bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature effects on partitioning of 14C assimilates in tall fescue (Festuca arundinacea Schreb.)
Authors: PRUD'HOMME M. P. , GASTAL F. , BELANGER G. , BOUCAUD J. 
Published: April 2006

SUMMARYFructan synthesis and carbon partitioning to roots of tall fescue (Festuca arundinacea Schreb.) were studied with a 14C‐labelling technique at three growth temperatures: 24/17 °C, 16/10 °C and 8/5 °C (day/night). Plants at 16/10 °C and 8/5 °C had an increased proportion of assimilates allocated to the root system; 10 d after exposure at 14CO2, the relative carbon partitioning to the roots averaged 12.5, 16.3 and 26.8 % respectively, at 24/17 °C, 16/10 °C and 8/5 °C. Chilling temperatures induced an increase in the amounts of sucrose and fructans in leaves. Interestingly, a similar pattern occurred in roots where low‐DP fructans (DP < 8) are the predominant non‐structural carbohydrate constituent. Incorporation of 14CO into root oligo‐ and polysaccharides showed a progressive movement of radioactivity from sucrose to fructans. These results show that the roots can serve as a carbon storage organ and that fructan synthesis depends on sucrose supply. The function of the fructan stored in the roots is unknown.
The uptake of glucose, fructose and sucrose into the lower epidermis of leaf discs of pea (Pisum sativum L. cv. Argenteum)
Authors: AKED J. , HALL J. L. 
Published: April 2006

SUMMARYThe pea mutant, Pisum sativum L. cv. Argenteum, has been used to investigate the sugar uptake characteristics of leaf epidermal tissue. The uptake rates from either 1 mol m−3 glucose, fructose or sucrose into whole leaf discs of cv. Argenteum and of P. sativum cv. Onward were very similar; uptake was linear over a 3 h period, with glucose taken up faster than the other two sugars in both cultivars. A similar pattern for uptake was observed into the lower epidermis of cv. Argenteum. Furthermore, uptake from 1 mol m−3 3‐O‐methylglucose was markedly slower than from 1 mol m−3 glucose. The epidermal tissue showed some day to day variation in uptake rates; however, the basic pattern of uptake was consistent. Kinetic analysis of sugar uptake revealed the presence of two transport components. At concentrations greater than 1 mol m−3 a linear component predominated with fructose entering the epidermis faster than glucose and sucrose. An increase in the pH of the exogenous medium from 5 to 8 caused a slight but steady drop in the rate of uptake of glucose, fructose and sucrose; glucose uptake had a pH optimum of about 5. Glucose and fructose competed with one another and also with sucrose for uptake into the epidermis. Sucrose was not, however, an effective competitor against glucose and fructose. The uptake of glucose, fructose and sucrose was inhibited by about 20–30 % by 0.05 mol m−3 erythrosin B and 1 mol m−3 parachloro‐mercuribenzene sulphonic acid (PCMBS). Carbonyl cyanide m‐chlorophenylhydrazone (CCCP) at 0.05 mol m−3inhibited the uptake of glucose and fructose (60–70%) but did not substantially inhibit sucrose uptake.
Effect of powdery mildew infection on concentrations of apoplastic sugars in pea leaves
Authors: AKED J. , HALL J. L. 
Published: April 2006

SUMMARYIntercellular washing fluid (IWF) was extracted by centrifugation from healthy and mildew‐infected pea leaves. The level of cytoplasmic contamination of the IWF was estimated to be 0.3% for healthy leaves and 0.7% in mildew‐infected leaves as assessed by the presence of malate dehydrogenase activity. The IWF was analyzed for sugars using gas liquid chromatography and the glucose oxidase assay. Changes in the concentrations of glucose, fructose and sucrose showed different trends over an infection time course. Glucose and sucrose concentrations fluctuated over the 7 d period following infection but almost always showed higher levels in infected tissues than in the controls. Fructose concentrations were low and showed a greater increase over 7 d in infected compared to healthy leaves. The pattern of efflux of sucrose from pre‐loaded healthy and mildew‐infected pea leaf discs suggests that the plasma membranes of cells from infected pea leaves might be more leaky than those of healthy pea leaves. The implications of apoplastic sugar levels for nutritional aspects of the plant‐pathogen interaction are discussed.
Effects of amino acids and sugars on zoospore taxis, encystment and cyst germination in Pythium aphanidermatum (Edson) Fitzp., P. catenulatum Matthews and P. dissotocum Drechs.
Authors: DONALDSON S. P. , DEACON J. W. 
Published: April 2006

SUMMARYNineteen L‐amino acids, the corresponding D‐amino acids and 10 sugars were tested as elicitors of zoospore taxis, encystment and cyst germination in Pythium aphanidermatum (Edson) Fitzp., P. catenulatum Matthews and P. dissotocum Drechs. Selected compounds were also tested for promotion of germ‐tube growth and competition in zoospore taxis. Each fungus responded to a different spectrum of compounds at different stages of development; for example, in P. aphanidermatum L‐glutamine elicited taxis but not germination, whereas glucose elicited germination but not taxis. At each stage of development the fungi showed common responses to some compounds but different responses to others. For example, all fungi showed positive taxis to L‐aspartic acid, L‐asparagine, L‐glutamic acid, L‐glutamine and L‐alanine, but differed in taxis to sugars. Nevertheless, all three fungi responded to the same broad range of compounds at one stage or another. The compounds that elicited germination did not always promote growth, and D‐amino acids had no effect at any stage, indicating that taxis, encystment and germination were receptor‐mediated. However, some non‐attractant amino acids interfered with chemotaxis, to different degrees in the three fungi.The findings are discussed in relation to host‐location mechanisms, including host‐differential taxis to roots. Variations in chemoresponses of Pythium are suggested to involve receptors for a common range of compounds, differentially active at different stages of the pre‐infection sequence.
The development of endomycorrhizal root systems
Authors: AMIJEE F. , STRIBLEY D. P. , TINKER P. B. 
Published: April 2006

SUMMARYConcentrations of phosphorus in shoot and soluble carbohydrates (fructose, glucose, sucrose and fructans) in root were measured in non‐mycorrhizal and vesicular‐arbuscular (VA) mycorrhizal (Glomus mosseae) leek plants (Allium porrum) raised at six concentrations of soil phosphate. In conditions when an increased concentration of soil phosphate reduced VA mycorrhizal infection, the concentrations of soluble carbohydrates in the root were at a maximum. Therefore the hypothesis that greater concentrations of soluble carbohydrates in roots favour VA mycorrhizal infection is discounted. There was a specific effect of VA mycorrhizas, in that infected roots contained a larger concentration of sucrose than did uninfected roots, in plants with similar phosphorus concentrations in dry matter of shoots.We conclude, first, that increased phosphorus supply from either phosphate addition to soil or VA mycorrhizal infection increases concentration of soluble carbohydrates in leek roots and, secondly, that the VA mycorrhizal root behaves as a particularly strong physiological sink when there is an excess concentration of sucrose in the host.
Mineral nutrition in the tripartite interaction between Frankia, Glomus and Alnus at different soil phosphorus regimes
Authors: JHA D. K. , SHARMA G. D. , MISHRA R. R. 
Published: April 2006

SUMMARYPhosphate uptake by a tripartite association involving Frankia, Glomus and Alnus was studied in containerized seedlings of Alnus nepalensis D. Don. The response of non‐mycorrhizal plants to P fertilization was more pronounced than their mycorrhizal counterparts. The yield of nodulated mycorrhizal plants was greater at low than at high P doses. At the highest P application, however, reduction in nodulation as well as nitrogenase activity was observed. Mycorrhizal infection was reduced by phosphate application, but markedly stimulated nodulation in Alnus seedlings. The nitrogen content of the nodule was higher than that of the shoot of nodulated mycorrhizal plants. Nodule dry weight, nitrogenase activity and nodule nitrogen content increased with increase in P application up to quantities typical of those in soil, after which it declined.
The effects of cadmium on ectomycorrhizalPinus sylvestrisL.
Authors: COLPAERT JAN V. , VAN ASSCHE JOZEF A. 
Published: April 2006

SUMMARYThe toxicity of a sublethal cadmium concentration to ectomycorrhizalPinus sylvestrisL. seedlings was studied. Nine mycorrhizal strains, collected from a Zn‐ and Cd‐polluted soil or from an unpolluted area, were compared for their ability to increase Cd tolerance in their host plant. Plants were cultivated in a semi‐hydroponic system that allowed visual observation of the root systems. The degree of soil colonization as well as the density of the extramatrical mycelium was determined. The water use of the host plants was carefully monitored during the treatment period. Cadmium concentrations were determined in all plant parts. Although Cd addition resulted in decreases in transpiration in the non‐mycorrhizal plants, disturbances in water relations could be more or less pronounced in the mycorrhizal pines. The treatment strongly influenced the growth of the fungi in the substrate: several mycobionts hardly survived in the polluted substrate. Fungi producing a large mycelial biomass showed the greatest effect in overcoming toxicity. Some s trains were even able to increase their turnover growth when treated with cadmium. In a dense extramatrical mycelium the potential for Cd retention increases, while the individual hyphae are exposed to a lower Cd concentration than in a sparse mycelium. A protective effect against cadmium toxicity in the host was observed with all mycobionts, since Cd uptake was highest in the non‐mycorrhizal seedlings. The treatment had no effect on the growth of the seedlings or on the concentrations of the other cations, probably due to the relatively low toxicity and the relatively short observation period. The results are discussed in relation to thein vitroCd tolerance of the fungi.
Interacting effects of ozone and water stress on the stomatal resistance of beech (Fagus sylvatica L.)
Authors: PEARSON M. , MANSFIELD T. A. 
Published: April 2006

SUMMARYThree‐year‐old beech trees were exposed to episodes of ozone pollution over a period of 128 d beginning in May 1991. The episodes were artificially created to correspond with the meteorological conditions under which ozone pollution normally occurs. The target concentrations were 60, 80, 100 and 120 ppb, and the cumulative dose was slightly greater than that in the UK at the present time, but not above that on parts of the European mainland.The effects of ozone on stomatal behaviour were observed both for trees that were well watered and others that were deprived of water for a period of time. In the well‐watered trees there was increased stomatal resistance in the presence of ozone, but in the unwatered trees ozone reduced the increase in stomatal resistance that occurred as water stress developed. These data suggest that the effects of ozone on beech might be deleterious in two respects: (1) when the trees are well supplied with water there may be reduced CO2 uptake for photosynthesis; (2) if the stomata remain partially open when drought occurs, it may be difficult for the trees to control their water economy at critical times.It is emphasized that these findings apply to young trees under semi‐controlled conditions, and further research will be needed to explore the responses of mature trees in the field.
Absorption of nitrogen dioxide by barley in open‐top chambers
Authors: JENSEN E. S. , PILEGAARD K. 
Published: April 2006

SUMMARYFoliar absorption of nitrogen dioxide in barley (Hordeum vulgare L.) exposed to mean NO2 concentrations of 4 and 37 ppb was studied in open‐top chambers. The possible compensation for insufficient supply of nitrogen in the growth medium by increased uptake of NO2 from the air was investigated by growing plants with sub‐optimal and optimal N supply. The amount of NO, derived from fumigation was estimated using the 15N dilution technique, in which the nitrogen derived from the growth medium was labelled with 15N. The absorption of NO2‐N from polluted air contributed 5–6% of the total N. An additional 3–5% was derived from other N sources, probably also of gaseous origin. Thus, total absorption from gaseous sources in the NO2‐fumigated plants was estimated to be approximately 10% of total N. The amount absorbed from aerial sources was proportional to the top weight. The amount of NO2 absorbed was highest in the plants with optimal N supply. However, in plants grown with sub‐optimal N, there was a relatively higher contribution to total N from the NO2‐N.
Effect of polyamine biosynthesis inhibitors on mycelial growth and concentrations of polyamines in Ophiostoma ulmi (Buism.) Nannf.
Authors: BIONDI S. , POLGROSSI I. , BAGNI N. 
Published: April 2006

SUMMARYSeveral inhibitors of polyamine biosynthesis reduced mycelial growth of the fungus Ophiostoma ulmi (Buism.) Nannf. cultured on malt extract‐agar medium. Growth inhibition was particularly evident when expressed in terms of fresh weight rather than colony diameter. Of the different drugs tested, the most effective was difluoromethylarginine (DFMA), while difluoromethylornithine (DFMO) and methylglyoxal(bis)guanyl‐hydrazone (MGBG) plus cyclohexylamine (CHA) reduced growth only by 75 and 62% respectively. The growth inhibition by DFMO + DFMA, measured as colony diameter, was apparently reversed by putrescine (PUT), but not when expressed in terms of fresh weight. Spermidine (SPD) was the most abundant polyamine in control cultures, followed by PUT and spermine (SPM). PUT was no longer detectable 8 d after inoculation. On day 10, DFMO and DFMA, alone and in combination, caused a significant reduction in cellular SPD concentrations, while exogenously supplied PUT restored the levels of this polyamine to control values. MGBG + CHA caused a conspicuous accumulation of PUT and an approximately 50% reduction in SPD titres. DFMA, alone or in combination with DFMO and with or without PUT, led to increased cellular levels of SPM. The latter polyamine, but not PUT or SPD, strongly retarded growth when added to the growth medium. As suggested by the effectiveness of DFMA in inhibiting growth, arginine decarboxylase activity was shown to be prevalent over ornithine decarboxylase activity in this fungus.
Interactions between callus cultures of European beech, indigenous ascomycetes and derived fungal extracts
Authors: HENDRY S. J. , BODDY LYNNE , LONSDALE D. 
Published: April 2006

SUMMARYAscomycete fungi from the Xylariaceae and Diatrypaceae responded in three distinct ways when grown in dual culture with callus material of beech (Fagus sylvatica L.). Growth of the putative weak pathogens Biscogniauxia nummularia (Bull.) O. Kuntze and Eutypa spinosa (Pers.) Tul. & C. Tul. was stimulated whilst the saprotrophs Ustulina deusta (Hoffm.) Lind. and Xylaria polymorpha (Pers.) Grev. were unaffected by the presence of callus. Sapwood‐colonizing fungi displayed a range of responses, with Diatrype stigma (Hoffm.) Fr. being unaffected, Diatrype disciformis (Hoffm.) Fr. stimulated, and Hypoxylon fragiforme (Pers.: Fr.) Kickx and ‘Hypoxylon purpureum’ inhibited by the presence of callus. Changes in morphology were evident in many of the fungi during interactions, with yeast‐like forms being produced by those members of the Xylariaceae which have been recognized as endophytes. Reciprocally, high concentrations of cell free extracts of some of the Xylariaceous fungi resulted in necrosis or inhibition of callus growth, while at sub‐lethal concentrations marked stimulation of growth was evident. The importance of these results with respect to pathogenicity testing and elucidation of the biology of tree–fungus interactions is discussed.
The fructosyltransferase of Streptococcus salivarius
Authors: JACQUES NICHOLAS A. 
Published: April 2006

SUMMARYThe nature of the fructans produced by oral streptococci and the β‐D‐fructosyltransferases (FTFs) that synthesize them from sucrose are considered in this review. Models for the apparent unique surface expression and secretion of the FTF produced by Streptococcus salivarius are discussed in light of recent evidence obtained from the cloning and sequencing of the ftf from this organism.
Purification and some properties of fructan: fructan fructosyl transferase from dandelion (Taraxacum officinale Weber)
Authors: LÜSCHER M. , FREHNER M. , NÖSBERGER J. 
Published: April 2006

SUMMARYA fructan: fructan fructosyl transferase (FFT, EC 2.4.1.100) was purified 61‐4‐fold from roots of Taraxacum officinale Weber. The enzyme is a glycoprotein with an apparent molecular weight of 49000 as determined by SDS‐polyacrylamide gel electrophoresis. FFT activity was detected by 1‐kestose‐dependent nystose production. The enzyme was most active at pH 6·5 and was stable at 30°C (1 h). Separation by preparative iso‐electric focusing yielded four different forms with iso‐electric points around pH 4·8. The purified enzyme was active on different oligofructans of the inulin series, but not on melezitose, 6‐kestose, neokestose, maltopentaose or sucrose as the sole substrate.
Fructan‐hydrolyzing activities from Lolium rigidum Gaudin
Authors: BONNETT G. D. , SIMPSON R. J. 
Published: April 2006

SUMMARYFructan‐ and sucrose‐hydrolyzing activity was extracted from plants of Lolium rigidum Gaudin. Sucrose‐hydrolyzing activity varied 30‐fold between different plant parts and parts of different ages. In contrast, fructan‐hydrolyzing activity only varied two‐fold. At least four β‐fructofuranosidase activities were partially purified from mature vegetative tissues of Lolium rigidum. The β‐fructofuranosidases were characterized by their different elution patterns on various chromatographic media and their relative rates of hydrolysis of sucrose and fructan extracted from different sources. Fructan‐hydrolyzing activities were partially purified that hydrolyzed fructan containing predominantly 2–1 glycosidic linkages relatively more rapidly than fructan containing predominantly 2–6 glycosidic linkages. β‐fructofuranosidases that were relatively more active against fructan than sucrose when compared with activity present in the crude extract, were inhibited by sucrose. It is concluded that it is necessary to use appropriate fructan substrates and to consider the possible involvement of all β‐fructofuranosidase activities in hydrolysis of fructans in grasses.
Effects of soil temperature and nitrogen status on kinetics of 15NO3− uptake by roots of field‐grown Agropyron desertorum (Fisch. ex Link) Schult
Authors: BASSIRIRAD HORMOZ , CALDWELL MARTYN M. , BILBROUGH CAROL 
Published: April 2006

SUMMARYPlant NO8‐ acquisition is largely determined by root uptake capacity. Although root uptake capacity has been shown to be sensitive to both root temperature and previous nitrogen (N) supply in hydroponic systems, the uptake capacity response to similar environmental factors under field conditions has not been investigated. Using 15NO3−, root uptake capacities were determined in excised roots of Agropyron desertorum (Fisch. ex Link) Schult grown in the field at two soil temperatures and two N fertilization treatments. Variation in soil and root temperatures was achieved by application of clear plastic film or insulating mulch to the soil immediately around the target plants. Uptake rates were measured at six different assay solution concentrations (from 1 to 1000 μM external 15NO3− concentration range). Two months after the imposition of soil N and temperature treatments, a biphasic transport system (a high‐affinity) saturable phase and a low‐affinity transport phase) was apparent in low N‐treated plants. Nitrate uptake capacity in the low‐concentration range (1–500μM) was significantly reduced in N‐fertilized plants compared with unfertilized control plants and the effect was more pronounced at high (27 °C) than low (17 °C) soil and assay temperatures. Furthermore, high soil N status inhibited the expression of a low‐affinity NO3− transport system which was clearly apparent at external NO3− concentration ranges between 500 and 1000 mM in plants grown at low soil N. Prior soil N and temperature history may ultimately determine root ability to exploit NO3− flushes which can result from changes in soil environmental conditions.
Hydraulic conductivity and anatomy along lateral roots of cacti: changes with soil water status
Authors: HUANG BINGRU , NOBEL PARK S. 
Published: April 2006

SUMMARYTo help understand root function for desert plants at different levels of water availability, cellular and water‐conducting properties were examined for young lateral roots of Ferocactus acanthodes (Lem.) Britton & Rose and Opuntia ficus‐indica (L.) Miller. Hydraulic conductivity (Lp), radial conductivity (LR), and axial conductance (Kh) were determined for root segments in wet soil, during drought, and after rewetting. All three parameters increased with distance from the root tip under wet conditions and during drought for both species, with larger increases occurring under wet conditions. Lp decreased with drought duration up to 35 d for both species, due to dehydration of cortical cells, suberization of periderm, and embolism of xylem vessels; Lp and LB decreased more for O. ficus‐indica, and Kh decreased more for F. acanthodes. The increase in Kh with distance from the root tip and the decrease with duration of drought were associated with the changes in the number of conducting xylem vessels. After 7 d of rewetting, new secondary lateral roots developed, enhancing water uptake, especially for O. ficus‐indica. Rewetting also caused water uptake for primary lateral roots to return to approximately the original value under wet conditions, mainly because decreases in emboli led to recovery of axial flow.
Survival of Acer pseudoplatanus L. (sycamore) seedlings on metalliferous soils
Authors: TURNER ANDREW P. , DICKINSON NICHOLAS M. 
Published: April 2006

SUMMARYSeeds and seedlings of Acer pseudoplatanus L. (sycamore) were collected at sites contaminated by metals, originating either from mining spoil or from aerial deposition from metal processing industry, and at a number of relatively uncontaminated sites. Seedling growth was examined in relation to site of origin, both in nutrient solutions with elevated metal concentrations and in reciprocal transplant experiments in soils from the sites. Metal tolerance was not detected and there was no significant difference between plants from the different sites of origin. It was found, however, that roots could proliferate in uncontaminated zones of the soil and that, even in contaminated soils, most seedlings used in growth tests survived for at least three years despite impaired growth. Seedlings growing at the contaminated sites showed phytotoxic symptoms associated with high metal levels, but apparently healthy seedlings and saplings of different ages were also found. Some form of low level innate tolerance may be involved but it is suggested that phenotypic plasticity is more important than previously thought, potentially allowing survival until favourable conditions are encountered either temporally or spatially.