bluuebunny/crossref_metadata_2025 huggingface dataset:
CONTROL OF DEVELOPMENT IN CHENOPODIUM ALBUM L. BY SHADELIGHT
Authors: CHILD RICHARD , MORGAN D. C. , SMITH HARRY
Published: May 2006

Summary

Many open‐habitat species are capable of perceiving and reacting to the reduced red: far‐red ratio of vegetational shade. A well‐documented example is the arable weed Chenopodium album, which responds most noticeably by a dramatic increase in height. Here this characteristic response is considered in greater detail, together with other morphogenic modifications elicited by shadelight quality. To enable such modifications to be interpreted in terms of differences in light quality, particular attention was paid to the minimization of fluence‐rate differences between simulated daylight and simulated shadelight treatments. It was found that the greater stem extension in simulated shadelight results mainly from an increase in cell elongation. Individual internodes also showed an acceleration of the extension growth phase, and a reduction in the time taken for completion of their growth, in simulated shadelight. There was no evidence to suggest that the rate of leaf formation was affected; however, apical dominance was enhanced resulting in the suppression of axillary outgrowth.

Total leaf area was relatively unaffected by the different light quality regimes; however, leaves of higher insertion expanded more rapidly in simulated shadelight. Leaves which developed in this treatment had reduced stomatal frequencies on both surfaces, together with a reduction in photosynthetic pigment content on a leaf area basis. The possibility that these modifications are part of a coordinated response to shadelight, and the site of light quality perception, are discussed.
THE INFLUENCE OF VESICULAR‐ARBUSCULAR MYCORRHIZA ON GROWTH AND WATER RELATIONS OF RED CLOVER
Authors: HARDIE KAY , LEYTON L.
Published: May 2006

Summary

Vesicular‐arbuscular (VA) mycorrhizal infection of red clover grown in phosphate deficient soils enhanced the concentration of P in the tissues, stimulated growth of root and shoot but reduced the root/shoot ratio. Addition of phosphate to well below the optimum level also stimulated growth and enhanced P status of non‐mycorrhizal plants, but their yields and P concentrations were much smaller than those of mycorrhizal plants and their root/shoot ratios were unaffected.

The hydraulic conductivities of the root systems were very much higher in mycorrhizal than in uninfected plants. This could be partly attributed to the greater lengths and diameters and hence total surface areas of the mycorrhizal roots. Per unit length of root, the conductivities of the mycorrhizal roots were still two to three times higher, suggesting that this was mainly due to hyphal growth in the soil.

When soil water was not limiting, the lower root resistances combined with larger leaf surface areas and possibly also lower leaf diffusion resistances resulted in very much higher transpiration rates and fluxes in mycorrhizal than in non‐mycorrhizal plants. Under conditions of water stress, however, the leaf diffusion resistances of mycorrhizal plants were higher and transpiration fluxes lower compared with uninfected plants but, because of their higher total water demands, they wilted more rapidly. Mycorrhizal plants were able to extract soil moisture down to lower water potentials than non‐mycorrhizal plants (difference about 1 MPa) but, possibly because of their lower leaf water potentials and higher root conductivities, they recovered turgor more rapidly than non‐mycorrhizal plants when soil water was restored. Thus, the mycorrhizal habit is an advantage to the host plant in times of moisture stress.
THE ASSESSMENT OF NITROGEN FIXATION AND THROUGHPUT BY LICHENS
Authors: MILLBANK J. W.
Published: May 2006

Summary

Using specially made controlled environment chambers, the rates of nitrogen fixed in the field by the lichens Peltigera membranacea, P. polydactyla and Lobaria pulmonaria have been estimated under simulated seasonal conditions. The chambers permitted direct comparisons between short term acetylene reduction estimates and long term incorporation of 15N2 labelled gas. Large thallus samples minimized variation, and the overall figures of N2 fixed integrated the effects of fluctuations in temperature, daylength, light intensity and thallus moisture content. Empirical factors have been derived to relate short term rates of acetylene reduction to long term rates of N2 incorporation. Under predominantly moist conditions, factors of 8 to 10 were found. Drier summer conditions can result in factors in excess of 20. Estimated rates of total nitrogen input were 4 to 6 kg ha−1 per year. In dry exposed situations rates can be approximately half this figure.
EFFECT OF SOME ORGANIC CARBON SOURCES ON THE DARK CALCIFICATION OF THE FRESHWATER GREEN ALGA GLOEOTAENIUM
Authors: PRASAD P. V. DEVI , CHOWDARY Y. B. K.
Published: May 2006

The effect of glucose, acetate or succinate on the dark calcification of Gloeotaenium, a freshwater green alga, was studied. Under normal conditions calcification does not occur in this alga in darkness but addition of acetate or succinate induced calcification whereas glucose failed to do so. The induction of calcification by acetate was inhibited by dinitrophenol and that by succinate was inhibited by malonate. It is concluded that no separate light‐dependent mechanism of calcification exists in Gloeotaenium and that oxidative phosphorylation may be supplying, at least partly, the energy required for calcification.
SALT UPTAKE AND RESPIRATION OF EXCISED BEECH MYCORRHIZAS
Authors: HARLEY J. L.
Published: May 2006

When excised beech mycorrhizas aged in aerated water absorb ammonium from NH4C1 solutions in the presence of low concentrations of 32P‐labelled KH2PO4, the incorporation of 32P in the tissues during a 2‐min period was greater than when ammonium was not supplied. At the same time, the respiratory rate was also greatly increased. The destination of the phosphate incorporated was similar whether ammonium was present or not. The results are consistent with the view that the respiratory rate of aged beech mycorrhizas is limited by the rate of phosphate turnover and the availability of phosphate acceptors, and that the absorption of ammonium increases this turnover.
GROWTH RESPONSES OF ENDOMYCORRHIZAL ONIONS IN UNSTERILIZED COAL WASTE
Authors: Khan A. G.
Published: May 2006

The effects of the widespread vesicular‐arbuscular (VA) endophytes, namely Glomus macrocarpus var macrocarpus, Glomus mosseae, and Sclerocystis rubiformis and those of E3 (a strain of Endogone introduced from Rothamsted Experimental Station) on growth of onions were compared in unsterilized coal washery waste from the Coal‐Cliff Collieries in the Illawarra region of New South Wales. Mycorrhizal onions were significantly larger (P < 0.05), with respect to all the growth measurements than NM controls. Different VA endophytes had quantitatively different effects on the growth; the S. rubiformis was always poorest and E3 most consistently good. This is because S. rubiformis produced more localized infection, while the growth of E3 was more general producing, under similar conditions, more extramatrical hyphae than any other endophyte used. Among widespread species G. mosseae was the most efficient at stimulating plant growth. The possible role of VA mycorrhizas in plant colonization of coal spoil areas is discussed.
THE MYCORRHIZAL RELATIONSHIPS OF AUSTRALIAN ORCHIDS
Authors: WARCUP J. H.
Published: May 2006

The symbiotic associations of Australian orchids have been examined by isolating Rhizoctonia endophytes from orchids growing in the field and by symbiotic germination of orchid seed. Many Rhizoctonia isolates fruited and were identified to their perfect states.

The isolation studies showed considerable specificity in association between many orchids and their endophytes. In particular Sebacina vermifera was generally associated with Caladenia and several related genera. Tulasnella calospora was closely associated with Diuris and Orthoceras and it and other species of Tulasnella with Thelymitra and Dendrobium. Ceratobasidium cornigerum was associated with Prasophyllum and Pterostylis and, with other species of Ceratobasidium, with orchids of the subtribe Sarcanthinae. Specificity, however, was not absolute for different Rhizoctonias may occur in an orchid either alone or with the more usual endophyte. A few orchids had a wide range of endophytes commonly present.

Symbiotic germination studies generally substantiated the field isolations but showed further levels of specificity in that isolates of a fungus often differed markedly in their ability to germinate seed of a host or of different hosts under the conditions used.

With orchids specificity seemed to occur at different levels, from species to at least subtribe, though the data are imprecise. If there is specificity to subtribe then there are some anomalies in classification. For instance all Caladeniinae sampled were associated with Sebacina vermifera except Lyperanthus which was associated with a wide range of other fungi. Microtis and Prasophyllum, though not considered closely associated, are placed together in the Prasophyllinae; their endophytes are quite different.
A TECHNIQUE FOR THE ESTABLISHMENT OF MYCORRHIZAL INFECTION IN ORCHID TISSUE GROWN IN ASEPTIC CULTURE
Authors: BEARDMORE JANE , PEGG G. F.
Published: May 2006

Two techniques for producing large quantities of mycorrhizal and non‐mycorrhizal orchid tissue for experimental purposes are described.

Protocorm‐like masses of Dactylorhiza purpurella (T. & T. A. Steph.) Soó, were grown axenically in darkness on 2 % sucrose mineral salts medium with growth supplements at 22 °C. These cultures, derived from seed, were substantially larger than the original protocorms.

Mycorrhizal infection of this tissue was achieved successfully in 100 ml conical flasks in which the protocorm‐like tissue was suspended on water agar only and the fungus inoculated on an adjoining cellulose, mineral salts slope.

Infection, using several Rhizoctonia strains in this double‐culture system gave consistent mycorrhizas characteristic of natural protocorms and with extensive colonization of cortical tissue. Alternative inoculation methods using a single aqueous or agar medium and with recognized mycorrhizal strains, gave variable infection, frequently resulting in pathogenicity and host death. The advantage of the double culture system in providing large quantities of orchid mycorrhizal tissue for experimental studies is discussed.
ANATOMY, HISTOCHEMISTRY AND CYTOLOGY OF DORMANT AND STRATIFIED APPLE EMBRYOS
Authors: DAWIDOWICZ‐GRZEGORZEWSKA A.
Published: May 2006

The following sequence of structural changes which are related to the utilization of storage materials have been shown to occur in the apple embryo: degradation of protein bodies, degradation of lipid bodies, appearance and degradation of starch. These processes take place in the embryonic axis during stratification and in the cotyledons during the germination of stratified embryos. Important differences were observed in the localization of these processes during the early post‐embryonic (up to 12 days) growth of dormant and stratified embryos. It is concluded that during the germination of dormant embryos the embryonic axis influences certain hydrolytic processes in cotyledons by delaying and inhibiting their progress, whereas in non‐dormant embryos these are stimulated by the embryonic axis.
THE SOLUTE AND WATER RELATIONS OF AGROSTIS STOLONIFERA ECOTYPES DIFFERING IN THEIR SALT TOLERANCE
Authors: AHMAD I. , WAINWRIGHT S. J. , STEWART G. R.
Published: May 2006

The water, ion, proline, amide, amino acid and quaternary onium contents of ecotypes of Agrostis stolonifera isolated from salt marsh, spray zone and inland habitats were determined over a range of external salt concentrations. When grown at high salinites the plants exhibited inhibition in the root water absorption and reduction in the shoot water content, these being most pronounced in the inland ecotype and least in the salt marsh ecotype. In the presence of salt the accumulation of Na+ and Cl− in both shoots and roots was accompanied by a decline in tissue potassium content. At high salinities the increase in tissue ion content was greatest in the inland ecotype and least in the salt marsh ecotype. Proline, asparagine, glutamine, serine and glycine betaine showed increases in response to salinity, these being most pronounced in the salt marsh ecotype. The inland and spray zone ecotypes exhibited marked decreases in the aspartate and glutamate contents when grown at high salinities.

With polyethylene glycol or mannitol in culture solutions, the salt marsh ecotype exhibited a greater ability to resist losses in shoot water content and to increase shoot proline, asparagine, glutamine and serine contents, than the inland and spray zone ecotypes.

Changes in the solute and water status are discussed in relation to salt tolerance of the ecotypes.
FREEZE‐ETCH ULTRASTRUCTURE OF A PROCHLORON SPECIES ‐ THE SYMBIONT OF DIDEMNUM MOLLE
Authors: COX GUY , DWARTE D. M.
Published: May 2006

A species of Prochloron, a genus of photosynthetic prokaryotes containing chlorophylls a and b and lacking phycobilins, has been investigated by the freeze‐etch technique and thin sectioning. The thylakoids show a high level of stacking; particle distributions on fracture faces of the membranes resemble those of chloroplasts more than those of cyanophytes. Polyhedral bodies (carboxysomes?) are surrounded by a unit membrane which probably derives from the thylakoids. Vacuole‐like areas are seen in freeze‐etch replicas to contain a structured substance, probably a reserve material.
OVULE DEVELOPMENT INORNITHOGALUM CAUDATUM(LILIACEAE) WITH A REVIEW OF SELECTED PAPERS ON ANGIOSPERM REPRODUCTION
Authors: TILTON VARIEN R. , LERSTEN NELS R.
Published: May 2006

Ornithogalumovules are bitegmic: the inner is initiated first, but both attain maturity at the same time. Both integuments are derived from the epidermal layer of the nucellus and are covered by a cuticle. Inner integument cells define the micropyle and those which line it are secretory. An outer integument is present only on the distal (non‐funicular) side of the ovule. Its proximal portion apparently is fused congenitally with the funiculus. A funiculus attaches the ovule (and seed) to placental tissue. Proliferation of cells at the base of the funiculus contributes to development of the obturator. Funicular curvature causes the ovules to assume an anatropous orientation. A procambial strand branches from a ventral vein of the carpels and differentiates acropetally in the funiculus. At ovule maturity, vascular tissue terminates in the chalaza a few cells removed from the hypostase. Terminal cells of the vascular bundle consist only of tracheary elements with annular thickenings.
SEEDLING SURVIVORSHIP IN NATURAL POPULATIONS OF NINE PERENNIAL CHALK GRASSLAND PLANTS
Authors: SILVERTOWN JONATHAN W. , DICKIE JOHN B.
Published: May 2006

Seedling survivorship in cohorts of nine perennial species of chalk grassland is reported. Heavy (> 80%) mortality in the first year occurred in six of the species with still higher values of mortality expected before any individuals in a cohort flowered. The observations are compared with the results of previous studies.
CHANGES IN POLY(A) RNA METABOLISM IN RELATION TO STORAGE AND DORMANCY‐BREAKING OF HAZEL SEED
Authors: JARVIS B. C. , SHANNON P. R. M.
Published: May 2006

The amounts of abscisic acid (ABA) in different parts of the seed have been investigated during dry storage, which induces dormancy. ABA occurs within the embryonic axis as well as in testa and cotyledon. The amount of ABA in the whole seed markedly declines during dry storage, although there is a transient increase within the embryonic axis. The incorporation of 32PO43‐ into poly(A)‐rich RNA within the axis declines during dry storage. Imbibition results in increased poly(A) RNA synthesis but the presence of the testa is inhibitory to this synthesis. GA3 on the other hand promotes synthesis. Poly(A) RNA synthesis within isolated embryonic axes is inhibited by ABA. These results are discussed with respect to the induction, maintenance and breaking of dormancy.
VESICULAR—ARBUSCULAR MYCORRHIZAL SPORE POPULATION AND INFECTIVITY OF SAFFRON (CROCUS SATIVUS) IN IRAN
Authors: KIANMEHR H.
Published: May 2006

VA mycorrhizal infection of saffron (Crocus sativus L.) was assessed in the major growing areas of Khorasan, the northeastern province of Iran. Endomycorrhizal spore population was high in January and low in July. Particularly heavy VA infection occurred in April. When spores of Glomus macrocarpus, recovered from soils, were tested as inoculum on other bulbous plants including onion and crocus, the responses were variable.
NUMBER AND STRUCTURE OF ANTHERS IN FIG SYCONIA IN RELATION TO BEHAVIOUR OF THE POLLEN VECTORS
Authors: GALIL J. , MEIRI LIORA
Published: May 2006

Structure and functioning of anthers have been studied in Ficus carica L., F. sycomorus L. and F. religiosa L. Polleniferous figs of F. carica produce numerous male flowers with plenty of pollen (multistaminate type). Mature anthers contain a normal fibrous layer and open spontaneously. On the other hand, figs of F. sycomorus produce a comparatively small number of male flowers, their anthers have a degenerated endothecium and do not dehisce normally.

In pollination (pollen loading and unloading) the great differences occurring in the organization of the androecium of F. carica and F. sycomorus may be seen to be associated with different behaviour patterns of their specific pollen vectors, the agaonid wasps Blastophaga psenes and Ceratosolen arabicus, respectively. While the pollinators of F. carica become passively coated with pollen on their exit from the native fig (topocentric pollination), the pollen vectors of F. sycomorus help in opening of the anthers and load the pollen purposively, by direct lifting of the pollen from the anthers on to special pockets on the body of the insect (ethodynamic pollination). Thus, in the context of pollination, the complementary nature of the characteristics of the two participants of fig symbiosis is evident.
MICRO‐SPATIAL HETEROGENEITY AND SEEDLING DEMOGRAPHY IN SPECIES‐RICH GRASSLAND
Authors: SILVERTOWN JONATHAN W.
Published: May 2006

It is suggested that spatial niche‐separation between grassland species occurs in the regeneration phase and that the differential response of species to micro‐variations in leaf cover may allow coexistence at high density. A technique for measuring heterogeneity in leaf‐cover on a scale of 1‐cm2 units (micro‐cover) and the demography of seedling cohorts of Reseda lutea and Anthyllis vulneraria in relation to this heterogeneity is described. Densities of seedlings were significantly higher in micro‐sites of low micro‐cover for R. lutea and for one of the three cohorts of A. vulneraria studied. No relationship was found between mortality and density of seedlings or micro‐cover. The ultimate causes of these distribution patterns of seedlings and their consequences for the maintenance of species diversity in grassland are discussed.
EFFECT OF SEASON, SOIL FAUNA AND WATER CONTENT ON THE DECOMPOSITION OF CATTLE DUNG PATS
Authors: DICKINSON C. H. , UNDERHAY V. S. H. , ROSS V.
Published: May 2006

Experiments were carried out with artificially‐placed, cattle dung pats to determine the effects of season, soil fauna and water on their disappearance. The method involved processing whole pats so as to overcome problems due to the existence of distinctly different zones within the mass of dung. Weight loss measurements were used to measure the loss of dung. The organic matter, nitrogen and mineral ion contents of the dung were measured to determine if qualitative changes occurred in the faeces during decomposition. Dung pats set up in early autumn disappeared more rapidly than pats put out in spring. In both seasons the most rapid changes occurred when the pats were subject to irrigation as well as the natural rainfall. By contrast, pats covered for the duration of the experiments suffered the smallest dry wt losses and minimal changes in all the other parameters which were measured. No differences were observed in the rate of change in pats placed on a fine mesh netting, which excluded earthworms and other large soil invertebrates, and pats which were placed on a large mesh netting. Leaching of mineral ions from the dung was only significant when the pats were also losing substantial amounts of dry matter. These data are discussed in relation to patterns of cattle dung decay elsewhere in the world.
THE VEGETATION OF BRITISH SALTMARSHES
Authors: ADAM PAUL
Published: May 2006

The basis for a classification of the vegetation occurring on British saltmarshes is discussed and a dichotomous key, using floristic information, to the majority of plant communities on British marshes is presented.

Brief descriptions of the communities are given, including information on their position in the saltmarsh zonation and their geographical distribution.
INFLUENCE OF SOIL WATER STRESS ON WILTING AND WATER RELATIONS OF DIFFERENTLY OSMOTICALLY ADJUSTED WHEAT PLANTS
Authors: JENSEN C. R.
Published: May 2006

Summary

During a pretreatment period of 1 week, spring wheat plants (Triticum aestivum, L., cv. ‘Sappo’) grown in a sandy soil in pots were adjusted to three levels of soil water osmotic potential induced by watering the plants with a nutrient solution (minus 0·5 bar) and further additions of KNO3 (minus 3 and minus 6 bar). After leaching of the soil, the plants were exposed to two drying cycles separated by rewetting. With severe water stress at the end of drying cycle 1, reduction of wilting was highly correlated with lowering of leaf osmotic potential due to the KNO3pretreatment. Turgor potential was highest and decreased at lowest soil water matric potentials in KNO3 pretreated plants. Recovery after rewatering was seemingly most accelerated in KNO3 pretreated plants due to a larger potential difference between leaf and soil water. The leaf and soil water matric potentials at which stomata closed were lowered as a result of both KNO3 pretreatment and the effect of previous water stress on leaf osmotic potential.
SPECIFICITY IN THE GUNNERA‐NOSTOC ENDOSYMBIOSIS
Authors: BONNETT HOWARD T. , SILVESTER WARWICK B.
Published: May 2006

Summary

The cyanobacterium, Nostoc, and the angiosperm, Gunnera, form a symbiotic association in which glandular cells host an intracellular population of heterocystous Nostoc cells. Symbiotic and free‐living isolates of Nostoc and Anabaena were assayed for their ability to infect, fix nitrogen and supply nitrogen to Gunnera. The range of cyanobacteria acceptable to Gunnera was found to be circumscribed by the genus, Nostoc, but included six different isolates within that genus. The effectiveness of the various Nostoc isolates was compared in terms of their activities at both the inter and intracellular levels of symbiotic association.
ULTRASTRUCTURE OF THE SEAGRASS RHIZOSPHERE
Authors: KUO J. , MCCOMB A. J. , CAMBRIDGE M. L.
Published: May 2006

Summary

Bacterial colonies, fungi and other micro‐organisms occur in the rhizosphere and peripheral root tissues of seagrasses of the genus, Posidonia. Fungi penetrate the epidermal cells and lyse the thick polysaccharide materials in the walls of the hypodermal cells. A suberin lamella in the wall of the hypodermal cell is more resistant but fungi and bacteria occur both within the lumen of hypodermal cells and in cortical cells adjacent to the hypodermis. It is suggested that these micro‐organisms in the rhizosphere and peripheral root tissues may be involved in nutrient uptake and nitrogen fixation into seagrasses.
QUANTITATIVE BIRCH (BETULA L.) POLLEN SEPARATION BY ANALYSIS OF SIZE FREQUENCY DATA
Authors: PRENTICE I. C.
Published: May 2006

Summary

The Gordon—Prentice maximum likelihood method for estimating proportions of morphologically overlapping pollen taxa in a mixture requires knowledge of the underlying frequency distributions. This requirement is hard to fulfil when size is the discriminating character. However, if normality can be assumed the underlying distributions can be inferred from the data. This indirect approach ‐ due to Usinger ‐ permits reliable separation of Betula species in northwest European pollen diagrams. Techniques for separating mixtures of known distributions and for estimating underlying normal components are compared and assessed. For illustration, birch pollen size data from a Late Weichselian/early Holocene sequence in Finnmark, Norway (H. C. Prentice, unpublished) are subjected to a simple graphical technique to derive (two) normal components and then to the Gordon‐Prentice method and an analytical least‐squares method to estimate proportions. The inferred distributions are broadly consistent with Usinger's for Betula nana and Betula pubescens. The results show an Allerød‐Younger Dryas fall in the pollen percentage of Betula nana, a Betula pubescens rise at the beginning of the Holocene (interpreted as long‐distance pollen transport), and a subsequent major Betula nana expansion concurrent with the regional Ericales maximum.
LIMITATIONS OF PHOTOSYNTHESIS IN DIFFERENT REGIONS OF THE ZEA MAYS LEAF
Authors: MIRANDA VALENTINE , BAKER NEIL R. , LONG STEPHEN P.
Published: May 2006

Summary

The progressive development of the photosynthetic apparatus occurring along the length of the Zea mays leaf offers a convenient system with which to examine the limitations to photosynthetic CO2 assimilation during biogenesis of a C4 leaf. Changes in light‐induced O2 evolution and CO2 assimilation, chlorophyll content, activity of PEP‐carboxylase, NADP‐malic enzyme and the ‘R5P system’ (consisting of d‐ribose‐5‐phosphate‐keto isomerase, ATP‐d‐ribulose‐5 phosphate 1‐phosphotransferase and d‐ribulose‐1,5‐bisphosphate carboxylase) and fluorescence emission characteristics were examined along the length of the second leaf of 7‐day‐old plants grown under a diurnal light regime. The results suggest that the major limitation to CO2 assimilation in the leaf sheath lies within the chlorenchyma and is either energy supply for carboxylation or the capacity of key photosynthetic enzymes. In the leaf blade stomatal resistance to CO2 diffusion constitutes a major fraction of the total leaf resistance to CO2 assimilation implicating the stoma as the major limiting factor to photosynthetic CO2 assimilation.
AN ECOPHYSIOLOGICAL STUDY OF THE SALT SECRETION OF FOUR HALOPHYTES
Authors: ROZEMA JELTE , GUDE HENK , POLLAK GAD
Published: May 2006

Summary

Plants of Spartina anglica, Limonium vulgare, Armeria maritima and Glaux maritima were collected in the field and grown on different concentrations of NaCl, KCl and CaCl2. Salt secretion, ion content, water content and transpiration rates were determined. The highest sodium secretion was found in Spartina anglica, a species from the most saline habitat; and a somewhat lower secretion rate in Limonium vulgare. The lowest rates were found in Glaux maritima and Armeria maritima. The sodium secretion efficiency, i.e. the ability to maintain an unchanged internal sodium content, was highest in Spartina anglica. Spartina anglica is the most successful in the removal of excessively absorbed salt, since it secretes 60% of the absorbed sodium. The values for Limonium vulgare, Glaux maritima and Armeria maritima were 33, 20 and 4% respectively. The species studied differ in the preferential sequence of ion secretion as well as in secretion rate and efficiency. This preferential sequence of ion secretion seems to be similar in members of the same taxonomic group (Plumbaginaceae). The comparability of the secretion parameters is discussed with regard to morphological differences between the species.
ULTRASTRUCTURAL ASPECTS OF ENDOMYCORRHIZAS IN THE ERICACEAE II.
Authors: BONFANTE‐FASOLO P. , BERTA G. , GIANINAZZI‐PEARSON V.
Published: May 2006

Summary

The endomycorrhizal infection in Vaccinium myrtillus is limited to the cortical cells of the fine hair roots; the fungi responsible have simple septa with associated Woronin bodies (Ascomycetes). Hyphae penetrating into cells are surrounded by a layer of inner host wall material which diminishes with intracellular development of the fungus. In living cells hyphae are separated from host cytoplasm by continuous host plasmalemma and there is no evidence of their lysis or digestion by the plant cell. This biotrophic relationship (living host cell and fungus) appears to predominate in late summer and autumn when new root formation and mycorrhizal infection are most important. During other periods of the year living or dead fungus in moribund host cells seem to be the most common situation.
BACTERIUM‐LIKE ORGANELLES IN THE VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS CALEDONIUS
Authors: MACDONALD R. M. , CHANDLER MURIEL R.
Published: May 2006

Summary

Bacterium‐like organelles (BLOs) were found by electron microscopy in the vesicular‐arbuscular (VA) mycorrhizal fungus Glomus caledonius. They were morphologically similar to those found by others in other V A mycorrhizal fungi, in the ectendomycorrhizal fungus Endogone flammicorona and in the Discomycete Scutellinia. They occurred free in the cytoplasm of Glomus caledonius reproductive spores and in the intercellular hyphae and thick arbuscule branches in infected roots. They were irregularly coccal with diameters of 0·3 ± 0·06 μm and had a conspicuous cell membrane and simple cell wall and appeared to divide by median constriction and separation. The fungal cytoplasm did not show any cytopathic effects in the vicinity of the BLOs.

A competely different type of bacterium colonized and eroded the walls of reproductive spores of Glomus caledonius. These bacteria did not enter the fungal cytoplasm and had a thick complex wall and peripheral membranes. In contrast to BLOs, their cytoplasm was clearly differentiated into electron‐dense and transparent areas.
CARBON METABOLISM OF SPARTINA ALTERNIFLORA LOISEL IN RELATION TO THAT OF ASSOCIATED NITROGEN‐FIXING BACTERIA
Authors: BOYLE C. D. , PATRIQUIN D. G.
Published: May 2006

Summary

Relationships between the carbon metabolism of the C4 salt‐marsh grass, Spartina alterniflora Loisel, and that of root and rhizosphere soil diazotrophs were investigated. Experiments involving addition of carbon compounds demonstrated that acetylene reducing activity (ARA) of both populations was dependent upon compounds from roots soluble in 80% ethanol. Of these, sugars (glucose, fructose and sucrose) were most effective in increasing ARA of the soil diazotrophs, while organic acids (malate) increased ARA of root diazotrophs. ARA of both populations was dependent upon carbon sources from large carbon pools. 14CO2 labelling of plants demonstrated that sugars were the only quantitatively significant photosynthates translocated to the roots and that these entered large carbon pools. After longer periods, labelled sugars were detected in rhizosphere soils where they were metabolized (possibly by diazotrophs) to form acidic and basic compounds. The possibility that dark CO2 fixation by roots or bacteria provided malate for the root diazotrophs was investigated.
THE EFFECT OF NITROGEN AVAILABILITY ON GROWTH AND CELLULOLYSIS BY SERPULA LACRIMANS
Authors: WATKINSON S. C. , DAVISON E. M. , BRAMAH J.
Published: May 2006

Summary

The effect of sodium nitrate level on three parameters of growth of Serpula lacrimans was investigated and compared with nitrogen levels normal in wood. The results showed that mycelial extension from a wood food base over non‐nutrient substrata is probably not limited by nitrogen availability, but that the rate of increase in mycelial biomass and of cellulose decomposition probably are. The nitrogen required for cellulolysis could be translocated to the site of cellulolysis when supplied at a distance from it. The results are discussed in relation to the biology of the fungus.
SPATIAL DEVELOPMENT OF POPULATIONS OF CORIOLUS VERSICOLOR
Authors: WILLIAMS E. N. D. , TODD N. K. , RAYNER A. D. M.
Published: May 2006

Summary

Various combinations of dikaryons and monokaryons of the wood‐rotting Basidiomycete Coriolus versicolor (L. ex Fr) Quél. were inoculated evenly spaced into Petri dishes containing 3% malt agar, or birch logs placed in a woodland site. The resulting patterns of colonization were similar to those found in natural populations of the fungus, with individual dikaryons present in discrete regions delimited by zones of mutual antagonism. Different dikaryons had similar growth rates and occupied approximately equal areas or volumes when inoculated simultaneously on to agar or into wood respectively. Simultaneous and sequential inoculation of sexually compatible monokaryons on to agar demonstrated that growth rate of the monokaryons and patterns of dikaryotization and nucleus migration between them are likely to be crucial determinants of the spatial distribution of dikaryons in a population. Monokaryons inoculated into logs in the field quickly became dikaryotized, and the resulting dikaryons contained diverse mating‐type factors indicating the presence of a heterogeneous spore rain.
THE AZOLLA‐ANABAENA AZOLLAE RELATIONSHIP
Authors: KAPLAN D. , PETERS G. A.
Published: May 2006

Summary

The fixation of 15N2 and its transport were studied as a function of leaf development along the main stem axes of Azolla.

Main stem axes dissected from Azolla caroliniana Willd. plants, and sequential groups of leaves along the axes, had 25 to 35 % less nitrogenase activity than the undissected controls when assayed immediately. However, they exhibited activities equivalent to those of the intact controls when allowed to recover for 12 h or more prior to assaying. Nitrogenase activity was determined as a function of leaf age by measuring 15N2 fixation and C2H2 reduction in parallel samples. The reduction of both substrates was very low in the apical region, increased rapidly with leaf maturation and plateaued prior to declining as leaves began to senesce. Whereas the nitrogen content and dry matter decreased with increasing leaf age, the C:N ratio increased. These findings are consistent with the demonstration that nitrogen fixed by the endophytic Anabaena in mature leaves is transported toward the stem tip where undifferentiated but actively dividing filaments of the endophyte are associated with the apex and leaf primordia.
GERMINATION OF THE DIMORPHIC FRUITS OF BIDENS PILOSA L.
Authors: FORSYTH C. , BROWN N. A. C.
Published: May 2006

Summary

Dimorphic fruits of Bidens pilosa were tested separately for differences in germinability and seedling development. The long achenes were found to germinate readily under a wide range of conditions while the short achenes showed fairly exacting germination requirements. Germination of the short achenes was found to be enhanced by red light treatment, scarification, applied hormones, leaching and increased oxygen tensions. Seedlings originating from short achenes showed lower survival rates and initially slower development than those originating from the long achenes. The implications of the morphological differences and differences in germination and development of the two achenes are discussed.
THE EFFECTS OF SALINITY AND WATERLOGGING ON THE GROWTH AND CATION UPTAKE OF SALT MARSH PLANTS
Authors: COOPER ALAN
Published: May 2006

Summary

Festuca rubra, Juncus gerardii, Armeria maritima, Plantago maritima, Aster tripolium, Triglochin maritima, Puccinellia maritima and Salicornia europaea from a salt marsh near Portaferry, County Down, were grown on drained and waterlogged salt marsh soils under saline and non‐saline conditions. Shoot and root yields and the concentrations of sodium, potassium, calcium, magnesium, manganese and iron in the shoots were determined after a 2‐month growing period. The tolerance of the plants to waterlogging and salinity differed in a way which was correlated with their position on the salt marsh ecotone.

The growth of upper marsh species, but not that of lower marsh species, was strongly limited by both salinity and waterlogging. Only Salicornia europaea gave its maximum yield on the saline treatments and only Puccinellia maritima showed a preference for waterlogged soils. Reduced yields on the saline treatments were associated with large increases in shoot sodium concentrations but in general, salinity and waterlogging had little effect on shoot cation concentrations. It is suggested that factors other than the greater availibility of iron and manganese on araerobic salt marsh soils are involved in determining species distribution along the salt marsh ecotone.
INFLOW OF PHOSPHATE INTO MYCORRHIZAL AND NON‐MYCORRHIZAL PLANTS OF TRIFOLIUM SUBTERRANEUM AT DIFFERENT LEVELS OF SOIL PHOSPHATE
Authors: SMITH S. E.
Published: May 2006

Summary

During early growth of mycorrhizal and non‐mycorrhizal plants of Trifolium subterraneum fertilized with soluble (Na2HPO4) phosphate, inflow of phosphate (moles P absorbed per unit length root per unit time) into mycorrhizal roots from soil exceeded that into non‐mycorrhizal roots over a range of levels of phosphate. High rates of uptake (up to 45 × 10−15 mol phosphate cm−1 s−1) were associated with reductions in root: shoot dry wt ratios.

The length of mycorrhizal root per plant was little affected by fertilization with phosphate. However, rapid growth of roots at high levels of Na2HPO4 resulted in reductions in percentage root length infected by mycorrhizas. Results are discussed with respect to rates of uptake by whole plants and to differences in distribution of phosphate between roots and shoots in mycorrhizal and non‐mycorrhizal plants.
LOCALIZATION AND CHANGES IN CATECHIN AND TANNINS DURING DEVELOPMENT AND RIPENING OF COTTONSEED
Authors: HALLOIN JOHN M.
Published: May 2006

Summary

Tannnins and their precursor, (+)‐catechin, are localized primarily in the pigmented layers of the cottonseed coat and in seed linters. Lesser quantities are localized in the nucellus and in the palisade parenchyma of embryo cotyledons. Oxidation of seed coat tannins during seed ripening is accompanied by seed coloration and reduction of seed coat permeability to water. Localization and changes in cottonseed flavanols and tannins during seed development and ripening are consistent with their proposed functions as (1) chemical barriers against infection by fungi, (2) physical barriers against absorption of water, and (3) chromogens in baked products containing cottonseed products.
THE OCCURRENCE OF BACTERIUM‐LIKE ORGANELLES IN VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: MACDONALD R. M. , CHANDLER MURIEL R. , MOSSE BARBARA
Published: May 2006

Summary

Bacterium‐like organelles (BLOs), morphologically indistinguishable from those which occur in Glomus caledonius and Acaulospora laevis have been found in the spores of Glonius mosseae, Gigaspora margarita, Gigaspora heterogama and an unidentified white reticulate vesicular‐arbuscular mycorrhizal spore. Morphologically different BLOs were also found in Gigaspora margarita and the white reticulate spores. The significance of the organelles is discussed.
ROLE OF TEMPERATURE IN THE SEASONAL DORMANCY OF SEEDS OF VERONICA HEDERIFOLIA L.
Authors: ROBERTS H. A. , NEILSON JUNE E.
Published: May 2006

Summary

High temperatures (10 to 30 °C) promoted after‐ripening of fresh, imbibed seeds of Veronica hederifolia L. and overcame dormancy of seeds buried in the soil. Low temperature (4 °C) inhibited after‐ripening and also tended to induce dormancy in physiologically non‐dormant seeds. This response, however, was not sufficient to account for the increase in dormancy which occurs during late autumn and winter in seeds buried in the field.
THE EFFECT OF A FOREIGN POLLEN ON OVULE DEVELOPMENT IN DIERVILLA LONICERA (CAPRIFOLIACEAE)
Authors: THOMSON JAMES D. , ANDREWS BRENDA J. , PLOWRIGHT R. C.
Published: May 2006

Summary

When pollen from Hieracium floribundum Wimmer and Grab. (Compositae) was applied to stigmas of Diervilla lonicera Mill. (Caprifoliaceae) in mixtures with Diervilla pollen, Diervilla fecundity was strongly depressed. While this phenomenon is unlikely to be of importance to Diervilla under field conditions, this property of Hieracium pollen may have stronger effects on other ecological associates. The only other reported instance of inhibitory pollen is from Parthenium hysterophorus L., which, like Hieracium, has allelopathic properties.
PERTURBATION OF PHOSPHOLIPID MEMBRANES BY GIBBERELLINS
Authors: PAULS K. P. , CHAMBERS J. A. , DUMBROFF E. B. , THOMPSON J. E.
Published: May 2006

Differential scanning calorimetry and electron spin resonance have been used to characterize the association of gibberellic acid4 and gibberellic acid, (a GA4/GA7 mixture) with phospholipid membranes. The GA4/GA7 mixture lowered the temperature and reduced the co‐operativity of the main phase transition of liposomes prepared from dipalmitoylphosphatidylcholine (DPPC), distearylphosphatidylcholine (DSPC) and dipalmitoylphosphatidylglycerol (DPPG), and eliminated the pretransition. The reduction in co‐operativity of the main transition was not accompanied by a reduction in transition enthalpy, indicating that the gibberellins simply perturb the bilayer rather than complex with the phospholipid molecules. Perturbation was markedly greater at pH values approaching the pKa of the gibberellin carboxyl group than at pH 7. Moreover, the negatively charged DPPG was less susceptible to perturbation than the zwitterionic phosphatidylcholines. Perturbation by GA8, a physiologically inert gibberellin, was virtually imperceptible. Electron spin resonance of GA4/GA7‐treated liposomes of phosphatidylcholine (PC) and phosphatidylglycerol (PG) confirmed the results obtained by differential scanning calorimetry and also indicated that the gibberellins associate with the surface of the phospholipid membranes rather than penetrate into the interior of the bilayer. The data are consistent with the proposal that gibberellins can influence membrane behaviour by modulating the physical properties of the lipid bilayer.
PLANT‐INDUCED CHANGES IN THE RHIZOSPHERE OF RAPE (BRASSICA NAPUS VAR. EMERALD) SEEDLINGS
Authors: GRINSTED M. J. , HEDLEY M. J. , WHITE R. E. , NYE P. H.
Published: May 2006

Rape (Brassica napus, var. Emerald) plants were grown in thin layers of a phosphate‐deficient soil supplied with a P‐free nutrient solution containing N solely as NO3− (3.5 × 10−3 M). Inter‐root competition (excluding root hairs) for soil P began on the 14th day of growth, after which all soil in the thin layer was considered to be rhizosphere soil. During subsequent plant growth the pH in the rhizosphere decreased as much as 2.4 units (from pH 6.5 to 4.1) before rising slightly towards the end of the experiment (35th day). The pH decrease was associated with an increase in solution P concentration in the depleted rhizosphere soils, compared to the P concentration attained when similar amounts of P were desorbed from unplanted control soils by shaking them in 10−2 M Ca(NO3)2 at the original soil pH of 6.1. P desorption in 10−2 M Ca(NO3)2 at pH values between 6.2 and 4.5 indicated that a decrease in the soil pH from 6.5 to 4.1 could result in at least a 10‐fold increase in the P released into solution, which would be available for plant uptake. These results may explain reports in the literature that rape is efficient in absorbing P from P‐deficient soils.
DEVELOPMENT OF EXTERNAL HYPHAE BY DIFFERENT ISOLATES OF MYCORRHIZAL GLOMUS SPP. IN RELATION TO ROOT COLONIZATION AND GROWTH OF TROYER CITRANGE
Authors: GRAHAM J. H. , LINDERMAN R. G. , MENGE J. A.
Published: May 2006

The hypothesis was tested that the amount of external hyphae of a vesicular‐arbuscular mycorrhizal (VAM) fungus extending from roots out into soil is not always proportional to the extent of colonization of the root cortex. Growth enhancement and amount of external hyphae were compared for eight isolates of five Glomus spp. that differed in their geographic origin and capacity to enhance growth of Troyer citrange, but were similar in their capacity to extensively colonize Troyer citrange roots. In general, isolates from California increased growth in a P‐deficient (9.8 mg kg−1) California soil more than did non‐native isolates from Florida soils. The difference between the capacity of California and Florida isolates to enhance growth was not a function of the degree to which they colonized the roots since all had colonized over 95% of the root length by the time of harvest. Differences in growth enhancement did appear, however, to be a function of the amount of external hyphae that had developed as estimated by the weight of soil they had bound into aggregates. This study suggests that isolates of VA mycorrhizal fungi may differ in their capacity to develop an external hyphal system independent of their capacity to colonize the root cortex, and that we cannot assume that high levels of colonization will necessarily mean the fungus has also developed the mycelium in the soil necessary to transport nutrients responsible for plant growth enhancement.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE
Authors: BRADLEY R. , BURT A. J. , READ D. J.
Published: May 2006

Plants with ericoid mycorrhizas successfully colonize acidic soils containing high levels of heavy metals. While mycorrhizal infection normally enhances uptake of mineral elements, such a function in metalliferous soils would be disadvantageous. The role of infection in heavy metal tolerance was therefore investigated in three ericaceous species. Plants of Calluna vulgaris, Vaccinium macrocarpon and Rhododendron ponticum were grown in the mycorrhizal and non‐mycorrhizal conditions in sand containing a dilute nutrient solution supplemented with Cu or Zn at 0, 10, 25, 50 and 75 and 0, 25, 50, 100, 150 mg−1 respectively. Fungal endophytes isolated from these host plants were also grown in pure culture over a wide range of concentrations of both metals. Mycorrhizal plants showed some growth in all metal treatments, whereas non‐mycorrhizal plants failed to grow in all but the lowest metal levels. The endophytes all grew vigorously up to 75 mg Cu 1−1 and 150 mg Zn 1−1. In all but one case, the mycorrhizal plants had a significantly lower concentration of metal in their shoots. Concentrations of metal in roots were higher in mycorrhizal plants. It is proposed that the hyphal complexes of the endophyte provide adsorptive surfaces within the cortical cells of the host roots, thus facilitating exclusion of metals from the shoot and avoidance of metal toxicity. The ecological significance of these observations is discussed.
EFFECT OF REDUCED SOIL MOISTURE AVAILABILITY ON LEAF MORPHOLOGY AND IN VITRO DRY MATTER DIGESTIBILITY OF FESTUCA ARUNDINACEA GENOTYPES WITH CONTRASTING LEAF TENSILE STRENGTH
Authors: SILCOCK R. G. , WILSON D.
Published: May 2006

Twelve genotypes of Festuca arundinacea Schreb. differing in leaf size and leaf tensile strength were grown in pots with either adequate or very restricted watering. When leaves expanded under moisture stress their length, width, specific leaf area (SLA) and tensile strength were reduced but leaf dry wt was unaffected. However, the reduction in SLA was inversely proportional to original leaf strength. Leaf tensile strength was directly related to leaf length, SLA and mesophyll cell wall thickness. In vitro dry matter digestibility was inversely related to leaf strength but was not consistently reduced by moisture stress. However, in genotypes where moisture stress markedly reduced leaf strength, digestibility was increased. The results are discussed in relation to possible improvements in plant growth under moisture stress in the field and the usefulness of leaf tensile strength as a selection criterion in plant breeding programmes.