and soluble carbohydrate status of the roots. The percent and total colonization by Glomus sp. was reduced to a much greater extent than S. calospora when the soil P status was increased. When both fungi were inoculated together, S. calospora was unaffected by the presence of Glomus sp. or the P status of the soil; Glomus sp., however, was reduced to a far greater extent when in the presence of S. calospora than compared to when it was inoculated alone, Associated with the decreases in colonization by Glomus sp., when inoculated alone, with S. calospara and with increases in the level of P applied to the soil, were decreases in the concentration of soluble carbohydrates within the root. We propose that root carbohydrates directly influence the outcome of competition between these two isolates during the colonization of subterranean clover.
The effect of rain in the dry‐season on the formation of vesicular‐arbuscular mycorrhizas in the growing season of annual clover‐based pastures
Authors: BRAUNBERGER P. G. , ABBOTT L. K. , ROBSON A. D. 
Published: April 2006

SUMMARYIn a mediterranean climate with hot dry summers and cool winter growing seasons, rain in summer may initiate seed germination and seedling emergence in annual clover‐based pastures. If soil moisture becomes limiting and the seedlings die before the onset of winter rains then a‘false break’has occurred. The effect of false breaks on the formation of mycorrhizas in subterranean clover (Trifolium subterraneum L.) in the winter growing season was investigated.Undisturbed cores were collected in the summer from two annual clover‐based pastures in Western Australia. The cores were treated with one or two false breaks, or left dry. For each false break, 3 centimetres of water were applied to the surface of the core over a 3 day period and then the cores were let dry in glasshouse conditions. The second false break and the growing season were initiated after the complete death of plants that had emerged in the previous cycle. The growing season was simulated by watering all cores to field capacity and planting to a uniform stand of subterranean clover.Mycorrhizal colonization in the growing season was decreased by false breaks with little difference between One and two false breaks. In one soil, the percentage of the root length containing arbuscules (AC%) at 14 d after planting in the growing season was decreased from 52 to 33% by false breaks and at 42 d after planting from 16 to 46%. In the other soil, the AC% at 28 d after planting in the growing season was decreased from 72 to 55% by false breaks. Assessment of the morphology of the mycorrhizas indicated that colonization by fine endophytes was decreased but colonization by Acaulospora spp., Glomus spp. and Scutellospora and Gigaspora spp. was not decreased by false breaks. Shoot phosphorus concentration at 14 d after planting and shoot dry mass at 42 d after planting were decreased by false breaks in only one soil.
Fungal endophytes from the leaves and twigs of Quercus ilex L. from England, Majorca and Switzerland
Authors: FISHER P. J. , PETRINI O. , PETRINI L. E. , SUTTON B. C. 
Published: April 2006

SUMMARYLeaves of Quercus ilex taken from sites in England, Majorca and Switzerland have been studied to detect the influence of the geographic position of the host within and outside its native range on the composition of its endophytic fungal assemblages. Samples of stem tissue of Q. ilex collected from the Swiss trees were also studied to confirm tissue‐specific differences. Sixty different fungal taxa were isolated, but only 28 were frequent. Of the total number of isolates from the leaves from the Swiss, British and Spanish sites 87%, 31% and 63%, respectively, were coelomycetes. Four species of Phomopsis, which includes Phyllosticta ilicina (=Phomopsis ilicina v. d. Aa, ined.), were the most frequent endophytes of leaves and were either absent or rare in the twig units. Two distinct kinds of sterile mycelia were common in twigs. Swiss and Spanish trees possessed fungal assemblages distinct from those present in Britain. Naturalized stands were distinguished from native stands by the presence of rather cosmopolitan and non‐specific fungal taxa, rare or absent in the samples collected in the native stands. Samples derived from the native stands were colonized by more host‐specific fungi. The relative frequency of two sterile mycelia in the Swiss and Spanish sites determined their separation. Phyllosticta (Phomopsis) ilicina, the most numerous leaf colonizer, was virtually absent from the bark and the xylem. The frequent occurrence of coelomycetes as endophytes of woody trees is briefly discussed.
Late‐glacial and Holocene vegetation history of the Flow Country, northern Scotland
Authors: CHARMAN DANIEL J. 
Published: April 2006

SUMMARYThe vegetation history of an important conservation area, the Flow Country in northern Scotland, is described using the results of pollen analysis from two closely spaced cores from the Cross Lochs, eastern Sutherland. Buried lake sediments and shallower surface peats yield a continuous record covering the Devensian Late‐glacial and the Holocene. The earliest Late‐glacial pollen spectra recovered suggest a transition from open habitat to more stable communities, dominated by *Empetrum heath. This Windermere Interstadial vegetation shows some variability, with a phase of increased growth of juniper and birch, followed by deteriorating climate and less stable soil conditions in the transition to the Stadial, with Huperzia selago and Salix. There are poorly defined Loch Lomond Stadial and Stadial‐Holocene transition periods, characterized by Rumex/Oxyria, after which much warmer, Holocene conditions occur, with a succession of birch‐juniper and birch‐hazel woodland. Birch persists in small amounts locally, but the presence of other arboreal pollen is thought to be mostly due to long distance pollen transport. From c. 5500 BP, the landscape is largely treeless, apart from a brief phase of local pine forest c 4500–4000 BP. These changes are compared with other pollen records for northern Scotland. The trends in the Late‐glacial vegetation are broadly similar to those displayed by other sites, although many of the changes appear to be less extreme than for areas to the south and west. The lack of Artemisia during the Loch Lomond Stadial in the east Sutherland and Caithness area is particularly noteworthy. This may imply more extensive snow cover. The early Holocene is similar to the rest of northern Scotland, but invasion of Betula was more rapid and the later growth of this genus and hazel was not so dense. The lack of pine in the early Holocene allies the site with eastern Caithness and the Northern Isles, rather than north‐west Scotland and the Grampians. It is suggested that the effects of early human populations on such marginal forest areas may have been underestimated in the past. The paradoxical existence of pine macrofossils with no pollen evidence in several areas of Scotland is explained, at least in part, by the lack of temporal precision of pollen diagrams rather than by low pollen productivity, extremely localized occurrences of the species or strong prevailing winds.
Immunomagnetic isolation of viable intracellular hyphae of Colletotrichum lindemuthianum (Sacc. & Magn.) Briosi & Cav. from infected bean leaves using a monoclonal antibody
Authors: PAIN NAOMI A. , GREEN JONATHAN R. , GAMMIE FIONA , O'CONNELL RICHARD J. 
Published: April 2006

SUMMARYA method is described for isolating intracellular hyphae (IH, i.e. infection vesicles and primary hyphae) of Colletotrichum lindemuthianum (Sacc. & Magn.) Briosi & Cav. from infected leaves‐of bean (Phaseolus vulgaris L.). 1H were recovered from homogenates of infected leaves after filtration through a 45 μm nylon mesh and isopyenic centrifugation on Percoll. 1H were then affinity‐purified by immunomagnetic separation using Dynabeads coated with monoclonal antibody UB25, specific for IH surface glycoproteins. The method yielded 7 × 104 IH g‐1 f. wt leaf tissue, with 27% purity and 62% viability, as judged by staining with fluorescein diacetate. The Viability of isolated IH was confirmed by their ability to grow in nutrient medium and by the normal ultrastructure of their cytoplasm. The host plasma membrane and matrix layer which surround IH in planta were absent from isolated IH. Staining with lectins. Calcofluor and aniline blue showed that the walls of IH contain N‐acetylgalactosamine. α‐linked mannose residues and β‐linked polysaccharides, including‐chitin and β‐1,3‐glucans. Potential uses of the isolated IH are discussed.
Inorganic carbon acquisition by aquatic photolithoatrophs of the Dighty Burn, Angus, U.K.: uses and limitations of natural abundance measurements of carbon isotopes
Authors: RAVEN J. A. , JOHNSTON A. M. , NEWMAN J. R. , SCRIMGEOUR C. M. 
Published: April 2006

SUMMARYThe 13C/12C ratio (expressed as δ13C) of benrhic photolithotrophs. in the Dighn Water (= Burn) were measured fur comparison with that of the potential inorganic carhun sources. CO2 and HCO3‐, in the Burn. The Burn water contains an average of 65.7 mmol m‐3 CO2 with δ13C of ‐14.7% and 1600 mmol m‐3 HCO3‐ with δ13C of ‐4.%. δ13C values of riparian vegetation were also measured as contributors, after respiration in the soil or the Burn, to the δ13C of inorganic carbon in the Burn. The potential range of differences in 13C/12C between dissolved CO2 and plant organic C is set by the intrinsic 13c/12C discrimination (α value) in CO2 fixation by Rubisco. Main results and conclusions are. as follows, (i) A literature survey suggests that there is no convincing evidence that the α, Values (rate constant for 12CO2 fixation relative to that for 13CO2 fixation by Rubisco in the absence of CO2 transport limitation) for the‘lower plants’in the Burn (diatoms, green and red algae, mosses) are significantly different from the well‐established αp values for the flowering plum enzyme. (ii) In confirmation of earlier work, the semi‐erect 'streamer’gametophytes of the red alga Lemanea mamillosa and the moss Fontinalis antipyetica have δ13C values which can only be interpreted in terms of diffusive CO2 entry with minimal limitation of photosynthesis by CO‐ diffusion, (iii) The serui‐erect grren alga Cladophora glomerata and the flowering plant Ranunculus penicillatus ssp. pseudofluitons (formerly var. calcareus) are‐ both able to use HCO3‐. Their δ13C values indicate that, if the HCO3‐ ‐use system does not (as is likely) discriminate significantly between 13C and 12C, then a substantial fraction of the inorganic C made available to Rubisco must return to the medium, carrying 13C‐inorganic C not fixed by Rubisco. (iv) Two sets of δ13C data from different hydrodynamic regimes distance from leading edge of a flat stone; different size of thalli) show that the attainable differences in situ in thickness of the diffusion boundary layer do not alter the fractional limitation of photosynthesis of Cladophora by external diffusion of inorganic C, considered with HCO3 use. (vi) The entrusting red alga Hildenbrandia rivularis has a δ13C value suggestive of CO2 as the inorganic C source, but not entirely ruling nut HCO3‐. Marine species of both Hildenbrundia and Cladophora have δ13C values which, even when corrected for source inorganic C δ13C values, are 10%, more positive than the freshwater species. (vii) Mats of pennate diatoms were shown by pH‐drift to by able to use HCO3‐; the relatively high (i.e. not very negative) δ12C value of these mats could relate to a relatively‘non‐leaky’HCO3‐ aequisition mechanism and/or to limitation by external diffusion (e.g. through the mat).
Hydraulic architecture, water relations and vulnerability to cavitation ofClusia uvitanaPittier: a C3‐CAM tropical hemiepiphyte
Authors: ZOTZ GERHARD , TYREE MELVIN T. , COCHARD HERVÉ 
Published: April 2006

SUMMARYClusia uvitana Pittíer (Clusiacea) is a tropical hemiepiphyte that has been shown to display a high plasticity in the expression of CAM in response to the environment. When water is available CO2is taken up mostly during the‐ day. This study of the water relations and hydraulic architecture has revealed that leaf water potentials, £ ranged from 0‐7 to ‐0.9 MPa and changed very little with time or water availability. The absolute hydraulic conductivity of stem segments(K,)and the specific conductivity (K1) were comparable to many other temperate and tropical species, but the leaf specificity conductivity (K1) was 1/3 to 1/30 that of many other species. So stems supported high leaf areas per unit of hydraulic conductivity.C uvitanawas very vulnerable to cavitation, reaching 50 % loss of hydraulic conductivity at stem £=1.3 MPa. The species survives in spite of low K1and high xylem vulnerability, because the CAM physiology insures low transpiration rates and high ability to evade dehydration.
Origin of the epidermis in root meristems
Authors: CLOWES F. A. L. 
Published: April 2006

SUMMARYA survey of root meristems shows that in general, closed meristems, those with separate regions generating outer and inner tissues, derive the epidermis with the cortex in monocotyledons and with the cap in dicotyledons. Open meristems, where the cells between the stelar pole and cap divide transiently producing an unstable boundary between the cap and the rest of the root, also show a distinction between the classes, monocotyledons displaying greatest affinity between epidermis and cortex, dicotyledons between epidermis and cap.Exceptions in monocotyledons occur where there is a discrete epidermal meristem, an anticlinally dividing, monostromatic sheet of cells between cortex and cap. This condition has been reliably found only in a few floating plants and it is associated with the root being derived from both pericycle and endodermis of the mother organ. This is uncommon as a permanent feature in angiosperms though not confined to those with discrete epidermises. The mother tissue producing the epidermis depends on the species. In many other monocotyledons with closed meristems the epidermis is functionally discrete, for the branching of the epidermal cell files from, the cortical files is seen within the quiescent centre, i.e. it occurred during the meristem's initiation.Exceptions in dicotyledons occur in the Nymphaeales. In their closed meristems the epidermis is part of the cortical complex and in their open meristems its affinity with the cortex is manifest by early separation of the cap creating a cylindrical cleft in some genera. Differentiation of epidermal trichoblasts is also by a mode more characteristic of monocotyledons. Nelumbo roots, previously described as lacking an epidermis, as in gymnosperms, have closed meristems of dicotyledonous type and epidermises without distinctive trichoblasts, supporting Nelumbno's transfer from the Nymphaeales.The survey has corrected many errors of observation and interpretation in the literature enabling better use to be made of the mode of origin of root epidermises in discussing evolution and the new reclassification of angiosperms.
Is acclimation required for success in high light environments? A case study using Mycelis muralis (L.) Dumort (Asteraceae)
Authors: OSBORNE BRUCE A. , CLABBY GERRY T. , HORSLEY DAVID , NOLAN PETER F. 
Published: April 2006

SUMMARYIn the field significant differences in maximum photosynthetic O2‐exchange rate (Pm) were found between leaves of Mycelis muralis (L.) Dumort (Asteraceae) collected from woodland and exposed habitats, with the highest values in the exposed sites‐ However, there were no differences in the Pm of leaves collected from plants growing in grikes (fissures in the limestone pavement), of exposed limestone pavement, despite a greater than four‐fold difference in the integrated daily irradiance. Leaves of plants from the open pavement had lower photon yields (ø1) and higher dark respiration rates and light compensation points, in comparison to shaded plants. Under controlled environmental conditions the highest Pm of leaves from plants subjected to variations in irradiance were found at the intermediate (8‐6 mol photon m‐2 d‐1 growth light level used. At the highest growth irradiance 17.3 mol photon m‐2 d‐1 used in the laboratory both Pm and øl were reduced, although the latest plant biomass was found at this irradiance. No changes were found in the chlorophyll a:b ratio over the same range of irradiances. Examination of plant populations of M. muralis, collected from open or shaded habitats and exposed to growth irradiances that covered the range over which increases in photosynthesis were, observed in the laboratory (0.86‐8.6 mol photon m‐2 d‐1), resulted in changes in leaf structure and pigment composition. The chlorophyll a:b ratio was low and largely independent of irradiance or the origin of the plant population. Differences in total chlorophyll content were small with the lowest values m the Durrow woodland populations at both irradiances. No variations were found in a number of chloroplast thylakoid structural features. In particular, the ratio of oppressed to non‐appressed membranes was unchanged by growth at the two irradiances, consistent with an invariant chlorophyll a:b ratio. Based on peaks in the difference spectra the woodland populations had mi enhanced in vivo absorption at λlD= 650 and 706 nm when grown at low irradiance. These peaks were absent from the population collected from the open limestone pavement. The significance of the enhanced absorption at low irradiance and the possibility that these peaks represent long‐wavelength forms of chlorophyll a (λlD = 706) and b (λlD = 650) is discussed. A particular feature of plants grown at high irradiance was an enhanced anthocyanin content in comparison to those grown at low irradiance. This was associated with an increase in absorptance. particularly in the green region (λlD = 550 nm) of the visible spectrum. Overall these results suggest that complete acclimation of photosynthesis and an ability to modulate light‐harvesting is not a prerequisite, for success in a high light environment.