bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular weight and humification index as predictors of adsorption for plant‐ and manure‐derived dissolved organic matter to goethite
Authors: Ohno T. , Chorover J. , Omoike A. , Hunt J. 
Published: May 2006

SummarySorptive retention of organic matter is important in maintaining the fertility and quality of soils in agricultural ecosystems. However, few sorption studies have been conducted that use dissolved organic matter (DOM) characteristic of agricultural amendments. We investigated the sorption to goethite (α‐FeOOH) of DOM extracted from: (i) above‐ground biomass of wheat straw (Triticum aestivum L.), maize residue (Zea mays L.), soybean residue (Glycine max (L.) Merr.), and hairy vetch residue (Vivia billosa L.); (ii) below‐ground biomass from maize, soybean, canola (Brassica napus L.), and green bean (Phaseolus vulgaris L.); and (iii) beef, dairy, poultry, and pig animal manures. The apparent molecular weight (MWAP) of the DOM was measured by high performance‐size exclusion chromatography and ranged from 312 to 1074 g mol−1. The carboxyl‐group content of the DOM measured by potentiometric titration ranged from 4.84 to 21.38 mmol(−) g−1 carbon. The humification index (HIX) determined by fluorescence spectrometry varied from 1.15 to 4.33. Sorption was directly related to both MWAP and HIX values of the DOM. Molecular weight analysis of the solution prior to and after sorption indicated that the DOM molecules > 1800 g mol−1 were preferentially sorbed, resulting in fractionation of the DOM upon reaction with goethite. The multiple regression equation, based only on MWAP and HIX parameters, explained 76% of the variance in amount of DOM sorbed. The results indicate that MWAP and HIX are important factors in controlling the sorption of DOM to mineral surfaces. Amendment with materials that release DOM of higher molecular weight and greater humification will result in enhanced initial sorption of DOM to soil solids, thereby contributing to accumulation of a larger soil organic C pool.
PIGMENTS FROM THE BOTTOM DEPOSITS OF AN ENGLISH LAKE
Authors: FOGG G. E. , BELCHER J. H. 
Published: May 2006

SummaryAcetone‐soluble pigments in the sediments of Esthwaite Water, English Lake District, have been separated and characterized chromatographically and spectrophotometrically. Chlorophyll degradation products similar to those described from North American lakes have been found to predominate but α‐ and β‐carotene, lutein, and two unidentified epiphasic‡carotenoids were also present. In an attempt to relate the amounts of these pigments at different depths to the ecological history of the lake and its catchment area, total amounts of chlorophyll degradation products, of epiphasic carotenoids (mainly β‐carotene), and of hypophasic‡carotenoid (lutein), have been determined in samples taken at 10 cm intervals from a core reaching down into the glacial clays. The amounts of each of these three types of pigment were found to show a general correlation with the amounts of organic matter at different depths in the deposits and certain fluctuations appear to be related to ecological changes in the past. The ratio of chlorophyll degradation products to epiphasic carotenoids has been found to remain nearly constant down to 100 cm, indicating that no appreciable decomposition of these pigments has occurred since the sediments were laid down, and below this to fluctuate in a rather regular manner with peaks at about 53 cm intervals (a statistical examination of these fluctuations is included as an appendix). The ratio of chlorophyll degradation products to hypophasic carotenoid has been found to vary in a similar manner except for a general trend indicating the slow decomposition of lutein. These results suggest the occurrence of regular cyclic ecological changes from the Boreal period onwards which were interrupted at about A. D. 1000 by forest clearance.
BALLISTICS IN CERTAIN ASCOMYCETES
Authors: INGOLD C. T. 
Published: May 2006

SummaryHorizontal spore discharge has been studied in the genera Daldinia, Sordaria, Pleurage and Ascobolus. The average distance of discharge for the full spore‐complement of the ascus increases with the size of the projectile. In Pleurage taenioides a consideration of the form of the ascus jet, as caught on a rapidly rotating disk, suggests that as the four spores are shot from the ascus the vigour of discharge tends to fall with the escape of successive spores.
PHYSIOLOGICAL STUDIES OF GERMINATION IN THE GENUS AVENA
Authors: DRENNAN DONALD S. H. , BERRIE ALEX M. M. 
Published: May 2006

SummaryThe development of amylase activity has been studied in dormant and germinating grains of Avena sativa, A. fatua and A. ludoviciana. Little activity was present in dry grains but activity increased considerably during the first few days in germination conditions in non‐dormant grains. Dormant grains showed no increased activity during considerable periods in the imbibed condition.α‐Amylase development was responsible for the bulk of the increased amylase activity but β‐amylase development also occurred. The increased amylase activity was first noted in the endosperm and did not take place until after the resumption of growth in the embryo in all three species. Parts of grains of A. sativa cultured independently showed no capacity to develop increased amylase activity in a manner similar to that of the whole grain.It is suggested that the development of amylase activity is brought about in the endosperm in response to a stimulus from the growing embryo, and that development of increased amylase activity is thus a post‐germination change. The association of this aspect of metabolism with the dormant condition in the wild oats must therefore be dismissed as a potential cause of dormancy.
PLASTID ULTRASTRUCTURE IN THE BARREL CACTUS, ECHINOCACTUS ACANTHODES
Authors: THOMSON WILLIAM W. , PLATT KATHRYN 
Published: May 2006

SummaryThe unique feature of the plastids in the stem of the barrel cactus is the presence of exceedingly large and often numerous plastoglobuli. In the outer green tissue the chloroplasts are similar in ultrastructure to those of other angiosperms except for the presence of numerous plastoglobuli of various sizes and the absence of starch. In the inner, light‐green transition zone adjacent to the cortical tissue, the chloroplasts have large and small plastoglobuli but also contain some starch. The dominant features of the plastids in the cortical and pith tissues are plastoglobuli, accumulations of phytoferritin and the reduction or absence of grana and starch. These observations suggest that the primary storage product in cactus plastids are lipids which accumulate into plastoglobuli. In the transition zone the plastoglobuli are fewer in number than in the outer green tissue and the large plastoglobuli contain regions of electron translucency both of which are indications that the plastoglobuli are being degraded. A possible relationship between the plastoglobuli and starch through gluconeaogenesis is suggested by the tight association of microbodies with the chloroplasts in this tissue. The plastids in the light‐green transition zone, cortical and pith tissue are irregular in shape which is interpreted to indicate that the form of the plastids in these tissues is dynamic.
MODERATE‐TERM WATER STRESSES AND ASSOCIATED CHANGES IN SOME PHOTOSYNTHETIC PARAMETERS IN COTTON
Authors: JONES HAMLYN G. 
Published: May 2006

SUMMARYCotton plants (Gossypium hirsutum L., var Deltapine smoothleaf) were subjected to 1‐ or 2‐week periods of mild water stress using an osmotic soil cell. The treatments were severe enough to affect seriously several photosynthetic parameters, while good night‐time recovery of plant water‐potential minimized effects on development and leaf expansion.Most measurements were made soon after rewatering, owing to very high stomatal resistances in the stressed plants. The stressed plants had lower rates of potential photosynthesis and lower rates of actual photosynthesis (at normal ambient CO2 concentrations) than the controls. Both stomatal and intracellular resistances and the corresponding ‘photosynthetic limitations’ were greater in the stressed plants than the controls. Most of these parameters showed fairly complete recovery 24 hours after rewatering. Parallel changes were observed in the activities of carbonic anhydrase, ribulosediphosphate carboxylase and 14C fixation by leaf slices, all of which were lower in the stressed plants.Although activities of all the processes studied showed parallel changes, there was evidence that the major factor causing reduced photosynthesis in the stressed plants was stomatal closure. There was some evidence that the photosynthetic system adjusted itself to water stress over the periods studied.
THE PATHWAY OF TRANSPORT OF APPLIED INDOLYL‐ACETIC ACID THROUGH INTERNODE SEGMENTS
Authors: WANGERMANN ELISABETH 
Published: May 2006

Summary Helianthus internode segments were fitted with apical donor blocks containing [14C]IAA and [3H]sucrose, and plain agar basal receiver blocks. After transport, donors, tissue and receivers were oxidized in an ‘Oxymat’ and 14C and 3H counted separately. Ageing the segments before transport, or pretreatment with TIBA, greatly reduced the amount of 14C in the receivers, but had no effect on the 3H count.Profiles of 14C were determined after transport of [14 C]IAA through similar segments ringed to various depths, or with the pith interrupted. Interruption of the vascular bundles, but not of the pith, caused accumulation of I4C above the cut in segments transporting IAA basipetally; no accumulation was caused by ringing segments transporting IAA acropetally.It is concluded that active polar transport of IAA takes place in or near the phloem, but by a different mechanism from the one involved in sucrose transport through the phloem of intact plants.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE
Authors: STRIBLEY D. P. , READ D. J. 
Published: May 2006

SummaryThe major soluble carbohydrates of mycorrhizal and non‐mycorrhizal roots of the cultivated cranberry, Vaccinium macrocarpon Ait., have been identified and quantitatively analysed. Mycorrhizal roots contained two sugars, mannitol and trehalose, not found in uninfected roots. As these sugars are abundant in extracts of endophyte mycelium grown in liquid culture, they appear to be of fungal origin. Analysis of neutral sugars derived by acid hydrolysis of insoluble residues showed an accumulation of a mannose‐containing polymer in mycorrhizal roots. Mannose was a principal component of insoluble polymers in the endophyte.All soluble carbohydrates in the root, including mannitol and trehalose, became labelled after feeding 14CO2 to the shoots. Sucrose was the most strongly labelled sugar in both types of root. Mannose present in hydrolysates of mycorrhizal roots was more heavily labelled than that derived from uninfected roots but most 14C in insoluble fractions was found in glucose polymers.The hypothesis that the endophyte derives a supply of carbohydrate from its host plant is discussed.
ON HORMONES AND WEEPING: ASYMMETRIC HORMONE DISTRIBUTION AND THE PENDULOUS GROWTH HABIT OF THE WEEPING MULBERRY, MORUS ALBA VAR. PENDULA
Authors: RECHES S. , LESHEM Y. , WURZBURGER J. 
Published: May 2006

SummaryThe possibility that asymmetric hormone distribution causes downward bending of weeping mulberry (Morus alba var. pendula) twigs was investigated. By extraction, bioassay and gas chromatography it was shown that while upper and lower twig sections had no differences in auxin activity, the two sides differed considerably in content of GA and ABA. The lower side contained high levels of endogenous GA while the upper side had higher concentrations of ABA. The significance of these results and their possible role in the weeping habit of tree growth are discussed. It is suggested that the high GA levels coupled to low ABA content induce greater lignification on the lower side of the twig and that this tissue is less sensitive to auxin and has a lower growth response than the upper side of the twig thus causing a downward inclination of growth.
CARBOHYDRATE COMPOSITION AND METABOLISM OF SENECIO SQUALIDUS L. LEAVES INFECTED WITH ALBUGO TRAGOPOGONIS (PERS.) S. F. GRAY
Authors: LONG D. E. , COOKE R. C. 
Published: May 2006

SummaryThe soluble and insoluble carbohydrates of healthy and Albugo‐infected leaves of Senecio squalidus were determined qualitatively. Quantitative analyses were made of the soluble carbohydrates. Trehalose was synthesized within pustules by the fungus but no acyclic polyols were found. Accumulation of hexoses around pustules together with increased hydrolysis of exogenous sucrose by pustular material indicated increased invertase activity within infected tissues. It is suggested that host‐fungus movement of carbohydrates in Albugo is maintained by hydrolysis of host sucrose and uptake of hexoses, followed by accumulation of trehalose within the mycelium and spores.
THE BIOLOGY OF DAUCIFORM ROOTS IN THE SEDGE CYATHOCHAETE AVENACEA
Authors: LAMONT BYRON 
Published: May 2006

SummarySmall, carrot‐shaped roots produced by Cyathochaete avenacea (Cyperaceae) were investigated. Quantitative data are given on their comparative morphology, anatomy and soil‐plant relationships. While factors controlling their formation appear to have much in common with those controlling proteoid root formation, their origin and structure are quite different. The cyperaceous roots become endomycorrhizal late in their development. These root structures are essentially distinct from any described in other families, and the term ‘dauciform’ is proposed to distinguish them.
THE LOCATION OF REFUGIA OF CORYLUS AVELLANA L. DURING THE WEICHSELIAN GLACIATION
Authors: DEACON JOY 
Published: May 2006

SummaryA survey was made of all existing radiocarbon dates relating to the Corylus rise in Europe in order to find the possible areas of refugia of Corylus during the Weichselian glaciation. Using the radiocarbon dates an isochron map was drawn which indicated areas of refugia off the west coast of the British Isles, south‐west Scandinavia and in south‐western Europe. The possible routes of migration of Corylus are indicated on this. On the basis of the radiocarbon dates the rates of migration of Corylus along the possible routes have been calculated and show that migration from northern refugia was faster than that from southern refugia.The climatic and edaphic conditions in the suggested refugia during the Weichselian glaciation and their importance in relation to the survival of Corylus are discussed. The number of radiocarbon dates is inadequate for definite conclusions to be drawn on the location of refugia and so the need for an extensive programme of radiocarbon dating of important pollen strati‐graphic events in Europe is stressed.
IN VITRO BUD FORMATION IN STEM SEGMENTS OF AILANTHUS ALTiISSIMA
Authors: CARUSO JOHN L. 
Published: May 2006

SUMMARYExcised internodal segments of Ailanthus altissima were grown aseptically on a defined nutrient medium which lacked added growth regulators. Vascular cambium, phloem or cortex, depending upon which of these tissues is exposed, undergoes tangential cell divisions and produces new tissue on top of the explant. Buds appear in surface layers of the newly formed tissue. Seasonal controls of this process are evident from the greater amount of regeneration in samples collected in spring (March‐May).
THE PALAEOHISTORY OF THE GREY ALDER (ALNUS INCANA (L.) MOENCH.) AND BLACK ALDER (A. GLUTINOSA (L.) GAERTN.) IN FENNOSCANDIA
Authors: TALLANTIRE P. A. 
Published: May 2006

SUMMARYThe available 14C‐dated and broadly context‐dated pollen and macrofossil data for the immigration and spread of the two species of alder within Fennoscandia and certain adjacent countries is presented. The phases of immigration and regional spread take place during certain periods of time (e.g. 6500, 6000, 5000 and 4500 14C years B.C.) and over certain restricted geographical areas. The latter yield a picture of climatic regionalism, with limits akin to that of the present day. Along its present, diffuse northern boundary Alnus glutinosa, on the evidence from Tran‐delag in Norway, appears to have become established only in a late phase of the broad climatic optimum, after 2000 B.C., and to have lost ground again after c. 700 B.C., though the course of later events is confused by human activity. A tabulation of the postulated ecological requirements of the two species of alder at various stages of their life histories is attempted. Details of the sites mapped are included in an appendix.
VEGETATIONAL HISTORY OF THE IPSWICHIAN/EEMIAN INTERGLACIAL IN BRITAIN AND CONTINENTAL EUROPE
Authors: PHILLIPS LINDA 
Published: May 2006

SUMMARYThe vegetational history of the Ipswichian (last) Interglacial in Britain is discussed in terms of the behaviour of the various trees and shrubs, the marked opening of the vegetation in the latter part of the interglacial, and climatic indications given by the plant assemblages. The vegetational history of the correlative Eemian Interglacial of the European mainland is surveyed geographically, with particular reference to the differences between the Continent and Britain, and to the variations in the flora and vegetational history between north‐west Europe, Poland and southern Europe north of the Alps. Special attention is given to the behaviour of Tilia, Taxus, Acer, Picea and Abies.
SUPEROXIDE DISMUTASE, CATALASE AND GLUTATHIONE PEROXIDASE: SOLUTIONS TO THE PROBLEMS OF LIVING WITH OXYGEN
Authors: Halliwell B. 
Published: May 2006

SUMMARYRecent research suggests that H2O2 is a normal metabolite in both plants and animals and is not particularly cytotoxic. The impact of H2O2 on cell metabolism is discussed with particular reference to photorespiration. Catalase may function by preventing the formation of excessive concentrations of H2O2 and by using H2O2 in the peroxidatic oxidation of compounds such as methanol and formic acid. Radicals (such as OH and O2‐) and ‘excited’ oxygen are far more damaging to living organisms. The formation of these radicals in biological systems is described. Superoxide dismutase plays a key role in protection against such radicals, but glutathione peroxidase is also involved.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE IV. THE EFFECT OF MYCORRHIZAL INFECTION ON UPTAKE OF 15N FROM LABELLED SOIL BY VACCINIUM MACROCARPON AIT.
Authors: STRIBLEY D. P. , READ D. J. 
Published: May 2006

SUMMARYMoorland soil was labelled with 15N by long incubation with glucose and [15N] ammonium sulphate. Excess ammonium was then removed by acid‐washing and the soil sterilized by gamma‐irradiation. The distribution of label between four N fractions of the soil was determined.Shoots of mycorrhizal plants of the cultivated cranberry, Vaccinium macrocarpon Ait., grown on this soil for 6 months, were heavier, contained more nitrogen and a greater concentration of N on a dry‐weight basis than those of non‐mycorrhizal plants. Species of Trichoderma and Aspergillus, isolated from moorland soil, did not similarly stimulate growth of sterile plants.The 15N‐excess (atom per cent) of shoots from mycorrhizal Vaccinium plants was lower than that of shoots of uninfected plants. The endophyte neither affected growth nor 15N enrichment of Festuca ovina L. nor caused net mineralization in infected soil. The hypothesis that mycorrhizal roots can absorb nitrogen compounds unavailable to non‐mycorrhizal plants is discussed.
NITRATE UTILIZATION BY SPECIES FROM ACIDIC AND CALCAREOUS SOILS
Authors: HAVILL D. C. , LEE J. A. , STEWART G. R. 
Published: May 2006

SUMMARYNitrate utilization by calcicole and calcifuge species has been measured using a field assay for nitrate reductase. Certain calcifuge species, notably members of the Ericaceae, showed no detectable enzyme activity in the field and very low values in the laboratory even after nitrate feeding. It is concluded that these species have a restricted ability to utilize nitrate. Other calcifuge species and all the species from calcareous soils had detectable nitrate reductase activities in the field and responded to nitrate addition by large increases in enzyme activities. Some of these species were used to compare nitrate utilization in a number of acidic and calcareous soils. Nitrate was utilized in all the soils, but utilization was minimal in ombrogenous peat. A comparison of closely adjacent acidic and calcareous soils showed that nitrate is an important source of inorganic combined nitrogen in at least some acidic soils.
THE USE OF NUMERICAL METHODS TO DESCRIBE POPULATION DIFFERENTIATION
Authors: JARDINE N. , EDMONDS J. M. 
Published: May 2006

SUMMARYWe discuss, with examples, the use of numerical methods to describe and compare patterns of differentiation between populations of organisms at low taxonomic levels. The role of such methods as adjuncts to the orthodox methods of experimental taxonomy is illustrated by an account of differentiation in Solarium L. Section Solatium (Maurella).
RIBOSOMAL RNA, FRACTION I PROTEIN SYNTHESIS, AND RIBULOSE DIPHOSPHATE CARBOXYLASE ACTIVITY IN DEVELOPING AND SENESCING LEAVES OF CUCUMBER
Authors: CALLOW J. A. 
Published: May 2006

SummaryThe synthesis of chloroplast ribosomes and Fraction I protein appear to be discrete events in the life of a leaf. Expanding cucumber leaves incorporated exogenous precursors of RNA and protein synthesis into chloroplastic rRNA and Fraction I respectively but, after full expansion, the synthesis of both of these components was greatly reduced while incorporation into cytoplasmic rRNA and other soluble proteins was still proceeding. It is suggested that the overall synthesis of whole molecules of Fraction I is controlled by the rate of synthesis, in the chloroplast of the large sub‐unit of Fraction I and that this in part is related to the availability of 70S ribosomes.RuDPcarboxylase activity paralleled Fraction I protein content in developing leaves, but as the leaves senesced, the enzymatic activity declined at a faster rate than the loss of Fraction I protein.
SOME OBSERVATIONS ON THE GROWTH OF LATERAL ROOTS OF VICIA FABA L. AND THEIR RESPONSE TO COLCHICINE TREATMENT
Authors: MACLEOD R. D. 
Published: May 2006

SummaryThe effect of colchicine treatment on the number of cells in prophase was investigated in the apical meristems of 2‐mm‐, 1‐cm‐and 4‐cm‐ long lateral roots of Vicia faba. Colchicine was most effective in causing an initial drop in prophase numbers in the 2‐mm‐long roots, while it had a less drastic effect on the 1‐cm laterals and no significant effect at all on the 4‐cm ones. Also, while a significant increase in the number of cells in prophase was found 24 h following the start of treatment in the 1‐cm‐long roots, no significant increase took place in the 2‐mm or 4‐cm laterals. Thus, elongating lateral roots at different developmental stages do not respond to colchicine in the same way.Mitotic index and labelling index were also found to differ in control lateral roots of different lengths, as a result of fluctuations in the proportion of cells with a short cycle time during root elongation. These results, and the changes found in the response of lateral roots to colchicine as they lengthen, have been discussed with respect to growth hormone levels in developing roots.