bluuebunny/crossref_metadata_2025_split huggingface dataset:
DEVELOPMENTAL CHANGES IN LEAF EPICUTICULAR WAXES IN RELATION TO FOLIAR PENETRATION
Authors: BAKER E. A. , HUNT GRACE M. 
Published: May 2006

SUMMARYChanges in surface properties during expansion of the leaves of eight plant species have been examined in relation to the uptake of 1‐naphthylacetic acid. Rates of wax production ranged from 0·1 ng cm‐2 h‐1 for sugar beet leaves to 6.2 nm cm‐2 h‐1 for leaves of Eucalyptus globulus. Individual leaves of all species maintained different rates of wax production at their adaxial and abaxial surfaces. Rates of synthesis of wax fractions and their constituent homologues varied with surface and leaf age. The homologue distribution shifted towards components of longer chain length as the leaves expanded. Morphological changes in wax deposits were small and limited largely to increases or decreases in the density of the plate waxes. Rates of penetration of 1‐naphthylacetic acid varied between species, between leaf surfaces and with age of tissue. The highest rates of uptake were confined to the period when the leaves expanded most rapidly. The decrease in penetration rate with increase in age of the tissue, common to most plants, was greatest for grape vine and Eucalyptus globulus leaves both of which maintained high rates of wax production during expansion.
EFFECT OF COPPER DEFICIENCY ON PHENOLIC AND OTHER CONSTITUENTS OF WHEAT CELL WALLS
Authors: ROBSON A. D. , HARTLEY R. D. , JARVIS S. C. 
Published: May 2006

SummaryBefore decreasing yield significantly, copper deficiency affected the amounts of phenolic compounds released (by treatment with sodium hydroxide) from the cell walls separated from young leaves of wheat. Effects of changes in copper supply on the amounts of phenolic compounds released followed closely its effect on copper concentration in the plant parts. More ferulic and less p‐icoumaric acid was released from the walls of young leaves of copper‐deficient plants than from those of copper‐adequate ones; these differences were less marked in older than in younger leaves. Copper deficiency decreased the lignin, hemicellulose and acetyl contents of cell walls only in severely deficient plants.
CELL DEATH AND CELL WALL PAPILLAE IN THE RESISTANCE OF OAK SPECIES TO POWDERY MILDEW DISEASE
Authors: EDWARDS M. C. , AYRES P. G. 
Published: May 2006

SummaryA quantitative study was made of the infection processes of Microsphaera alphitoides, powdery mildew, on seedlings of three oak species, Quercus robur (leaves highly susceptible until mature), Q. cerris (moderately resistant) and Q. borealis (highly resistant), to determine the mechanisms underlying their different resistances to disease. Some inhibition of spore germination occurred on mature leaves of Q. robur, and on leaves of Q. cerris and Q. borealis, but the number of appressoria formed from germinated spores was not affected either by oak species or leaf age. Formation of elongating secondary hyphae (ESH) from appressoria was strongly inhibited on mature leaves of Q. robur and on leaves of Q. cerris, and was completely inhibited on leaves of Q. borealis. At this stage of infection, host resistance was expressed most effectively.Challenged cells and the host cell wall around the fungal penetration point were examined by light and scanning electron microscopy (SEM). SEM studies of the leaf surface around the penetration point showed no difference between susceptible and resistant leaf surfaces and, in neither case, was there any evidence of chemical dissolution of cuticle or epicuticular wax. In light microscope investigations, limitation of ESH formation was associated with two factors. First, death of the challenged host cells occurred within 12 h of infection. This was a normal component of the resistance of Q. cerris but was uncommon in Q. robur and Q. borealis. Second, material was deposited in the form of a papilla on the inside of the epidermal cell wall, opposite the penetration point of the fungus. Large dome‐shaped papillae, which histochemical tests showed were typically lignified, were not penetrated by the fungus, while smaller, cone‐shaped, non‐lignified papillae failed to inhibit fungal development. Both types of papillae could occur in the same leaf but their frequency reflected the resistance of the host species. Lignified papillae were most common in resistant leaves.
DIRECT MEASUREMENT OF TRANSLOCATION OF CARBOHYDRATE IN THE LICHEN, CLADONIA CONVOLUTA, BY QUANTITATIVE AUTORADIOGRAPHY
Authors: TAPPER Y R. 
Published: May 2006

SummaryTranslocation of carbohydrate between Trebouxia and its associated fungal partner in the lichen, Cladonia convoluta, has been examined directly using quantitative autoradiography. This technique allows measurements to be made without disrupting the symbiotic association and avoids the rapid physiological changes that occur when the symbionts are isolated. The quantity of photosynthetically‐fixed carbon transferred from Trebouxia was higher than measured by previous methods. Release of carbohydrate from Trebouxia was reduced by several metabolic inhibitors indicating at least a partial dependence on energy for the overall process.
MICROBIAL FERMENTATION OF GRASS RESIDUES TO ORGANIC ACIDS AS A FACTOR IN THE ESTABLISHMENT OF NEW GRASS SWARDS
Authors: GUSSIN E. J. , LYNCH J. M. 
Published: May 2006

SummaryExtracts from anaerobically decomposed shoots of a range of grass species were toxic to other grasses and clover. This phytotoxicity was less after 20 days than after 10 and seemed to be caused by organic acids. The residues produced byFestuca rubra, Alopecurus pratensisandAgrostis stoloniferawere the most toxic. After aerobic decomposition for 10 days extracts from these three species were phytotoxic, but after a further 10 days decomposition they caused a stimulation in grass and clover root growth. These results are discussed in relation to the poor establishment that sometimes follows reseeding old pasture land.
INHERITANCE OF TRIAZINE RESISTANCE IN POA ANNUA: CONSEQUENCES FOR POPULATION DYNAMICS
Authors: DARMENCY H. , GASQUEZ J. 
Published: May 2006

SummaryA chloroplast triazine resistant population of Poa annua from a triazine treated area was compared with one from an adjacent untreated area. A study of morphological characters and isoenzymes showed that the resistant population contained as much polymorphism as the susceptible one. One phenotype, on an isozyme basis, was much more frequent in each habitat, suggesting the importance of natural selection in each population. The possibility of a ‘founder effect’ within the resistant population is discussed.A dominant esterase allozyme was used to estimate the outcrossing rate giving an estimate of 13 % under greenhouse conditions. Transmission of herbicide resistance was also tested and found to be mainly inherited maternally (0·1% transmission via pollen). Paternal transmission is therefore not important for gene flow. Allogamy would appear responsible for the high degree of polymorphism found in the resistant population.
PRETREATMENT EFFECTS OF CADMIUM ON THE ROOT GROWTH OF HOLCUS LANATUS L.
Authors: BROWN HELEN , MARTIN M. H. 
Published: May 2006

SummaryA cadmium tolerant and a non‐tolerant population of Holcus lanatus were subjected to a pretreatment with either no or low (0·2 μg Cd ml−1) concentrations of cadmium prior to normal tolerance testing in 1·0 μg Cd ml−1 solution. When pretreated roots were not removed prior to the tolerance test, the cadmium pretreatment resulted in significantly greater root growth of both populations in the test solution relative to plants given no cadmium pretreatment. Repeating the tolerance test on plants which had had their pretreated roots excised prior to testing showed no significant effect of any pretreatment on subsequent root growth in either population. There was an overall difference between the two populations in terms of their response to pretreatment and test concentrations in that when exposed to cadmium, plants of the tolerant population grew significantly better than those of the non‐tolerant population. The data presented provide evidence for a stimulation of cadmium tolerance following low‐level exposure of roots to cadmium. The mechanisms associated with these effects are not clear although cadmium tolerance in animals is known to show similar trends.
METAL UPTAKE IN TERRICOLOUS LICHENS
Authors: GOYAL R. , SEAWARD M. R. D. 
Published: May 2006

SummaryThe nature of the accumulation patterns within the lichen is assessed in terms of metal localization within the different thallus components (i.e. rhizinae, thallus without rhizinae, phycobiont, mycobiont) and the importance of substrate concentrations in controlling localization. Peltigera canina, P. polydactyla, P. rufescens, Cladonia furcata, C. impexa and C. uncialis from a wide range of natural and man‐influenced sites in the British Isles were analyzed for Cr, Cu, Fe, Mn, Ni, Pb and Zn; Cladonia spp. were used for comparative purposes. Metal accumulation capacity (μg g−1) of the rhizinae was maximum for Fe, Mn and Pb. However, the phycobiont was found to have maximal accumulation capacity for Cu, Ni and Zn. The metal accumulation capacities by rhizinae and thallus without rhizinae as well as phycobiont and mycobiont without rhizinae were found to be interrelated and were dependent upon the biologically‐available metal concentrations in their associated soils as well as the type of substrate. The total amounts (g) of metals localized within the different thallial components, from two major types of environment (i.e. with background and enhanced metal concentrations), are presented; rhizinae accumulate the highest concentrations of all metals under enhanced environments.
SOME OBSERVATIONS ON THE SIZE AND SHAPE OF LICHEN ASCOSPORES IN RELATION TO ECOLOGY AND TAXONOMY
Authors: PENTECOST ALLAN 
Published: May 2006

SummaryThe length, breadth and volume of a large sample of ascospores from lichenized and non‐lichenized ascomycetes were compared and found to be approximately log‐normally distributed. Lichen ascospores were also classified into sizes and types and their distribution in relation to the substratum colonized was analyzed using x2. The distributions were found to be heterogeneous with certain spore types and sizes more frequent on some substrata than others. These results are discussed with reference to the survival, germination and atmospheric dispersal of ascospores.Ascospore length and breadth was measured in a single plant of Opegrapha chevallieri Leight. (Loculoascomycetes) and found to be normally distributed. Taxonomic implications are considered.
ULTRASTRUCTURE OF THE ENVELOPE OF CODIUM A USTRALICUM (SILVA) CHLOROPLASTS IN THE ALGA AND AFTER ACQUISITION BY ELYSIA MAORIA (POWELL)
Authors: BRANDLEY BRIAN K. 
Published: May 2006

SummaryFour fracture faces of Codium australicum (Silva) chloroplast envelopes are characterized in the alga and after incorporation into Elysia maoria (Powell). The outer membrane generally has a lower density of particles than the inner in both alga and animal. Both inner and outer envelope faces in the animal are significantly different to those in the alga in terms of particle size distributions. The outer envelope also differs in terms of particle densities. No evidence was found for a phagosome membrane surrounding the chloroplast in the animal. The chloroplast surface area is the same in the alga and in the animal, but the plastid volume increases in the animal. Changes in the envelope membranes may be related to functional aspects of the chloroplast‐sacoglossan association.
AN UNUSUAL HETEROMORPHIC INCOMPATIBILITY SYSTEM
Authors: PHILIPP M. , SCHOU O. 
Published: May 2006

SummaryBased on measurements of floral parts and experiments, Anchusa officinalis L. is shown to have a distylous breeding system. Dimorphism is found in the style length/anther height ratio, in stigma morphology and in pollen and corolla size. Plants are self‐incompatible but intra‐ and intermorph compatible. Long‐styled plants outnumbered short‐styled in all populations. Stigmas in short‐styled flowers receive a larger quantity of pollen than those of long‐styled.
AN INVESTIGATION INTO THE USE OF THE ‘‐DEME’ TERMINOLOGY
Authors: BRIGGS D. , BLOCK M. 
Published: May 2006

SummaryThe ‘‐deme’ terminology was coined by Gilmour and associates to bring order to the confusion of terms used for classifying plants at or below the species level.During the past decade details of key‐words in titles and abstracts of scientific papers have been stored in computer data banks. Using an on‐line system in a search of five data bases, an estimate of the use of the ‘‐deme’ and other technical terms has been made. We have discovered, in a search of nearly 8 million papers, that the ‘‐deme’ terminology has rarely been used by biologists (only 115 uses). Moreover in 74% of cases the terminology has not been employed in accordance with the intentions of its authors, the term ‘‐deme’ being incorrectly used to denote ‘a local interbreeding population’. The use of various terms in describing variation, at and below the species level, is discussed.
COMPARISON OF THE ONION PLANT (ALLIUM CEPA) AND ONION TISSUE CULTURE
Authors: TURNBULL A. , GALPIN I. J. , SMITH J. L. , COLLIN H. A. 
Published: May 2006

SUMMARYTissue cultures of onion, differentiated into roots and shoots, were examined for total flavour precursor levels, composition of the flavour precursors and activity of the enzyme alliinase. Comparisons were made with undifferentiated callus and with the roots and shoots of germinating seedlings and shooting bulbs.Undifferentiated callus contained none of the major flavour precursor compound, 5‐trans‐prop‐1‐enyl‐L‐cysteine sulphoxide, but in the differentiated tissue this compound was present in both redifferentiated roots and shoots. In intact plants, more flavour precursor accumulated in rapidly growing roots and shoots.Onion bulb tissue and callus tissue from a long established cell clone and a newly initiated clone were examined under the electron microscope. The major structural component in the onion bulb cells, which was absent in the callus, was a larger number of vesicles in the cytoplasm and central vacuole. Since callus does not produce the onion flavour precursor compounds, possibly, in normal onion tissue, the vesicles are part of the flavour producing system, either as a store for the flavour precursors or for the degradative enzyme alliinase; in this way both parts of the system may be spatially separated until the tissue is damaged or cut.
THE DIFFERENTIAL ABILITY OF AQUATIC PLANTS TO UTILIZE THE INORGANIC CARBON SUPPLY IN FRESH WATERS
Authors: ALLEN E. D. , SPENCE D. H. N. 
Published: May 2006

SUMMARYThe photosynthetic activity of 15 species of microalgae and macrophytes was measured by continuous recording of oxygen concentration, and/or the change in pH, in bathing solutions of known alkalinity and carbon concentration. The microalgae had considerably greater apparent affinities for HCO3− and slightly greater apparent affinities for CO2, than the macrophytes (including several previously established HCO3‐users), while the macrophytes had larger apparent affinities for CO2 than for HCO3− and larger diffusive resistances to CO2. For species with different affinities for CO2 and HCO3−, assimilation rate in a solution of constant alkalinity showed a distinct reduction when the CO2 concentration decreased to a value typical of each species; a list of such ‘CO2 compensation points’ is presented. (The same CO2 compensation point was obtained for Elodea canadensis by extrapolation of rate‐substrate curves in solutions of which the pH was varied at each of three constant total carbon concentrations). At still lower total carbon values, any assimilation was held to be due to HCO3− uptake, and HCO3− compensation points for some species are given. Rather than ‘users’ and ‘non‐users’ of HCO3− it is concluded that a gradation exists, use depending on HCO3− as affected by alkalinity and pH of the bathing solution, and on the species' HCO3‐compensation point. Natural rates of photosynthesis of macrophytes and some microalgae are usually functions of exogenous [CO2] while those of other microalgae are functions of [CO2] and [HCO3−], with competitive effects at high pH in solutions of prevailingly low alkalinity. In characterizing the response of aquatic plants to inorganic carbon supply, a knowledge of CO2 and HCO3− compensation points is therefore essential.
FUNGAL GROWTH IN A LATTICE: A TENTATIVE EXPLANATION FOR THE SHAPE OF DIAMOND‐CANKERS IN SYCAMORE
Authors: RAYNER A. D. M. , BEVERCOMBE G. P. , BROWN T. C. , ROBINSON A. 
Published: May 2006

SUMMARYThe characteristic shape of diamond‐cankers in sycamore may be attributable to spread of fungal infection via the medullary rays. The rays become densely filled with fungal hyphae in infected bark, and when viewed tangentially are arranged in a lattice‐like array with angles between the diagonal rows similar to the apical and side angles of diamond‐cankers observed in the field. Computer simulation has shown how a range of types of random growth processes could result in diamond‐shaped patterns if a fungus spread through such a lattice, with each ray serving as a centre from which its neighbours could become occupied and act in turn as centres.
ECOLOGICALLY‐LINKED VARIATION IN MORPHOLOGY, ACETYLENE REDUCTION, AND WATER RELATIONS IN PSEUDOCYPHELLARIA DISSIMILIS
Authors: SNELGAR W. P. , GREEN T. G. A. 
Published: May 2006

SUMMARY Pseudocyphellaria dissimilis (Nyl.) D. Gall and P. James in litt populations were shown to possess different morphologies which correlated with the evaporative demand of their environment. The variations in morphology consisted of increased thallus thickness, mostly from increased medulla thickness, and increased rhizine length in the more exposed population. These changes confer a decreased surface/volume ratio and increased water storage in the form of external water that could be removed by blotting but not shaking. A consequence of these changes was a slower drying down rate. No differences in water loss rate per unit area were found between populations indicating that no morphological modifications exist to decrease water loss. Preliminary work on the acetylene reduction rates of the populations demonstrated a considerable difference in rates between the individual populations' and indicated that acetylene reduction could be another useful indicator of physiological adaptation.
THE EXPLOSIVE RELEASE OF POLLEN IN FLOWERS OFHYPTIS(LAMIACEAE)
Authors: BRANTJES N. B. M. , DE VOS O. C. 
Published: May 2006

SUMMARYThe Brazilian speciesHyptis paulianaEpling probably has an ornithopilous flower, in which explosive pollen presentation is effected by the sudden release of the stamens from a petal lobe, called a carina. Two hinges are situated in the suspensor of this carina. Pressure in large epidermal cells of the suspensor, in combination with the stiffness of collenchymatic, deeper cell layers, produces the force for the explosion. Shortly before anthesis the filaments elongate so that the stamens enter deep into the carina. At anthesis two hinges in the suspensor plate unfold and the stamens keep the carina in this excitable position. A disturbance causes the anthers to slip from the carina, which then can flip back, while the anthers swing up and eject the pollen on to the flower visitor. In the receptive phase the stamens bend down and the style elongates. In the Lamiaceae, subfamily Ocimoideae, it seems likely that an explosive mechanism has evolved at least twice.
EXPERIMENTAL STUDIES ON THE DISTRIBUTION OF THE SEXES OF MERCURIALIS PERENNIS L.
Authors: WADE K. M. 
Published: May 2006

SUMMARY(1) Populations of flowering male and female shoots of Mercurialis perennis were grown in three experiments under different light screens: (i) the sexes grown together in a replacement series under a screen transmitting 11 % incident light; (ii) the density of the plants varied under an 11 % light screen; and (iii) the sexes grown separately with Holcus mollis under light screens transmitting 31 % and 2% incident light.(2) In the replacement series with mixed sexes, the males grew more than the females at (male:female) 10:10 while the females grew more at 17:3 and 3:17. The sexes grew similarly in monoculture. The results for total yield of the plants suggest that competition between the sexes was less than that within them.(3) In the density experiment, the males grew more than the females as the density increased from 20 to 30 plants/box and both grew similarly at 42 plants/box.(4) It is suggested that observed uneven sex ratios in natural populations of shoots may be a result of the sexual differences in growth as the density of the plants increases.(5) In the replacement series with H. mollis under the 31 % light screens the males grew more than the females at (M. perennis: H. mollis) 3:17 while the females grew more at 17:3. These results suggest that males may persist longer in association with other species.(6) No consistent results were obtained from the H. mollis replacement series under the 2 % light screens.(7) The sexes grew similarly more under the 31 % compared to the 11 % light screens, suggesting that neither is physiologically intolerant to increased sunlight.
A STUDY OF THE INTRACELLULAR AND INTERCELLULAR DISTRIBUTION OF THE DATURA STRAMONIUM LECTIN USING AN IMMUNOFLUORESCENT TECHNIQUE
Authors: JEFFREE C. E. , YEOMAN M. M. 
Published: May 2006

SUMMARYThe intracellular and intercellular distribution of the lectin in seeds, stem and callus of Datura stramonium was visualized by means of an indirect immunofluorescent technique employing antibodies, raised in a rabbit against highly purified lectin obtained from Datura seeds. The lectin was detected in the protoplasts of all cells tested, apparently associated with the plasmalemma and the membranes of cell organelles. Cell walls appear to be free of lectin. In stems, where lectin concentrations are very low, epidermis, endodermis and phloem are the richest sources. The significance of the distribution of the D. stramonium lectin is discussed in relation to the possible functions of this molecule.
PHYSIOLOGICAL INTERACTIONS DURING THE INITIAL STAGES OF EMBRYOGENESIS IN CULTURES OF DAUCUS CAROTA L.
Authors: WARREN GRAHAM S. , FOWLER MICHAEL W. 
Published: May 2006

SUMMARYSomatic globular embryos of carrot develop abnormally when transferred at low density to fresh, minus‐auxin medium, whereas normal development ensues after transfer to conditioned medium, or to fresh medium at high densities. It is suggested that a critical level of an ‘embryo factor’ is required to co‐ordinate cell division and morphogenesis. Embryo death occurs after the heart stage in minus‐auxin cultures of low embryogenic potential. This behaviour may result from the production of auxin as these cultures show some plus‐auxin characteristics. The decline in the capacity for normal embryogenesis which often accompanies repeated subculture is suggested to result, in part, from a combination of these factors.