bluuebunny/crossref_metadata_2025 huggingface dataset:
THE RELATIONSHIP BETWEEN CADMIUM UPTAKE AND HEAVY METAL TOLERANCE IN THE LICHEN GENUSPELTIGERA
Authors: BECKETT R. P. , BROWN D. H.
Published: May 2006

Summary

Intra‐ and extra‐cellular Cd uptake were investigated in members of the lichen genusPeltigerasampled from sites with contrasting metal status.Peltigera membranacea(Ach.) Nyl. from a disused Zn mine, previously shown to be tolerant to Zn‐induced inhibitions of photosynthesis, displayed a reduced rate of Cd uptake into the cell compared withPeltigeraspp. from unpolluted sites, suggesting metal exclusion was a tolerance mechanism. Although some differences in extracellular Cd uptake were found, these appeared to be a reflection of inter‐specific variation rather than environmentally‐induced alterations in Cd‐binding capacity. Exposure to a mixture of Cd and Mg showed that intracellular Cd uptake was less inhibited by Mg when lichens originated from the Zn mine, also implying that mine‐site plants had modified uptake systems. Although intracellular Cd uptake is normally light‐stimulated inPeltigera, lichens from the Zn mine lacked this response, suggesting that algal uptake was reduced more than fungal uptake. Photosynthetically Zn‐tolerantP. hymenina(Ach.) Delise from a disused Pb mine, more moderately polluted than the Zn mine, had intracellular Cd uptake rates comparable to those found in lichens from background localities. In addition, treatment of lichens for 1 week with low concentrations of Zn, previously shown to induce photosynthetic Zn and Cd tolerance, had no effect on intracellular Cd uptake. Tolerance in these instances must have been achieved by some other means. It is suggested that a severe metal stress may be required before metal tolerance by exclusion occurs.
THE EFFECTS OF ELEVATED CO2 ON PLANTS
Authors: GARBUTT K. , BAZZAZ F. A.
Published: May 2006

Summary

Four populations of Phlox drummondii and one population each of Datura stramonium and Abutilon theophrasti were grown in six growth chambers at 300, 600 and 900 μ l l−1CO2, all other environmental variables remaining constant. Changes in timing and numbers of flowers produced were species‐ and population‐dependent. In general, P. drummondii and D. stramonium flowered earlier under high CO2 while A. theophrasti was not affected. Significant population × CO2 interactions were found for several flower production characters in P. drummondii, indicating differential response to elevated CO2 levels even within a species. In D. stramonium, increased biomass in high CO2 caused significantly larger fruits to be formed, but there was no significant increase in seed number.

In A. theophrasti, individual seed weight increased with increasing CO2, but total seed weight per plant remained constant.

These results are discussed in relation to their possible implications to plant community structure, and the effects on higher trophic levels (e.g. pollinators and plant predators). Qualitative as well as quantitative changes in plants in response to high CO2 must be studied with care to ensure correct predictions of the effects of the global rise in CO2.
LIGHT AFFECTS THE DEPOSITION OF NO2 TO THE FLACCA MUTANT OF TOMATO WITHOUT AFFECTING THE RATE OF TRANSPIRATION
Authors: MURRAY A. J. S.
Published: May 2006

Summary

The flacca mutant of Lycopersicon esculentum Mill., in which stomata remain open in darkness, was used to deomonstrate an effect of light on the inward flux of NO2. This effect was not associated with a change in stomatal conductance. However, a flux was still measurable in the dark and the nature of this is discussed. The normal mechanism of ion transport in leaves is suggested as one factor in the determination of the net flux of NO2 onto this mutant tomato.
SAMPLING STRATEGIES FOR MYCORRHIZAL RESEARCH
Authors: REICH LEE , BARNARD J.
Published: May 2006

Summary

Variance components were determined for the percentage of mycorrhiza formation in roots of apple trees (Malus) and the numbers of mycorrhizal spores extracted from the soil environment of trees growing in the field. For spore counts and root infection, variability was least from tree to tree. With both of the commonly used methods of rating percentage infection, variability was greatest between samples. For counting soil‐extracted spores, the greatest variation was at the subsample level.
GROWTH OF EXPERIMENTALLY RECONSTRUCTED THALLI OF THE LICHEN PARMELIA CONSPERSA
Authors: ARMSTRONG R. A.
Published: May 2006

Summary

The centres of thalli of Parmelia conspersa (Ehrh. ex Ach.) Ach. were removed, the major lobes were separated from each other and from the substratum, and then the lobes were glued back together in their original configuration. The mean radial growth, the pattern of seasonal growth, and the degree of variation in growth between lobes of the reconstructed thalli, were similar to those of control thalli. When lobes were removed from thalli and glued apart from one another, the pattern of seasonal growth and the degree of variation in lobe growth were unaffected, but annual growth rates were reduced compared with lobes reconstructed into a thallus. Glueing the lobes together in a different configuration and constructing thalli in which each lobe came from a different ‘donor’ thallus did not influence the mean radial growth of the lobes or the degree of variation in lobe growth. These results suggest that although major lobes of P. conspersa are influenced by the proximity of their neighbours there is little chemical exchange between them. In addition, some thalli may form as a result of the fusion of lobes or propagules derived from different individuals.
DIFFERENCES BETWEEN SEXES IN FLORAL MORPHOLOGY, NECTAR PRODUCTION AND INSECT VISITS IN A DIOECIOUS SPECIES,SILENE DIOICA
Authors: Kay Q. O. N. , Lack A. J. , Bamber F. C. , Davies C. R.
Published: May 2006

Summary

Silene dioica(L.) Clairv. was studied in several wild populations near Swansea and in an experimental population to determine the extent of differences between the sexes in floral morphology, nectar production, and insect visits to flowers, and the effects of these differences on seed set.

Male flowers are larger than female flowers and are borne more densely over a longer period. Male flowers have longer and more frequently white corona scales which may mimic the projecting white styles of female flowers. Male and female flowers were observed to secrete similar quantities of nectar sugar on the first morning of opening, but female flowers secreted more than males subsequently, and the total volumes of nectar secreted by female flowers were considerably greater. Male plants varied more than females in the total quantity of nectar sugar secreted per flower. Nectar concentration was nearly always greater in male flowers than in female flowers.

Bumblebees, particularlyBombus hortorum(L.),B. pascuorum(Scop.) andB. terrestris(L.), were the most important visitors to the. flowers ofS. dioicain the study sites, with some honeybees [Apis mellifera(L.)], butterflies (mainly Pieridae) and hoverflies (Syrphidae). Some visitors, including those that were most numerous at some sites, made most or all of their visits illegitimately. In the field in 1980 many visitors were observed to discriminate in favour of male flowers, which were much more numerous than female flowers. In the experimental population in 1981, many visitors discriminated in favour of female flowers, which were more numerous than in the field populations but were still substantially outnumbered by male flowers. Some individual bumblebees showed a change in preferences during the day, disciminating in favour of female flowers only during the afternoon, when the nectar resources available from female flowers were proportionately greater. The total numbers of visits that were observed to female and male flowers in the experimental population corresponded closely with the total quantities of nectar sugar available from each sex. The importance of the different insect visitors and of their discrimination between sexes in pollination is discussed. Seed set did not appear to be reduced by discrimination or insufficiency of pollinator visits in closely spaced plants, but was reduced in plants isolated by distances of 15 m or greater.
POLLEN DIAGRAMS FROM DUBH LOCHAN, NEAR LOCH LOMOND
Authors: Stewart Duncan A. , Walker Agnes , Dickson James H.
Published: May 2006

Summary

The main features of the vegetational history revealed by study of two sets of cores from Dubh Lochan, near Loch Lomond are as follows:

 There was a brief pioneer phase during the end of the Younger Dryas period after the disappearance of the Loch Lomond glacier. Dwarf shrubs and herbs, including arctic‐alpines and pteridophytes, predominated.

 There followed a brief phase of Empetrum and Juniperus in the earliest Flandrian.

 Next came the expansion of tree Betula and then Corylus at 9350 years B.P. Together these dominated for up to 3000 years, with the arrival of Ulmus and Quercus and expansion of the latter, towards the end of the period.

 There followed a temporary expansion of Pinus and the development of mixed Quercus forest with Alnus before 6000 years B.P. The Ulmus decline at 4900 years B.P. was well marked.

 Major differences in the pollen spectra of the two cores in terms of the regional, extra local and local components occur during the last 4000 to 5000 years B.P. A hydroseral succession from open water through a Salix carr to a Myrica carr was noted only from the marginal core.

 Though pollen indicative of human disturbance occurs from the Ulmus decline onwards and expands towards the top of the sequences, the area has stayed under Quercus forest with Alnus and Betula, there having been no substantial disforestation until the last 1000 years.
ABSCISIC ACID TRANSPORT AND METABOLISM IN GRAPEVINE (VITIS VINIFERA L.)
Authors: LOVEYS B. R.
Published: May 2006

Summary

Radioactive abscisic acid (ABA) was applied to leaves of potted grapevines (Vitis vinifera L.). During a 24‐h experimental period, the ABA was extensively metabolized within the leaf to phaseic acid (PA), 4′‐dihydrophaseic acid (DPA) and abscisyl‐β‐D‐glucopyranoside (ABAGE), together with a number of unknown metabolites. ABA was transported out of the leaf to the roots. The major metabolite in roots was DPA and, 24 h after application of ABA to the leaves, only 5% of the radioactivity in the roots was present as ABA. Very little ABAGE was formed by roots. Xylem sap, expressed from canes or collected by root pressure exudation, also contained labelled material, a high proportion of which was unmetabolized ABA.

It is suggested that export of ABA from leaves to roots and subsequent transport back to the leaves via the xylem occur naturally in unstressed grapevines and that this forms an integral part of the stomatal control mechanism.
THE RELATION BETWEEN THE BRITISH AND THE EUROPEAN FLORAS
Authors: WALTERS S. M.
Published: May 2006

The paper presents a brief and personal history of the main developments in British vascular plant taxonomy and distribution studies in a European setting since the Second World War. It assesses the importance of the‘European view', and considers recent and current work under two main heads: the factual information itself, and the presentation of the facts, especially in the form of dot distribution maps.
NEWFERRY AND THE BOREAL‐ATLANTIC TRANSITION
Authors: SMITH A. G.
Published: May 2006

Summary

The establishment and expansion of alder [Alnus glutinosa (L.) Gaertner] in Britain between approx. 8000 and 5000 years ago is discussed in relation to changes of climate and sea‐level, and to human influences.

Detailed pollen analyses of Mesolithic layers at Newferry, Co. Antrim are presented. Evidence from this and other sites suggest widespread disturbance of forest cover which, by locally reducing competition, (cf. McVean, 1956) appears to have been one of the factors in the establishment of alder.

Estuarine habitats are suggested as having importance in the spread of alder but the onset of climatic wetness was probably not a key factor (as bas often hitherto been supposed) other than in the sense of being permissive.
RELATIONSHIPS BETWEEN TOLERANCE TO HEAVY METALS IN AGROSTIS CAPILLARIS L. (A. TENUIS SIBTH.)
Authors: And M. O. HUMPHREYS , NICHOLLS M. K.
Published: May 2006

Summary

Heavy‐metal tolerance was investigated in Agrostis capillaris L. (A. tenuis Sibth.) using a standard rooting test on plants originating from a copper‐contaminated site (Parys Mountain) and a lead‐contaminated site (Goginan). Six F1 families obtained by interpopulation hybridization and F2 and backcross generations derived from one of them were screened. Estimates of the genetic and environmental components of phenotypic correlation were obtained in terms of both root length and tolerance index. Results are discussed in relation to problems of interpretation of evidence for multiple‐ or co‐tolerance based on tolerance indices and phenotypic correlations.
POLLEN FLOW IN DIMORPHIC TURNER A SUBULATA (TURNERA CEAE)
Authors: And N. RAMA SWAMY , BAHADUR BIR
Published: May 2006

Summary

Turner a subulata J. E. Smith is heterostylous with pin and thrum flower forms and is self–incompatible but cross‐compatible. Pin and thrum flowers produce the same number of pollen grains. Only 3·07% of the pollen produced participates in the pollination. Pin stigmas receive an average of 425 pollen grains and thrums 327. Stigmas of pin flowers receive more thrum than pin pollen grains. Thus in compatible pollinations, pollen flow from the thrum to the pin form was greater than in the reverse direction.
CARBON FLUXES IN LEAF BLADES OF BARLEY
Authors: FARRAR S. C. , FARRAR J. F.
Published: May 2006

Summary

Gas exchange, mass of carbohydrates, and turnover of carbohydrates, have been followed diurnally in barley leaf blades. Mature second leaf blades store sucrose, which occurs in at least two types of pool which turn over at different rates. Over a light‐dark cycle, photosynthesis, sucrose synthesis and translocation all show appreciable changes in rate but are not obviously related; nor is the rate of translocation a function of the total concentration of sucrose in the leaf. In the dark, starch mobilization starts immediately and that of sucrose increases, maintaining the mean rate of translocation in the dark at 77 % of that in the light. Fructans are turned over but show little diurnal variability in mass.
CARBOHYDRATE ACCUMULATION IN OSMOTICALLY STRESSED CYANOBACTERIA (BLUE‐GREEN ALGAE): INTERACTIONS OF TEMPERATURE AND SALINITY
Authors: WARR S. R. C. , REED R. H. , STEWART W. D. P.
Published: May 2006

Summary

The effects of temperature and salinity on the carbohydrate accumulation profiles of a range of unicellular cyanobacteria (blue‐green algae) have been studied. Four isolates of Synechocystis sp. which usually accumulated glucosyl‐glycerol produced a second carbohydrate, sucrose, when grown in a seawater‐based medium at high temperature (35°C). In contrast, three sucrose‐accumulating isolates of Synechococcus, grown over a range of temperatures and salinities, did not produce a second detectable low molecular weight carbohydrate in any experimental treatment. The interaction of temperature and salinity was further examined in Synechocystis PCC 6714. Sucrose production was found to be favoured by high temperature and low salinity. The rate and extent of sucrose accumulation differed in cells grown at 20 and 37 °C reaching an upper asymptote 12 h after upshock at 37 °C and 24 h after upshock at 20 °C followed by a decrease to an approximately constant level after 96 h. This is the first demonstration of the accumulation of sucrose as a second osmotically active carbohydrate in cyanobacteria.
EFFECTS OF SOIL MOISTURE STRESS ON THE WATER RELATIONS AND WATER USE OF GROUNDNUT STANDS
Authors: BLACK C. R. , TANG D.‐Y. , ONG C. K. , SOLON A. , SIMMONDS L. P.
Published: May 2006

Summary

The work described here formed part of a detailed study of the effects of temperature and water stress on growth and development in groundnut(Arachis hypogaeaL.). Stands of plants were grown in controlled environment glasshouses at mean air temperatures of 25, 28 and 31 °C. Half of each stand was irrigated whenever soil water potential at 10 cm reached –20 kPa. The other half received no further irrigation after sowing, when the soil profile was at field capacity. The effects on plant water status, stomatal conductance and water use were investigated regularly during the growing season.

Leaf water potential (Ψ1), turgor potential (Ψp) and stomatal conductance (g1) were already reduced in unirrigated plants by 29 d after sowing (DAS), when leaf area index (LAI) was still below 0.5; g1was more strongly affected than water status. These differences persisted throughout the season as stress increased, g1was poorly correlated with Ψ1and Ψpand of ten exceeded 2 cm s−1in wilted leaves. LAI was not affected before 40 to 45 DAS but was reduced by 20 to 25 % in unirrigated plants between 60 DAS and final harvest. The decreases in g1and LAI reduced canopy conductance by up to 40 %. The conservative influence of decreased g1in unirrigated plants was negated by increases in leaf‐to‐air vapour pressure difference caused by their higher leaf temperatures. Transpiration rates were therefore similar in both treatments and the lower total water use of the unirrigated stand resulted entirely from its smaller LAI. Unirrigated plants made less vegetative growth but produced more pegs and pods. However, impaired pod‐filling reduced pod yields by around 35 %.
ION CHROMATOGRAPHIC DETERMINATION OF LEVELS OF ANIONS IN PLASTIDS FROM FUMIGATED AND NON‐FUMIGATED BARLEY SEEDLINGS
Authors: WELLBURN A. R.
Published: May 2006

Summary

A range of aqueous and non‐aqueous methods for chloroplast preparation were tested to establish suitable methodology for routine analysis of plastid anion content using high performance ion chromatography (HPIC). Aqueous methods of plastid isolation failed to provide a satisfactory procedure for analysis of anions (other than chloride) but three different non‐aqueous methods all gave satisfactory and effective procedures.

The simplest non‐aqueous method was used to analyse the anions in chloroplasts from 9 d old barley seedlings which had been grown in clean air or fumigated for the last 1 to 3 d of growth with high, but not unrealistic, concentrations (0.28 ppm) of either SO2 or NO2. Amounts of chloride, phosphate, sulphate, sulphite, nitrate and nitrite were detected in plastid preparation from both clean air and polluted seedlings. NO2 fumigation had no effect on chloride, phosphate, sulphate or sulphite content but increased the levels of nitrite and decreased those of nitrate especially on the second day of treatment. Similar atmospheric concentrations of SO2 had no effect on chloride content but increased the levels of phosphate, sulphate and sulphite as well as having a similar influence as NO2 upon nitrate and nitrite content. Again all these effects of SO2 were greatest on the second day of fumigation.
MYCORRHIZAL FUNGI AT EIGHTEEN APPLE ROOTSTOCK PLANTINGS IN THE UNITED STATES
Authors: MILLER DIANE DOUD , DOMOTO PAUL A. , WALKER CHRISTOPHER
Published: May 2006

Summary

Vesicular‐arbuscular mycorrhizas of apple (Malus domestica Borkh.) from 18 sites in the USA were examined. Species of Endogonaceae were identified from soil, and their relative abundance determined from spore extractions. There were no evident patterns in geographic distribution of fungi. A range of three to eight species was found among sites, Glomus being more common in number of species and spores than Gigaspora, Acaulospora, or Sclerocystis. Pot cultures made with soil from some sites yielded species not recovered by sieving. Colonizing ability of all fungi isolated was assessed with apple and sorghum. Colonization potential of soils was determined by dilution techniques with apple as the host. Roots from all sites were endomycorrhizal, but not ectomycorrhizal. Proportion and intensity of colonization were negatively correlated with soil Zn and, at most sites, P levels. Colonization of rootstock clones varied among, but not within sites. Soil colonization potential was highly correlated with degree of root colonization in the field, and there was no evidence that any location lacked adequate inoculum potential for apple.
COLONIZATION AND EFFICACY OF DIFFERENT ENDOMYCORRHIZAL FUNGI WITH APPLE SEEDLINGS AT TWO PHOSPHORUS LEVELS
Authors: MILLER DIANE DOUD , DOMOTO PAUL A. , WALKER CHRISTOPHER
Published: May 2006

Summary

Six species of vesicular‐arbuscular mycorrhizal fungi originally isolated from orchard soils were evaluated at low phosphorus (approx. 30 mg kg−1) and high phosphorus (approx. 180 mg kg−1) levels for root colonization and effects on growth of apple (Malus domestica Borkh.) seedlings. Fungi tested were Gigaspora calospora (Nicol. & Gerd.) Gerd. & Trappe, Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, Glomus maculosum sp. ined., Glomus manihotis Howeler, Sieverding & Schenck, Glomus bitunicatum sp. ined., and two isolates of Glomus occultum Walker. Trees grew larger and had higher leaf P concentrations at high soil P than at low soil P regardless of mycorrhizas. At low P, fungal species differed in percentage root length colonized, intensity of colonization, types of mycorrhizal structures formed, and number of spores produced. Fungal species also differed in effects on plant growth. At harvest, five treatments were taller than the non‐mycorrhizal control trees, and two were not. Stem diameter and total dry weight were increased by only three treatments. At high P, no treatment resulted in greater than 5 % of root length colonized, and endogonaceous fungi had little influence on plant growth.
Studies ON THE MYCORRHIZAS OFPINUS SYLVESTRISL. PRODUCEDIN VITROWITH THE BASIDIOMYCETESUILLUS VARIEGATUS(Sw.exFr.) O. KUNTZE
Authors: WARMBRODT ROBERT D. , ESCHRICH WALTER
Published: May 2006

Summary

The structure and development of the endodermis and vascular cylinder of ectomycorrhizas ofPinus sylvestrisL. formedin vitrowith the basidiomyceteSuillus variegatus(Sw. ex Fr.) O. Kuntze were studied by light and electron microscopy. With the exception of the sieve elements, the cells of the vascular cylinder and endodermis differentiate relatively close to the apical meristem of the slow growing mycorrhizal rootlets. The endodermis is uniseriate and delimits a vascular cylinder which in most cases is diarch. All endodermal cells develop casparian strips in their anticlinal walls and approximately 50% of them undergo no further changes. The walls of the remaining endodermal cells however, are apparently impregnated with suberin or lipid‐like substances and these cells subsequently disintegrate and collapse. The vascular cylinder of the mycorrhizal rootlets consists of a mostly uniseriate pericycle, tracheids with circular‐bordered pits, sieve cells, variable numbers of vascular parenchyma cells and peripheral phloem parenchyma cells, the so‐called precursory phloem cells. The latter are characterized by high numbers of microfilament bundles and numerous, large aggregates of plasmodesmata which occur in thickened regions of the wall. Upon maturation of the sieve cells, the peripheral phloem parenchyma cells disintegrate and may eventually collapse. Typical albuminous (Strasburger) cells were not encountered in the material examined. By consideration of the structure and distribution of plasmodesmata among the various cell types the feasibility of symplastic and apoplastic transport within the mycorrhizal rootlets is discussed.
UPTAKE AND ACCUMULATION OF ZINC, LEAD AND COPPER IN ZINC AND LEAD TOLERANT ANTHOXANTHUM ODORATUM L.
Authors: QURESHI J. A. , THURMAN D. A. , HARDWICK K. , COLLIN H. A.
Published: May 2006

Summary

The amount of zinc, lead or copper accumulated in plants from zinc and lead tolerant and non‐tolerant populations of Anthoxanthum odoratum L. varied depending on whether the plants were tolerant of the metal and on the period of exposure to the solution containing the metal. After one day in zinc, lead or copper‐containing solutions, both tolerant and non‐tolerant plants showed a similar uptake and distribution of each metal, suggesting that uptake was independent of the tolerance characteristics. After 11 d of exposure to each metal, more lead and zinc were present in the roots of tolerant plants than in the roots of non‐tolerant ones. However, there was no change in the uptake and distribution of copper in plants after 11 d of exposure. The evidence for the presence of a mechanism to exclude toxic metals from the shoots is discussed.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYLIS GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P.
Published: May 2006

Summary

The influence of the outer covering structures (palea, lemma and pericarp) on the germination response to light and alternating temperatures was investigated in two populations of Dactylis glomerata L. Removal of the palea and lemma was less effective than light or alternating temperatures in promoting germination. Despite quantitative differences, both populations responded similarly to all three factors. Statistical analysis of data transformed to probits indicated mainly additive effects when factors were combined. Selective surgical treatments showed that the structural integrity of the pericarp was also important in germination control. Removal of the palea and lemma followed by the making of a shallow incision in the pericarp close to the embryo, stimulated germination in a very high proportion of individuals (94 %) even at a constant temperature (16°C) in the dark. Elevated oxygen levels promoted germination of intact seeds suggesting that the outer coverings might restrict oxygen access. Evidence is presented that positive pressures (0.03 MPa) applied during gassing led to a reduction in germination.
SYNERGISM BETWEEN CALCIUM IONS AND ABSCISIC ACID IN PREVENTING STOMATAL OPENING
Authors: DE SILVA D. L. R. , HETHERINGTON A. M. , MANSFIELD T. A.
Published: May 2006

Summary

The inhibition of stomatal opening inCommelina communisL. by abscisic acid (ABA) appears to be dependent on the availability of calcium ions. Incubation of epidermal strips in 10−6mol m−3ABA had little effect in the absence of calcium, and a factorial experiment showed a highly significant calcium x ABA interaction. The effect of calcium appeared to be on the later stages of the opening process, and might have been the result of an inhibition of potassium uptake by the guard cells. There was no detectable effect of ABA when EGTA was used to chelate calcium from the apoplastic space.

The data are consistent with the hypothesis that ABA increases the permeability of the plasma membranes of the guard cells to calcium. Calcium might then operate as a second messenger to regulate the ionic fluxes that determine guard cell turgor.
DIFFERENTIAL EXPRESSION OF DIEL ACID METABOLISM IN TWO LIFE FORMS OF LITTORELLA UNIFLORA (L.) ASCHERS
Authors: AULIO K.
Published: May 2006

Summary

The shoreweed Littorella uniflora (L.) Aschers. possesses two life forms differing from each other both in morphological and in biochemical characteristics. The submerged (isoetid) form showed marked fluctuations in the levels of malic acid, as well as in the total titratable acidity, thus meeting the most important biochemical requirement of Crassulacean Acid Metabolism (CAM). In contrast, the terrestrial form, which depends on atmospheric sources of CO2, showed negligible variations in the levels of malate. The isoetid form has wax‐covered, functionless stomata, whereas the stomata of the terrestrial form are operative. Comparison of the two genetically uniform types of Littorella strongly supports the hypothesis that the CAM‐like carbon pathway is selected in submerged plants as an adaptation to the carbon shortage which they experience in daytime.
THE INFLUENCE OF NATURAL AND IN VITRO BUD FLUSHING ON ADVENTITIOUS BUD PRODUCTION IN SITKA SPRUCE [PICEA SITCHENSIS (BONG.) CARR.] BUD AND NEEDLE CULTURES
Authors: SELBY C. , HARVEY B. M. R.
Published: May 2006

Summary

The adventitious bud forming ability of Sitka spruce [Picea sitchensis (Bong.) Carr.] buds was found to be dependent upon the time of year at which they were introduced into culture. Adventitious bud production was at a maximum in the latter weeks of March, immediately prior to their natural flushing time, a period when the buds are naturally forming initials for lateral buds and bud scales and are in a highly active physiological state. Throughout the dormant period cultured buds were able to form adventitious buds; however, once the buds were in an advanced state of natural flushing their capacity for organogenesis declined and they became callused and senescent. The enhancement of adventitious bud production with the onset of natural flushing, and the detrimental effects of bud overdevelopment, were simulated by flushing dormant buds in vitro on a cytokinin free medium using juvenile tissues. In vitro flushing of buds from mature trees did not increase their organogenic capacity. Increasing tree age also significantly reduced the number of adventitious buds forming throughout the natural growth cycle.

Adventitious bud production in needle cultures, using needles excised from buds flushed to varying extents in vitro, was also found to be reliant upon their developmental state. Needles needed to be in an immature state (approx. 1 to 2 mm long) to produce optimum organogenesis on their basal tissues. Needles that were more differentiated became callused and senescent in culture.

To maximize shoot multiplication rates with Sitka spruce bud and needle cultures, tissues need to be in a carefully controlled stage of differentiation. This can probably be best achieved by flushing dormant buds in vitro to precise extents prior to adventitious bud induction.
THE INFLUENCE OF THE PERIODIC FRUITING (FLUSHING) CYCLE ON THE BIOCHEMICAL DEVELOPMENT OF AGARICUS BISPORUS SPOROPHORES
Authors: MINAMIDE TAKAHISA , HAMMOND JOHN B. W.
Published: May 2006

Summary

Soluble carbohydrate content, glucose 6‐phosphate dehydrogenase (G6PD) activity and amount, and DNA and RNA content were measured in the tissues of fruit bodies of Agaricus bisporus (Lange) Imbach. developing at different stages of the periodic fruiting cycle. Trehalose content, G6PD activity and G6PD protein were maximal at flush emergence independent of the stage of development of the sporophore. Mannitol accumulated in growing sporophores both during and between the flushes of fruit body production. The RNA content of the gill tissue consistently increased in fruit bodies developing during the flush but sporophores growing between flushes showed a decline in RNA content after early gill development. Gill DNA content doubled just prior to sporulation in sporophores growing during the flush but not in those developing between flushes. The mycelial control of the biochemical development of the fruit body is discussed.
SOME FACTORS INFLUENCING VIABILITY OF ECTOMYCORRHIZAL FUNGAL INOCULUM
Authors: LAPEYRIE F. F. , BRUCHET G.
Published: May 2006

Summary

Several criteria have been established for more effective utilization of inoculum of Pisolithus tinctorius (Mich. exPers.) Ckr. & Couch and of Paxillus involutus (Batsch. ex Fr.) Fr. P. tinctorius inoculum prepared on vermiculite‐peat moss medium can be stored up to 19 weeks at 3 °C without damage but P. involutus inoculum cannot be stored for more than two weeks. At 24 °C neither inoculum retained viability for long, emphasizing the need for such inoculum to be applied to host roots in a way which permits rapid infection.

A blended inoculum prepared from P. tinctorius grown in liquid culture had a maximum activity, at the age of three weeks, which coincided with its maximum ATP concentration, suggesting that ATP might prove to be a valuable guide to inoculum potential. This inoculum is most tolerant of blending procedures and establishes itself better on both nutrient‐rich and nutrient‐poor substrates when previously grown on nutrient‐poor media.
ENDOPHYTES OF WILD ORCHIDS NATIVE TO ITALY: THEIR MORPHOLOGY, CARYOLOGY, ULTRASTRUCTURE AND CYTOCHEMICAL CHARACTERIZATION
Authors: MARCHISIO V. FILIPELLO , BERTA G. , FONTANA A. , MANNINA F. MARZETTI
Published: May 2006

Summary

Isolates of Rhizoctonia sp. obtained from the terrestrial orchids Dactylorhiza sambucina (L.) Soó, D. maculata (L.) Soó and Platanthera bifolia (L.) L. C. M. Richard, collected in Piedmont (Italy) were studied in the following characters: macroscopic and microscopic morphology, growth rate, ultrastructure of the septal pore apparatus, number of nuclei per cell and cytochemistry of the hyphal and monilioid cells. On the basis of cultural and morphometric characters, the isolates were divided into three groups, which are described in detail. No perfect stage was produced in culture. Although the identification of species of Rhizoctonia‐like fungi without perfect stages is extremely difficult, a comparison of our data with that in the literature leads to the probable identification of group I isolates as a species of Ceratobasidium, group II isolates as a species of Thanatephorus and those of group III as a species of Tulasnella or Sebacina.
THE EFFECTS OF SULPHUR DIOXIDE ON NET CO2 ASSIMILATION IN THE LICHEN EVERNIA MESOMORPHA NYL.
Authors: HUEBERT D. B. , L'HIRONDELLE S. J. , ADDISON P. A.
Published: May 2006

Summary

Physiologically active thalli of the lichen Evernia mesomorpha Nyl. were very sensitive to short‐term fumigations with low concentrations of gaseous sulphur dioxide. Net CO2 assimilation rate (NAR) was significantly reduced after exposure to 0.085 μl l−1 (250μg m−3) SO2 for 1 h or more, and the reduction increased with increasing concentration. Duration of exposure had no significant effect on NAR, indicating the importance of rate of SO2 uptake rather than the total amount absorbed. Respiration was significantly reduced after 4 h or more of exposure to 0.265 μl l−1 (639 μg m−3) SO2 or higher. Recovery of NAR after fumigation was dependent on both SO2 concentration and duration of fumigation, and on the time allowed for recovery. Virtually complete recovery occurred within 24 h after episodes with up to 0.355 μl l−1 (856 μg m−3) SO2 for 1 h and 0.085 μl l−1 SO2 for 4 h. Above these levels, recovery was incomplete or nonexistent after 24 h in clean air. The level of sensitivity found can be attributed to the environmental conditions during fumigation, which prevented thallus desiccation and inactivity. Based on this study, neither the concept of dose (concentration × time) nor that of ‘threshold’ levels of SO2 fumigations are supported. Peak exposures to SO2 for short periods may be of primary importance in determining the survival of lichens in industrial areas.
NITROGEN OXIDES PRODUCED DURING CO2 ENRICHMENT
Authors: MORTENSEN LEIV M.
Published: May 2006

Summary

Plants were grown in chambers with CO2 enrichment (1000 μl 1−1) and with or without the addition of 0.85 μl 1−1 nitrogen oxides (NOx).

The following species were tested: Lactuca sativa (lettuce), Cucumis sativus (cucumber), Lycopersicon esculentum (tomato), Saintpaulia ionantha, Rosa, Kalanchoe blossfeldiana, Chrysanthemum×morifolium, Helxine soleirolii, Hedera helix, and Nephrolepis exaltata. All species responded positively to an increase in CO2 level from 330 to 1000 μl 1−1. The dry weights of tomato, roses and Saintpaulia responded negatively to the addition of NOx. In tomato, the reduced dry weight was due to reduction in shoot length and leaf area. In roses the stem was shorter and in Saintpaulia the leaves smaller when NOx was added. Furthermore, the time to flowering increased and number of flowers/flower buds decreased in Saintpaulia.
ACCURATE ESTIMATION OF STOMATAL APERTURE FROM SILICONE RUBBER IMPRESSIONS
Authors: WEYERS JONATHAN D. B. , JOHANSEN LIV G.
Published: May 2006

Summary

The potential of low viscosity silicone‐based impression material for measuring stomatal aperture on intact leaves was investigated. It was found that the probability of successful replication of Commelina communis L. stomata depended on the width of the stomatal pores. The wider pores in a sample were more likely to be measured, so the resulting estimated mean was an overestimate of the true mean. This bias in estimates of stomatal aperture from impressions was studied and quantified. A transformation is described which was used to adjust apparent aperture measurements from impressions to give more accurate estimates of stomatal apertures on intact leaves of C. communis. Maximum absolute errors due to the bias usually occurred at apparent apertures on impressions of between 2 and 5 μm but were proportionally greatest below 3μm, where they often exceeded 40%. At a given aperture, the error depended upon the dispersion of the stomatal apertures about their mean and was greatest when this was large.
FUNGAL POPULATION AND COMMUNITY DEVELOPMENT IN CUT BEECH LOGS
Authors: COATES D. , RAYNER A. D. M.
Published: May 2006

Summary

More than 450 beech (Fagus sylvatica L.) logs, 10 to 20 cm in diameter and 30 to 40 cm long, were cut from freshly felled trees and placed upright 1 m apart with their bases buried up to 10 cm deep in the ground in a plot of about 600 m2 in a mixed deciduous woodland in the Forest of Dean, Gloucestershire, UK. Fungal colonization via the aerial and buried cut surfaces was studied – in some cases following inoculation of basidiospores – using a combination of direct and indirect techniques.

A wide variety of ascomycetes, basidiomycetes and fungi imperfecti were identified, by direct observation or following direct incubation of wood samples, from the vicinity of the aerial cut surface within the first six months after cutting. Some such as Coriolus versicolor (L. ex Fr.) Quél. subsequently increased in occurrence, whereas others, including Chondrostereum purpureum (Fr.) Pouz. declined.

Isolation onto malt agar from thin sections of wood revealed the presence of some fungi, notably a Fusarium sp., not detected by direct means. In addition, homokaryons of the basidiomycetes Bjerkandera adusta (Willd, ex Fr.) Karst. and C. versicolor were isolated from near the aerial cut surface up to two years after cutting, and, lower down, mostly up until six months after cutting (thereafter heterokaryons predominated). Moreover, evidence was obtained that small volumes of discoloured, but not strongly decayed wood, sometimes contained large numbers of mutually antagonistic individuals (up to 30 per cm3) of the decay species B. adusta, C. versicolor and Stereum hirsutum (Willd. ex Fr.) S. F. Gray.

Vertical penetration from the aerial cut surface showed a marked lag phase, such that for the first six weeks after cutting, overt colonization was restricted to about 3 mm depth. Thereafter the depth occupied increased rapidly.
THE PERFORMANCE OF AGROSTIS CAPILLARIS L. GENOTYPES, DIFFERING IN COPPER TOLERANCE, IN RYEGRASS SWARDS ON NORMAL SOIL
Authors: NICHOLLS M. K. , McNEILLY T.
Published: May 2006

Summary

Sample sub‐populations, each of six plants, were chosen for high, mid and low tolerance of copper from each of two naturally‐occurring copper tolerant populations and from tolerant individuals selected from a cultivar of Agrostis capillaris L. The naturally‐occurring ecotypes came from a closed sward community at Drws y Coed, and from an open community at Parys Mountain, both copper mines in North Wales. Clonal replicates of all plants were introduced into swards of perennial ryegrass cvs. S23 or S24, growing on normal soil at the University of Liverpool Botanic Gardens. S23 plots were cut eight times between June 1977 and July 1978, whilst S24 plots were cut 3 times during the same period. Half the experimental plots received N, P, K, fertilizer; the rest received none.

Plants selected from the cultivar (selected) produced most dry matter, and with infrequent defoliation flowered freely in competition with ryegrass. Those taken from Parys Mountain mine spoil produced least dry matter and no inflorescences. Drws y Coed plants were intermediate in dry matter and inflorescence production. These results may reflect differences in population density in the habitats from which the populations were sampled.

Sub‐populations chosen for high, mid or low copper tolerance within the selected and Drws y Coed populations did not differ significantly in dry matter yield. By contrast under certain circumstances Parys Mountain plants with low tolerance outyielded other more tolerant plants.

These results are considered with respect to growth strategies adopted by plants growing on and off copper mine sites.
EFFECT OF ENVIRONMENT ON PERCENTAGE FEMALE RAY FLORETS PER CAPITULUM AND OUTCROSSING POTENTIAL IN A SELF‐COMPATIBLE COMPOSITE (SENECIO VULGARIS L. VAR. HIBERNICUS SYME)
Authors: ABBOTT RICHARD J. , SCHMITT JOHANNA
Published: May 2006

Summary

Ten lines of radiate groundsel (Senecio vulgaris L. var. hibernicus Syme) were raised in growth cabinets over a wide range of nutrient and temperature conditions to determine the effect of environment on female ray floret number, total floret number, percentage female ray florets and seed number per capitulum. Despite considerable variation in percentage female ray florets per capitulum among capitula within lines, the mean expression of the character remained relatively stable over all environments and lines tested with a mean over all treatments equal to 16–4%. Thus, the marked variation in outcrossing rate that has been reported for radiate groundsel in the wild is unlikely to result from variations in mean percentage of female ray florets per capitulum induced by changes of temperature or nutrient status.

The most frequent number of ray florets per capitulum recorded was 8, a Fibonacci number, found in 39·6 % of 821 capitula sampled. Moreover, the overall mean for total floret number was 56 which approximates very closely to another Fibonacci number, 55. This might suggest that the expected proportion of ray to total florets in each capitulum, based on Fibonacci numbers, would be 8/55 or 14–54%. The actual recorded mean value for percentage ray florets per capitulum exceeded this ‘expected’ value as most capitula surveyed bore more than 8 florets (59–2 % of sample).

Seed set per capitulum was always below 100 % and varied over environments. A consequence of this finding is that future studies of the relationship between percentage female ray florets per capitulum and outcrossing potential in self‐compatible Compositae will need to consider the distribution of seed produced by female ray florets and hermaphroditic disc florets within the capitulum.
THE BLUE LIGHT EFFECT AND ITS INTERACTION WITH PHYTOCHROME IN THE CONTROL OF NITRITE REDUCTASE ACTIVITY IN SORGHUM BICOLOR WILLD.
Authors: RAJASEKHAR V. K. , SOPORY SUDHIR K.
Published: May 2006

Summary

Irradiation with red light for 5 min stimulated nitrite reductase activity in 5‐d‐old etiolated seedlings of Sorghum bicolor. The stimulation was less when measured after a subsequent dark period of 12 h than after one of 24 h. A short period of irradiation with blue light did not alter the enzyme activity nor did it elicit any effect even if given for 4–6 h prior to the red light irradiation. Exposure to blue light for 12 h prior to the red light treatment increased the enzyme activity, when measured after 12 h of darkness, to the same level as that obtained by red light irradiation alone followed by 24 h of darkness. Blue light given continuously for 24 h increased nitrite reductase activity and this increase was inhibited by 6‐methylpurine (5 μg ml−1) or cycloheximide (25 μg ml−1). Transfer of seedlings to continuous white light for 6 h after treatment with a pulse of red light followed by 24 h of darkness, or with continuous blue light for 24 h, revealed an independent action of blue light and light operating via phytochrome, in the control of nitrite reductase activity. The accumulation of nitrate was unaffected either by a red light pulse followed by a subsequent dark period, or by continuous blue light. In contrast, continuous white light led to an increased accumulation of nitrate.
THE CONTROL OF LEAF GROWTH OF BETULA AND ACER BY PHOTOENVIRONMENT
Authors: TAYLOR GAIL , DAVIES W. J.
Published: May 2006

Summary

Leaf extension of one‐year‐old seedlings of silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.), was measured using linear variable transducers (LVDTs) interfaced to a microcomputer. Birch and sycamore seedlings exhibited contrasting patterns of leaf extension during a diurnal cycle with a 16 h photoperiod. Birch leaves grew more rapidly when illuminated; growth during the photoperiod was approximately doubled when compared with growth in the dark. Mean relative growth rates ±SE at ‘lights‐on + 3 h’ and ‘lights‐off + 5 h’ were 0.0136 ± 0.0016 and 0.0066 ± 0.0005 h−1 respectively. In direct contrast, growth of sycamore leaves was increased when leaves were darkened; mean relative growth rates + SE at ‘lights‐on+3 h’ and ‘lights‐off + 5 h’ were 0.0056 ± 0.0005 and 0.0094 ± 0.0008 h‐1 respectively.

When leaves of birch and sycamore were darkened, increased leaf turgor was measured in both species, but only in sycamore was this higher night‐time turgor associated with a higher rate of leaf growth.

Cell wall extensibility (WEX), an indication of the ability of cell walls to loosen and extend irreversibly, and cell surface pH were assessed in darkened and illuminated leaves of both species. An increase in WEX was measured when birch leaves were illuminated (P≤ 0.001) and this was accompanied by a decline in cell surface pH (P≤ 0.001). However, when leaves of sycamore were illuminated, WEX declined (P≤ 005) and cell surface pH increased (P≤ 0.001).

The ability of these species to survive beneath a woodland canopy is discussed in relation to the cellular factors controlling their leaf growth.
PHYTOALEXINS, WATER‐STRESS AND STOMATA
Authors: PLUMBE ALISON M. , WILLMER C. M.
Published: May 2006

Summary

There are certain features shared by phytoalexins (which can be loosely defined as microbial stress compounds) and water‐stress compounds such as ABA. Therefore, a study was made to determine if phytoalexins behaved in a similar fashion to water‐stress compounds and in this report phytoalexin accumulation in water‐stressed leaves was investigated.

Phytoalexins were not detected in mildly water‐stressed leaf tissue of Pisum sativum L. or Vicia faba L. However, if plants were severely water‐stressed resulting in damaged and dead areas in their leaves, a fungitoxic substance corresponding to pisatin was detected in the damaged areas of pea leaves and, to a lesser extent, in areas which recovered full turgor, while a number of fungitoxic substances, two of which corresponded to wyerone and wyerone acid, occurred in the damaged and recovered areas of V. faba leaves.

Thus, although phytoalexins may accumulate in severely water‐stressed leaves they do not apparently behave in a similar manner to water‐stress compounds such as ABA which would be expected to accumulate in leaves even under mild water‐stress.