bluuebunny/crossref_metadata_2025 huggingface dataset:
New pollen‐analytical researches in Corsica: the problem of Quercus ilex L. and Erica arborea L., the origin of Pinus halepensis Miller forests
Authors: REILLE MAURICE
Published: April 2006

The pollen‐analytical study of eight sites (two glacial lakes and six coastal marshes) has been carried out (nine pollen diagrams, 472 pollen spectra). The total absence of Quercus ilex forest in Corsica during the Atlantic and the vegetation contrast existing at that time between the western and the eastern sides of the island are demonstrated. On the western site, Erica arborea constituted the only regional vegetation from the coast up to about 1500 m. Human action is responsible for the establishment of Quercus ilex in this climax vegetation during the Sub‐boreal. It is also shown that the only Pinus halepensis forest present today in Corsica has been introduced on the island during the nineteenth century.
The anthocerote chloroplast: a review
Authors: VAUGHN KEVIN C. , LIGRONE ROBERTO , OWEN HEATHER A. , HASEGAWA JIRO , CAMPBELL ELLA O. , RENZAGLIA KAREN S. , MONGE‐NAJERA JULIAN
Published: April 2006

This review covers previous data, together with new information from our laboratories, on the subject of the anthocerote chloroplast. Unlike all other archegoniates, most species of anthocerote have pyrenoids in their chloroplasts. The pyrenoid is the site of accumulation of the first enzyme in the C3 photosynthetic cycle, ribulose bispbosphate carboxylase/oxygenase. Unlike most algae, the hornwort pyrenoid is composed of distinct subunits, numbering up to several hundred. Pyrenoid morphology is quite variable among the genera in shape, fine structure, and distribution of inclusions. Another unique feature of the anthocerote chloroplast is the presence of thylakoids that connect adjacent granal stacks at right angles to the long axis of the granum (so‐called channel thylakoids), resulting in a 'spongy’arrangement of the thylakoid system. The granal stacks of anthocerotes are like the‘pseudograna’of green algae because they lack the highly‐curved end membranes typical of all other embryophytes. The channel thylakoids are enriched in photosystem (PS) I and the grana are enriched in PS II. The chloroplast envelope is a double membrane structure with regions of appression, much like that of other green plants. The apieal cell of the gametophyte contains chloroplasts similar to the mature chloroplasts of the thallus, although certain gametophytic tissues may contain underdeveloped plastids. Chloroplasts in cells around Nostoc colonies and in cells invaded by mycorrhizal fungi have thylakoids mainly in pairs, and small or absent pyrenoids. A number of similarly reduced plastids are noted in the placental cells at the sporophyte/gametophyte junction and in developing spores. The greatest reduction is observed in spermatid cell plastids, which at maturity consist of only a small starch grain surrounded by the envelope. Chromoplast‐like organelles are found in the cells of the antheridial jacket in some genera; these contain numerous osmiophilic globules that are probably pigment aggregations. Colourless bead‐like plastids occur in the rhizoids; these seem to develop by fragmentation of the single chloroplast in the rhizoid initials, concomitant with the loss of chlorophyll. Chloroplast division is a tightly controlled process and, in uniplastidic species, always occurs just before nuclear division, with the participation of a unique system of chloroplast‐associated microtubules. The number of chloroplasts per cell is quite variable in some genera, although most species have but a single chloroplast in each cell of the gametophyte. Chloroplast shape is also variable from ellipsoidal, dumbbell‐shaped, to irregular. These data indicate that the anthocerote chloroplast is unique among the embryophytes and are in line with the notion of an isolated position in the plant kingdom. Certain features of chloroplast morphology appear to be typical of certain genera and might prove useful in taxonomic decisions at the generic level.
Symplastic transport of Lucifer Yellow in mature leaf blades of barley: potential mesophyll‐to‐sieve‐tube transfer
Authors: FARRAR JOHN , SCHOOT CHRIS van der , DRENT PETER , van BEL AART
Published: April 2006

Intermediate veins of mature barley leaves were exposed by partial enzymic removal of mesophyll cells. Lucifer Yellow was iontophoresed into a variety of cell types and its symplastic transfer followed by fluorescence microscopy. Dye transfer from mesophyll cells into the parenchymatous bundle sheath (PBS) and from PBS to mestome sheath (MS) occurred readily. Dye transfer around and along both PBS and MS was rapid. Following injection into PBS or MS dye could be seen moving within sieve tubes, thus providing a demonstration of potential mesophyll‐to‐sieve tube transfer.
Regeneration of the discrete root epidermis of Pistia stratiotes L. after perturbation of the meristem
Authors: CLOWES F. A. L.
Published: April 2006

Perturbation of meristems of adventitious roots of Pistia resulted in abnormal patterns of cell division in the quiescent centre including the pole of the normally discrete epidermis. Two of the methods used, radiation from incorporated tritiated thymidine and cold treatment, also produced abnormal patterns in the lateral primordial present within the apices of the adventitious roots. Cells of the monostromatic epidermal shell divided periclinically in some roots and some primordia where all previous divisions would have been anticlinal. In other meristems, the normally quiescent cells of the stelar and cortical poles grew and divided to displace the former epidermal pole and cap initials.

Recovery from the perturbation resulted in the organization of a meristem which assembled a new monostromatic epidermal layer apparently discrete from the new cap initials below and the new cortical pole cells above. The new epidermal pole formed continuously with the old and, though the pattern of planes and rates of mitosis initiating and maintaining it must be determined as in normal ontogeny, some additional influence of the epidermis left intact above the region of abnormal activity appears to operate.
Increased photosynthesis and resistance to rust infection in upper, uninfected leaves of rusted broad bean (Vicia faba L.)
Authors: MURRAY D. C. , WALTERS D. R.
Published: April 2006

Photosynthesis and resistance to rust infection were studied in upper, uninfected leaves of broad bean, Vicia faba L., where the lower two leaves were infected with rust, Uromyces viciae‐fabae (Pers.) Shroet. Following inoculation of the lower leaves, rates of net photosynthesis were significantly increased in the upper, uninfected, fully‐developed leaves and the young developing leaves, compared to controls. In contrast, photosynthesis was substantially reduced in the lower, rusted leaves. When 14CO2 was fed to the upper, uninfected leaves of rusted plants, there was a considerable increase in labelled assimilate in those leaves, compared to controls. In addition, there was substantial movement of labelled assimilate into lower, rusted leaves, into young, developing leaves and into roots. On the other hand, there was a substantial reduction in labelled assimilates moving into shoot apices.

Upper, uninfected leaves of rusted beans exhibited Increased resistance to rust infection. Thus, the percentage leaf area covered with rust and the number of pustules per cm2 were reduced in these leaves compared to controls. This resistance to rust infection was greatest when the upper leaves were challenged 1 d after inoculation of the lower leaves with rust and decreased with increasing time after inoculation of the lower leaves. Young, developing leaves on rusted beans also exhibited increased resistance to rust infection. When photosynthesis in the upper leaves was reduced to near control values or well below control values by shading, resistance to rust infection in those leaves was also reduced, although not in proportion to the reduction in photosynthesis. It is suggested that the increased photosynthesis in upper, uninfected bean leaves probably facilitates maximum expression of resistance to infection in those leaves.
Amino acid and amide metabolism in the hulls and seeds of developing fruits of garden pea, Pisum sativum L.
Authors: Aspartate V. , MURRAY DAVID R.
Published: April 2006

Pea plants (Pisum sativum L. cv. Melbourne Market), each with a single developing pod, were pulse‐fed [4‐14C]aspartate through the cut stem at stages from 11 to 32 d after full blossom. The distribution of radioactivity in soluble metabolites of the hull, seedcoats, embryo sac liquid and embryo was determined by 2‐dimensional paper chromatography and radioautography after feeding intervals of 6 h, 24 h or 48 h. At the earliest stage, radioactivity was recovered mainly in sucrose, serine, homoserine and threonine in the hull. At the 15‐16 d stage, threonine became the major derived amino compound secreted into the embryo sac, and sucrose became the predominant derivative recovered from both hull and seed tissues. Stem‐fed aspartate can therefore be transferred to stem phloem, and sucrose synthesized from aspartate in stems and leaves can be transferred to phloem in both organs.
Transfusion tissue of pine needles as a site of retrieval of solutes from the transpiration stream
Authors: CANNY M. J.
Published: April 2006

The fluorescent tracers sulphorhodamine G (SR) and pyrene trisulphonate (PTS) were used to explore the functions of cells and tissues within the pine needle, following their progress after feeding through the transpiration stream. The distributions of tracer in the needles were stabilized for fluorescence microscopy by rapid freezing and freeze‐substitution, and anhydrous embedding and sectioning. After short pulse + chase times (up to 2 h), SR and PTS accumulated at higher‐than‐xylem concentrations in the transfusion tracheids on the flanks of the vascular strand, but did not pass out through the endodermis. The accumulations occurred locally where the transpiration water was separated from the tracers and passed into the symplast of the transfusion parenchyma and endodermis. After a 24 h water chase, SR had entered the symplast through the transfusion parenchyma, and spread through the endodermis and palisade. It is argued that this is evidence of active H+‐ATPase systems lowering the external pH of the transfusion parenchyma, and characterizes these cells as scavenging cells similar to those found in the bundle sheath systems of legume leaves. The transport of SR through the endodermis and palisade is the first clear evidence that this tracer can also function as a symplastic tracer. The hypothesis that the transfusion parenchyma acts to scavenge solutes from the transpiration stream was tested by loading the stream with [14C]aspartate and examining the subsequent distribution of 14C by dry autoradiography. After a pulse + chase of (0.75 + 3) h, 14C was found concentrated in the transfusion parenchyma, and at even higher levels in the Strasburger cells. It is proposed that major functions of the transfusion tissue of gymnosperms are (a) the concentrating of solutes from the transpiration stream and (b) the retrieval from the stream of selected solutes that are returned to the phloem through the Strasburger cells, or forwarded through the endodermis to the palisade.
Temperature effect on fructan oligomer contents and fructan‐related enzyme activities in stems of wheat (Triticum aestivum L.) during grain filling
Authors: BANCAL PIERRE , TRIBOÏ EUGÈNE
Published: April 2006

Two 2 m2 stands of wheat were grown under controlled conditions from 2 d after anthesis until harvest. Day and night temperature were 18 and 10 °C respectively in crop 1, whereas they were shifted to 28 and 20 °C 5 d after anthesis in crop 2. CO2 exchange rates of the canopies were continuously measured. Samples of 20 plants were collected from each crop two or three times a week. Grain filling was monitored as were various carbohydrates and enzyme activities in stems. Sugar reserves were highly correlated with the difference between cumulative photosynthesis and dry matter stored in grains. Fructan accumulated up to 150 mg culm−1 2 wk after anthesis in crop 1; but it ceased to accumulate in crop 2 as soon as high temperature was applied, because the increased metabolic rates resulted in higher carbon requirement for grain filling. The fructan was mostly phlein or highly 2–6 linked oligomers with a degree of polymerization up to 15. 6‐Kestose was the most abundant, reaching 70 mg culm−1 in crop 1. 1‐Kestose content never exceeded 25 mg culm−1 and it remained roughly constant from anthesis to harvest. No temperature‐related difference in amount of 1‐Kestose was noticed. Four kestotetraoses were quantified, 6,6‐ followed by l&6‐kestotetraose were the most abundant of them. The (2–1) linkages in bulk kestotetraose decreased from 40 % of total at anthesis to 10 % at maximum grain fresh weight. This chemical shift of the fructan reserves in the two crops was accelerated but not enhanced by elevated temperature. (2‐l)‐Fructan exohydrolase increased as soon as temperature was enhanced. However, in both crops its activity peaked at maximum grain dry weight only. Sucrose‐sucrose fructosyl transferase was constant at 01 nkat culm−1 in crop 1, whereas its activity decreased in crop 2 when temperature increased. Little change in invertase activity can be reported in both crops later than 1 wk after anthesis.
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

Fructan 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

The 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

Intercellular 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

Nineteen 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

Concentrations 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

Phosphate 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

The 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

Three‐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

Foliar 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

Several 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

Ascomycete 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

The 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

A 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

Fructan‐ 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

Plant 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

To 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

Seeds 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.
Copper tolerance of Acer pseudoplatanus L. (sycamore) in tissue culture
Authors: TURNER ANDREW P. , DICKINSON NICHOLAS M.
Published: April 2006

The growth of Acer pseudoplatanus L. (sycamore) callus tissue on solid and liquid growth media containing elevated copper concentrations was studied in an attempt to understand the responses of trees to metal contamination and to provide an index of tolerance which may show a parallel expression of tolerance to the whole plant. Callus growth on solid media was very variable, but was significantly reduced at 10 mg l−1, with necrosis occurring at 20 mg l−1; copper was readily removed from the media in direct proportion to its concentration. Cell suspension cultures differed in their response to copper according to their site of origin. In cultures originating from uncontaminated sites, growth was inhibited at 12.5 and 15.0 mg l−1 Cu, but cultures originating from mature trees at a metal‐contaminated site were not affected by these concentrations. This metal tolerance trait was stable in cell culture through repeated sub‐culturing on uncontaminated media for periods of more than 12 months. The trait was not present in a culture derived from a (non‐tolerant) seedling at the metal‐contaminated site, but it was induced in one non‐tolerant culture by repeated exposure to high metal levels. The significance of these findings is discussed in the context of the possession of appropriate genetic variation in trees for surviving the impact of metal contamination.
Calcium amelioration of aluminium toxicity effects on root hair development in soybean [Glycine max (L.) Merr.]
Authors: BRADY D. J. , EDWARDS D.G. , ASHER C.J. , BLAMEY F. P. C.
Published: April 2006

Low activities of the monomeric aluminium (Al) species, Al3+, Al(OH)2+ and Al(OH)2+ in solution reduce root growth and root hair development in soybean [Glycine max (L.) Merr.]. Calcium (Ca) ameliorates to a certain extent the toxic effects of Al on root growth, but the interactive effects of Ca and Al on root hair development are not known. In the absence of added Al in solution culture, Ca concentration over the range 500–2000 μM had little effect on root growth or root hair development of soybean cv. Fitzroy. Where the sum of the activities of the monomeric Al species was 2 μM, taproot elongation and lateral root development of soybean was suppressed in solution with 500 μM Ca. The length of the root hair zone was only 10% of that in plants not exposed to Al, and scanning electron microscopy revealed a low density of root hairs. Increasing the Ca concentration to 2000 μM largely overcame these deleterious effects. The results are discussed in relation to the role of root hairs as infection sites for Bradyrhizobium, and the known effects of Al in suppressing nodulation in soybean.
Ion distribution in relation to leaf age inLeptochloa fusca*(L.) Kunth (Kallar grass)
Authors: BHATTI A. SAEED , STEINERT SABINE , SARWAR G. , HILPERT ANDREA , JESCHKE W. DIETER
Published: April 2006

UsingLeptochloa fusca(Kallar grass) plants, the distribution of K, Na, Mg and Ca between leaves of various ages has been studied. Plants grown in a salt‐affected, reclaimed field, in a solution culture and in soil in pots at 10, 100 and 125 mM NaCl have been analyzed. Despite the presence of salt‐secreting glands onLeptochloa fuscaleaves, Na concentrations increased strongly with leaf age, while K concentrations were highest in young leaves and decreased with increasing leaf age. This was due to K retranslocation, which was clearly intensified at higher external NaCl concentration. The data point to the importance of K recycling in this halophyte and also to the use of Na by this salt‐secreting species for turgor maintenance in mature and old leaves. Both Mg and particularly Ca concentrations increased with leaf age, indicating that xylem import surpassed phloem export even for the phloem‐mobile ion, Mg. In young leaves, Mg concentrations exceeded those of Ca.
Promotion of germination of fynbos seeds by plant‐derived smoke
Authors: BROWN N. A. C.
Published: April 2006

Fynbos is the dominant vegetation type in the Cape floristic region. Periodic fires are a natural phenomenon in fynbos and fire‐stimulated seed germination has been reported for a number of fynbos species. Amongst the factors proposed as being directly responsible for the effects of fire are: heat fracturing hard seed coats, heat stimulating seed embryos, high‐temperature desiccation of seed coats, ethylene and ammonia in smoke stimulating seed germination, and unknown chemical factors in plant‐derived smoke and smoke extracts stimulating germination. In this study 28 fynbos species were screened for a seed germination response to smoke and/or smoke extract treatments. Twelve of these species showed a statistically significant enhancement of germination in response to treatment. For the first time smokeper sehas been shown to act as a seed germination cue for fynbos species in the Asteraceae, Ericaceae and Restionaceae, and for the first time smoke extracts have been shown to enhance germination in fynbos species of Proteaceae. The most marked response to both smoke and smoke extracts was shown by seed ofSyncarpha vestita(syn.Helichrysum vestitum)(Asteraceae).
Palaeoenvironmental investigations directly associated with a neolithic axe ‘quarry’ on Beinn Lawers, near Killin, Perthshire, Scotland
Authors: TIPPING RICHARD , EDMONDS MARK , SHERIDAN ALISON
Published: April 2006

A peat column containing two discrete layers of debitage from the production of neolithic axe ‘rough‐outs’ at Creag na Caillich, above Killin, Perthshire, was sampled to obtain an understanding of the environmental changes taking place at the site prior to, during and immediately after utilization of the stone resource. The column was subject to sedimentological analyses, and to ‘high‐resolution’ palynological analyses, including pollen preservation and microscopic charcoal counts. Five radiocarbon dates were obtained.

The site, at 750 m OD, is thought to have been just below the tree‐line, within hazel‐birch woodland, with some elm, but close to its upper limit. Peat inception at c. 5950 cal BP is thought to have been climatic in origin, in the absence of evidence for anthropogenic activity. Slight anthropogenic modifications to the scrubby woodland, with a decline of elm, are recorded from c. 5250 cal BP, close to the lower axe debitage layer. Clearance at this time appears not to have been for grazing, but was possibly for fires. The modification of the montane grass‐heath to an ‘anthropogenic’ grassland under grazing pressure occurred later, from c. 4600 cal BP, prior to the second period of axe ‘manufacture’ at c 3800 cal BP.
Spatial diversity in the mid–Flandrian vegetation history of North Gill, North Yorkshire
Authors: TURNER JUDITH , INNES J. B. , SIMMONS I. G.
Published: April 2006

The results of investigating a series of 11 pollen and stratigraphic profiles in peats along a 350 m stream section are described. Each profile has a small pollen catchment overlapping little with its neighbour's and the diagrams therefore show fine spatial resolution of the vegetational history. Fine temporal resolution is provided by 1 cm, or for certain sections 1 mm, interval samples. There is evidence that during the Mesolithic distinct patches of the local forest vegetation, of the order of tens rather than hundreds of metres in diameter, were managed by burning and the regular lopping of branches, for periods of up to a few hundred years each. Peat inception is thought to have occurred as early as the 9th millenium BP in some parts of the stream and up to 3000 yr later in others. Lopping and burning was the immediate cause at most sites within the channel of the gill, although fine–scale topographic and geological variation affected the timing. The developing peat was bordered by an alder carr in the lower and middle reaches of the stream. Radiocarbon dating of the mid–Flandrian Ulmus decline shows it to be asynchronous. It was caused by a combination of factors including disease and the affect the mesolithic management practices had had on the soil earlier in the Flandrian.
Partial characterization of enzymes of nitrogen metabolism in Chlorella autotrophica Shihira & Krauss
Authors: AHMAD IFTIKHAR , HELLEBUST JOHAN A.
Published: April 2006

Chlorella autotrophica shows a major decline in the intracellular concentrations of glutamine synthetase (GS) isoenzymes, GS1 and GS2, and a marked increase in the concentration of NADPH‐dependent glutamate dehydrogenase (GDH) when nitrate is replaced by ammonium as the sole nitrogen source. NADH‐dependent GDH shows very little change under these conditions. The apparent Km for ammonium of both GS isoenzymes is around 50 μM and that of NADPH‐GDH is around 15 mM. There is little change in the latter when the NADPH concentration in the assay medium is decreased, or when cells are harvested at different growth phases. In vitro kinetic analysis of GS1 and GS2 indicate low affinities of these isoenzymes for substrates other than ammonium. Both GS1 and GS2 require about 10 mM ATP, 20 mM Mg2+ and 70 mM glutamate for maximum activities. The rate response curves obtained for GS2 show nonlinear kinetics for glutamate and Mg2+. The double reciprocal plots for activity vs. substrate concentration for GS2 show dual kinetics with respect to glutamate concentrations, with a low Km value of about 10 mM and a high Km value of 40 mM. The rate response curve for GS2 for Mg2+ is sigmoidal. The Km values for glutamate measured for aspartate aminotransferase (AsAT) and alanine aminotransferase (AlAT) are in the same range as those measured for the two GS isoenzymes. The algal aminotransferases have very low Km values (18–55 μM) for 2‐oxoglutarate.
Purification and characterization of fructan: fructan fructosyltransferase from Jerusalem artichoke (Helianthus tuberosus L.)
Authors: LÜSCHER M. , FREHNER M. , NÖSBERGER J.
Published: April 2006

Fructan: fructan fructosyltransferase activity (FFT, EC 2.4.1.100) from Helianthus tuberosus L. was purified 221‐fold by a basic procedure involving ammonium sulphate precipitation, lectin chromatography and ion‐exchange chromatography. The resulting FFT preparation was separated into three protein bands, of apparent molecular weight 72800, 60 500 and 56 200, by denaturing polyacrylamide gel electrophoresis. These proteins showed affinity to sucrose‐Eupergit. FFT proteins with a molecular weight of 72800 were isolated by preparative native gel electrophoresis, and yielded six distinguishable forms on separation by analytical isoelectric focusing. Proteins from the basic purification were separated by preparative isoelectric focusing into several forms with isoelectric points between pH 4.3 and 4.5. Samples from the gel with FFT activity were analyzed by denaturing polyacrylamide gel electrophoresis. Three samples contained only protein with the molecular weight 72800, and one sample contained only protein of apparent molecular weight 60500. The remaining samples contained a mixture of proteins with molecular weights of 72800, 60500 and 56 200.

FFT was detected by 1‐kestose‐dependent nystose production. The enzyme was most active at pH 65, and up to 80 % of the activity was retained on pre‐incubation (1 h) at temperatures of up to 40 °C. FFT transferred fructosyl groups from oligofructans [degree of polymerization (DP) 3–8] of the inulin series. No glycosyl transfer occurred with 6‐kestose, neokestose, maltose, raffinose and maltotriose as the sole substrate. Sucrose efficiently accepted fructosyl units from oligofructans with a Km of approximately 0.2 mM. The rate of fructosyl transfer increased with degree of polymerization (from DP 4). 1‐kestose was shown to be an efficient donor of fructosyl units to sucrose.