bluuebunny/crossref_metadata_2025_split huggingface dataset:
A HISTOCHEMICAL STUDY OF PHENOLIC MATERIALS IN MYCORRHIZAL AND UNINFECTED ROOTS OF EUCALYPTUS FASTIGATA DEANE AND MAIDEN
Authors: LING‐LEE M. , CHILVERS G. A. , ASHFORD A. E. 
Published: May 2006

SUMMARYThe distribution of phenols in uninfected and mycorrhizal Eucalyptus fastigata roots has been examined by application of a range of histochemical tests to thin sections.The vacuoles of most cap cells and many epidermal cells of E. fastigata mycorrhizas contain considerable quantities of phenolic materials. Cap cells of uninfected fine roots similarly contain materials with the staining properties of phenols, but uninfected root epidermal cells rarely do. It is suggested that accumulation of phenols in the epidermal cells of mycorrhizas is a response to the presence of the fungal symbiont. Further evidence is provided that the hyphae of the fungal symbiont penetrate and grow through the phenolic materials of the outer root cap cells. No evidence was found to suggest that these areas contain appreciable quantities of polysaccharide.Phenols were also detected in the endodermis and outermost layer of cortical cells. Judged on their staining reactions, these seem to be chemically different from those of the cap and epidermis. They are present in both mycorrhizal and uninfected roots, but appear much closer to the tip in the former. The outer layer of cortical cells has other specialized features, including the presence of a suberin layer in the walls, which are characteristic of mature differentiated endodermal cells in E. fastigata. These features are discussed from the viewpoint that the outer cortical layer acts as a barrier to further hyphal penetration in eucalypt mycorrhizas.
THE LOCATION OF THE RESISTANCE TO WATER MOVEMENT IN THE SOIL SUPPLYING THE ROOTS OF TRANSPIRING PLANTS
Authors: FAIZ S. M. A. , WEATHERLEY P. E. 
Published: May 2006

SUMMARYPrevious work has shown that when plants are rooted in unsaturated soil and subjected to high rates of transpiration, the depression of water potential in the leaves (ΔΨ1) may rise to as much as 15 bars, but falls to less than half this value on reducing or stopping transpiration. This fluctuation in water stress in the plant has been interpreted as due to changes in the depression of water potential of the soil at the root surface (ΔΨs) arising dynamically as a result of the hydraulic resistance of the soil. Major gradients of ΔΨs could arise in the soil either around each individual root (perirhizal) or between the root zone and the surrounding root‐free water supplying zone (pararhizal).To decide between these two hypotheses, experiments were made on Helianthus plants subjected to conditions in which pararhizal gradients were unlikely to arise. The above pattern of stress development and recovery were clearly demonstrated, thus favouring the perirhizal hypothesis. The data indicate that under these experimental conditions, the drop in water potential across the perirhizal soil was about the same as that through the plant (approx. 6 bars).
EFFECT OF GIBBERELLIC ACID ON POLYPHENOL OXIDASE ACTIVITY IN DE‐EMBRYONATED WHEAT AND BARLEY GRAINS
Authors: JENNINGS P. H. , DUFFUS C. M. 
Published: May 2006

SUMMARYDe‐embryonated grains of wheat and barley showed various responses when incubated with gibberellic acid (GA3). Amylase activity in the three cultivars studied showed similar responses to GA3 concentration and period of incubation. Changes in o‐diphenolase and monophenolase activities of polyphenol oxidase (o‐Diphenol: oxygen oxidoreductase, E.C.I. 10.3.1) which occurred when de‐embryonated grains were incubated in the absence of GA3, were enhanced by the hormone. Activity was promoted in extracts from wheat half‐grains, but inhibited in extracts from the two barley cultivars. Whereas monophenolase activity was detected primarily in extracts of the wheat aleurone layer, it was only detectable in the barley endosperm extracts. The inhibitory effect of GA3 on monophenolase activity in the barley cultivars is discussed.
GIBBERELLIN EFFECTS WITHIN HAZEL (CORYLUS AVELLANA L.) SEEDS DURING THE BREAKING OF DORMANCY I. A DIRECT EFFECT OF GIBBERELLIN ON THE EMBRYONIC AXIS
Authors: ARVIS B. C. J. , WILSON D. 
Published: May 2006

SUMMARYGibberellin Ai breaks the dormancy of hazel seed. Both GA1 and GA3 are transported more readily from embryonic axis to cotyledon than in the reverse direction. Since both gibberellins stimulate axis growth more rapidly when applied directly to it than when applied to the cotyledon, it seems likely that gibberellins directly affect the axis. This is confirmed by a rapid response of excised axes to gibberellic acid in liquid culture.
EFFECT OF GIBBERELLIC ACID AND SOME POLYPHENOLS ON THE FLOWERING OF IMPATIENS BALSAMINA
Authors: NANDA K. K. , KUMAR SURINDER 
Published: May 2006

SUMMARYChlorogenic acid, tannic acid and gibberellic acid (GA3) all induce floral buds in I. balsamina under strictly non‐inductive photoperiods. Floral bud initiation is hastened when 100 mg/l GA3 is used in combination with both polyphenols, the effect being most pronounced with 100 mg/l chlorogenic acid. 1 and 100 mg/l each of chlorogenic and tannic acids increase the number of floral buds also when used in combination with 100 mg/l GA3 as compared with 100 mg/l GA3 alone.
THE CYANOPHYTE‐HEPATIC SYMBIOSIS II. NITROGEN FIXATION AND THE INTERCHANGE OF NITROGEN AND CARBON
Authors: STEWART W. D. P. , RODGERS G. A. 
Published: May 2006

SUMMARYFree‐living and symbiotic phycobionts of Anthoceros punctatus and Blasia pusilla reduce acetylene and fix 15N2; gametophytes and sporophytes without algae do not. Nitrogenase activity by free‐living and symbiotic Nostoc is higher under microaerobic than aerobic conditions in the light, and is higher in the light than in the dark. The free‐living Blasia phycobiont grows heterotrophically on sucrose and less well on fructose and glucose; hetero‐trophic growth on galactose is negligible. There is a transfer of 15N from the alga, via the gametophyte to the sporophyte of Anthoceros. About 98% of the extracellular nitrogen liberated into the medium by excised Nostoc colonies is in the form of ammonia; there is negligible liberation of peptides and amino acids. The capacity to excrete ammonia is lost after 72 h of growth free from the liverwort. Excised Nostoc colonies show a negligible capacity to fix CO2 photosynthetically and autoradiographic studies show a transfer of fixed carbon from Blasia gametophytes to the algal cavities. Sucrose may be the main extracellular carbon compound liberated by Blasia gametophytes. In Anthoceros, nitrogenase activity can be sustained for days when alga‐containing gametophytes are placed in the dark, if the sporophytes remain exposed to the light. This indicates a transfer of photosynthate from the sporophyte, via the gametophyte, to the alga.
THE RESPONSE OF LICHEN GROWTH TO TRANSPLANTATION TO ROCK SURFACES OF DIFFERENT ASPECT
Authors: ARMSTRONG R. A. 
Published: May 2006

SUMMARYThalli of four saxicolous lichens on slate rock fragments were transplanted from rock surfaces to horizontal boards and then to south‐east‐facing and north‐west‐facing rock surfaces. The radial growth rate of Physcia orbicularis and Parmelia conspersa thalli declined after transplantation to north‐west‐facing rock surfaces and was unchanged after transplantation to south‐east‐facing rock surfaces compared with growth rate on the boards. The radial growth rate of P. glabratula ssp. fuliginosa thalli declined after transplantation to south‐east‐facing rock surfaces and was unchanged after transplantation to north‐west‐facing rock surfaces compared with growth rate on the boards. The radial growth rate of P. saxatilis thalli was similar on the horizontal boards, south‐east‐facing and north‐west‐facing rock surfaces. Those results are discussed in relation to the aspect distributions of the four lichens in South Gwynedd, Wales.
THE EXTRACTION, COMPOSITION AND INTRA‐CELLULAR DISTRIBUTION OF PROTEIN IN EARLY MAIZE GRAINS FROM AN ARCHAEOLOGICAL SITE IN N.E. ARIZONA
Authors: DERBYSHIRE E. , HARRIS N. , BOULTER D. , JOPE E. M. 
Published: May 2006

SUMMARYMaize grains from an archaeological site in N.E. Arizona have been examined by light microscopy and electron microscopy. Their endosperm tissue was intact and was similar to that of modern maize although some of the features seen in other non‐viable seeds were present; the embryos, however, were discoloured and damaged. Protein has been extracted from both endosperm and embryos although only a small quantity was extracted from the latter. The protein sub‐unit profiles of these extracts and of storage protein fractions prepared by serial extraction of endosperm meal in salt, alcohol and sodium dodecyl sulphate (SDS) solutions have been determined after electrophoresis in SDS‐acrylamide gels. The data obtained indicate that zein and glutelins similar to modern maize proteins were the major storage proteins but that their proportions differed to those in modern maizes; these conclusions are supported by the amino acid composition of the wholse seed meal. It is suggested that these procedures may be applicable to other archaeological samples of seeds including those of other species and that the data so obtained may be of use in cultural studies and in botanical studies of crop plant origins and evolution.
EFFECTS OF PLANT HORMONES PRESENT IN BACTERIAL CULTURES ON THE FORMATION AND RESPONSES TO VA ENDOMYCORRHIZA
Authors: AZCÓN R. , DE AGUILAR C. AZCÓN‐G , BAREA J. M. 
Published: May 2006

SUMMARYThe growth and infection levels in mycorrhizalLavandula, LycopersicumandMedicagoplants were compared after treatment with preparations fromRhizobium, Azotobacterand phosphobacteria (aPseudomonas).The bacterial cultures are known to contain growth substances. Ceil‐free supernatants and in some instances, the whole bacterial culture, behaved as the pure plant hormone in improving dry weight and infection levels compared with mycorrhizal control plants.
A PROCEDURE FOR THE SIMULTANEOUS MEASUREMENT OF NET CO2‐EXCHANGE AND NITROGENASE ACTIVITY IN LICHENS
Authors: CRITTENDEN P. D. , KERSHAW K. A. 
Published: May 2006

SUMMARYA sensitive and rapid procedure is described for the simultaneous measurement of mean rates of net CO2‐exchange and nitrogenase activity (acetylene reduction) in cyanophilic lichens. It involves a reaction gas chromatographic technique for the determination of CO2 and ethylene. Data on concurrent rates of net CO2‐exchange and nitrogenase activity in Peltigera canina (L.) Willd. var. praetextata (Florke em. Sommerf.) Hue and Stereocaulon paschale (L.) Hoffm. at different levels of thallus water content are presented in order to illustrate the application of the new method.
LICHENS OF THE SUGAR LIMESTONE REFUGIUM IN UPPER TEESDALE
Authors: GILBERT O. L. , EARLAND‐BENNETT P. , COPPINS B. J. 
Published: May 2006

SUMMARYThough the grassland associated with the sugar limestone outcrops in Upper Teesdale supports the richest terricolous lichen assemblage of any calcareous site so far discovered in England or Wales it may not have acted as a significant refugium for late‐glacial lichens. A possible reason for this is suppression by open canopy forest during the boreal and atlantic periods. The current high density of terricolous lichens may, to some extent, be a result of intensive grazing over the last few centuries which has favoured the development of an extremely short, open sward offering a wide range of microhabitats.
Studies IN THE VEGETATIONAL HISTORY OF SCOTLAND
Authors: BIRKS HILARY H. , MATHEWES ROLF W. 
Published: May 2006

SUMMARYThis paper describes palaeoecological studies at Abernethy Forest by means of pollen and macrofossil analysis and radiocarbon dating. It also illustrates the value of stratigraphic macrofossil analysis in conjunction with pollen analysis in increasing the range and detail of palaeoecological reconstructions of past vegetation and environment.A new, large diameter core from Abernethy Forest was radiocarbon dated, and the presence of Late Devensian sediments was confirmed. Clear vegetational changes were recorded. A pioneer grass‐sedge vegetation colonized the bare moraine. It developed into a shrub tundra, dominated by Empetrum and Be tula nana as a result of the climatic warming during Allerød time. The Younger Dryas climatic deterioration led to the formation of species‐rich open vegetation, in which Artemisia was very abundant.At the opening of the Flandrian, at about 9700 B.P., Juniperus and Betula nana scrub developed, which was later colonized by tree Betula and then Corylus. From about 7225 B.P. Pinus dominated the forest.Throughout, the specific determinations and local derivation of macrofossils enhanced the reconstruction of the upland vegetation. In addition, macrofossils provided the majority of the evidence for the progression of the hydrosere through lake to bog communities.The complementary nature of pollen and macrofossil analyses from the same core is emphasized by a direct comparison of seed and pollen influxes.
CELL WALL STRUCTURE AND ELONGATION GROWTH IN ZEA MAYS COLEOPTILE TISSUE
Authors: DARVILL A. G. , SMITH C. J. , HALL M. A. 
Published: May 2006

SUMMARYData from pulse‐chase studies on the turnover of glycosidic linkages in cell walls of maize coleoptile sections and other work on the effect of auxin or low pH on sugar release from ‘sheets’ of cells derived from the same tissue are presented. The qualitative and quantitative effects of auxin and low pH on sugar release from cell sheets are almost identical in the short term. Using a recently derived model of the maize coleoptile cell wall, a hypothesis is proposed concerning the role of auxin‐induced proton release in the cleavage of glycosidic linkages in relation to growth.
PLANT AND LEAF RESISTANCE TO GASEOUS AIR POLLUTION STRESS
Authors: TAYLOR G. E. 
Published: May 2006

SUMMARYLevitt's (1972) revision of stress phenomena in plants provides a scheme for analysing the response of vegetation to gaseous air pollution. Total plant resistance is a consequence of two general mechanisms, (i) pollution stress avoidance and (ii) stress tolerance. Stress tolerance is subdivided further into strain avoidance and strain tolerance. Many of the environmental, physiological and morphological factors known to influence the susceptibility of plants to air pollution are discussed using this format. The value of this approach is the systematic framework it provides for analysing, relating and interpreting the factors affecting variable leaf and plant resistance to gaseous air pollution stress.
RESPONSE TO SOIL MOISTURE SUPPLY IN THREE LEGUMINOUS SPECIES
Authors: FOULDS W. 
Published: May 2006

SUMMARYDetached nodules of Medicago lupulina, Lotus corniculatus and Trifolium repens were able to reduce acetylene for a period of 8 h in moist conditions, but the rate fell after 2 h when water stress was applied. Under moist conditions, nodules of Medicago lupulina and Trifolium repens, when measured while attached to or detached from the host plant, possessed the most rapid rate of N2(C2H2)‐fixation. Nodules of Lotus corniculatus showed by far the slowest rates. Relatively mild drought had less effect on N2(C2H2)‐fixation of L. corniculatus than the other two species. This legume also suffered fewer fatalities, maintained a relatively high shoot turgidity and shedded fewer root nodules during periods of desiccation. Under similar drought conditions, the N2(C2H2)‐fixation rate of Medicago lupulina nodules was drastically reduced and about half of the root nodules were lost. However, only half the plants died. The same severity of desiccation caused similar reductions of N2(C2H2)‐fixation in Trifolium repens as well as a very high fatality rate and massive loss of nodules. Severe and prolonged desiccation greatly affected N2(C2H2)‐fixation in all three species.
HORMONES IN PLANTS BEARING NITROGEN‐FIXING ROOT NODULES: THE NODULE AS A SOURCE OF CYTOKININS IN ALNUS GLUTINOSA (L.) GAERTN.
Authors: WHEELER C. T. , HENSON I. E. 
Published: May 2006

SUMMARYLevels of endogenous cytokinins in various parts of nodulated and non‐nodulated alder plants were estimated using the soybean callus bioassay. In three separate experiments, differences in levels of total plant cytokinin activity were attributed primarily to growth differences between plants, other than nodulation. The higher percentage of total plant cytokinin activity found in the leaves of non‐nodulated plants may be related at least in part to the better development of the root system of these plants compared to those with nodules.In other experiments growth differences were minimized by comparing intact plants with plants which were either denodulated or root‐pruned or both. All three surgical treatments had similar effects, reducing levels of cytokinins in the stems, while leaf cytokinin levels were not affected greatly. The relative stability of leaf cytokinin levels was also evident following leaf detachment. Factors responsible for the maintenance of cytokinin levels in the leaf are discussed.The results suggest that nodules are unlikely to make a major contribution to shoot cytokinin content, although export of endogenous cytokinins from the nodules cannot be excluded entirely.
INTERACTION BETWEEN A VA MYCORRHIZA AND AZOTOBACTER AND THEIR EFFECTS ON RHIZOSPHERE MICROFLORA AND PLANT GROWTH
Authors: BAGYARAJ D. J. , MENGE J. A. 
Published: May 2006

SUMMARYLarger populations of bacteria and actinomycetes were recovered from the rhizospheres of tomato plants inoculated with the mycorrhizal fungus Glomus fasciculatus and Azotobacter chroococcum, either individually or together, than from those of non‐inoculated plants. Plants inoculated with both Glomus fasciculatus and Azotobacter chroococcum had greater numbers of bacteria and actinomycetes in the rhizosphere than plants inoculated with either Glomus fasciculatus or Azotobacter chroococcum alone. The fungal population of the rhizosphere was unaffected by inoculation with Glomus fasciculatus but reduced by inoculation with Azotobacter chroococcum. Inoculation of tomato with Glomus fasciculatus increased the Azotobacter chroococcum population in the rhizosphere which was maintained at a high level for a longer time. Inoculation of tomato roots with A. chroococcum enhanced infection and spore production by Glomus fasciculatus. The dry weights of tomato plants inoculated with both G. fasciculatus and Azotobacter chroococcum were significantly (62%) greater than non‐inoculated plants. These results suggest a synergistic or additive interaction between Glomus fasciculatus and Azotobacter chroococcum.
A SCANNING ELECTRON MICROSCOPY STUDY OF ‘VESICULAR BODIES’ IN MYCORRHIZAL ROOTS OF PINUS MUGO (TURRA)
Authors: WILLS B. J. , COLE A. L. J. 
Published: May 2006

SUMMARYThe formation of vesicular bodies in mycorrhizal short roots of Pinus mugo has been investigated using the scanning electron microscope. They appear to bear a relationship to the Hartig net but their exact nature is as yet unexplained.
UPTAKE OF FUBERIDAZOLE AND THIABENDAZOLE BY PENICILLIUM DIGITATUM, CUNNINGHAMELIA ECHINULATA AND POTATO SLICES
Authors: GREENAWAY W. , WARD S. , WHATLEY F. R. 
Published: May 2006

SUMMARYThe resistance of Cunninghamella echinulata to the systemic fungicides fuberidazole (FEZ) and thiabendazole (TBZ), and that of Penicillium digitatum to TBZ, may be due to active secretion of the fungicides from the hyphae. There was no clear evidence that secretion of FEZ was the cause of FEZ resistance in P. digitatum.Both the uptake and release of FBZ and TBZ by potato slices appeared to be passive processes.
SALT TOLERANCE IN PASTURE GRASSES
Authors: VENABLES ANNE V. , WILKINS D. A. 
Published: May 2006

SUMMARYSamples of six species of grass from a salinized pasture were grown in culture solution with varying concentrations of sodium chloride added. The rates of root growth showed a high correlation with the conductivity of water extracts of the soils of origin. The results can be interpreted as evidence for strong selection for the appropriate level of response to salt at each point on the salinity gradient. Salt tolerance was found to be highly heritable in Festuca rubra.
ECOPHYSIOLOGICAL ASPECTS OF ZINC TOLERANCE IN SILENE MARITIMA WITH.
Authors: BAKER A. J. M. 
Published: May 2006

SUMMARYZinc uptake by a range of zinc‐tolerant and non‐tolerant populations of Silene maritima was studied by means of long‐term water‐culture experiments. The pattern of zinc uptake and transport in mine populations differed from coastal and arctic‐alpine populations. All mine populations showed some degree of restricted transport from root to shoot; some also accumulated zinc in the roots. Uptake characteristics could be correlated with soil zinc analyses but did not relate directly to indices of zinc tolerance obtained by short‐term measurements of radicle elongation.
AUXIN TRANSPORT CHARACTERISTICS AND CELLULAR ULTRASTRUCTURE OF DIFFERENT TYPES OF PARENCHYMA
Authors: WANGERMANN ELISABETH , WITHERS LYNDSEY ANN 
Published: May 2006

SUMMARYSecondary xylem tissue of Coleus and Helianthus internodes, and both parenchyma and vascular tissue of Zea and Triticum coleoptiles, were found to be capable of active polar auxin transport; pith parenchyma from Coleus and Helianthus internodes was not. Electron microscopy revealed the presence of ‘plasmalemmasomes’ in parenchyma cells from tissues known from present and previous work to contain the transport system, and their absence from cells of tissues known to lack the transport system. A possible link between the presence of plasmalemmasomes and the capacity for polar auxin transport is discussed.
FURTHER INVESTIGATIONS INTO THE LOCATION AND MAGNITUDE OF THE HYDRAULIC RESISTANCES IN THE SOIL:PLANT SYSTEM
Authors: FAIZ S. M. A. , WEATHERLEY P. E. 
Published: May 2006

SUMMARYIn a previous paper (Faiz and Weatherley, 1977), evidence was put forward for the development of steep gradients of water potential in the soil surrounding the individual roots of rapidly transpiring plants (perirhizal gradients). In this paper, similar experiments are described in which additional data on the dimensions of the root system, distribution of soil water potentials within the rooting zone and the water potentials of the roots themselves were obtained. It was found with experiments on soil that the surface area of the root system was × 60 the cross‐sectional area of the pararhizal pathway (cross‐sectional area of the pot) through which water moved to the root zone from the water table below. Since the volume rate of flow through the peri‐ and pararhizal zones was the same, the velocity of movement up to the individual root was therefore only 1/60 of that through the soil supplying the root system. Under conditions of rapid transpiration, the gradient of water potential in that part of the pararhizal pathway immediately beneath the root zone was found to be about 1 bar cm−1. Thus it would be expected that the perirhizal gradient would be 1/60 of this, i.e. it would be negligibly small. However, the actual perirhizal drop in water potential was found to be about 8 bars through a distance of 0.1 cm, i.e. the gradient was 80 bars cm−1. Such a steep gradient would require the hydraulic conductivity of the soil in the perirhizal zones to be 4 orders of magnitude lower than that in the pararhizal pathway. An even greater discrepancy was found with fine sand. The soil within the rooting zone had a somewhat lower water content than that in the pararhizal zone, but it is not thought that this, and some other imponderables which are discussed, could account for this enormous discrepancy. It is concluded that in these experiments, measurable perirhizal gradients were unlikely to develop. Nevertheless, a considerable drop in water potential (about 8 bars in these experiments) between the soil and the root surface remains to be explained. The hypothesis is put forward that it is at the soil:root interface that a high resistance barrier can arise.