bluuebunny/crossref_metadata_2025 huggingface dataset:
DISPERSAL, GERMINATION AND EARLY ESTABLISHMENT OF HALOPHYTES AND GLYCOPHYTES ON A GRAZED AND ABANDONED SALT‐MARSH GRADIENT
Authors: BAKKER J. P. , DIJKSTRA M. , RUSSCHEN P. T.
Published: May 2006

Summary

In a study of an abandoned salt‐marsh on Schiermonnikoog in the Netherlands, including an area where cattle grazing had been resumed, it was discovered that upper salt‐marsh and dune species did not spread to the lower salt‐marsh. Glass‐house experiments, carried out on germination and dry matter production under increasing salinities, suggested that the high salinity of the lower salt‐marsh was an important factor. On a grazed area of formerly abandoned salt‐marsh, lower salt‐marsh species spread to the upper salt‐marsh and dune. This could be partly due to the better germination of lower salt‐marsh species than upper salt‐marsh and dune species, since the salinity of the uppermost cm was higher temporarily and locally in the grazed than in the abandoned salt‐marsh. The canopy structure determining the amount of light reaching the soil also seemed to be an important factor enabling lower salt‐marsh species to spread. In experiments, in which seeds of different taxa were sown into vegetation, lower salt‐marsh species became established, particularly in the grazed area. The results of glass‐house experiments, on germination and dry matter production under a range of light intensities, were consistent with studies of early establishment in upper salt‐marsh and dune species in both the grazed and abandoned areas. Tidal seed dispersal resulted in the occurrence of lower salt‐marsh species in the seed bank and seedling populations in the low and open canopy of the grazed upper salt‐marsh and dune. Seed transport by cattle and geese could be important in the dispersal of some halophytes of the lower salt‐marsh.
DIFFERENTIAL TOLERANCE OF THREE CULTIVARS OF AGROSTIS CAPILLARIS L. TO CADMIUM, COPPER, LEAD, NICKEL AND ZINC
Authors: SYMEONIDIS L. , MCNEILLY T. , BRADSHAW A. D.
Published: May 2006

Summary

Root growth of seedlings of the Agrostis capillaris L. cultvars Parys (copper tolerant), Goginan (lead/zinc tolerant), and Highland (non tolerant) was measured after 14 d growth in solution cultures with increasing concentrations of Cd, Cu, Pb, Ni and Zn.

Increasing inhibition of root growth of all three cultivars occurred with increasing concentrations of all five metals, Highland being most affected. In Cu, Parys was least affected; in Pb and Zn Goginan was least affected. Parys and Goginan thus display specific resistence to these metals. They are also similar in having greater root lengths at higher metal concentrations of all five metals than Highland. They thus exhibit non‐specific low level tolerance to metals other than those present at toxic levels in the soils from which they were derived.
INTERPOPULATION VARIATION IN TOLERANCE TO CADMIUM, COPPER, LEAD, NICKEL AND ZINC IN NINE POPULATIONS OF AGROSTIS CAPILLARIS L.
Authors: SYMEONIDIS L. , MCNEILLY T. , BRADSHAW A. D.
Published: May 2006

Summary

Samples of 15000 seeds from each of nine populations of Agrostis capillaris L. were screened for ability to root in solution cultures containing cadmium, copper, lead, nickel, and zinc at levels which severely inhibited root growth in non‐metal‐tolerant seed population samples.

Differences were found in the extent to which tolerant individuals could be selected from the populations. Only the copper‐tolerant cv. Parys and lead‐/zinc‐tolerant cv. Goginan had relatively high frequencies of individuals tolerant to each metal. Screening one population did not reveal any tolerant individuals.

The ability to root in such solutions may reflect the potential populations have to evolve metal‐tolerant populations. Populations exhibit considerable variation in this respect and the potential to evolve tolerance is clearly a characteristic of populations, not the species.
PALAEOECOLOGY OF ALNUS (ALDER): EARLY POST‐GLACIAL RISE IN A VALLEY MIRE, NORTH‐WEST WALES
Authors: CHAMBERS F. M. , PRICE S.‐M.
Published: May 2006

Summary

Data are presented in summary form in both percentage and influx radiocarbon‐dated pollen diagrams from a site (MYG) in a valley mire near Moel y Gerddi, Ardudwy, 4 km north‐east of Harlech, north‐west Wales.

Evidence indicates that this valley mire was dominated by alder (Alnus) carr soon after the inception of peat growth, which dates from 8700 B.P. These data confirm the notion of an early empirical limit of Alnus in north‐west Wales (advanced in a previous paper) and, compared with other sites in Wales and the rest of Britain, indicate a very early rational limit here for Alnus (c. 8465 B.P.).

Ideas on the migration route and on the spread of Alnus into Britain in the Post‐glacial may need substantial revision in the light of this evidence for an earlier presence of Alnus in upland Ardudwy, north‐west Wales, than yet known from lowland south‐east England.

Conceivably, Mesolithic activity might have facilitated the local establishment of Alnus; the evidence for this in upland Ardudwy is evaluated.
AMINO ACID AND AMIDE METABOLISM IN THE HULLS AND SEEDS OF DEVELOPING FRUITS OF GARDEN PEA, PISUM SATIVUM L.
Authors: Murray D. R.
Published: May 2006

Summary

Pea plants (Pisum sativum L. cv. Melbourne Market), each with a single developing pod, were pulse‐fed with [14C]homoserine supplied through the cut stem at stages of pod development ranging from 12 to 21 d after full blossom. The pods were removed after 24 h and the hulls and seed components were frozen for later analysis. Except at the youngest stage, or unless the pod had been enclosed in foil to prevent the development of chloroplasts, the seeds received a higher proportion of total label in the fruit (about 60%). The distribution of label in soluble metabolites of the hull, seedcoats, embryo sac liquid and embryo was determined by paper chromatography and radioautography. The results indicate turnover of homoserine within the hull, and confirm that the seedcoats are responsible for a shift in metabolism leading to secretion of threonine into the embryo sac instead of homoserine.
NITROGEN OXIDES PRODUCED DURING CO2 ENRICHMENT
Authors: MORTENSEN LEIV M.
Published: May 2006

Summary

Eight cultivars of Lycopersicon esculentum (tomato) and six cultivars of Lactuca sativa (lettuce) were subjected to CO2‐enriched air (1000 μ11−1) containing 0.7 or 0.9 μll−1 nitrogen oxides (NOx).

CO2 enrichment without NO2 significantly increased the dry weight of all tomato (35–81%) and lettuce cultivars (25–101%). In six of the eight tomato cultivars the dry weight was reduced by the addition of NOx. The mean relative growth rate (RGR) decreased by 4–19% depending on the cultivar. This meant that the benefit of CO2 enrichment was almost completely eliminated in most of the cultivars. Marginal leaf necrosis appeared in some of the cultivars, while in others no visible injury developed. None of the lettuce cultivars was significantly affected by the addition of NO x.
CARBON ECONOMY OF SOYBEAN–RHIZOBIUM–GLOMUSASSOCIATIONS
Authors: HARRIS D. , PACOVSKY R. S. , PAUL E. A.
Published: May 2006

Summary

Carbon uptake and allocation in plants that were largely dependent on microbial symbionts for N and P was compared to that in plants given inorganic fertilizer. Soybeans (Glycine maxL. Merr.) were grown in sterilized soil and were either left uninoculated, or were inoculated withRhizobium japonicum(Kirschner), or bothR. japonicumandGlomus fasciculatum(ThaxtersensuGerd.). Uninoculated plants were given N and/or P fertilizer at rates required to produce plants similar in size to inoculated plants. Carbon flows to plant parts, root nodules and vesicular‐arbuscular mycorrhizas were measured in six‐ and nine‐week‐old plants by determining the distributions of14C after pulse labelling with14CO2.

Root nodules in non‐mycorrhizal plants utilized 9% of total photosynthate; this was increased to 12% in nodulated, mycorrhizal plants. Mycorrhizas used 17% of the total photosynthate of six‐week‐old plants; this fell to 8% after nine weeks. Rates of14CO2fixation in leaves of nodulated or nodulated plus mycorrhizal plants were up to 52% higher than in plants without microbial symbionts. Part of the increase was due to higher specific leaf area in plants colonized by symbionts, but other factors such as source‐sink relationships, starch mobilization and leaf P concentrations were also involved in the host‐plant adaptations to the C demand of the microbial endophytes.
LACK OF SPREAD OF ENDOMYCORRHIZAS OF CENTAURIUM (GENTIANACEAE)
Authors: McGEE P. A.
Published: May 2006

Summary

Seedlings of Centaurium died in the absence of inoculum of vesicular‐arbuscular (VA) mycorrhizal fungi in a soil low in nutrients. The morphology of endomycorhizas of Centaurium and Eustoma grandiflora (Raf.) Shim, differed from that of commonly studied VA mycorrhizal hosts in that coils, arbuscules and vesicles were formed but rapidly collapsed.

Endomycorrhizal infection spread down the roots of Centaurium erythraeq Rafn. when it was grown with a companion plant, Trifolium dubium Sibth. but when grown alone infection was restricted to the vicinity of the inoculum. Several different VA mycorrhizal plants did not become mycorrhizal when inoculated with mycorrhizal roots of Centaurium.
THE LOCALIZATION AND FREQUENCY OF HAUSTORIA IN COLONIES OF BROWN RUST ON BARLEY LEAVES
Authors: KNEALE J. , FARRAR J. F.
Published: May 2006

Summary

Serial sections were taken through colonies of brown rust (Puccinia hordei Otth.) on barley leaf blades. Fungal haustoria occurred in cells of the mesophyll, parenchymatous bundle sheath and epidermis (excluding guard cells) but not within the mestome sheath or vascular bundles. Within a colony, each cell contained 1.2 to 2 haustoria; each colony had about 104 haustoria on a total hyphal length of about 1 m. Surface areas of haustoria and intracellular hyphae were calculated and used to show that all of the hexose needed to sustain fungal growth and respiration could be taken up through either cell type.
GROWTH ANALYSIS OF ACHILLEA MILLEFOLIUM L. (YARROW) IN THE PRESENCE AND ABSENCE OF A COMPETITOR –HORDEUM VULGAREL. (BARLEY)
Authors: BOURDǑT G. W. , FIELD R. J. , WHITE J. G. H.
Published: May 2006

Summary

The performance of Achillea millefolium L., from early summer until early spring, in the presence and absence of Hordeum vulgare L. was assessed by growth analysis. Growth analytical quantities were derived for a 307 d experimental period from splined cubic polynomial exponential functions fitted to dry matter and leaf area data.

Ontogenetic drifts in the net assimilation rate and leaf area ratio of A. millefolium were highly modified by interference from H. vulgare resulting in a diminished total plant relative growth rate and maintenance of the vegetative state. The relative growth rate of A. millefolium increased during the autumn and early winter in response to rises in net assimilation rate and leaf area ratio induced by the harvesting of the H. vulgare. During the post‐harvest period, the relative growth rate of the rhizome increased and exceeded those of leaf and total weight resulting in a substantial increase in rhizome dry matter during autumn and winter and a pronounced rise in the rhizome weight ratio.
EFFECTS OF IRRADIANCE AND SPECTRAL QUALITY ON THE GERMINATION OF VERBASCUM THAPSUS L. AND OENOTHERA BIENNIS L. SEEDS
Authors: GROSS KATHERINE L.
Published: May 2006

Summary

Germination of Verbascum thapsus L. and Oenothera biennis L. seeds was investigated over a range of irradiance levels and under different canopy types in the laboratory. Both species colonize early successional and disturbed habitats, and their seedlings establish only in bare soil. In the laboratory, Verbascum seeds germinated to equivalent levels (70 to 80%) over a broad range of irradiance levels and required only brief exposure to light (5 s) to germinate subsequently in darkness. In contrast, germination of Oenothera seeds increased with irradiance to a maximum of approximately 80% at 13 W m−2. Oenothera seeds also required a longer duration of exposure (1 h) to induce germination, and percentage germination increased directly with exposure time to a maximum of 80 % after 22 h of exposure. Germination of both species was significantly reduced in light filtered through leaves, but the responses differed under different canopy types. Exposure to red and blue light had no effect on germination of Verbascum seeds but had an inhibitory effect on that of Oenothera seeds. The results are discussed in relation to the observed patterns of seedling emergence and survival of these species in the field; a possible evolutionary basis is suggested for their differences in response to light.
SUGGESTED INVOLVEMENT OF CALCIUM AND CALMODULIN IN THE RESPONSES OF STOMATA TO ABSCISIC ACID
Authors: DE SILVA D. L. R. , COX R. C. , HETHERINGTON A. M. , MANSFIELD T. A.
Published: May 2006

Summary

A requirement for calcium during the inhibition of stomatal opening by abscisic acid (ABA) was reported in a previous study, and evidence is now presented which gives further indications of the part played by calcium. Calcium‐channel blockers (lanthanum, verapamil and nifedipine) reduced the ability of stomata to respond to ABA. A calcium ionophore (A 23187) reduced stomatal opening, presumably because it mimicked the effect of ABA in increasing permeability of the plasma membrane to calcium. In the presence of three calmodulin antagonists, the inhibitory effect of ABA was much reduced. The synthetic auxin naphth‐l‐ylacetic acid (NAA) prevented stomatal opening, but this action did not appear to be dependent on calcium ions.

It is suggested that the action of ABA on guard cells requires a free passage of calcium ions into the cytosol. They may act as second messengers, interacting with calmodulin to produce the overt cellular responses to ABA.

Although the data presented apply only to stomata, these experiments may have provided insight into the basic mechanism by which ABA acts on cellular processes. It is suggested that some reported effects of Ca2+on the action of other plant growth substances could have resulted from complex interactions involving endogenous ABA.
HOST DETERMINANTS OF MYCORRHIZAL DEPENDENCY OF CITRUS ROOTSTOCK SEEDLINGS
Authors: GRAHAM J. H. , SYVERTSEN J. P.
Published: May 2006

Summary

Seedlings of five citrus rootstocks were grown in a low phosphorus (P) sandy soil and were either (1) inoculated with Glomus intraradices Schenck & Smith, (2) non‐inoculated and fertilized with P, or (3) non‐inoculated without added P. The order of mycorrhizal dependency (MD) of the five rootstocks was sour orange = Cleopatra mandarin > Swingle citrumelo > Carrizo citrange > trifoliate orange. The less dependent rootstocks, trifoliate orange and its hybrid Carrizo citrange, had greater leaf P, finer roots (greater length per unit of dry root) and slower growth rates than sour orange and Cleopatra mandarin. Rootstocks with lower MD also generally had greater hydraulic conductivity of roots, and greater transpiration and CO2 assimilation rates. Under well‐watered conditions, VAM plants of all five rootstocks did not differ in morphology, anatomy or physiology from non‐mycorrhizal plants fertilized with P of similar size, growth rate and P status.
THE CYANOBACTERIUM‐ZAMIA SYMBIOSIS: AN ULTRASTRUCTURAL STUDY
Authors: LINDBLAD P. , BERGMAN B. , HOFSTEN A. V. , HÄLLBOM L. , NYLUND J. E.
Published: May 2006

Summary

Filamentous cyanobacteria are found intercellularly in a zone between inner and outer cortex of coralloid roots, growing below the soil surface, from the cycad Zamia skinneri Warsc. The zone is transversed by elongated Zamia cells interconnecting the two cortex layers. These host cells show characteristics of transfer cells, i.e. considerably expanded cell walls, numerous mitochondria and amyloplasts. An involvement of these cells in the transfer of solutes between cyanobacterium and host is therefore suggested. The cyanobacterium belongs to the genus Nostoc and consists of vegetative cells, heterocysts and a few akinetes. Healthy vegetative cells contain thylakoids with phycobilisomes, carboxysomes, cyanophycin and glycogen granules. Thus, no distinct subcellular modifications due to a symbiotic mode of life in the absence of light were observed.
THE TIMING OF DIVISION IN CHLAMYDOMONAS
Authors: McATEER MARY , DONNAN LORRAINE , JOHN PETER C. L.
Published: May 2006

Summary

The duration of the cell cycle of Chlamydomonas is determined by two timed periods which each follow an initiating stimulus. A commitment timer, initiated by the beginning of growth in autonomous daughter cells, is dependent upon concurrent growth and controls the time of first commitment to divide. Division processes, which are then initiated, occupy a second timer period of 6 h duration at 25°C.

Absence of division control by an endogenous oscillator was indicated by an unfluctuating ability to resume cycles of consistent duration when daughter cells were held in darkness or when growing cells in light were subjected to darkness. A consistent time from the beginning of daughter growth to commitment was also observed when daughter formation was delayed by an earlier temperature reduction. Ethanol, which commonly affects circadian oscillators, did not disturb synchrony.

The division cycle is controlled by growth and not by direct response to light, since commitments ceased when growth was prevented by lack of CO2 in the light. Growth in daughter cells initiated the timer leading to commitment since commitment was reached at similar times after resupply of CO2 or reillumination. Division synchrony in diurnal cycles of periodic illumination is not caused by entrainment of an oscillator but by the growth requirement of the hourglass timer leading to commitment. A model of division control is presented.
THE ABSENCE OF AN EFFECT OF THE Na/Ca RATIO ON SODIUM CHLORIDE UPTAKE BY RICE (ORYZA SATIVA L.).
Authors: YEO A. R. , FLOWERS T. J.
Published: May 2006

Summary

The effect of the Na/Ca ratio in the growth medium on the response of the salt‐sensitive crop species Oryza sativa L. to NaCl salinity was investigated. No effects on growth or salt concentration in the shoot were found over a range of Na/Ca ratios (5 to 25) considered likely to be commonly encountered in saline situations in the field, and even at extreme Na/Ca ratios (100 to 500) there were only marginal increases in NaCl entry to the shoot. Increasing the Ca concentration in the growth medium over a wide range did not, therefore, ameliorate the effects of salinity on rice seedlings. Polyethylene giycol at low, osmotically negligible, concentrations reduced the movement of CI to the shoot by 60 to 70% even in the presence of adequate (3.5 mol m−3) Ca. It is concluded that membranes of rice roots respond weakly to Ca and that they are capable of better permeability control than is evoked by Ca ions. The relevance of this to the salt sensitivity of rice is discussed.
MEMBRANE INTEGRITY IN LEAVES OF BARLEY INFECTED BY BROWN RUST: AN EXAMINATION USING TRACER EFFLUX AND IN VIVO CHLOROPHYLL FLUORESCENCE
Authors: AHMAD I. , FARRAR J. F. , WHITBREAD R.
Published: May 2006

Summary

The kinetics of ion efflux from leaf discs were used to show that there is no general increase in the permeability of plasmalemma or tonoplast resulting from infection of barley leaves by brown rust (Puccinia hordei Otth.). An assay of in vivo chlorophyll fluorescence showed that there were clear differences between chloroplasts in healthy and diseased tissue, but overall the thylakoid lamellae function well in rusted barley leaves. We conclude that in this biotrophic system there is no gross impairment of host membrane integrity, and show that delivery of host nutrients to the apoplast is at rates greatly in excess of those needed to accommodate fungal nutrient uptake. This does not preclude localized effects of the pathogen on host membranes.
SOME PHYSIOLOGICAL EFFECTS OF TWO SEED‐TRANSMITTED VIRUSES ON FLOWERING, SEED PRODUCTION AND SEED VIGOUR IN NICOTIANA AND CHENOPODIUM PLANTS
Authors: WALKEY D. G. A. , BROCKLEHURST P. A. , PARKER J. E.
Published: May 2006

Summary

The effects of infection by spinach latent (SLV) and arabis mosaic virus (AMV) upon flowering, seed production and seed vigour, were studied in Nicotiana and Chenopodium species. Infection frequently caused mother‐plants to produce flowers earlier than healthy plants, and AMV induced C. amaranticolor Coste & Reyn., which normally flowers only under ‘short‐day’ conditions, to flower in ‘long‐days’.

Infection with SLV or AMV generally caused a significant reduction in normal seed numbers and a corresponding increase in aborted seed. Mean seed weights were often lower from infected than from healthy plants, but in some infections lower seed production was correlated with a compensatory increase in the weight of individual seeds. The viability of seeds from infected plants was slightly reduced in some instances but, even when seed viability was not affected, tests of accelerated ageing indicated that seed vigour was impaired.
REPRODUCTIVE ECOLOGY OF BANKSIA GRANDIS (PROTEACEAE)
Authors: ABBOTT IAN
Published: May 2006

Summary

The reproductive characteristics of Banksia grandis Willd. were studied in the northern jarrah forest of Western Australia. Most flowering occurs in November, with maturation of fertile (seed‐bearing) infructescences taking about 12 to 14 months. Number of inflorescences produced by a tree is not closely related to its diameter at breast height (DBH). Trees become reproductive at mean DBH of 4–5 cm and fruit successfully at mean DBH of 6.7 cm. Trees of DBH < 10 cm produce fewer fertile infructescences than trees of larger DBH. Moderate‐intensity fire markedly reduces production of inflorescences for at least three flowering seasons.

Less than 2% of flowers on an average inflorescence set fruit, and only 1 to 5% of inflorescences develop into fertile infructescences. The cause of the latter was investigated experimentally. Although insect larvae (Lepidoptera, Coleoptera) damage infructescences, inflorescences sprayed with insecticide do not develop differently from those not so treated. Insect damage is least in inflorescences produced in late November and early December but there is no corresponding increase in development of fertile infructescences. Ants do not protect inflorescences from insect damage and insects are of little significance as predators of seed within the follicle. Whether fruit development is limited by pollination could not be adequately assessed. Low fruit set in B. grandis may result from shortage of resources, with many flowers and inflorescences allowing B. grandis the option of setting large numbers of fruits should favourable conditions prevail.
SPEED OF DEVELOPMENT OF RADIATE AND NON‐RADIATE PLANTS OF SENECIO VULGARISL. FROM HABITATS SUBJECT TO DIFFERENT DEGREES OF WEEDING PRESSURE
Authors: KADEREIT J. W. , BRIGGS D.
Published: May 2006

Summary

In a cultivation experiment, plants of both radiate and non‐radiate Senecio vulgaris L. (S. vulgaris ssp. vulgaris var. hibernicus Syme and var. vulgaris) from intensively weeded habitats develop more quickly from sowing to first fruiting than plants from less intensively‐weeded habitats. Within the same habitat, non‐radiate plants are quicker from sowing to first fruiting than radiate plants. This shortening of the life‐cycle is achieved by a faster development from sowing to the formation of the first capitulum buds, resulting in shorter plants with fewer leaves on the main axis. In contrast, the development from anthesis to first fruiting takes longer in quick‐developing plants, and the number of achenes on the first fruiting capitulum as well as the potential reproductive output is smaller. This is explicable in terms of reduced availability of resources resulting from the smaller number of leaves in the quick‐developing plants.

The possible origin of the two populations of radiate S. vulgaris is discussed.
SALT TOLERANCE IN SUAEDA MARITIMA (L.) DUM. FINE STRUCTURE AND ION CONCENTRATIONS IN THE APICAL REGION OF ROOTS
Authors: HAJIBAGHERI M. A. , YEO A. R. , FLOWERS T. J.
Published: May 2006

Summary

Anatomy and ion concentrations have been studied in the roots of the halophyte Suaeda maritima (L.)Dum. growing in saline and non‐saline conditions. The roots were fine with only three layers of cortical cells. Salinization of the growth medium resulted in cellular vacuolation commencing closer to the apex than in non‐salinized plants and led to an increase in root dimensions through increased cell (vacuole) size but not increased cell numbers: the Casparian strip developed much closer to the apex and was twice as long in salt‐grown plants. Ion concentrations were determined in sections (1 mm) of root. The apical 1 mm was predominantly non‐vacuolate, with a K+ concentration greater than 100 mol m−3 and a Na: K ratio less than 2, even when growing in 340 mol m−3 NaCl. The adaptive value of the anatomical observations are discussed and the ion concentration data assessed in relation to current concepts of the haiophyte cell.
THE INFLUENCE OF SO2 AND NO2 ON THE GROWTH, DEVELOPMENT AND GAS EXCHANGE OF BETULA PENDULA ROTH
Authors: FREER‐SMITH P. H.
Published: May 2006

Summary

SO2 and NOx are main primary pollutants which often occur together in Europe. In three experiments, Betula pendula Roth, was exposed to SO2 and NO2, at concentrations of between 30 and 90 nl l−1, in controlled conditions during the first year of growth. In addition, single plant chambers were used to examine the net fluxes of SO2 to the shoots.

The effects of continuous exposure to this range of concentrations of SO2+ NO2 varied from a 20% increase to a 32% decrease in total dry weight. This contrast of responses came about because the doses of pollutant and light conditions were altered. Foliar injury and subsequent decreases of growth occurred when exposure concentrations exceeded 70 nl l−1 of both gases, although the onset of dormancy influenced the responses which were observed. Premature loss of leaves was the main symptom of chronic injury‐ in SO2 and the threshold concentration for this effect was about 50 nl l−1. When grown in conditions of poor light B. pendula made changes of partitioning so that leaf growth was favoured, and also showed greater phytotoxic effects as a result of exposure to SO2 and SO2+ NO2. In conditions of large PFD and longdays the toxic effects of SO2 were lost so that significant interactions in the effects of SO2 and photoen vironment were detected. SO2 also caused decreases in root–shoot ratio and increases in LAR but NO2 did not influence partitioning in this way. Stomatal conductance was influenced by fumigation with 40 nl l−1 SO2 and there were slight decreases of net photosynthesis in the presence of 55 nl l−1 SO2. The rates of deposition of SO2 were largely controlled by stomatal conductance and no emission of H2S was detected. Cuticular deposition of SO2 varied, making up between 11 and 25% of the total flux and becoming of greater importance as the stomata closed.
THE CHARACTERIZATION AND ESTIMATION OF POLYPHOSPHATES IN ENDOMYCORRHIZAS OF THE ERICACEAE
Authors: STRAKER C. J. , MITCHELL D. T.
Published: May 2006

Summary

Metachromatic staining demonstrated the presence of polyphosphate granules in endophytes isolated from root systems of Vaccinium macrocarpon Ait., Rhododendron ponticum L., Calluna vulgaris (L.) Hull, Erica hispidula L. and E. mauritanica L. The granules accumulated in response to high concentrations of phosphorus in the external medium and during the lag phase of growth. Nucleic acid‐polyphosphate co‐precipitates prepared from endophytes were separated by means of polyacrylamide gel electrophoresis and the molecular weights of polyphosphate of three endophytes were between 3000 and 4700. Inoculated root systems of Vaccinium macrocarpon had significantly more acid‐labile polyphosphate than non‐mycorrhizal roots. The results are compared with studies of polyphosphate in ecto‐ and vesicular‐arbuscular mycorrhizas and are discussed in relation to ultrastructural analyses and the role of polyphosphate in the phosphorus nutrition of ericaceous plants in heathlands.
INTERACTIONS BETWEEN MATING AND SOMATIC INCOMPATIBILITY IN THE BASIDIOMYCETE STEREUM HIRSUTUM
Authors: COATES D. , RAYNER A. D. M. , BODDY LYNNE
Published: May 2006

Summary

Experimental systems for studying the migration of nuclei into mating‐type compatible homokaryons across a pre‐existing or developing somatic incompatibility barrier are described. Using these systems with Stereum hirsutum Willd. ex Fr. it was found that different donor nuclei migrated from implants at more or less equal rates through acceptor homokaryons. However, access of nuclei across a somatic incompatibility barrier was subject to delay, selectively favouring those non‐sib‐related to the acceptor, as opposed to sib‐related nuclei. The selective delay was greater across a pre‐formect than a developing barrier, and in the latter case there was evidence of suppression of the somatic incompatibility reaction associated with passage of non‐sib nuclei.
PHOTOSYNTHESIS AND CARBOHYDRATE METABOLISM IN DETACHED LEAVES OF LOLIUM TEMULENTUM L.
Authors: HOUSLEY T. L. , POLLOCK C. J.
Published: May 2006

Summary

Mature leaves of Lolium temulentum L. remained photosynthetically competent for some days following excision. During this time, amounts of soluble carbohydrate rose markedly and there was substantial accumulation of sucrosyl‐fructans. Cell‐free extracts of excised leaves showed enhanced ability to synthesize oligofructosides from sucrose in vitro. Excised leaves were capable of the synthesis of fructans from exogenous sucrose applied in the dark. Exposure of leaves to 14CO2 immediately following excision led to movement of radioactivity from sucrose into higher oligosaccharides and the distribution of 14C suggested the presence of multiple pools of sucrose within the leaf. These results are discussed in relation to the control of reserve accumulation during periods of fluctuation in sink demand.
EVOLUTION OF XYLEM RESULTED IN A REQUIREMENT FOR BORON IN THE APICAL MERISTEMS OF VASCULAR PLANTS
Authors: LOVATT CAROL J.
Published: May 2006

Summary

Critical review of the literature regarding the influence of boron on the metabolism of vascular plants shows that the cessation of cell division in the apical meristem is the earliest and most prevalent result of boron deficiency in vascular plants. Furthermore, the literature, in general, can be interpreted to support the view that perturbations in auxin metabolism, increased signification, phenol accumulation and reduced sucrose transport are probably secondary effects of boron deprivation resulting from the decrease or complete cessation of plant growth. It is proposed that the acquisition of a role for boron essential to the normal functioning of the apical meristem was a consequence of the evolution of xylem and the subsequent passive transport of boron in the transpiration stream. This resulted in the accumulation of boron at the transpiration terminus, i.e. the shoot apex of a primitive vascular plant. Thus, it was in the shoot apex that boron, for the first time in the evolution of life, reached a concentration sufficient to influence the metabolism of an organism. In support of this hypothesis, evidence is presented that demonstrates that boron probably was not available in the environment at a concentration great enough to result in its being a primordial essential nutrient. The accumulation of boron in the shoot apex resulted in the acquisition of an essential role for boron in vascular plants, thereby imparting the selective advantage of preventing boron toxicity. In addition, the accumulation of boron in the shoot apex to a concentration sufficient to influence the metabolism of a eucaryotic cell presents the possibility that boron may be required by vascular plants in a metabolic pathway that is not unique to them, but one which they may have in common with non‐vascular plants and, potentially, all living organisms. A possible role for boron in maintaining an adequate supply of one or more species of pyrimidine nucleotide or in facilitating their utilization is proposed.
COPPER TOLERANCE IN TWO LEGUME SPECIES FROM A COPPER MINE HABITAT
Authors: WU LIN , KRUCKEBERG A. L.
Published: May 2006

Summary

Lupinus bicolorLindl. andLotus purshianus(Benth.) Clem. & Clem, plants growing on copper mine waste in northern California exhibited considerably greater copper tolerance at 0.2 mg copper 1−1in nutrient solution than plants from an adjacent meadow. Effective nitrogen fixation in the copper‐enriched soils is suggested from acetylene reduction assays.
WHY DO PLANTS HAVE CYTOCHROME P‐450? DETOXIFICATION VERSUS DEFENCE
Authors: HENDRY GEORGE
Published: May 2006

Evidence is presented which suggests that cytochrome P‐450, in plants, probably functions as in all other eukaryotic organisms, principally as a detoxification mechanism. In plants this function is largely suppressed during tissue maturation coinciding with cell vacuolation. The consequential accumulation and isolation of potential toxins within vacuoles provides higher plants with an anti‐herbivore defence of evolutionary significance.
MANNITOL DOES NOT INHIBIT GLYCOLYTIC ENZYMES IN ROOTS OF PINUS SYLVESTRIS AND FAGUS ORIENTALIS
Authors: JIRJIS RAIDA , RAMSTEDT MAURITZ , SÖDERHÄLL KENNETH
Published: May 2006

Glucose‐6‐phosphate dehydrogenase, hexokinase and phosphoglucose‐isomerase extracted from roots of Pinus sylvestris L. or Fagus orientalis Lipsky were not inhibited by mannitol at concentrations up to 0.5 M in contrast to previous reports for these enzymes from Fagus sylvatica L. The Km‐values for the carbohydrate substrates were the same in the presence or absence of mannitol (50 mM).
THE EFFECT OF WINTER FIELD CONDITIONS ON THE DISTRIBUTION OF TWO SPECIES OF UMBILICARIA
Authors: SCOTT MARTHA G. , LARSON DOUGLAS W.
Published: May 2006

This paper describes the effects of transplantation on the ultrastructure and storage body distribution patterns in two saxicolous lichens which show a mutually exclusive distribution pattern. Umbilicaria vellea (L.) Ach., which grows in a snow‐free microhabitat, was transplanted into an adjacent habitat which received a deep winter snow cover and which supported populations of Umbilicaria deusta (L.) Baum. The reverse was done for U. deusta m the U. vellea habitat.

Effects of transplantation on storage body distribution were evident for U. vellea, but not for U. deusta. At the ultrastructural level, thalli of U. vellea showed clear signs of disruption including senescence of the algal cells and an increase in the amount of stored starch which was negatively correlated with a decline in photosynthesis in the same replicates. Lipid deposits in U, vellea were initially few in number and did not change as a result of transplantation. Changes were not observed for either species in the number of pyrenoglobuli in the pyrenoid body. Algal cells of U. deusta contained significantly larger amounts of starch and lipid than those of U. vellea and no overwintering treatment disrupted the fine structure of the plant. However, numbers of starch grains declined seasonally while thalli were under snow. Storage body distribution was found to be a stable feature of the algal cells and not dependent on short‐term fluctuations in net photosynthesis. It is possible that U. deusta accumulates large amounts of photosynthetic products in the autumn and uses these to maintain low metabolic levels during the winter. It may be that U. vellea is excluded from snow‐covered habitats because its thalli lack the ability to store photosynthetic products and have a pattern of gas exchange unsuited to overwintering under deep snow.
PHYTOALEXINS, WATER‐STRESS AND STOMATA
Authors: PLUMBE ALISON M. , WILLMER C. M.
Published: May 2006

The effects of several phenolic compounds, some of which accumulate in tissues under the stress of microbial attack, and of some‘water‐stress’ compounds (those which accumulate in leaf tissue under water‐stress and may cause stomata to close) on stomatal behaviour in epidermal strips of Commelina communis L. were studied.

The phenolics, p‐coumaric acid, caffeic acid, chlorogenic acid, salicylic acid and particularly sinapic acid, were strong inhibitors of stomatal opening. The effects on open stomata were less marked but sinapic acid brought about considerable closure while ferulic acid stimulated wider opening.

All the ‘water‐stress’ compounds except proline and glutamine, which had no effect on stomatal behaviour, inhibited opening and caused some closure of initially open stomata; ABA, farnesol, undecanoic acid, linoleic acid and a‐linolenic acid were all particularly effective.
FACTORS DETERMINING ANTHOCYANIN YIELD IN CELL CULTURES OF CATHARANTHUSROSEUS (L.)G. DON.
Authors: HALL R. D. , YEOMAN M. M.
Published: May 2006

The intense colour of anthocyanins has made it possible to identify the individual cells accumulating these compounds within cultures of Catharanthus roseus. Furthermore, the amount of anthocyanin per cell could be measured directly by microdensitometry thus revealing the degree of heterogeneity within the cell populations at any interval during the growth cycle. In this way the contribution to overall product yield of individual cells in the culture was assessed. It has been found using this approach that although some inter‐experiment variation occurs, intracellular anthocyanin concentration varies very little and is therefore likely to be controlled by a feedback inhibition mechanism. In general, attempts to enhance the mean intracellular concentration of the pigment through the manipulation of culture conditions have failed. A possible mechanism of metabolic control of intracellular anthocyanin accumulation is discussed. The proportion of cells accumulating anthocyanins, however, varied considerably in cultures grown under different conditions but nevertheless always remained low, never exceeding 20% of the total cell population. The cause of this poor response is unclear but it is suggested that a close metabolic interaction may exist between the cells in the culture to bring about this effect. The possible relevance of these observations to other culture systems accumulating secondary metabolites is discussed.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: SCHUBERT A. , HAYMAN D. S.
Published: May 2006

Several vesicular‐arbuscular mycorrhizal endophytes were inoculated separately on to onion plants in soils of low P status amended with five rates of Ca(H2PO4)2. H2O. Mycorrhizal infection was usually decreased by increasing additions of P, but the rate of root colonization and the infection plateau varied with different endophytes. Plant growth responses to mycorrhiza were large at low and medium P with Glomus mosseae and Glomus epigaeum and at medium P with Glomus macrocarpum and Gigaspora margarita. Glomus caledonium and Glomus sp.‘E3’were generally effective at low, medium and high P. Glomus clarum was ineffective at low P. The correlation between infection and growth response was higher for some endophytes than others. It was concluded that analysis of the VA symbiosis with any single endophyte cannot always be used as a basis for generalization about VA mycorrhizal fungi, and that the selection of field inoculants should take special account of endophyte behaviour in soils given extra phosphate.
THE EFFECT OF HIGH NUTRIENT ADDITION UPON SEASONAL PATTERNS OF MYCORRHIZAL DEVELOPMENT, HOST GROWTH, AND ROOT PHOSPHORUS AND CARBOHYDRATE CONTENT IN FRAXINUS PENNSYLVANICA MARSH
Authors: Douds D. D. , Chaney W. R.
Published: May 2006

The effects of Glomus macrocarpum and a high rate of nutrient addition upon growth, root carbohydrate and P content, and mycorrhizal development in green ash (Fraxinus pennsylvanica) seedlings were studied over two growing seasons. Mycorrhizal and simitaly growing non‐mycorrhizal seedlings had similar seasonal patterns in growth and in root carbohydrate and P content. No clear difference in mycorrhizal development as as result of nutrient treatment occurred until the middle of the second growing season when the percent root infection of seedlings that received low nutrient increased and that of seedlings that received high nutrient decreased. A seasonal cycle with two phases in the interaction of the VA mycorrhiza and host growth, root shoot ratios, root infection, root content of soluble sugars, starch and P, arbuscule and vesicle numbers, and spore population is proposed.
THE DEVELOPMENT OF MYCORRHIZAL ROOT SYSTEMS IN TRIFOLIUM SUBTERRANEUM L.: GROWTH OF ROOTS AND THE UNIFORMITY OF SPATIAL DISTRIBUTION OF MYCORRHIZAL INFECTION UNITS IN YOUNG PLANTS
Authors: SMITH S. E. , TESTER M. , WALKER N. A.
Published: May 2006

The development of young mycorrhizal root systems (up to 28 d) has been studied by growing Trifolium subterraneum L. in soil/sand mixtures with mycorrhizal inoculum mixed throughout the pots. Rates of initiation and of apical extension of main and first‐ and second‐order lateral roots were calculated by fitting spline functions to data collected from daily harvests. The average instantaneous rates of apical extension were found to be about 0.77, 0.2 and 0.06 cm d−1 respectively. These values were used, together with the size and distance from the root apex of the most apical mycorrhizal infection unit, to calculate the frequency of mycorrhizal infection close to the root apex (At) at 16 d. Values of At were found to be similar to average values for the whole main or lateral root system (A). We used plots of the size of infection units and their distances from the root apex, together with values of average rate of extension of roots (v) and rate of growth of infection units (B), to calculate the distances between entry points and the root apices at the time the entry points were formed. The results indicate that infection can occur not only immediately behind the root apex, but also to considerable distances (up to 55 mm) behind the apex in 16‐d‐old plants.
RACE‐SPECIFIC RESISTANCE IN GROUNDSEL (SENECIO VULGARIS) TO THE POWDERY MILDEW ERYSIPHE FISCHERI
Authors: HARRY I. B. , CLARKE D. D.
Published: May 2006

Two‐hundred‐and‐fifty lines of groundsel (Senecio vulgaris L.) were tested for their reactions to five different isolates of the powdery mildew fungus Erysiphe fischeri Blumer. Fifty‐one of the lines were also tested for their reactions to three further isolates. All the lines were tested using detached leaves but a number of them were also tested using seedlings. The seedling tests gave esentially the same results as the detached leaf tests. Over 50 % of the host lines were highly resistant (gave low infection types) to one or more of the mildew isolates and this resistance was isolate‐ or race‐specific. Eight specific resistance factors were differentiated by the eight mildew isolates used in the tests. Some of the resistance factors appear to be present in species of Senecio other than S. vulgaris. All eight mildew isolates were complex races with virulence for all but one of the specific resistance factors, the isolates differing from each other in the possession of avirulence for a unique specific resistance factor. The interactions between the host lines and mildew isolates are indicative of a gene‐for‐gene interaction but the genetic analysis required to establish this was not attempted. The majority of lines which were susceptible to each isolate developed the highest or most susceptible infection type. It is considered that tolerance of the parasite may operate together with race‐specific resistance in an overall survival strategy which has evolved to enable groundsel to cope with mildew attack.
EFFECTS OF NO, NO2 AND CO2 ON NET PHOTOSYNTHESIS, DARK RESPIRATION AND TRANSPIRATION OF POT PLANTS
Authors: SAXE HENRIK
Published: May 2006

Eight cultivars of the pot plants (Ficus elastica ‘Rdobusta’, Ficus benjamina, Hedera helix ‘Anne Marie’, Hedera canariensis‘Montgomery’, Hibiscus rosa‐sinensis‘Red’, Hibiscus rosa‐sinensis‘Moesiana’, Dieffenbachia maculata‘Compacta’ and Nephrolepis exaltata‘Bostoniensis’) most commonly grown in Danish commercial greenhouses were subjected to 4 d exposures to 1 ml 1−1of CO2, 1 ml 1−1 CO2+ 1 μ 1−1 NO, 1 μ 1−1 NO alone and 1 μ 1−1 NO2 alone. Effects on net photosynthesis and dark respiration of aerial parts and effects on whole plant transpiration were observed before, during and after exposures. The measurements were mathematically transformed to double relative values, to indicate the effects of the different gaseous treatments.

Carbon dioxide enrichment enhanced net photosynthesis by 40–9 % and subsequent dark respiration by 235 %, while transpiration was reduced. NO reduced photosynthesis (approximately 20 %) and transpiration (the latter at high CO2 only), but did not affect respiration. NO2 rarely had significant effects. All effects of the gaseous treatments on photosynthesis and transpiration were reversible and had independent mechanisms, while effects on respiration were non‐reversible.

On the average, 1 μ 1−1 NO was four times more inhibitory to photosynthesis than 1 μ 1−1NO2.

Short‐term effects (4 d) on photosynthesis of exposure to CO2+ NO correlated significantly (P < 0.03) with the long‐term effects (four to five months) on dry weight found using the same cultivars in similar treatments.
STOMATAL‐DEPENDENT AND STOMATAL‐INDEPENDENT UPTAKE OF NOx
Authors: SAXE HENRIK
Published: May 2006

NO2 uptake of eight pot plants (Ficus elastica ‘Robusta’, Ficus benjamina, Hedera helix ‘Anne Marie’, Hedera canariensis ‘Montgomery’, Hibiscus rosa‐sinensis ‘Red’. Hibiscus rosa‐sinensis ‘Moesiana’, Dieffenbachia maculata ‘Compacta’ and Nephrolepis exaltata‘Bostoniensis’) was shown to correlate with transpiration, while NO uptake had no significant dependence on stomatal opening. NO was taken up at a constant rate throughout the light period, while the uptake of NO2 decreased towards the end of the day in the same manner as transpiration. Uptake of NO in the dark was as high as in the light, while uptake of NO2 in the dark was reduced by as much as transpiration.

Relative to total pollutant uptake, the toxicity of NO towards photosynthesis is 22 times higher than that of NO2. NO must therefore have a mechanism of toxicity which is different from that of NO2.

A sufficiently high dose of NO (4 ml 1−1 for 5 hours) to reduce transpiration (close stomata) decreased photosynthesis less than a lower dose (1 μ1 1 −1 for 12 h). Since total NO uptake was not dependent on stomatal aperture, but stomatal closure reduced the effect of NO on photosynthesis, it is suggested that stomatas regulate the effective NO uptake, i.e. the small fraction of NO uptake that affects photosynthesis. The larger ineffective portion of the uptake is thought to be absorbed on the outer leaf surface.

The sensitivity of cultivars or species to NO or NO2 (i.e. effects on photosynthesis and transpiration) did not correlate with the uptake of either pollutant gas.