bluuebunny/crossref_metadata_2025 huggingface dataset:
STUDIES ON NITRATE REDUCTASE IN BRITISH ANGIOSPERMS
Authors: Al GHARBI A. , HIPKIN C. R.
Published: May 2006

Summary

Leaf 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

Summary

The 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

Summary

Leaf 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

Summary

Studies 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

Summary

Stomatal 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

Summary

One 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

Summary

Primary 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

Summary

Allelopathic 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

Summary

The 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

Summary

Seedlings 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

Summary

The 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.
SOME ASPECTS OF TXONOMY IN THE CRYPTOPHYCEAE
Authors: SANTORE U. J.
Published: May 2006

Summary

The unique and diagnostic characteristics of the Cryptophyceae are discussed and present knowledge of their taxonomy is summarized. It is proposed that the pigmented organisms can be assigned to four genera,Hemiselmis, Chroomonas, CryptomonasandPyrenomonasnom. nov.; the characteristics of these genera are reviewed. The validity of the pigmented generaIsoselmis, PlagioselmisandRhodomonasand the apochlorotic generaChilomonas, CyathomonasandPhyllomitusis considered and present knowledge of their taxonomy is summarized.
RELATIONSHIP BETWEEN MORPHOLOGICAL ADAPTATION TO GRAZING, CARBON BALANCE AND WATERLOGGING TOLERANCE IN CLONES OF DACTYLIS GLOMERATA L.
Authors: ETHERINGTON JOHN R.
Published: May 2006

Summary

Clonally‐propagated individuals of Dactylis glomerata L. derived from two contrasted habitats, respectively, moist soil with no grazing and drought‐prone soil under intense grazing, were tested for tolerance of waterlogging in soil culture. The clone of dry soil unexpectedly proved much more tolerant than the clone of moist soil. Measurements of 24 populations of D. glomerate grown in an experimental garden showed that the grazing pressure in the original habitat is reflected very strongly in the morphology of the garden‐grown plants. Adaptation to grazing comprises a short and narrow‐leaved, prolific tillering habit with production of very short inflorescences. Heavy grazing, or the cutting regime imposed in the waterlogging trial, is likely to do more damage to the upright, long‐leaved morphs of the ungrazed site. Measurements of carbon balance in intact plants and in defoliated tillers support this interpretation and also suggest that the larger oxygen consumption of the massive leaf bases of the ungrazed form might limit root penetration in oxygen deficient conditions. The greater length of roots in the dry soil clone is also discussed as a possible adaptation to water shortage in its cliff ledge habitat.
ON THE ECOLOGY OF SHORT‐LIVED FORBS IN CHALK GRASSLANDS: LIFE‐HISTORY CHARACTERISTICS
Authors: VERKAAR H. J. , SCHENKEVELD A. J.
Published: May 2006

Summary

The life‐histories of Carlina vulgaris L., Daucus carota L., Euphrasia officinalis L., Gentianella germanica (Willd). Börner, Linum catharticum L., and Scabiosa columbaria L. in a chalk grassland in the Netherlands are described on the basis of frequent observations during a period of three and a half years.

E. officinalis and a small part of the L. catharticum population were found to be annual. G. germanica and the major part of the L. catharticum population were biennial, whereas the other species took several years to reach maturity. All species except the major part of the Scabiosa columbaria population were monocarpic.

Vegetation cover influenced the occurrence of short‐lived forbs, but a large variation is found in the data. In D. carota, E. officinalis and Scabiosa columbaria seed production had a marked effect on seedling density in the following year.

Shoot growth in Scabiosa columbaria seedlings varied at various vegetation densities. Furthermore, a marked correlation was found between rosette size and the probability of becoming mature in the subsequent year.

Within one grassland, life‐history types within the group of short‐lived species are found to vary. On the one hand, there are the small‐seeded annuals with high mortality, but rather constant density of mature plants (Euphrasia), and on the other hand there are the more conservative life histories (Carlina, Daucus and Scabiosa), with larger seeds, lower mortality rates, but higher age of first reproduction and considerable variation in the density' of individuals.
ON THE ECOLOGY OF SHORT‐LIVED FORBS IN CHALK GRASSLANDS: SEMELPARITY AND SEED OUTPUT OF SOME SPECIES IN RELATION TO VARIOUS LEVELS OF NUTRIENT SUPPLY
Authors: VERKAAR H. J. , SCHENKEVELD A. J.
Published: May 2006

Summary

An experiment was set up in order to investigate semelparity and seed output of Daucus carota L., Linum catharticum L., Picris hieracioides L. and Scabiosa columbaria L. in relation to various levels of nutrient supply.

Some plants of Daucus carota and Scabiosa columbaria were found to flower within one growing season, when nutrient supply was at its highest, whereas the other species did not flower. In the second growing season almost all plants receiving a maximum supply of nutrients flowered and produced seeds. In Linum catharticum flowering plants were recorded in all treatments.

The reproductive plants of all species died after seed shedding, except those of Picris hieracioides and Scabiosa columbaria under high nutrient conditions which formed lateral shoots. These plants survived and were iteroparous.

Seeds produced early in the fruiting period were most numerous and heaviest in the treatments with highest levels of fertilization. In Daucus and Scabiosa a positive linear relationship between seed weight and germination success was found. Thus, the plants grown under the highest nutrient supply conditions showed the highest seed output in all species, although this was less clear m Linum. The significance of these results for the field situation is discussed.
POLLEN MORPHOLOGY OF THE GENUS SILENE L. (CARYOPHYLLACEAE), SECTIONS SIPHONOMORPHA OTTH AND AURICULATAE (BOISS.) SCHISCHK.
Authors: GHAZANFAR SHAHINA A.
Published: May 2006

Summary

Pollen morphology of the species of Silene of the Sections Siphonomorpha and Auriculatae is described. Species belonging to Section Siphonomorpha show only punctate tubuliferous/spinulose ektexine while species belonging to Section Auriculatae show punctate, reticulate and semi‐reticulate tubuliferous/spinulose ektexine. The study suggests the derivation of reticulate ektexine from punctate ektexine and the association of reticulate ektexines with sporophytically advanced taxa. It also emphasizes the retention of the Caryophyllaceae in the Centrospermae.
ANTHROPOGENIC CHANGES FROM NEOLITHIC THROUGH MEDIEVAL TIMES
Authors: DIMBLEBY G. W.
Published: May 2006

Summary

The long period covered by this paper probably saw the most drastic changes wrought by man on the plant cover of these islands in the whole of postglacial history. Much of our information about vegetation changes comes from those parts of the country where peats and mires are abundant, which leaves those areas which were the cradle of successive cultural groups largely unrepresented. Sources of environmental evidence are now emerging even from this unpromising background, an important element amongst which are man's own works. The evidence of changes wrought by man may come from non‐botanical as well as botanical material. Pollen, charcoal, phytoliths, seeds, mosses, and other macroscopic plant remains may be extracted, but indirect evidence may also be obtained from land snails, insects, bones (including small vertebrates), as well as from preserved soils and land surfaces.

In the various environments considered a trend from forest through clearance to pastoral or arable agriculture can usually be demonstrated. These changes may ultimately result in site deterioration on a large scale, the nature of which will depend upon the ecological conditions and the practices at work. In extreme cases peat may form or soil erosion take place. On base‐poor soils, soil acidification may become so intense that the land is no longer usable for traditional agriculture and is allowed to degenerate to moorland or heath. In early historic times much degraded land came into use again for hill‐grazing, a process which further depauperated both the flora and the soils.
THE FLORA AND VEGETATION OF BRITAIN: ECOLOGY AND CONSERVATION
Authors: PIGOTT C.D.
Published: May 2006

Summary

A main aim of studies of the British flora in future must be ecological, with plant ecology developed as a multidisciplinary and experimental science which has as its primary purpose the understanding of vegetation. The response of species to environment is largely mediated through the response of vegetation. It is essential to have an accepted and widely understood classification of British vegetation.

Destruction of the more natural types of vegetation, with accompanying loss of species, should be a matter of national concern as many communities are irreplaceable. Their loss represents irreversible damage to our cultural heritage and a deterioration of the quality of our environment. Ecological understanding of vegetation is necessary to ensure that conservation achieves its primary purpose.
THE INFLUENCE OF DRY STORAGE TEMPERATURE ON THE RESPONSE OF BROMUS STERILIS L. SEEDS TO LIGHT
Authors: HILTON JANET R.
Published: May 2006

Summary

The response of two populations of Bromus sterilis L. seed to light at 15°C was studied over 12 months when seeds were stored at different temperatures. White and red light inhibited the germination of both collections of seed, inhibition persisting for longer periods at low (4°C) than at high (23 °C) temperatures. The two populations of seed behaved similarly in their response to all light treatments.
ON THE DEVELOPMENT OF OSTEOSCLEREIDS IN SEED COATS OF PISUM SATIVUM L.
Authors: HARRIS W. M.
Published: May 2006

Summary

The development of osteosclereids during seed‐coat maturation in Pisum sativum was observed by light and electron microscopy. Osteosclereid precursors are small, densely staining cells which elongate and mature after the macrosclereids. The lateral cell walls in the region of the cell equator become heavily thickened preventing further expansion, while the ends of the cells retain their thin walls and continue to expand. This growth creates the bone‐shaped cell typical of osteosclereids. The cells become separated from each other by accelerated circumferential expansion of the cell layers above and below them and by cell layers. Cell wall synthesis in osteosclereids involves coated and smooth vesicles from the Golgi, and vesicles with fibrillar contents from the endoplasmic reticulum.
EFFECTS OF SOIL TRENCHING AND CORING ON THE FORMATION OF ECTOMYCORRHIZAS ON BIRCH SEEDLINGS GROWN AROUND MATURE TREES
Authors: FLEMING L. V.
Published: May 2006

Summary

Initially non‐mycorrhizal seedlings of birch (Betula pendula Roth.) were grown for a season around two 11‐year‐old birch trees on an experimental site south of Edinburgh. Some seedlings (non‐isolated) were planted in undisturbed positions, others (trenched) in volumes of soil isolated from the mature tree by trenches, and yet others (cored) in cores of soil (8 × 10 cm diameter) that had been removed and replaced immediately.

Mycorrhizas of Lactarius pubescens (Fr. ex Krombh.) Fr., Lactarius glyciosmus (Fr. ex Fr.) Fr., and Leccinum scabrum (Bull. ex Fr.) S. F. Gray and Leccinum roseofracta Watl. developed abundantly on the non‐isolated seedlings but usually very poorly on the trenched and cored seedlings. That some development of Leccinum mycorrhizas occurred in trenched areas is attributed to incomplete severance of roots. In contrast, mycorrhizas of other fungi, for example Hebeloma spp. and Inocybe spp., developed most abundantly on trenched and cored seedlings rather than on non‐isolated seedlings.

The results demonstrate an important difference between types of ectomycorrhizal fungus. Lactarius and Leccinum spp. seem to depend on a continuing supply of photosynthate from a mature tree in order to colonize seedling roots, whereas several other mycorrhizal fungi show no such dependence. The results also indicate an important role for mycelial strands in establishment of mycorrhizas by some fungi (Lactarius pubescens and Leccinum spp.) and thus parallel previous reports on the importance of mycelial strands in colonization of substrata by saprophytic and pathogenic fungi.
STUDIES ON METAL UPTAKE BY PLANTS FROM SERPENTINE AND NON‐SERPENTINE POPULATIONS OFTHLASPI GOESINGENSEHÁLÁCSY (CRYCUFERAE)
Authors: And R. D. REEVES , BAKER A. J. M.
Published: May 2006

Summary

Plants of a serpentine (S) and a calcareous (C) population‐type ofThlaspi goesingenseHálácsy were raised from seed in various serpentine and artificial limestone soils with and without Zn amendment. S‐ and C‐plants grown on metal‐enriched substrates accumulated similar, extremely high concentrations of Ni, Zn, Co and Mn in the above‐ground dry matter; they also showed a marked reduction of Ca uptake, which was combined with increased Mg uptake, in all the serpentine treatments. The fate of the Ni stored in seeds was followed when S‐plants were grown in normal soil. Nickel was conserved and merely diluted within the plant dry matter as growth proceeded. Seedlings transplanted from serpentine soil to non‐nickeliferous soil showed similar dilution effects, suggesting little or no overall Ni loss from the plant. The similar metal‐uptake characteristics and performance of plants from the two populations studied suggests a constitutional metal tolerance within the species and the existence of a non‐specific metal detoxification system.
SENESCENCE AND POST‐MORTEM CHANGES IN THE ULTRASTRUCTURE OF SPHAGNUM FUSCUM (KLINGGR.) SCHLEICH LEAF CELLS
Authors: KARUNEN PIRJO , KÄLVIÄINEN EEVA
Published: May 2006

Summary

Sphagnum fuscum (Klinggr.) Schleich leaves collected from various depths down to 40 cm from the surface were examined by light and electron microscopy and for their capacity to regenerate. Leaf cells never produced new plants: all regeneration in the subsurface samples was from small groups of cells on branches near the junction with the main stems.

Non‐hyaline leaf cells produced in the early summer are senescent by the autumn and dead within a year. Although all the organelles disintegrate these cells invariably contain large lipid globules even to a depth of 30 cm. Fungal hyphae were often found in the non‐hyaline leaf cells from all depths and were frequently associated with eroded lipid bodies. The hyphae spread from cell to cell through the end walls between adjacent non‐hyaline leaf cells at the sites of plasmodesmata. Lipids may be the major catabolite for the fungi within old shoots of Sphagnum.
QUANTITATIVE MICROANALYSIS OF MN, ZN AND OTHER ELEMENTS IN MATURE WHEAT SEED
Authors: MAZZOLINI A. P. , PALLAGHY C. K. , LEGGE G. J. F.
Published: May 2006

Summary

A scanning proton microprobe has been used to determine quantitatively the distribution of Mn, Zn and other elements in the mature wheat seed (Triticum aestivum cv. Gamenya). Both X‐ray and nuclear scattered proton data were collected during the irradiation of a 40 μm‐thick longitudinal section, and these were used to calculate absolute elemental concentrations for the various features of interest in the embryo region. Elemental maps were collected for a number of transverse and longitudinal sections (obtained from several seeds), but comprehensive analytical information was collected from one typical longitudinal section only. In the embryo, the concentration (by dry weight) of Mn was highest in the radicle (1400 ± 200 μg g−1 error is 1 SD) and lowest in the coleorhiza (200 ± 30 μg g−1), whereas Zn was highest in the scutellum (600 ± 100 μg g−1 and lowest in the leaf primordium (410 ± 70μg g−1). Comparisons with direct bulk chemical analysis of excised embryos showed agreement. The possible biological significance of the distribution of elements is discussed. An extensive appendix allows botanists to properly assess the techniques used.
DIEL PATTERNS OF CARBOHYDRATE METABOLISM IN LEAF BLADES AND LEAF SHEATHS OFPOA ANNUAL. ANDPOA×JEMTLANDICA(ALMQ.) RICHT.
Authors: BORLAND A. M. , FARRAR J. F.
Published: May 2006

Summary

A study was made of diel changes in carbohydrate content, net gas exchange and export from leaf blades and leaf sheaths inPoa annuaL. (a ruderal) andPoa×jemtlandica(Almq.) Richt. (a sub‐arctic grass). Sucrose was the most abundant form of carbohydrate in the leaf blades with lesser amounts of starch and fructans also present. The proportions of fixed carbon allocated to export, storage and respiration in leaf blades were similar, and carbohydrates showed broadly similar patterns of diel fluctuation, in both species. However, the relative rates of sucrose and starch accumulation and depletion and the diel patterns of export in the leaf blades were different in the two species. Starch was the predominant form of carbohydrate in the sheath, with soluble sugars and fructans also present. Starch and soluble sugars showed diel accumulation and depletion in the sheathsof Poa annuabut not inPoa×jemtlandica.The effects of extended darkness suggest that factors controlling carbohydrate metabolism in the sheath may be different to those operating in the leaf blade. The large fluxes of carbohydrate through the sheath suggest that it serves mainly as a thoroughfare for carbohydrates.
TRANSFER CELLS AND HARTIG NET IN THE ROOT EPIDERMIS OF THE SHEATHING MYCORRHIZA OF PISONIA GRANDIS R. BR. FROM SEYCHELLES
Authors: ASHFORD A. E. , ALLAWAY W. G.
Published: May 2006

Summary

Pisonia mycorrhizas found in Seychelles possessed transfer cells next to the fungal sheath and Hartig net. There were extensive wall‐ingrowths on outer‐tangential and radial walls of epidermal cells, and on parts of cortical cells, in contact with the mycorrhizal fungus. In general structure, having basidiomycete sheath, transfer cells, and Hartig net between epidermal cells only, the mycorrhizas resembled those from the Australian Great Barrier Reef; Seychelles material had poorer definition of the layers in the sheath and a better‐developed Hartig net. Mycorrhizal development was best at sites with coral sand, the characteristic habitat for P. grandis. At the one site which had soil derived from granite, only one mycorrhiza was found, although many roots were examined and most of these had hyphae at the root surface. In the older mycorrhizas the transfer‐cell walls changed from red‐purple staining to blue with toluidine blue (pH 4‐4), probably because of incorporation of phenolic material; the sheath showed damage and increased impregnation with dark‐coloured phenolic material. From these changes it is suggested that the mycorrhizal association is likely to be functional for only a short distance back from the tip. Comparison of mycorrhizal and non‐mycorrhizal roots suggested that the transfer cells were induced by the fungus, but that a complete sheath was not necessary for their formation. The transfer‐cell wall‐ingrowths were clearly distinguishable from ‘papillae’ formed in fungal invasion, by their morphology, staining properties, and appearance in the electron microscope. The unique structure of the Pisonia mycorrhiza puts it in a category of its own, and its discovery in Seychelles implies that the mycorrhizal habit is widespread in this species.
GERMINATION IN POPULATIONS OF SOLANUM DULCAMARA L. FROM CONTRASTING HABITATS
Authors: PEGTEL D. M.
Published: May 2006

Summary

Solanum dulcamara L. grows in widely contrasting habitats, from waterlogged and shaded to relatively dry and fully exposed sites. Representative seed samples from a number of populations were collected. Germination was studied under a variety of experimental conditions in order to determine whether populations from different habitats were genetically differentiated. Under the conditions employed in these experiments it was concluded that populations probably did not differ genetically in their germination responses.
EFFECT OF IRRADIANCE AND LIGHT QUALITY ON STARCH SYNTHESIS BY ISOLATED CHLOROPLASTS OF CODIUM FRAGILE
Authors: WILLIAMS MICHAEL L. , COBB A. H.
Published: May 2006

Summary

Net starch synthesis by isolated chloroplasts of the intertidal alga Codium fragile (Suringar) Hariot was determined by enzymic hydrolysis (amyloglucosidase/α‐amylase) of solubilized chloroplast samples followed by the measurement of the resultant glucose yields by hexokinase/glucose‐6‐phosphate dehydrogenase‐coupled reactions.

Net starch synthesis was only observed between 100 and 375 μmol m−2 s−1 (PAR) corresponding to irradiance values which supported saturating or super‐saturating rates of photosynthesis. Light filter inactivation of the light‐harvesting complex carotenoids siphonoxanthin and siphonein reduced net starch synthesis by 68 %. These findings are discussed in relation to photosynthesis in an intertidal zone environment.
FUNGAL POPULATION AND COMMUNITY DEVELOPMENT IN CUT BEECH LOGS
Authors: COATES D. , RAYNER A. D. M.
Published: May 2006

Summary

The spatial development, in beech logs exposed to air‐borne and soil‐borne inoculum, of mature fungal communities containing mutually or unilaterally exclusive mycelia of decay species is described and related to the ecological strategies and interaction of participant individuals. A combative heirarchy is recognized between (i) ruderal and/or stress‐tolerant individuals which are spatially dominant early on and then decline, through (ii) air‐borne combative individuals of decay fungi, such as Coriolus versicolor (L. ex Fr.) Quél. and Stereum hirsutum (Willd. ex Fr.) S. F. Gray, which establish mutually exclusive decay columns expanding away from the aerial cut surface, and culminating with (iii) highly combative individuals of mycelial cord‐formers such as Phallus impudicus (L.) Pers. and Phanerochaete velutina (DC ex Pers.) Parmasto, which invade slowly from the base, ultimately occuping large volumes of wood, causing intense decay, and replacing many of the pioneers.

Addition of basidiospore suspensions of Bjerkandera adusta (Willd. ex Fr.) Karst., C, versicolor, Hypholoma fasciculare (Huds. ex Fr.) Kummer or S. hirsutum to the aerial cut surface appeared to affect community dynamics and functioning markedly. Development of decay columns by air‐borne fungi was inhibited and associated with enhanced vertical penetration by basally‐colonizing fungi, and persistence of the relatively non‐combative species Xylaria hypoxylon (L. ex Hooker) Greville and Armillaria bulbosa. (Barla) Kile & Watling. Re‐cutting of the aerial cut surface resulted in community development patterns somewhat intermediate between those in naturally colonized and inoculated logs.
IRON‐INDUCED OXYGEN RADICAL METABOLISM IN WATERLOGGED PLANTS
Authors: HENDRY GEORGE A. F. , BROCKLEBANK K. JANE
Published: May 2006

Summary

Roots of the iron‐sensitive wetland plant, Epilobium hirsutum L., respond to oxygen‐depletion by enhanced uptake of ferrous ions. Evidence is presented for an iron‐catalyzed reaction within roots leading to super oxide radical formation and the induction of superoxide dismutase. The immediate product, H2O2, appears to accumulate in the absence of catalase and low activity of root peroxidases, resulting in hydroxyl radical formation, inhibition of protein synthesis, increased lipid peroxidation and gross cellular damage. Evidence for alternative ‘healthy’ responses is given. A scheme is presented which outlines a biochemical mechanism for iron‐mediated flood or waterlogging tolerance and intolerance in plants.
THE INFLUENCE OF IRRADIANCE ON ROOT REGENERATION IN STEM CUTTINGS OF MUNG BEAN
Authors: JARVIS B. C. , ALI A. H. N.
Published: May 2006

Summary

Cuttings from stock plants grown under continuous irradiance need a supply of borate for roots to develop. This requirement is alleviated, at least in part, by subsequent exposure of stock plants to periods of continuous darkness. Nevertheless, rooting capacity, as shown by responsiveness to supplied IBA, is enhanced by irradiating stock plants. Exposure of the region of regeneration to irradiance diminishes root formation, but exposure of the rest of the cutting enhances it in response to IBA. This effect is mediated via the leaves. In the absence of supplied auxin, irradiance of the leaves only enhances rooting when the hypocotyl is shaded.
INTERVENTION BY GIBBERELLIN AND CYTOKININ IN THE RELEASE OF APPLE EMBRYOS FROM DORMANCY: A REAPPRAISAL
Authors: BULARD C.
Published: May 2006

Summary

Embryos of Pyrus malus L. cv. Golden delicious, were isolated from the fruits and cultivated in aseptic conditions on solid media. Rate of cotyledon greening, evolution of germination percentage and growth of organs after germination were used to determine the extent of dormancy. Treatment with gibberellins and by chilling both induced an increase in the rate of cotyledon greening, in germination percentage as well as stimulating root growth. However, even the most active gibberellins, GA4, GA7, GA9, applied simultaneously at high concentration (5 mg l−1), could not completely reproduce the effects of optimum chilling treatment (9 to 12 weeks at 5 °C).

While progressive increases in germination percentages were found with duration (chilling) or concentration (gibberellins), there was no direct relationship between concentration and response in the case of kinetin. Low concentrations (10 or 100 ug l−1) were inactive, whereas concentrations equal to or greater than 1 mg l−1 induced large increases in germination percentage. The concentrations which stimulated germination also inhibited growth, especially of the root.
TANSLEY REVIEW No 3. THE STRUCTURE AND SYNTHESIS OF PLANT LECTINS
Authors: LORD J. M.
Published: May 2006

Summary

Lectins are a group of proteins and glycoproteins which possess specific binding sites for particular sugars. They are very abundant in certain plant tissues, for example the seeds of legumes. Although their biological role in plants has not been convincingly explained, details of their structure, synthesis and molecular biology are beginning to emerge.

Contents

Summary
351

I.
Introduction
351

II.
Structure of lectins
352

III.
Synthesis of lectins
359

IV.
Conclusion
363

References
363
EFFECT OF GROWTH CONDITIONS ON NADPH‐SPECIFIC GLUTAMATE DEHYDROGENASE ACTIVITY OF EUGLENA GRACILIS
Authors: FAYYAZ‐CHAUDHARY M. , JAVED QAMAR , MERRETT MICHAEL J.
Published: May 2006

Summary

Cells of Euglena gracilis Klebs, strain z Pringsheim, had high NADPH‐glutamate dehydrogenase (GDH) activity when grown on glutamate but activity was repressed completely in cells grown on ammonium (NH4+). Subcellular fractionation showed that NADPH‐GDH activity was located exclusively in the cytosol, while glutamine synthetase was present in the cytosol and chloroplasts. Despite high NADPH‐GDH activity NH4+ assimilation was completely inhibited by methionine sulphoximine (MSO), an inhibitor of glutamine synthetase. With MSO present, cells produced NH4+ and it was shown that greatest NH4+ production occurred with cells containing high levels of NADPH‐GDH activity and plentiful carbon supply. It is concluded that NADPH‐GDH has a catabolic function in Euglena generating NH4+ from glutamate under conditions of nitrogen limitation.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYLIS GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P.
Published: May 2006

Summary

A direct linear relationship between germination responses to light and alternating temperatures and storage period was recorded when seeds of three populations of Dactylis glomerata L. of contrasting origin were stored under cool dry laboratory conditions (15°C, 15% r.h.). Under these conditions the rate of after‐ripening in two batches of a Mediterranean population were independent of original dormancy level but lower than in populations originating from southern England and Western France. The effects of storage on germination responses were additive in all cases. In contrast, when seeds of a population from southern England were stored under natural conditions of temperature and humidity from August to April germination behaviour was dependent on the conditions used in germination tests. Evidence is presented that the rate of loss of primary dormancy under natural conditions exceeded that which occurred during controlled storage in the laboratory. An apparent simultaneous loss of primary dormancy and induction of secondary dormancy observed when seeds were stored under natural conditions is discussed. Dry storage at −75°C effectively arrested after‐ripening over a period of 110 weeks.
RECENT ACCUMULATION AND EROSION OF BLANKET PEAT IN THE WICKLOW MOUNTAINS, IRELAND
Authors: BOWLER MÁIRE , BRADSHAW RICHARD
Published: May 2006

Summary

Active peat erosion is widespread in the Wicklow mountains, and it has been suggested that peat accumulation has slowed or ceased in the area associated with the erosive processes. Analysis of the recent deposition of pollen and magnetic minerals at three sites shows that significant quantities of peat (6.5 to 16.5 cm) have accumulated within the last 150 years. The fallout of magnetic pollutants is far below that found in the Pennine peats, ruling out certain hypotheses about the causes of montane blanket peat erosion.
ANION ACCUMULATION BY THE MOSS HYLOCOMIUM SPLENDENS: UPTAKE AND COMPETITION STUDIES INVOLVING ARSENATE, SELENATE, SELENITE, PHOSPHATE, SULPHATE AND SULPHITE
Authors: WELLS J. M. , RICHARDSON D. H. S.
Published: May 2006

Summary

Arsenic and selenium uptake by the moss Hylocomium splendens (Hedw.) Br. et Sch. from solutions containing arsenate, selenite or selenate ions was investigated. Arsenate and selenite were accumulated only by living shoots. This moss was unable to take up selenate. Arsenate uptake was optimal between pH 3 and 5 whilst selenate uptake was greatest at pH 3. This difference is discussed in terms of speciation of these anions in solution.

Uptake of arsenate and selenite displayed saturation kinetics at pH 5 which could be described in terms of Michaelis‐Menten parameters with Km values of 418 ± 56 μM and 451±93 μM for arsenate and selenite respectively.

Competition studies revealed that pre‐incubation of moss shoots in phosphate solutions did not affect the subsequent uptake of either arsenate or selenite. However, the uptake of the latter ions was decreased if phosphate was included in the incubation medium. Phosphate was a competitive inhibitor of arsenate uptake with an inhibition constant (Km phosphate) of 82 μM. Phosphate and arsenate were non‐competitive inhibitors of selenite uptake with inhibition constants of 225 and 43 μM for phosphate and arsenate respectively. The results suggest that arsenate and selenite were accumulated via separate transport systems in H. splendens and it is proposed that these systems may normally be responsible, in part, for phosphate uptake by this moss.
ULTRAVIOLET PATTERNS IN THE TRAPS OF CARNIVOROUS PLANTS
Authors: JOEL D. M. , JUNIPER B. E. , DAFNI A.
Published: May 2006

Summary

A survey of u.v. patterns in the traps of carnivorous plants reveals that, similar to many flowers, certain traps show conspicuous u.v. patterns. These patterns are based on both u.v.‐absorption by the plant surface itself and u.v.‐absorption by nectar or pools of the digestive secretion. The results are discussed with respect to the possibility that u.v. patterns may attract prey to certain carnivorous plants.
STRUCTURE AND FUNCTION IN THE GRASS LIGULE: PRESENCE OF VEINED AND MEMBRANOUS LIGULES ON THE SAME CULM OF BRITISH GRASSES
Authors: CHAFFEY N. J.
Published: May 2006

Summary

Fifty‐six grass species, representing 18 tribes, were examined for the presence of both veined and membranous ligules in the same culm. This phenomenon was found in only nine species –Agrostis gigantea Roth., A. stolonifera L., Alopecurus pratensis L., Holcus lanatus L., H. mollis L., Phleum pratense L., Phalaris arundinacea L., Dactylis glomerata L. and Poa trivialis L. The abaxial epidermal anatomy of both ligule types is described for each species; the main differences noted were the presence of vascular tissue with associated chlorenchyma and stomata in the veined ligules. This heteroligulate condition is discussed in relation to possible functions of the grass ligule.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: WETHERED J. M. , METCALF E. C. , JENNINGS D. H.
Published: May 2006

Summary

When Dendryphiella salina was grown on non‐saline media, mannitol and arabitol were the only polyols present in the mycelium. In media made up with sea‐water or salinized by high concentrations of salts of potassium, sodium and magnesium, glycerol was also present. When mycelium grown in sea‐water was transferred to distilled water, the glycerol content dropped very rapidly to zero. The amounts of mannitol and arabitol also declined. Transfer of similarly grown mycelium to sea‐water alone reduced the rate of decline of glycerol, caused little change in the amount of mannitol and induced a rise in that of arabitol. These observations help to explain the absence of glycerol in mycelium in previous studies. The concentration (mol l−1) of solutes within mycelium were determined after 48 h growth in the presence of either sodium chloride, magnesium chloride, sodium sulphate, inositol or betaine at either 0.4 or 0.8 osmol kg−1water. There was a very similar total polyol concentration at each osmolality in the saline media irrespective of the salt, even though there could be different concentrations of individual polyols. With inositol in the medium, the same held if the endogenous concentration of that compound was included in the total. The same did not hold for betaine, in which medium growth was poor. The total polyol concentration increased in all cases with the osmolality of the medium. With respect to the total concentration of solutes present (excluding data for mycelium grown in betaine), polyols were 19 to 33 % of the total, α‐amino nitrogen, 11 to 34% and organic acids, 0 to 8 %. These percentages take into account data obtained by 24Na‐flux studies, which indicate that, in media containing sodium salts, much of the mycelial content of the cation may be located in the wall.
MYCOPHAGOUS MARSUPIALS AS DISPERSAL AGENTS FOR ECTOMYCORRHIZAL FUNGI ON EUCALYPTUS CALOPHYLLA AND GASTROLOBIUM BILOBUM
Authors: LAMONT BYRON B. , RALPH CATHERINE S. , CHRISTENSEN PER E. S.
Published: May 2006

Summary

The marsupial, Bettongia penicillata (Gray), is the major consumer of hypogeous fungi in eucalypt forest at Perup, Western Australia. The rate of excavation of sporocarps increases after fire.

The spores of at least 18 fungi were indicated in faecal pellets, 10 of which could be assigned to hypogeous sporocarps present at the site. Most spores belonged to the ectomycorrhizal genus Mesophellia.

Faecal pellets applied to seedlings of Eucalyptus calophylla R.Br. and Gastrolobium bilobum R. Br. in autoclaved soil induced the formation of seven ectomycorrhizal types accompanied by a marked stimulation of growth compared with the controls. Inoculation with fresh spores of two Mesophellia species failed to produce mycorrhizas, suggesting that digestion may be the usual pre‐treatment for germination.

It is concluded that this mammal is a reliable and efficient dispersal and inoculation agent for ectomycorrhizal fungi via its faeces, and that it plays a key role in re‐establishment of vegetation after fire.
VARIATION IN MORPHOLOGICAL AND PHYSIOLOGICAL TRAITS ASSOCIATED WITH YIELD IN LIMNANTHES SPP.
Authors: KREBS S. , JAIN S. K.
Published: May 2006

Summary

Biomass and seed yield variation among 10 accessions of two Limnanthes species, L. alba Benth. and L. douglasii R. Br., was examined by way of a yield component analysis involving 17 morphological characters. Seed yield estimates ranged from 735 to 1680 kg ha−1. While both taxa contained populations with high yield potential, species differences in phenology and resource allocation suggested different strategies for yield optimization. L. douglasii accessions produced large quantities of small‐sized seed, whereas L. alba entries maximized seed size at the expense of seed number, seed size and seed number being compensating components of yield in both species. Higher yields were associated with rapid initial growth and leaf development in L. douglasii, while delayed biomass accumulation and less leaf area appeared more favourable to seed production in L. alba. Early and asynchronous floral development were strong predictors of high yielding ability in both taxa. Selection for individuals which flower early and over a long period of time, with a higher seed output associated with a larger proportion of total above‐ground dry matter allocated to reproduction, was suggested as an appropriate breeding strategy in either species. Concurrent improvement of seed number and seed size may prove possible by indirect selection for fewer flowers per plant in L. douglasii or more flowers per plant in L. alba accessions, through manipulation of primary branch length and number.