bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of photosynthetically‐active radiation and simulated shadelight on the control of leaf growth of Betula and Acer
Authors: TAYLOR GAIL , DAVIES W. J. 
Published: April 2006

SUMMARYThe primary aim of the study was to quantify the effects of photosynthetically‐active radiation (PAR) on extension of leaves of silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.). Plants grown at 250 μmol m−2 s−1 were exposed to a range of fluence rates (0·680 μmol m− s−1) whilst enclosed in Perspex chambers in which temperature, vapour pressure deficit and photoenvironment were all controlled. Measurements of leaf extension, water relations, and cell wall extensibility (VVEX) were made at the end of a 3 h exposure period.For leaves of birch, reducing the fluence rate resulted in reduced leaf extension and a lowering of WEX. Exposure of sycamore seedlings for 3 h to different values of PAR had little effect on the growth of leaves and WEX remained constant. The characteristics of net photosynthesis also differed for the two species and photosynthesis and wall loosening may be linked.Since natural woodland shadelight, in addition to reduced PAR, also has a reduced R/FR ratio, a second group of seedlings were placed in a photoenvironment which simulated shadelight (low PAR, R/FR) for 28 d. This treatment reduced extension rate and final leaf size for both species. Measurements of extension, water relations and WEX made when seedlings were exposed to shadelight whilst held in the Perspex chambers revealed differences in the control of leaf growth for the two species.It is confirmed that leaves of birch are highly responsive to changes in PAR with cell wall loosening the most likely process controlling this response.
Altitudinal variation in nitrogenase activity of the Himalayan alder naturally regenerating on landslide‐affected sites
Authors: SHARMA EKLABYA 
Published: April 2006

SUMMARYNatural regeneration, root nodule biomass and nitrogenase activity (acetylene reduction) of Alnus nepalensis D. Don (alder) were estimated at ten different landslide‐affected elevated (1000–2500 m) sites in the Kalimpong forest division of the Eastern Himalayas. Alder regeneration was best in the middle zone (1500–2000 m) of this altitude range. Nitrogenase activities were between 5 and 19 μmol C2H4 g−1 nodule d. wt h−1 in a peak activity month (July). The activity was largely dependent on mean soil temperature and root nodule moisture. The highest rate of acetylene reduction was found in the rainy season (July) at the 1830 m elevation site. Nitrogenase activity was negligible at night and increased during the day with a midday maximum. Alder regeneration, seedling growth, root nodule biomass and nitrogenase activity were temperature dependent along the gradient of altitude and fell off below 1500 m and above 2000 m.
Underground transfer of nitrogen between pasture plants infected with vesicular‐arbuscular mycorrhizal fungi
Authors: HAYSTEAD A. , MALAJCZUK N. , GROVE T. S. 
Published: April 2006

SUMMARYExperiments were carried out to investigate the possibility that vesicular‐arbuscular (VA) mycorrhizal infection of grass (Lolium perenne L.) and clover (Trifolium repens L.) roots can enhance the exchange of nitrogen between the root systems of nitrogen‐fixing pasture legumes and associated grasses.The results showed higher rates of transfer of 15N applied as (15NH4)2SO4 to the clover plants to companion grass plants when the roots were mycorrhizal. In some cases but not all the grass grew better in the mycorrhizal treatments.An experiment in which the clover and grass roots were separated by a 60 μm (mean pore size) nylon mesh screen showed that translocation of the nitrogen was probably along the mycorrhizal hyphae. It was not clear from the data whether transfer was mediated by a common hyphal net or some other less direct means.
The biology of mycorrhiza in the Ericaceae XI. The distribution of nitrogen in soil of a typical upland Callunetum with special reference to the ‘free’ amino acids
Authors: ABUARGHUB S. M. , READ D.J. 
Published: April 2006

SUMMARYThe soil of a typical upland Callunetum was fractionated and the concentrations of nitrogenous components determined, emphasis being placed upon analysis of the distribution of ‘free’ amino acids both down the soil profile and through the year. The largest quantities of free amino‐compounds at all times of the year were found at the top of the profile, peak values occurring in September, October and November. Quantities of amino acids often exceeded those of extractable ammonium. The results are compared with those obtained in earlier studies of acidic organic soils and the significance of the findings is discussed with special reference to the nitrogen nutrition of mycorrhizal and non‐mycorrhizal ericaceous plants.
The biology of mycorrhiza in the Ericaceae
Authors: ABUARGHUB S. M. , READ D. J. 
Published: April 2006

SUMMARYThe results of qualitative and quantitative analysis of the individual ‘free’ amino acids of a Calluna heathland soil are reported. The distribution of each identified amino acid is described in relation both to its position in the soil profile and to time of year. The amino acids occurred in the following order of quantitative importance, histidine, glutamic acid, alanine, serine, aspartic acid, leucine, valine, glycine, arginine, isoleucine, lysine, phenylalanine, and tyrosine.The concentrations of total free amino acids obtained by summing the individual values agreed remarkably closely with those obtained by the ninhydrin procedure. Analysis of the amino acids in terms of acidic, neutral and basic categories indicated that the neutral category was quantitatively the most important. The results are compared with those obtained in previous qualitative and quantitative analysis of individual amino acids from organic soils and their significance is discussed in relation to the mycorrhizal status of ericaceous plants.
Pine root exudate stimulates the synthesis of antifungal compounds by the ectomycorrhizal fungus Paxillus involutus
Authors: DUCHESNE LUC C. , PETERSON R. L. , ELLIS BRIAN E. 
Published: April 2006

SUMMARYThe ectomycorrhizal fungus Paxillus involutus Fr. was grown in the presence of root exudate of Pinus resinosa Ait, for two weeks. The effect of root exudate on the synthesis of ethanol‐soluble antifungal compounds by P. involutus was determined by a bioassay based on microconidial germination of Fusarium oxysporum Schlecht emend, Sny. & Hans f. sp. pini. Cultivation of P. involutus on root exudate led to a greater than two‐fold increase in fungitoxic activity when compared to cultivation on modified Melin Norkrans medium in Petri dishes. Inoculation of P. resinosa root exudate with both P. involutus and a spore suspension of F. oxysporum led to an 80 % suppression of the sporulation of F. oxysporum when compared to controls lacking P. involutus. The increased resistance of P. resinosa P. involutus associations to Fusarium root rot may, therefore, be the result of biosynthesis of antifungal compounds by P. involutus which is stimulated by P. resinosa root exudate.
Comparison of colonization among half‐sib families of Medicago sativa L. by Glomus versiforme (Daniels and Trappe) Berch.
Authors: LACKIE S. M. , BOWLEY S. R. , PETERSON R. L. 
Published: April 2006

SUMMARYTwenty half‐sib families from within each of two populations of Medicago sativa L. (Pioneer 530 and OAC 78–101) were assessed for differences in ability to form vesicular‐arbuscular mycorrhizas (VAM) when grown in association with one VAM fungal species, Glomus versiforme (Daniels and Trappe) Berch. The families were grown under controlled environmental conditions using a culture‐pot system. Roots were cleared, stained and assessed for percent colonization. From the analyses of variance, the genetic variance and heritability of percent colonization were estimated. The mean percent colonization was 5.8 and 6.8% for the Pioneer 530 and OAC 78–101 populations, respectively. Significant (P < 0·05) differences in percent colonization were detected among half‐sib families derived from Pioneer 530 but not among half‐sib families derived from OAC 78–101. Significant (P < 0·05) pot and run effects were detected in the latter experiment which may have masked differences among the families. The estimate of narrow‐sense heritability of percent colonization in the Pioneer 530 population was 18·8% and the expected response to selection for percent colonization, if the top 10% of the population was selected, was 2·2% per cycle. This indicated that there was good potential for improving the extent of VAM colonization in the population of alfalfa. Further studies of host genotype‐VAM symbioses are warranted.
Recovery of net photosynthesis and dark respiration on rehydration of the lichen, Cladina mitis, and the influence of prior exposure to sulphur dioxide while desiccated
Authors: COXSON D. S. 
Published: April 2006

SUMMARYThe pattern of resaturation respiration and of rehydration recovery of net photosynthesis has been examined after pretreatment of desiccated thalli of the mat‐forming lichen species Cladina mitis (Sandst.) Hale & Culb, with sulphur dioxide. The recovery of photosynthetic activity lagged behind that of dark respiration in all treatments, pointing to the necessity of monitoring both processes when investigating rehydration phenomena. The exposure of desiccated thalli to sulphur dioxide concentrations of 0·2 and 1·0 μ11−1 (v/v in air) for periods of 2 and 3 weeks prior to rehydration resulted in the enhancement of subsequent photosynthetic activity in all treatments. These effects were greatest in the 0·2 μ11−1 treatment where, after 2 weeks fumigation, rates of net photosynthesis on recovery were nearly 40% higher than that of control replicates receiving no SO2. These results point to the importance of considering the effects of dry deposition on physiological processes and suggest that in some cases limited SO2 exposure may result in short‐term enhancement of photosynthetic uptake.
Increases in δ13 values of radish and soybean plants caused by ozone
Authors: GREITNER CAROL S. , WINNER WILLIAM E. 
Published: April 2006

SUMMARYThis greenhouse study was undertaken to determine whether changes in photosynthesis and conductance caused by air pollution also affected the δ13C value of plant tissue. Experiments with radish (Raphanus sativus L. cv. Cherrybelle) and soybean (Glycine max L. Merr. cv. Williams) exposed to ozone (O3) at 0.12 μl 1−1 showed significant growth reductions, 14–20 μl l−1 reductions in CO2 internal (C1), and + 0.3 to + 0.7% shifts in the δ13C values of leaves and roots. These results indicate that ambient (O3) may influence the δ13C values of plants found in many agricultural and industrial regions, and that O3 may act simultaneously to suppress growth and increase water use efficiency (WUE). Stable carbon isotope techniques may be useful for integrating the metabolic effects of O3 over long exposures to air pollution.
Oxalate salts in the leaves of plum (Prunus salicina L.) and cherry (P. avium L.)
Authors: SANCHEZ‐ALONSO F. , LACHICA M. 
Published: April 2006

SUMMARYChanges in the oxalate salts of plum (Primus salicina L., Golden Japan) and cherry (Prunus avium L., Napoleon) leaves have been studied over a single growing season. It has been shown that the oxalate content is higher in plum than in cherry trees; soluble oxalates are absent from the latter. In cherry trees all of the oxalic acid is precipitated as calcium oxalate. In plum trees, 2/3 of the content is present as calcium oxalate and the rest as potassium oxalate. The formation of calcium oxalate takes place in parallel with the formation and maturation of the fruit and ends once the fruit has been harvested. The substantial difference observed in oxalate content between the two species, despite their very similar total organic‐acid‐anion contents, indicates important differences in the mechanisms contributing to maintenance of charge balance.
Germination‐induced changes in acyl lipids and free sterols of olive pollen
Authors: RODRIGUEZ‐ROSALES M. P. , DONAIRE J. P. 
Published: April 2006

SUMMARYThe capacity of Olea europaea L. pollen grains to germinate has been studied. They germinated poorly when incubated in media with a pH higher than 5.55. However, germination was stimulated when a stream of air was passed through the incubation medium. Phosphatidylcholine, diacylglycerols, free fatty acids and triacylglycerols are the most abundant lipids in mature and germinated pollen. The level of diacylglycerol increases during germination while phosphatidylcholine, free fatty acids and triacylglycerols decrease, as compared with mature pollen. Overall, the fatty acid composition of mature pollen lipids is similar to that of germinated pollen. Compared to phospholipids and triacylglycerols, monoacyl‐, diacylglycerols and free fatty acids contain more laurate and myristate fatty acids. In relation to the amount of acyl lipids, free‐sterols are minor constituents of the lipid fraction from mature and germinated pollen, β‐sitosterol being the only significant component. The percentage of stigmasterol is significantly higher in mature than in germinated pollen.
The growth of dinoflagellates in laboratory cultures
Authors: DIXON G. K. , SYRETT P. J. 
Published: April 2006

SUMMARYThe growth rate ofAmphidinium carteraeHulburt in axenic culture was unaffected by gentle shaking (100 rpm); in contrast, growth rates ofAmphidinium klebsiiKof et Swezy,Scrippsiella trochoidea(Stein) Loeblich III andGyrodinium aureolumHulburt were lowered and the latter species was killed by shaking.Amphidinium carteraeandScrippsiella trochoideagrew taster under continuous illumination than under the two light/dark regimes tested. However, growth ofGyrodinium aureolumwas much slower under continuous illumination (0·15 divs d‐1) than in the photoperiods (0·21–0·36 divs d‐1). Growth rates ofAmphidinium carteraeaerated with elevated CO2(0·5% v/v) were saturated at a photon flux density of 80μE m‐2s‐1. Cells grown at the lowest irradiance used (15 μE m2s‐1) had the highest pigment (chlorophylla, cand carotenoids) per cell and the highest rate of photosynthesis both on a unit cell and a unit chlorophyll a basis. However, these cells showed no photoinhibition of photosynthesis when rates were measured at photon flux densities up to 150 μE m‐2s‐1.Culture filtrates failed to support any further growth ofA. carterae, S. trochoideaorO. aureolumwhen reinoculated with the same dinoflagellate species. However, the growth ofA. carterae, but not that of the other two species, resumed when fresh nutrients were added to culture filtrates.Cell yields ofA. carteraewere increased by over 50% by doubling the nutrient addition to be medium. The nutrient responsible for this increase appears to be nitrate. Nitrate and arginine were also good sole nitrogen sources for the growth ofA. carterae. However, ammonium supplied at the same concentration (1 mg atom N NI‐1) was toxic; growth was slower, motility was impaired and cells become enlarged and rounded. Lowering the ammonium concentration to 0·2 mg atom N 1‐1restored growth and cellular morphology to normal.
Ethylene and the responses of roots of maize (Zea mays L.) to physical impedance
Authors: MOSS G. I. , HALL K. C. , JACKSON M. B. 
Published: April 2006

SUMMARYThe response of the roots of maize seedlings to physical impedance was studied in glass chambers that enabled oots to be grown either unimpeded or in loosely packed small glass spheres (ballotini) and flushed with humidified iir or other gas mixtures. Impedance decreased root length when measured after approximately 40 h by 30‐60% and increased root diameter 10 cm behind the tip by a similar percentage. Fresh weight was reduced by up to 28‐40% while ethylene evolution from roots was increased 2‐ to 2·5‐fold. Supplying ethylene (5‐13 μl 1‐1) in the air flow to unimpeded roots simulated closely the effects of impedance.The volatile inhibitor of ethylene action, 2,5‐norbornadiene (approx. 900μl 1‐1), overcame the effects of ethylene (5·4 μl 1‐1) completely, but the growth of impeded roots was unchanged by norbornadiene. Similarly, aminoethoxyvinylglyeine ((0·5‐0·75 mmol M‐3) inhibited endogenous ethylene formation, but did not modify the growth responses of roots to impedance, even though ethylene production was suppressed to rates well below those of unimpeded roots. The concentration of abscisic acid was not affected by impedance.It is concluded that despite a widespread view to the contrary, ethylene is not the cause of the morphological ‐esponse of roots to physical impedance. Abscisic acid is also unlikely to be involved.
Authentic activity of the ethylene‐forming enzyme observed in membranes obtained from kiwifruit (Actinidia deliciosa)
Authors: MITCHELL THOMAS , PORTER ANDREW J. R. , JOHN PHILIP 
Published: April 2006

SUMMARYMembrane vesicles in the juice squeezed from the pericarp of ripe kiwifruit [Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson, formerly Actinidia chinensis Planch.] possess an activity of the ethylene‐forming enzyme which showed the essential features of the in vivo enzyme: a preference for the racemic mixture containing the (IR, 2S)‐enantiomer of 1 ‐amino‐2‐ethylcyclopropanc‐ 1 ‐carboxylic acid; a relatively high affinity for the natural substrate 1‐aminocyclopropane‐ 1 ‐carboxylic acid (Km of 125μM); only partial inhibition by excess eatalase and mM concentrations of FDTA, dithiothreitol and ascorbate. During post‐harvest ripening enzyme activity assayed in vitro developed in parallel with enzyme activity assayed in vivo. The kiwifruit enzyme was sensitive to salicylhydroxatnic acid and to a loss of structural integrity of the membrane vesicles. Although only 0·% of the activity measurable in vivo was recovered in vitro. the kiwifruit membranes provide a useful, easily prepared system for studying the ethylene‐forming enzyme in vitro.
Inoculation of mycelial cord‐forming basidiomycetes into woodland soil and litter II. Resource capture and persistence
Authors: DOWSON C. G. , RAYNER A. D. M. , BODDY LYNNE 
Published: April 2006

SUMMARYSubstantial mycelial cord systems of Hypholoma fasciculare (Huds. ex Fr.) Kummer, Phallus impudicus (L.) Pers., Phanerochaete (Ph.) velutina (DC ex Pers.) Parmasto, Phanerochaete laevis (Fr.) Erikss. & Ryv. and Steccherinum fimbriatum (Pers. ex Fr.) Erikss. had developed 2 years alter direct inoculation into the soil and litter of a range of woodland sites. Where species had been inoculated individually, the distribution patterns of the cord systems were strongly related m the availability and colonizability of various litter components. Where different species were co‐inoculated in columns and rows 14 × 17 cm apart. Ph. velutina frequently replaced the other species, forming extensive mycelial systems and bringing about considerable decay of the original inocula. However, established systems of S. fimbriatum often developed in close proximity to Ph. velutina. Where inoculum blocks were implanted amongst litter containing few available resources for colonization, outgrowth was strongly directed along rows of nearest‐neighbouring blocks.
The effect of the fungus, Balansia cyperi Edg., on growth and reproduction of purple nutsedge, Cyperus rotundus L.
Authors: STOVALL MARY E. , CLAY KEITH 
Published: April 2006

SUMMARYTwo growth trials were conducted in the greenhouse to determine the effects of the systemic clavicipitaceous fungus, Balansia cyperi Edg, on growth and tuber production of purple nutsedge (Cyperus rotundus L.). In the field, tubers collected from populations of infected plants were significantly smaller than tubers from populations of uninfected plants. There were no differences in percentage of tubers sprouting, or in time to sprouting, between infected and uninfected tubers collected and planted in the greenhouse in September 19S5. Infected tubers collected and planted in January 1986 showed significantly decreased percentage sprouting, and increased time to sprouting, compared with uninfected tubers. In both trials, after correcting for differences in initial tuber size, vegetative tiller (shoot) number increased and inflorescence number decreased for infected purple nutsedge compared to uninfected purple nutsedge. Plants were harvested after 20 weeks in the second trial. Total dry weight of infected plants was greater than total dry weight of uninfected plants, but ratios of below‐ground: above‐ground dry weight were the same. Infected plants produced significantly more, but smaller, tubers than uninfected plants. Greater vegetative growth and production of more tubers may provide and advantage to infected purple nutsedge in mixtures with uninfected plants and other plant species.
A pollen diagram from an interglacial deposit at Trysull, Staffordshire, England*
Authors: MORGAN A. V. , WEST R. G. 
Published: April 2006

SUMMARYA pollen diagram from freshwater sediments resting on glacio‐fluvial outwash at Trysull, Staffordshire, England shows a sequence relating to the development of temperate stage forest. Correlation with a nearby Hoxnian site at Nechells, Birmingham is suggested.
Cell expansion rate, temperature and turgor pressure in growing leaves of Lolium temulentum L.
Authors: THOMAS A. , TOMOS A. D. , STODDART J. L. , THOMAS H. , POLLOCK C. J. 
Published: April 2006

SUMMARYLeaf growth rate and the turgor pressure of cells in the expanding zone of leaves of Lolium temulentum were measured simultaneously. Growth rate was reduced over a range from 30μm min−1 to zero by reducing the temperature of the expanding zone from 20 to 2 °C. Turgor pressure remained constant at 05 MPa. This implies that growth reduction by low temperature is due to changes in cell wall rheology. Cell membrane hydraulic conductivity (Lp) was reduced with temperature as expected, but this was not sufficient to influence growth rate detectably.
The level of injury and needle ultrastructure of acid rain‐irrigated pine and spruce seedlings after low temperature treatment
Authors: REINIKAINEN JAANA , HUTTUNEN SATU 
Published: April 2006

SUMMARYFrost injury in three Finnish provenances of acid rain‐treated (pH 4 and 3) pine [Pinus sylvestris (L.)] and spruce [Picea abies (L.) Karst.] seedlings was studied by microscopical methods. Seedlings from southern and northern provenances were watered for seven weeks with artificially acidified rain during the hardening period in 1986. A cold treatment on the winter hardened seedlings was carried out in January by lowering the temperature gradually to −55°C. Afterwards the development of injury symptoms was followed visually and microscopically. The most prominent sign of freezing injury was needle discoloration. In addition, the stems and buds of the seedlings showed signs of severe injury. Under the light microscope the injury was exhibited as largened intercellular spaces and increased numbers of disintegrating cells. Diminution of the membraneous structures within the cytoplasm of mesophyll cells and rupturing of plasmalemma and tonoplast, as well as swelling of chloroplasts, were seen in damaged cells. The symptoms of freezing injury at ultrastructural level differed from those found in needles exposed to air pollutants.