bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE DEVELOPMENT AND ULTRASTRUCTURE OF ECTOMYCORRHIZAS
Authors: DUDDRIDGE J. A. , READ D. J. 
Published: May 2006

SummaryThe ultrastructure of representative types of ectomycorrhizal root of pine was analysed after collection at different times of year from March to June, using scanning and transmission electron microscopy. In the Pre‐Hartig net zone (PHZ) near the root apex, a well‐developed sheath is present in which are incorporated sloughed root cap cells. There is evidence of dissolution of the host cell wall adjacent to fungal elements in some cells. Sheath structure in the Hartig net zone (HZ) is similar to that in the PHZ, but the residual cells here are collapsed root hairs. Glycogen and polyphosphate granules are abundant in the sheath in March but their number declines in later months. The Hartig net is made up of a pseudoparenchyma of infolded fungal elements and the cortical cells adjacent to it are generally living. No basic difference between niycorrhizal and non‐mycorrhizal cortical cells was observed, thus indicating that, in contrast to pathogenic attack, no adverse reaction to the fungal presence occurs. Reasons for seasonal changes of storage compounds are discussed.
THE DEVELOPMENT AND ULTRASTRUCTURE OF ECTOMYCORRHIZAS
Authors: DUDDRIDGE J. A. , READ D. J. 
Published: May 2006

SummaryThe development of ectomycorrhizas of pine was followed experimentally using either sterile peat–vermiculite with nutrient solution or natural non‐sterile field soil. Roots were harvested sequentially and comparative analyses of their ultrastructure were obtained. Hartig net formation is initiated before the formation of a compact sheath in both types of synthesis but, while the net formed after 3 weeks in sterile culture and was complete after 6 and 8 weeks, in non‐sterile soil its initiation was delayed until 11 weeks and it had reached a depth of only one cortical cell after 19 weeks. While differences in gross morphology of mycorrhizas can be recognized, the structure of the host–fungus interface in the Hartig net region is comparable in mycorrhizas formed with different soils or different isolates. In the young Hartig net, separate host and fungal cell walls are distinguishable, while in the mature net they lose their integrity. No marked change of structure is observed within the cortical cells adjacent to the Hartig net and their organization is similar to that of cortical cells of non‐mycorrhizal lateral roots. The development and structure of the host–fungus interface is discussed in relation to its possible function.
MODIFICATION OF THE HOST‐FUNGUS INTERFACE IN MYCORRHIZAS SYNTHESIZED BETWEEN SUILLUS BOVJNUS (FR.) O. KUNTZ AND PINUS SYLVESTRIS L.
Authors: DUDDRIDGE J. A. , READ D. J. 
Published: May 2006

SummaryUltrastructural analysis of the host–fungus interface of mycorrhizas synthesized between Sutilus bovinus and Pinus sylvestris in media containing high concentrations of glucose reveals abnormalities of behaviour in both fungus and host. Vigorous fungal growth leads in some cases to isolation and death of host cortical cells. In other host cells, the wall adjacent to the fungus produces irregular ingrowths closely followed by the host plasmalernma. The cytology of these host cells is indicative of high physiological activity. Histochemical analysis shows the protuberances to be of a material similar to that of primary cell walls but with deposition of callose occurring late in their development. It is suggested that these structures may either represent a defence reaction on the part of the host to the presence of the fungus or that they may be similar to those wall ingrowths produced in transfer cells. Analogies between these structures and the latter are drawn and their possible function is discussed in relation to host and fungus nutrition and other types of transfer cell systems.
CHLORIDE TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK
Authors: RITCHIE R. J. , LARKUM A. W. D. 
Published: May 2006

SummaryRates of36Cl−labelling, efflux and uptake were measured onEnteromorphaplants grown in sea‐water (547 mM Cl−), and also in brackish water medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cl−, 20.4 mM Na+ and 0.5 mM K+]. Efflux experiments showed that, inEnteromorphaplants grown in seawater, light did not affect Cl−fluxes at the plasmalemma and tonoplast. Typical experiments exhibited two exchanged phases but a significant number (8/32) exhibited a single exchange phase; this was more likely to occur in darkness. Influx experiments also showed no effect of light on the tonoplast flux. Transfer of plants grown and labelled in seawater to low salinity medium caused a rapid loss of36C1−label; however, this was related to the change in osmotic potential of the medium rather than to changes in [Cl−o] or [K+0]. Exchange of36Cl−did not depend on [K+o] in seawater. Cyanide decreased36Cl−uptake in the dark but not in the light. In low salinity medium (ACBSW),36Cl−labelling and the plasmalemma flux inEnteromorphaplants were independent of light; however, the intracellular compartmentation of Cl−differed between light and dark. The tonoplast flux was also greater in the light. Intracellular Cl−was about 300 mmol kg−1in seawater plants and about 159 mmolkg−1in ACBSW plants. The cytoplasmic Cl−concentration ([CI−0]) based on compartmental analysis was about 200 mM inEnteromorphaplants in seawater and ACBSW medium. Use of this [Cl−0] value and the Nernst equation suggests active Cl−uptake in plants in both seawater and ACBSW. However it is unlikely that the cytoplasmic [Cl−] is above about 70 to 100 mM since many cytoplasmic enzymes are inhibited by high [Cl−0]. Taking this lower estimate of [C1−0], the Nernst criterion suggests passive accumulation of Cl−across the plasmalemma in seawater but active transport would be likely in plants in ACBSW medium. Where separate plasmalemma and tonoplast fluxes were detectable, plasmalemma fluxes were higher in low salinity medium than in seawater (about 500vs300 nmol m−2s−1); the tonoplast flux was about 30 nmol m−2s−1in seawater plants and about 20 and 10 nmol m−2s−1in light and dark, respectively, in ACBSW‐grown plants. In experiments where only a single exchange phase could be detected the apparent plasmalemma flux was only about 30 nmol−2s−1. Apparently the plasmalemma can exist in two permeability states to Cl−(0.2 to 1.0vs0.03 nm s−1).
STRUCTURE, ENVIRONMENTAL EFFECTS ON THEIR FORMATION, AND FUNCTION OF PROTEOID ROOTS INLEUCADENDRON LAUREOLUM(PROTEACEAE)
Authors: LAMONT B. B. , BROWN G. , MITCHELL D. T. 
Published: May 2006

SummaryProteoid roots are abundant on field and potted plants ofLeucadendron laureolum(Lam.) Fourcade, accounting for up to 40% of the root mass (in 9‐month‐old plants in sand), and up to 400 g−1of new season's roots (in 18‐month‐old plants in humus‐amended sand). There may be over 250 hairy rootlets per 10 mm of parent axis, giving a total surface area almost 15 times that of an equivalent mass of parent roots. Microsymbionts are absent, but chlorornycetin suppressed proteoid root formation, providing limited evidence of the need for a bacterial cofactor. Proteoid roots formed preferentially in humus‐amended sand but were elminated, with little effect on non‐proteoid roots, when organic fertilizer high in P was added. In the field, proteoid roots were confined to a 50 mm wide root mat just beneath the leaf litter around the parent plant. The greater soil volume explored directly by proteoid roots, despite lower soil P availability, may largely explain the greater rate of P uptake by plants in Clovelly sand than that m Hutton clay‐loam, although differential rates of solubilization and root respiration also appeared to be involved.
THE EFFECT OF MYCORRHIZAL INFECTION OF GOODYERA REPENS AND ITS CONTROL BY FUNGICIDE
Authors: ALEXANDER CLARE , HADLEY G. 
Published: May 2006

SummaryStudies of the orchid Goodyera repens Br. growing on agar media in association with its natural endophyte Rkizoctonia goodyerae‐repentis Constantin and Dufour showed that mycorrhizal plants of different developmental stages had significantly higher growth rates and level of P and N than did uninfected ones. Treatment of mycorrhizal plants with the fungicide thiabendazole stopped growth of external mycelium and caused a significant decrease in growth rate, P and N content, percentage infection and net assimilation rate. These results suggest that the mycorrhizal fungus enhances nutrient uptake and allows greater growth rates, a situation similar to that found in non‐orchid mycorrhizas.
INTERACTIONS BETWEEN ENDOMYCORRHIZAS AND SOIL NITROGEN AND PHOSPHORUS ON THE GROWTH OF RYEGRASS
Authors: HALL I. R. , JOHNSTONE P. D. , DOLBY R. 
Published: May 2006

SummaryIn two pot experiments with a soil deficient in P and N, vesicular‐arbuscular mycorrhizas stimulated the shoot growth of Lolium perenne L. greatest (24%) with the highest levels of applied P and/or N, and where the shoot N and P concentrations approached the normal agronomic range. It is suggested that applied N, and possibly P, resulted in mycorrhizas making a more important contribution to the plant's P or Cu status. Previous experiments purporting to show the mycorrhizal dependency of species are criticized if the levels of nutrients in the soil (other than P) which might have been limiting were not considered.Mycorrhizas reduced root/shoot ratios even in those treatments where a growth response was not detected.There was a negative relationship within treatments between responsiveness to mycorrhizas and the size of the non‐mycorrhizal plant. This may have relevance in plant breeding.
GENECOLOGICAL STUDIES OFURTICA DIOICAL.
Authors: POLLARD A. J. , BRIGGS D. 
Published: May 2006

SummaryThe stinging hairs ofUrtica dioica(stinging nettle) have often been described as defences against grazing; however, no experimental studies have tested this proposition. Variability in the number of stinging hairs borne by plants has been described, and is known to have a genetic basis. This variability extends to plants which are virtually stingless. Comparison of grazing preferences of two species of herbivores (rabbits and sheep) on plants of known stinging hair density revealed that: (1) Both herbivores preferentially grazed plants with lower stinging hair densities under controlled conditions; (2) In a field experiment in an area with intense rabbit grazing, higher grazing damage was observed on plants with lower stinging hair densities; (3) Patterns of grazing damage, and observations of herbivore behaviour, suggested that stinging hairs act to deter consumption of significant amounts of plant matter, even by herbivores which had not developed learned avoidance.It is likely that grazing by large mammals could act as a strong selective force for higher stinging hair densities in nettles. Theoretical treatments of plant‐herbivore interactions based on invertebrate grazing patterns may be too simplistic to apply to mammalian herbivores that are large, mobile, behaviorally complex, and yet dietarily generalist.
FREQUENCY AND GROUPING OF VESSEL ENDINGS IN ALFALFA (MEDICAGO SATIVA) SHOOTS *
Authors: WIEBE H. H. , GREER R. L. , VAN ALFEN N. K. 
Published: May 2006

SummaryVessel endings in various parts of the alfalfa (Medicago sativa L.) shoot were mapped by an India ink movement method. Stems were excised at various locations between the fifth and sixth nodes below the apex and placed in vials of India ink. Vessel endings were determined by examining the distance to which ink penetrated in the transpiration stream; the particles of India ink are too large to pass from vessel to vessel through pit membranes. The highest frequencies of vessel endings were found (1) in the petiolules and blades of the leaflets, (2) in the pulvinus of the petiole where the leaf traces emerge from the stem and anastomose while traversing the abscission zone, and (3) in the stem nodes where leaf traces arise and vascular bundles anastomose. The frequency of vessel endings was low and uniformly distributed throughout both internodes and petioles. Vessels were longest in the internodes and shortest in the leaflets. The regions where vessel endings were grouped coincided with those determined in other studies to be particularly susceptible to vascular blocking by macromolecules such as those produced by vascular wilt pathogens.
MICROPROPAGATION OF BIRCH AND MYCORRHIZAL FORMATION IN VITRO
Authors: GRELLIER B. , LETOUZE R. , STRULLU D. G. 
Published: May 2006

SummaryEctomycorrhizal syntheses between Paxillus involutus (Batsch.) Fr. and Betula pendula Roth, were carried out in controlled conditions. The fungal symbiont forms mycorrhizas with axenic seedlings and microcuttings derived from a clone produced in vitro of birch. The symbiosis stimulates the growth of the whole of the mycorrhizal plants. From a histological study of synthesized material, various stages of the mycorrhizal formation were described.
STUDIES ON NITRATE REDUCTASE IN BRITISH ANGIOSPERMS
Authors: Al GHARBI A. , HIPKIN C. R. 
Published: May 2006

SummaryLeaf tissue from over 100 species, representing 40 families (mostly native British plants from natural populations), was assayed for in vivo nitrate reductase (NR) activity. From studies on the optimal assay conditions for the leaf tissue of 18 species, an assay procedure suitable for most species was devised. Higher levels of NR activity were measured in the leaves of ruderal species (mean NR activity = 4.39 ± 0.84 μmolh−1 g−1 fresh weight) than in woodland‐edge species (mean NR activity = 1.36 ± 0.29 μmolh−1 g−1 fresh weight). A survey of NR activity in the leaves of 41 woody species showed that most contained significant levels of NR activity (> 1.0μmol h−1 g−1 fresh weight) suggesting that nitrate assimilation was appreciable in these species.
PATH ANALYSIS OF THE CHANGES IN QUANTITATIVE CHARACTERS IN JACK PINE
Authors: GOVINDARAJU D. R. 
Published: May 2006

SummaryThe magnitude of changes within a system of mutually dependent phenotypic variables in jack pine grown under two densities was studied using path analysis. The degree of relationship among morphological characters was found to be a function of density and the relative position of crown among the competing individuals. Path analysis could be used to gain an insight into the genetic, physiological and developmental aspects of self‐thinning, resource allocation and phenotypic plasticity.
LEAF DYNAMICS OF TROPICAL TREES RELATED TO SUCCESSIONAL STATUS
Authors: SHUKLA R. P. , RAMAKRISHNAN P. S. 
Published: May 2006

SummaryLeaf dynamics of two early successional and two late successional species of a tropical humid forest at Lailad in north‐eastern India were studied. Leaves produced during different months were found to have markedly different longevity, for all the species studied. The early successional species showed higher leaf turnover rates, reduced leaf longevity, more uniform production and fall of leaves under forest‐grown conditions than in open‐grown conditions (though with some fluctuation during the year) and an evergreen or leaf‐exchanging pattern of leanness. The late successional species had slower leaf turnover rates, longer leaf longevity, a peak of leaf production and a deciduous habit‐ It is concluded that differences in leaf dynamics of early and late species are related to the successional niches they occupy in the forest community.
BENTAZONE‐INDUCED STOMATAL MOVEMENT IN EPIDERMAL PEELS FROM CHENOPODIUM ALBUM L.
Authors: DUNLEAVY P. J. , COBB A. H. 
Published: May 2006

SummaryStudies of Chenopodium album L. epidermal peels have shown that stomata respond to light and CO2 in a manner typical of other species. Thus, light and reduced CO2 concentrations were found to cause stomatal opening in the presence of 10−1 M KCl, whilst darkness and ambient CO2 caused closure in the absence of KCl. The herbicide bentazone (10−4 M) caused closed stomata to open in the absence of KCl, whilst KCl‐stimulated opening was inhibited. Furthermore, closure of open stomata occurred in the presence of bentazone regardless of KCl availability. These findings are discussed in relation to the effects of other metabolic inhibitors on stomatal movement.
BENZATONE‐INDUCED STOMATAL MOVEMENT IN EPIDERMAL PEELS FROM CHENOPODIUM ALBUM L.
Authors: DUNLEAVY P. J. , COBB A. H. 
Published: May 2006

SummaryStomatal movement in abaxial epidermal peels of Chenopodium album L. in response to KCI and CO2 has been investigated in the presence or absence of the herbicide bentazone. In darkness, minimal stomatal opening was observed at 500μl 1−1 CO2 and low exogenous KCI concentrations, whilst considerable stomatal opening occurred at 50 and 100 × 10−2 M KCI, as reported with other species. 10−4 M Bentazone modified this response to produce wide opening at 0 to 10 × 10−3M KCI and inhibit opening at high KCI concentrations. This observation demonstrates the importance of exogenous KCI concentration in studies of the stomatal activity of metabolic inhibitors.In light, maximum stomatal opening was observed at 50 μ1 1−1 CO2 with only 5 × 10−3 M KCI but was gradually negated by increases in CO2 concentration up to 5000 μ1 1−1. Furthermore, stomata] opening induced by 100 × 10−3 M KCI in darkness was also inhibited by increased CO2 concentrations. In the presence of bentazone C. album stomatal responses to ambient CO2 concentrations were markedly altered. However, as with the response to light and KCI, the effect of this herbicide was reduced by increasing CO2 concentrations. It is suggested that bentazone may effect C. album stomatal movement by disrupting guard cell ion transport and that CO2 may directly control this process.
RESPONSE OF GUARD CELLS TO TEMPERATURE AT DIFFERENT CONCENTRATIONS OF CARBON DIOXIDE IN VICIA FABA L.
Authors: SPENCE R. D. , SHARPE P. J. H. , POWELL R. D. , WU H. 
Published: May 2006

SummaryOne of the least understood areas in guard cell movements remains the effect of CO2, particularly its effect on isolated guard cells. In this study the reactions of guard cells in both isolated epidermal strips and intact leaf sections from Vicia faba have been observed in a variety of temperatures and CO2 concentrations in both light and darkness. The results are consistent with the hypothesis that stomatal aperture in the isolated guard cell is the result of two temperature‐dependent systems. A decrease in aperture consistently observed at 30 to 35°C in the light reflects the transition from one system to the other. The low temperature system appears consistent with the chemiosmotic hypothesis of phosphoenolpyruvate carboxylase regulation of malate. It demonstrates some sensitivity to CO2 between 25 and 35 °C, resulting in a shift in optimum aperture to slightly higher temperatures. The high temperature system shows no apparent sensitivity to CO2. Stomata from intact leaf sections showed a considerable decrease in aperture as the CO2 concentration increased from 0 to 60 μl 1−1. The stomatal response threshold to CO2 appears to be at least as low as 60μ1 1−1 and centred in the mesophyll tissue. All observable CO2 responses in both strips and leaf sections disappeared at temperatures in excess of 35 °C in the light.
STRUCTURE OF COLUMELLA CELLS IN PRIMARY AND LATERAL ROOTS OF HELIANTHUS ANNUVS (COMPOSITAE)
Authors: STOKER R. , MOORE R. 
Published: May 2006

SummaryPrimary and lateral roots of sunflower (Helianthus annuus) were fixed in situ and the ultrastructures of their columella cells determined using stereology. The relative volumes of cellular components and the distribution of organelles in columella cells of primary and lateral roots were not significantly different. All organelles were distributed asymmetrically in columella cells of both types of roots. Nuclei tended to be located in the upper third of the cells, while vacuoles tended to be located in the middle third. Amyloplasts, dictyosomes and mitochondria were most frequent in the lower third of columella cells in both types of roots. These results suggest that the differential responses to gravity of primary and lateral roots of H. annuus are probably due to factors other than the ultrastructures of their columella cells.
DATURA STRAMONIUM ALLELOCHEMICALS: LONGEVITY IN SOIL, AND ULTRASTRUCTURAL EFFECTS ON ROOT TIP CELLS OF HELIANTHUS ANNUUS L.
Authors: LEVITT JUDY , LOVETT J. V. , GARLICK P. R. 
Published: May 2006

SummaryAllelopathic alkaloids from Datura stramonium seeds remained phytotoxic to Helianthus annuus for 15 weeks in soil under field conditions. Studies using transmission electron microscopy showed that these alkaloids retarded the metabolism of food reserves, particularly starch, in germinating H. annuus seeds. Structural damage to cells and organelles was not apparent.
CELLULAR LOCATION AND PROPERTIES OF INVERTASE IN MYCELIUM OF PUCCINIA GRAMINIS
Authors: WILLIAMS A. M. , MACLEAN D. J. , SCOTT K. J. 
Published: May 2006

SummaryThe sucrose‐hydrolyzing activity in mycelium of the wheat stem rust fungus (Puccinia graminis Pers. f.sp. tritici Erikss. & E. Henn.) grown in axenic culture was compared with that in mycelium of Penicillium expansum (Linkex F. S. Gray). In subcellular fractions and permeabilized cells from Pu. graminis, most activity was bound tightly to the cell wall, whereas, in Pe. expansum, the enzyme was soluble and appeared to be located in the periplasmic space. Particulate preparations from mycelium of Pu. graminis hydrolyzed sucrose to a mixture of hexoses with a fructose: glucose ratio of about 0.8; hence the activity was essentially that of an ‘invertase’ (E.C. 3.2.1. 26, β‐D‐fructofuranoside fructohydrolase). Despite this slight deficit in fructose, no direct evidence was obtained for fructan transferase activity. By contrast, the enzyme preparation from Pe. expansum exhibited more transferase than hydrolase activity. The wall‐bound enzyme from Pu. graminis showed a pH optimum of 5.0 to 5.5, and Km values at pH 5. of 3 and 40 mM for sucrose and raffinose, respectively. All attempts to solubilize substantially the wall‐bound activity were unsuccessful, even after removal of 63% of the particulate matter by polysaccharide‐degrading enzymes.
DICHOTOMOUS BRANCHING IN LATERAL ROOTS OF PINE: THE EFFECT OF 2‐CHLOROETHYLPHOSPHONIC ACID ON SEEDLINGS OF PINUS RADIATA D. DON
Authors: WILSON E. R. L. , FIELD R. J. 
Published: May 2006

SummarySeedlings of Pinus Radiata D. Don were grown in sand in a glasshouse and in nutrient solution in a controlled environment cabinet and treated with 2‐chloroethylphosphonic acid (CEPA) applied in solution to whole root systems. A wide range of concentrations of CEPA (0.1 to 120 mg 1−1) promoted dichotomous branching of secondary and tertiary roots, on most seedlings, whether growing in solution or in sand.There was considerable variation in the response of individual plants to CEPA, with some treated plants branching profusely and some scarcely or not at all. Absence of artificial aeration of the solution in which root systems were growing enhanced the effect of CEPA in promoting root forking.
DEVELOPMENT OF INFECTION BY A VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS IN BRASSICA NAPUS L. AND TRIFOLIUM SUBTERRANEUM L.
Authors: TOMMERUP I. C. 
Published: May 2006

SummaryThe sequence of stages involved in the development of infection by Glomus caledonium (Nicol. & Gerd.) Trappe & Gerd. in Brassica napus L. (spring rape) and Trifolium subterraneum L. (subterranean clover) was examined. When plants grown at similar relative levels of phosphate were compared, B. napus reduced the rate of all stages of the processes leading to colonization. Although maximum values of germination, hyphal extension, and appressorial formation and adhesion were similar in B. napus and T. subterraneum, in B. napus fewer appressoria produced penetration pegs and some penetration pegs failed to initiate colonies. In addition, in B. napus only a third of the colonies possessed arbuscules whereas in T. subterraneum all colonies had arbuscules. The rate of death of epidermal and cortical cells was similar between the species and did not explain the reduced colonization of B. napus. Chemical rather than physical factors associated with B. napus appeared to be involved in reducing the rate of development of each growth stage.