bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of native vesicular‐arbuscular mycorrhizal fungi after severe soil disturbance
Authors: STAHL PETER D. , WILLIAMS S. E. , CHRISTENSEN MARTHA
Published: April 2006

Field and greenhouse experiments were conducted to determine whether the VA mycorrhizal fungi present on a site before surface coal mining could form effective mycorrhizas in the disturbed soil on the site after mining. The disturbed soil had different physical, chemical and morphological characteristics than the soil on the site prior to perturbation.Artemisia tridentata subsp. WyomingensisBeetle and Young (Wyoming big sagebrush), inoculated or not with VA mycorrhizal fungi, was planted on the field site both as seed and as container‐grown seedlings. The native VA mycorrhizal endophytes produced only limited amounts of mycorrhizal infection in the disturbed soil (approximately 20% of total root length) and after 2 years were found to have no significant effect on the establishment, growth or survival of sagebrush plants. In the greenhouse study, mycorrhiza development and efficacy was compared in native sagebrush‐grassland soil and disturbed soil from the reclamation site with identical concentrations of mycorrhizal inoculum (19 propagules g−1). Mycorrhiza development in native soil greatly exceeded that in disturbed soil after 45 d growth (50vs.10% of total root length). Also, native mycorrhizal fungi effected significant increases in biomass production (+ 70%) and tissue phosphorus content (+ 70%) in sagebrush‐grassland soil but not in reclamation soil. The ecological implications of these results are discussed.
On the relative importance of convective and diffusive gas flows in plant aeration
Authors: BECKETT P. M. , ARMSTRONG W. , JUSTIN S. H. F. W. , ARMSTRONG J.
Published: April 2006

summary

The importance of through flow convection of gases is recognized hut the notion that convection of a non‐through flow type might play n major role in plant aeration is challenged. It is shown that this convection discovered recently in deep‐water rice, and which could operate also in almost any submerged root system, must be subordinate to diffusion in the plant's aeration process and will al best have only minimal influence on root aeration.
Interaction between Glomus mosseae and Erwinia carotovora and its effects on the growth of tomato plants
Authors: GARCIA‐GARRIDO J. M. , OCAMPO J. A.
Published: April 2006

summary

The effect of inoculation with Erwinia carotovora pv. carotovora on tomatoes with or without VA mycorrhizal infection by Glomus mosseae was studied in a greenhouse trial. E. carotovora decreased the growth of nonmycorrhizal tomato plants, but neither growth nor the percentage of total root length with VA infection were reduced in mycorrhizal plants. Protection of tomato against the pathogen and reduction in the number of colony‐forming units of E. carotovora in the rhizosphere of mycorrhizal plants were independent of concentration of P in the plant and the timing of inoculation with the two microorganisms. The possible mechanisms of the resistance induced in tomato plants by G. mosseae against E. carotovora are discussed.
The extent and time‐course of mountain blanket peat erosion in Ireland
Authors: Bradshaw Richard , McGEE Edward
Published: April 2006

Erosion of upland blanket pent is widespread in Britain and Ireland and suggestions for its initial causes have included recent human disturbance and changes in the mechanical stability of the peat masses through time. A survey of blanket peat in five mountain areas in Ireland revealed extensive erosion in all areas, and two cores of mountain lake sediment contained inwashed peat in their upper sections. Detailed analysis of the core from the Wicklow Mountains revealed pollen evidence for initial peatland development, tree clearance and eventual peat erosion. The inwashed peat contained abundant Sphagnum leaves.

Peat inwash began 1500 years ago in Donegal, N.W. Ireland and 3000 years ago in Wicklow near the east coast. The occurrence of erosion over these time periods does not suggest that recent human activity and changes in land‐use are the original causes of erosion. Recent human activity has merely intensified erosion that probably originated from peat flows or the development of natural drains in mature peat masses developing on sloping ground.
Phosphate influx and extracellular phosphatase activity in barley roots and rose cells
Authors: LEE R. B.
Published: April 2006

The rate of phosphate influx, and the activity of extracellular phosphatase, were measured simultaneously in root systems of intact, sterile barley plants (Hordeum vulgareL.) of widely differing P status. Similar measurements were made on suspension cultures of rose cells (Rosasp.) starved of P for various periods. Under the experimental conditions used, extracellular phosphatase activity greatly exceeded phosphate influx but there was a very significant correlation between the two. The possiblity of the extracellular phosphatase being involved in phosphate transport is discussed.
A correlation between intracellular calcium and incident irradiance in Nostoc 6720
Authors: SMITH R. J. , WILKINS A.
Published: April 2006

Recent reports of Ca2+ dependency in cyanobacterial processes, which include photosystem II, nitrogenase activity, heterocyst differentiation and trichome motility, question whether Ca2+‐mediated regulation is present in these phototrophic prokaryoles. Such regulation would require that the intracellular concentration of Ca2+ varies within an appropriate range. Several of these Ca2+‐dependent processes respond to treatments which artificially alter the intracellular Ca21+ content, but a physiological or environmental effect has not been demonstated.

The effect of changes in the incident irradiance upon the proportion of heterocysts and the intracellular content of Ca2+ in Nostoc 6720 have been investigated. Both the proportion of heterocysts (heterocyst frequency) and the cellular content of Ca2+ (assessed by 45Ca24 incorporation in long labelled cultures) were negatively correlated with incident irradiance. The efflux of Ca2+ from darkened cultures was decreased suggesting that the accumulation of intracellular Ca2+ at low incident irradiance might result from decreased efflux. Orthovanadate, a non specific inhibitor of Ca2+ in Anabaena variabilis, enhanced both the cellular content of Ca24 and heterocyst frequency which suggests that direct inhibition of Ca2+ efflux is able to mimic the effects observed on decreasing irradiance.
Fructan biosynthesis in excised leaves of Lolium temulentum L.
Authors: CAIRNS A. J. , POLLOCK C. J.
Published: April 2006

Following the initiation of soluble carbohydrate accumulation in excised illuminated leaves of Lolium temulentum L., extractable sucrose: sucrose fructosyl transferase activity rose concomitant with the onset of fructan synthesis Extractable enzyme activity was sufficient to account for rates of fructan accumulation in vivo The major trisaccharide products of transferase activity in vitro were isokestose and kestose. This differed from the patterns of trisaccharide accumulation in vivo, where isokestose and neokestose predominated.

Excised leaves treated with inhibitors of protein synthesis and of RNA metabolism accumulated water‐soluble carbohydrate at similar rates to control tissue, but did not convert sucrose into fructan. Inhibitor treatment also prevented increase in extractable sucrose: sucrose fructosyl transferase activity, suggesting that initiation of fructan biosynthesis was mediated by altered patterns of gene expression. These results are discussed in relation to the control of the synthesis of the oligofructosides characteristic of this tissue.
The form and outcome of mycelial interactions involving cord‐forming decomposer basidiomycetes in homogeneous and heterogeneous environments
Authors: DOWSON C. G. , RAYNER A. D. M. , BODDY LYNNE
Published: April 2006

The mycelial interactions of strains of six cord‐forming wood‐inhabiting basidiomycetes were studied both against each other and against other fungi including Armillaria species on 2% malt extract agar, in wood lengths, and in non‐sterile soil. Generally, cord‐formers could be ranked in a combative order Phanerochaete velutina (DC ex Pers.) Parmasto =Phanerochaete laevis (Fr.) Erikss. & Ryv. > Steccherinum fimbriatum (Pers. ex Fr.) Erikss. =Hypholoma fasciculare (Huds. ex Fr.) Kummer =Phallus impudicus (L.) Pers. > Tricholomopsis platyphylla (Pers. ex Fr.) Sing. However, the outcome of interactions varied considerably according to circumstances. For example, in soil systems it depended on the extent to which encounters occurred between mycelia growing out from the wood inoculum blocks or within the inocula themselves. This depended in turn on the relative size of the inoculum blocks used for each strain.

Encounters between like mycelia growing out into soil led to the formation of persistent mycelial connectives between the inoculum blocks. However, those between unlike mycelia elicited discolouration and lytic reactions following either contact ('mycelial interference') between different species, or fusion and somatic incompatibility between different strains of the same species. Such reactions were followed either by replacement of one system by the other, or the development of mycelium‐free zones of soil between deadlocked colonies.

After 3 months all pairings of cord formers against systems of Armillaria bulbosa (Barla) Kile and Watling, A. cepestipes Vel. f. pseudobulbosa Romagn. & Marxmuller and A. mellea (Vahl ex Fr.) Kummer in soil resulted in the colonisation of the Armillaria inocula to varying degrees and the death of virtually all associated rhizomorphs.
Secretory tissues in vascular plants
Authors: FAHN ABRAHAM
Published: April 2006

Secretory tissues occur in most vascular plants. Some of these tissues, such as hydathodes, salt glands and nectaries, secrete unmodified or only slightly modified substances supplied directly or indirectly by the vascular tissues. Other tissues secreting, for instance, polysaccharides, proteins and lipophilic material, produce these substances in their cells. The cells of secretory tissues usually contain numerous mitochondria. The frequency of other cell organelles varies according to the material secreted. In most glandular trichomes the side wall of the lowest stalk cell is completely cutinized. This prevents the secreted material from flowing back into the plant.

The salt glands in Atriplex eliminate salt into the central vacuole of the bladder cell but, in other plants, the glands secrete salt to the outside. Different views exist as to the manner in which salt is eliminated from the cytoplasm. According to some authors, the mode of elimination is an eccrine one, while others suggest the involvement of membrane‐bound vesicles.

Nectar is of phloem origin. The pre‐nectar moves to the secretory cells through numerous plasmodesmata present in the nectariferous tissue. Nectar is eliminated from the secretory cells by vesicles of either KR or dictyosomal origin. In some cases, both organelles may be involved but an eccrine mode of nectar secretion has also been suggested by some authors.

Carbohydrate mucilages and gums are synthesized by dictyosomes but virtually every cell compartment has been suggested as having a role on the secretion of lipophilic substances. Most commonly, plastids are implicated in the synthesis of lipophilic materials but KR may also play a part. In some cases lipophilic materials may be transported towards the plasmalemma in the KR.

Resin and gum ducts of some plants develop normally or in response to external stimuli, such as microorganisms or growth substances. Among the latter, ethylene is the most effective.

During the course of evolution, secretory tissues seem to have developed from secretory idioblasts scattered among the cells of the ordinary tissues. Subsequently ducts and cavities developed and finally secretory trichomes.

CONTENTS

Summary
229

I.
Introduction
230

II.
Salt glands
231

III.
Nectaries
236

IV.
Mucilages and gums
241

V.
Tissues secreting lipophilic material
242

VI.
Factors influencing the development of certain secretory tissues
246

VII.
Evolutionary considerations
248

References
250
Observations on chloroplast starch content and synthesis in the intertidal marine alga Codium fragile (Suringar) Hariot
Authors: WILLIAMS MICHAEL L. , COBB A. H.
Published: April 2006

A marked seasonal response was observed in the starch content of chloroplasts of Codium fragile sampled between November 1983 and November 1984. Chloroplast starch uniformly increased throughout the life‐cycle of this alga, reaching a maximum in the summer months of approx. 5 mg glucose equivalents/109 plastids when C. fragile was in the reproductive phase. Chloroplast starch content was found to be inversely proportional to the concentration of stromal phosphate, decreasing linearly from 5 to 2 mg glucose equivalents/109 plastids over a range of stromal phosphate values of 0·75–1·5 μmol PO4/109 plastids. Similarly, the net amount of starch synthesized over 3 h by isolated chloroplasts increased linearly with respect to initial chloroplast starch content. These observations are discussed in relation to the regulation of starch synthesis by variations in the stromal P1: PGA ratio.
Ectomycorrhizal ability of genetically different homokaryotic and dikaryotic mycelia of Hebeloma cylindrosporum
Authors: DEBAUD J. C. , GAY G. , PREVOST A. , LEI J. , DEXHEIMER J.
Published: April 2006

Ectomycorrhizas were synthesized under axenic conditions between Pinus pinaster (Ait.) Sol. and different mycelial cultures of Hebeloma cylindrosporum Romagnesi. These included a wild dikaryon and four sib‐homokaryons (one for each mating type) belonging to the progeny of this fruiting strain.

The homokaryotic mycelia formed typical ectomyeorrhizas showing a morphology and an ultrastructural organization similar to that of ectomyeorrhizas obtained with the parental dikaryon. The ultrastructural localization of acid phosphatase activities was also comparable for homokaryotic and dikaryotic mycorrhizas.

These results demonstrate that the ectomycorrhizal ability is not restricted to the dikaryotic state of fungal life‐cycle since homokaryotic mycelia also formed typical and functional ectomyeorrhizas. The formation of normal mycorrhizas by homokaryotic mycelia confirms the usefulness of H. cylindrosporum as a model for genetical studies and improvement of ectomycorrhizal fungi by means of chromosomal genetics.
Localization of uricase in mycorrhizas of Ophrys lutea Cav.
Authors: BARROSO J. , CASIMIRO A. , CARRAPIÇO F. , SLOMÉ M. , PAIS S.
Published: April 2006

Infected roots of Ophrys lutea present nymerous peroxisome profiles identified by diaminobenzidine (DAB) staining. The presence of uricase in these peroxisomes could also be recognized cytochemically. The activities of catalase and uricase, assayed using a crude fraction of peroxisomes, reached 0·8 μkat min−1 protein‐1 and 1·73 nakat min−1 mg protein−1 respectively. The role of uricase in purine metabolism is discussed in terms of host/endophyte interactions in O. lutea mycorrhzas.
Seasonal accumulation of mineral nutrients by kiwifruit 2. Fruit
Authors: CLARK C. J. , SMITH G. S.
Published: April 2006

Changes in the concentration, distribution and quantity of macro‐ and micronutrients in the skin and flesh of fruit from 30 mature kiwifruit vines (Actinidia deliciosa var. deliciosa cv. Hayward) were recorded over a growing season in two high‐producing orchards.

The concentration of copper, iron, nitrogen, phosphorus, potassium, sulphur and zinc in the flesh (seeds inclusive) declined sharply during the first 8 weeks of growth, reaching values which remained relatively constant, or declined only gradually, until harvest. For boron, calcium, magnesium and manganese flesh concentrations declined steadily throughout the season.

Concentrations of nitrogen, phosphorus and potassium in the flesh were generally higher, and those of calcium manganese and zinc consistently lower, than corresponding concentrations in skin over the entire maturation period (23 weeks). Flesh concentrations of copper, iron, magnesium and sulphur exceeded those in the skin but only during the early stages of fruit development (up to 11 weeks after pollination). Boron concentrations in flesh and skin were similar during the season.

The quantity of all nutrients increased throughout the season to be at a maximum by harvest The rate of accumulation of each element was greatest during the first 8 weeks of growth corresponding to the cell division phase of fruit development. There was 61–75% of the total calcium, manganese and zinc content taken up during this time, compared with 37–54% of the content of other nutrients. In the subsequent 15 weeks of development rates for nutrient accumulation declined. In the case of boron, calcium, magnesium, manganese, potassium and zinc there was minimal accumulation in the final 6 weeks prior to harvest.

A mass How‐vascular transport model based on carbon and water influxes was used to predict the relative importance of phloem and xylem supply, and to partition nutrient accumulated by fruit over two time intervals; 2–8, and 8–17 weeks of growth. The model implies that where transpiration rates and phloem carbon concentrations are both high (i.e. approx. 6 ml water fruit−1 day−1 early in the season or 2 ml water mid season, and > l00 mg C ml−1), transport of nutrients occurs primarily via phloem. The only exceptions under these conditions are calcium, manganese and zinc which are translocated preferentially in xylem.
Nickel toxicity in mycorrhizal birch seedlings infected with Lactarius rufus or Scleroderma flavidum II. Uptake of nickel, calcium, magnesium phosphorus and iron
Authors: JONES MELANIE D. , HUTCHINSON THOMAS C.
Published: April 2006

Non‐mycorrhizal Betula papyrifera Marsh, seedlings and seedlings infected with Lactarius rufus (Scop, ex Fr.) Fr. or Scleroderma flavidum E. & E. were treated with nutrient solutions containing 85 μM Ni or no Ni for 21 weeks. Ni was concentrated in the roots, with the highest concentrations being in the roots of plants infected with S. flavidum; Ni concentrations in stems were lowest in these seedlings. In general, Ni reduced the concentration of P, Mg, Ca, and Fe in shoot tissues. The concentration of P was correlated with that of Ni in the stems and roots. High P concentrations in the roots of S. flavidum‐infected seedlings could be correlated with potential Ni‐binding sites, allowing the Ni to be detoxified. Although Ni treatment reduced chlorophyll concentrations in L. rufus infected and uninfected seedlings, this did not appear to be related to differences in tolerance caused by the fungi.
The iron and molybdenum use efficiencies of plant growth with different energy, carbon and nitrogen sources
Authors: Raven John A.
Published: April 2006

Iron has many catalytic roles in photosynthesis, respiration and nitrogen assimilation; molybdenum is involved in NO3 and (usually) N2 reduction. This paper concentrates on computing the efficiency of use of Fe and Mo in growth of organisms growing with different mixtures of the major resources photons, carbon and nitrogen. This computed efficiency is defined as mol C assimilated (mol catalytic metal in the organism)‐1 s‐1. The efficiency is computed from the known in vivo involvement of Fe‐ and Mo‐containing enzymes, the specific reaction rate of these enzymes, the specific rate of these enzymes in vitro, and the growth requirements for the products of the reactions, for organisms using different energy, carbon and nitrogen sources. The predicted Fe use efficiency is greater for chemo‐organotrophic than for photolithotrophic growth with a given nitrogen source, and increases in the order N2 NO3‐ NH4+ for growth with different nitrogen sources in the presence of constant photon and carbon availability. The predicted changes with variations in nitrogen source are greater than those with variations in photon and carbon source. These predicted values may be compared with observed metal use efficiencies, defined as mol C assimilated (mol total metal in the organism)‐1 s‐1. Relatively few such observed values are available From the literature. For Fe in photolithotrophically growing microalgae the observed values can be as low as 16–17% of the predicted values, i.e. 83–84% of the Fe in the organism is not accounted for by known catalytic uses of Fe if the catalysts are operating at their maximum specific reaction rates. One possibly discordant prediction relates to the Fe and Mo cost of N2 fixation; the computations suggest that in vitro estimates of nitrogenase activity may be less than those sometimes found in vivo. The predictions also have possible implications for resource availability interactions (photons, carbon, nitrogen, Fe, Mo) in natural conditions.
Effects of nitrogen‐deprivation, and recovery from it, on the metabolism of microalgae
Authors: SYPETT P. J. , PEPLINSKA A. M.
Published: April 2006

Initial rates of uptake of the ammonium analogue, [14C] methylammonium increased during N‐deprivation of the microalgae, Dunaliella primolecta Butcher, Tetraselmis subcordiformis Butcher (Wille), Chlomydomonas reinhardtii Dangeard. Amphidinium carterae Hulburt and Phaeodactylum tricornum Bohlin.

The C:N ration of P. tricornutum increased from 7.4 to 19.8 during 48 h of N‐deprivation; the ability to take up [14C] methylammonium increased 50–fold during this time. Intracellular glutamate and glutamine were measured fluorimetrically; the contend of glutamate fell during N‐deprivation but that of glutamine was low and changed little. The activity of glutamine synthetase (transferase) in cells permeabilized by toluene treatment approximately doubled during the first 4 h of N‐deprivation, irrespective of whether the cells had been grown with NO2 or NH4+ as N cource: thereafter the activity of thia enzyme decreased slowly. The activity of nitrate reductase was high in NO3 grown cells and decreased during N‐deprivation. In NH4+ grown cells, nitrate reductase activity was low and increased markedly during 4 h of N‐deprivation; therefore it fell slowly.

The addition of NH4+ to N‐deprived cells was followed by an immediate and large fall in the ability to take up [14C] methylammonium. In contrast, the addition of NO3 produced an initial small drop in the ability to take up [14C]methylammonium followed by another drop after 4.6 h; 8 h after NO3 addition the initial rate of [14C]methylammonium uptake was similar to that of N‐replate cells. These falls in ability to take up methylammonium were reversed when NH4+ or NO3 were removed; the reversals were not prevented by addition fo cycloheximide (an inhibitor of protein synthesis). Changes in intracellular glutamate and glutamine were followed during the periods following NO3 and NH4+ addition and removal. There was evidence fro a negative correlation between glutamine content and the rate of uptake of mehtylammonium
The physiology of basidiomycete linear organs II. Phosphate uptake by rhizomorphs of armillaria mellea
Authors: CAIRNEY J. W. G. , JENNINGS D. H. , RATCLIFFE R. G. , SOUTHON T. E.
Published: April 2006

This study shows that rhizomorphs can be produced readily in the laboratory for use in physiological and biochemical experimental. Apical and sub apical segments can be excised and treated experimentally like roots. The mean rate of phosphate uptake by apical segments as a function of phosphate concentration is very similar to that of rhizomorphs produced under more unnatural conditions. Phosphate uptake is bioasic with Km and Vmax ehemical analysis and NMR indicates that there is a sizeable amount of orthophosphate within the hyphae, located in tow pools‐cytoplasmic and vacuolar with the bulk of the orthophosphate in the vacuole. Cytochemical, electrophoretic and NMR studies show that a significant proportion of the phosphorus is in the form of polyphosphate. It would seem that initially moist of the phosphate absorbed enters the vacuole as orthophosphate and there is little direct incorporation into polyphosphate.
Inoculation of mycelial cord‐forming basidiomycetes into woodland soil and litter I. Initial establishment
Authors: DOWSON C. G. , RAYNER A. D. M. , BODDY LYNNE
Published: April 2006

Almost 1000 wood blocks, 8 cm3, of beech (Fagus sylvatica L.), colonized by the mycelial cord‐forming basidiomycetes Hypholoma fasciculare (Huds. ex Fr.) Kummer., Phallus impudius (L.) Pers., Phanerochaete (Ph.) laevis (Fr.) Erikss & Ryv., Ph. Velutina (DC ex Pers.) Parmasto, Steccherimum fimbriatum (Pers. ex Fr.) Erikss. and Tricholomopsis platyphylla (Pers. ex Fr.) Sing, were placed at the soil‐litter interface in five different woodland sites. All species except T. platyphylla grew out radially from the blocks to form a network of mycelial cords ramifying amongst the litter and upper soil horizons. Initial outgrowth was more strongly related to microclimatic factors than to availability of nutrient resources, and after 3 months significantly greater (P<S 0.05) mean radial extension had occurred from blocks implanted during spring than from those implanted in winter or mid‐autumn, Systems of H. fasciculare and Ph. Velutina were always of significantly greater (P<0.05) radius than those of the ther species after 3 and 6 months.
Interactions between ozone and plant cuticles
Authors: KERSTIENS GERHARD , LENDZIAN KLAUS J.
Published: April 2006

Beech (Fagus sytvatica L.) and ivy (Hedera helix L.) plants, as well as isolated cuticles of the adaxial leaf surfaces of Citrus aurantium L., Ficus elastica Roxb. var. decora and Hedera helix L., were exposed to environmentally realistic ozone concentrations (up to 130 nl −1)in combination with acid fog (pH 3.0) for several months. Isolated Citrus, Ficus and Hedera cuticles and cuticles isolated from adaxial leaf surfaces of Hex aquifolium L. and Prunus laurocerasus L. and from fruits of Capsicum annuum L. and Lycopersicon esculentum Mill, were fumigated with 2.5 % (v/v) ozone for 1 or 2 h in dry and moist conditions, respectively. The water permeance (P) of the non‐isolated cuticles of the astomatous adaxial leaf sides of beech and ivy and of the isolated cuticles was not altered by expositure to a realistic ozone stress. Fumigation with very high ozone concentrations decreased P of isolated Ficus and Hedera cuticles by about 20% and increased P of all other isolated cuticles by up to 200% (Capsicum). In some cases the 2 h fumigation under moist conditions had no significant effect upon P. The different effects are tentatively explained in terms of the structure of the cuticles.
Synthesis in Vitro, microanalysis and 31P‐NMR study of metachromatic granules in birch mycorrhizas
Authors: GRELLIER B. , STRULLU D. G. , MARTIN F. , RENAUDIN S.
Published: April 2006

The synthesis in vitro of metachromatic granules was demonstrated in the mycelia of Paxillus involutus (Batsch) Fr. both in pure culture and associated with birch (Betula pendula Roth) roots. X‐ray microanalysis revealed the presence of phosphorus and calcium in the granules of mycorrhizas. Phosphorus‐31 NMR spectroscopy was used to identify intracellular orthophosphate and polyphosphates. In the mycelin, orthophosphate represented the major form of phosphorus accumulation, and a small pool of polyphosphate was detected in the oldest phases of culture. On the other hand, an important NMR resonance corresponding to polyphosphates was identified in the spectra of synthetic mycorrhizas. The association between a mycelium and a root seems to modify the metabolism of fungus considerably.
The role of proteins in the nitrogen nutrition of ectomycorrhizal plants
Authors: ABUZINADAH R. A. , READ D. J.
Published: April 2006

Plants of Betula pendula L, were grown on a medium continuing protein as sole nitrogen source, and the ability of fungi representing a range of nutritional categories to provide them with access to protein‐N was examined by determining changes of dry weight and nitrogen accumulation with time following sequential harvests.

Three fungi known to be ectomycorrhizal all gave access to the nitrogen but large differences in their effectiveness were observed, an ‘early stage’ fungus providing significantly more N than either a ‘late stage’ fungus or a facultative associate. The saprotroph Oidiodendron griseum Roback also facilitated N transfer to the plants whereas they obtained no such supply in the uninoculated condition, or when grown with an ericoid endophyte and a saprotroph isolated from the seed coat. The process of nutrient transfer from fungus to host is seen as the key rate limiting step determining growth response of the host. The physiological and ecological implications of the results are discussed.
The biology of mycorrhiza in the Ericaceae
Authors: LEAKE J. R. , READ D. J.
Published: April 2006

Hymenoscyphus ericae utilizes protein as a sole source of nitrogen through the production of an extracellular proteinase. A sensitive procedure for assay of the enzyme is described and is used to determine the major characteristics of the enzyme. The enzyme has a sharp pH optimum at 2.2 with little activity above pH 5.0. Values for Km and Vmax of the enzyme were determined.

Pepstatin, a specific inhibitor of carboxyl (acid) proteinases, almost completely inhibited activity, confirming that the enzyme is of this type.

The characteristics of the enzyme are compared with those described for other microbial acid proteinases and the results are discussed in relation to physiological ecology both of the fungus and of its host plant.
Predicting tree frequencies from pollen frequency: an attempt to validate the R value method
Authors: SCHWARTZ MARK W.
Published: April 2006

Pollen‐tree correction factors are presented using regression analysis of pre‐settlement tree and pollen frequency data from 32 small lakes (1–10 ha) in Wisconsin. Regression results using vegetation samples from various sized areas around each lake for Fagus grandifolia (Ehrh.) and Tsuga canadensis (Carr.), are consistent with my initial design of using vegetation data for the single township in which a lake was found to compute the regression results. Pollen‐tree correction factors from pre‐settlement and modern data were compared for all major pollen types. Notable differences were found between pre‐settlement data and modern data sets for Wisconsin in Betula spp, T. canadensis, and Quercus spp. Little difference was observed in the fit of the regressions for these data sets. Estimations of pre‐settlement relative tree frequencies, derived from the application of modern correction factors on pre‐settlement pollen frequencies, were compared to measurements of pre‐settlement vegetation. The reconstruction of pre‐settlement vegetation was incongruous with measurements of pre‐settlement tree frequencies. It is unclear, given minor differences in the data sources for modern and pre‐settlement data, whether the observed differences in regression results are artifacts of the data sets, or reflect differences in pollen‐tree representation between the two time periods sampled. Regardless, the error associated with prediction of tree frequencies from pollen frequencies is shown here to preclude any assurance of accuracy with normal pollen count levels.
Fructan biosynthesis in excised leaves of Lolium temulentum L. III. A comparison of the in vitro properties of fructosyl transferase activities with the characteristics of in vivo fructan accumulation*
Authors: CAIRNS A. J. , WINTERS A. , POLLOCK C. J.
Published: April 2006

The induction of fructan biosynthesis in excised, illuminated leaves of Lolium temulentum L. is accompanied by a concomitant increase in extractable sucrose: sucrose fructosyl transferase (SST) activity. In leaves treated with the L‐isomer of 2‐(4,methyl‐2,6,‐dinitroanilino)‐N‐methyl propionamide (L‐MDMP) fructan biosynthesis in vivo occurs in the absence of such an increase in extractable SST. suggesting that the activity measured in vitro is not an obligatory component of fructan biosynthesis in vivo.

Sucrose:sucrose fructosyl transferase preparations from L. temulentum catalyse the formation of isokestose and kestose from sucrose. The rates of synthesis of these trisaccharides were determined in the range of sucrose concentration 10‐700 mol m−3. Increase in total trisaccharide synthesis was linear with respect to substrate concentration. Isokestose was Formed over the entire range whilst kestose synthesis was inactive below 8O mol m−3. Neither isokestose nor kestose synthesis was saturated at 700 mol m −3. The Km for isokestose synthesis was high at 380 mol m−4. Conventional kinetic analysis of kestose data failed, indicating that this activity does not obey classical Michaelis‐Menten kinetics.

The intracellular sucrose concentration in leaf tissue was estimated to be 100 mol m−3. At this substrate concentration, isokestose synthesis would be Functioning well below the measured Km and kestose synthesis would be operating at the extreme lower limit of its activity range.

Higher oligosaccharide products of fructosyl transferase incubations were not representative of the oligofructans which accumulate in the leaf. This data casts further doubt on the physiological significance of the measured fructosyl transferase activities.

Isokestose synthesis was localized in vacuoles derived from leaf mesophyll protoplasts, confirming current theories of fructan biosynthesis. However, in view of the anomalous characteristics of fructosyl transferases in vitro, we propose that unambiguous assignment of the subcellular compartmentation of fructan metabolism in leaves of Lolium temulentum should await a fuller understanding of the enzymology of fructan biosynthesis in this species.
Inhibition of the shikimate pathway in the leaves of vascular plants exposed to air pollution
Authors: KATOH T. , KASUYA M. , KAGAMIMORI S. , KOZUKA H. , KAWANO S.
Published: April 2006

Intermediate products of tannin biosynthesis, i.e., glucose, shikimic acid and phenolics, Were determined in order to estimate the sites of inhibition of tannin synthesis, which had previously been observed in leaves of Japanese Cedar (Cryptomeria japonica D. Don.) collected from the surroundings of a steam power station. The effects of SO2, on tannin biosynthesis were also investigated in experimental fumigations of C. japonica saplings. The results of these studies indicated that inhibition of aromatic ring formation, i.e., the process converting shikimic acid to phenylalanine and tyrosine (the later shikimate pathway), was caused by slight air pollution.
Stimulation of ectomycorrhizal infection of Pinus radiata by some microorganisms associated with the mantle of ectomycorrhizas
Authors: GARBAYE J. , BOWEN G. D.
Published: April 2006

Microorganisms were isolated from inside the mantle of ectomycorrhizas formed by the fungus Rhizopogon luteolus Fr. and Nordh on the roots of Pinus radiata D. Don. growing in a sandy podzol. Different isolates of these microorganisms were then tested for their effect on three stages of mycorrhizal infection : growth of the fungus into the soil, growth along the root, and mycorrhiza formation. Experiments were performed in axenic and non‐axenic conditions. A significant microbial population was present within the mantle of ectomycorrhizas (Gram negative bacteria being dominant) and a majority of these had a stimulating effect on mycelial growth of R. luteolus and/or mycorrhiza formation. These results suggest that some specific microbial communities have evolved to live in close association with ectomycorrhizal fungi in their symbiotic state, with mutual benefit. The potential use of such‘helper’microorganisms for improving the efficiency of ectomycorrhizal inoculation in forest nurseries is discussed.
Studies on nitrogen metabolism of Terfezia spp. and Tirmania spp.
Authors: EWAZE JULIET O. , AL‐NAAMA MENHEL M.
Published: April 2006

Species of the truffle fungi Terjezia and Tirmania are widespread in the south of Iraq in association with roots of Helianthemum spp., the dominant plants of the area. The truffle mycelia and ascocarps reduced nitrate at much higher rates than did Helianthemum rootlets, suggesting that absorption of nitrate is particularly enhanced by the fungal symbiont.

Measurements of the specific activity of representative enzymes of the ornithine cycle indicated that this cycle was operative in ascocarp tissue and led to the acccumulation of urea. It is suggested that this may serve an osmotic function, assisting spore liberation.
Rate of accumulation of fructan oligomers in wheat seedlings (Triticum aestivum L.) during the early stages of chilling treatment
Authors: BANCAL P. , GAUDILLÈRE J. P.
Published: April 2006

summary

The accumulation of soluble carbohydrates was studied during chilling of 2‐week‐old wheat (Triticum aestivum L.) seedlings. The extracts were analysed using a C18 HPLC method separating hexoses, sucrose and a wide range of oligofructan. Isomers were recognized and their content determined. The amounts of hexoses, sucrose and the trisaccharides 1‐kestose and 6‐kestose increased at the beginning of the treatment. The accumulation rate of 1‐kestose, the trisaccharide generally considered to be the precursor of fructan, increased ten fold with some delay. Heavier fructan accumulated even later. In leaf blades, 1–3 molecular species with a degree of polymerization from 4 to 8 were detected. Five of these accounted for 90% of this pool at day 5. In leaf bases the amount of carbohydrates was lower but more species of fructan were detected. The sequence of accumulation was the same as in the blades. These results are discussed in relation to current models ot fructan synthesis.
The possibility of determining the age of colonies of clonally propagating herbaceous species from historic records: the case of Aster novi‐belgii L. (first recorded as A. salignus Willd.) at Wicken Fen Nature Reserve, Cambridgeshire, England
Authors: BRIGGS D. , BLOCK M. , JENNINGS S.
Published: April 2006

summary

For a number of species, population biologists have estimated the age of apparent clones. In studying a colony of naturalized Aster novi‐belgii L. (first recorded as Aster salignus Willd.) growing at Wicken Fen Nature Reserve, Cambridgeshire, England, we have attempted to determine from a considerable body of historic records, its age, structure and development. While it is highly likely that the records refer to the colony in its present position on the Fen, there is uncertainty about its age and conflicting information about its position.

A. novi‐belgii is a self‐incompatible species. Plants of the Wicken colony exhibit little variation and preliminary tests show that their achenes are sterile. As a working hypothesis, for further testing, we suggest that all the plants may be of a single clone.

Population biologists, who are interested in determining the age and development of clones of plants, are likely to be disappointed both by the extent and the vagueness of historic records. This situation is understandable as the information was recorded for taxonomic purposes. The hope is expressed that the intensive studies now being made of populations of plants will result in the long‐term survival in the public domain of detailed records and maps, which will enable future generations to study the age and development of clones of herbaceous species.
Ecological genetics of salt resistance in the clonal perennial, Agrostis stolonifera L.
Authors: KIK C.
Published: April 2006

Summary

Large population differentiation in salt resistance, as determined by a rooting technique, was detected among four ecologically contrasting populations at. Agrostis stolanifera L., with known genotypic compositions. It was found that an inland meadow population had a significantly lower salt resistance than the more maritime populations; and that only the inland meadow population had a significant genetical component for salt resistance.

The possible adaptive value of salt resistance, as measured by the rooting technique, was evaluated in a transplant experiment in a natural salt marsh. It was found that relative root growth is a reasonable indicator of the complex of factors determining salt resistance. A detailed analysis of the relationship between salt resistance and survival within each of the four populations of A. stolonifera suggested that genotype x environment interaction and trade‐offs between characters governing salt resistance might play a significant role.
Enzymatic, lectin, and morphological characterization and classification of presumptive cyanobionts from Azolla Lam
Authors: ZIMMERMAN WILLIAM J. , H.ROSEN BARRY , LUMPKIN THOMASA.
Published: April 2006

Summary

A number of cyanobacterial strains from the Azolla Lam. symbiosis, all independently isolated by different researchers, were simultaneously evaluated in order to document distinguishing traits. Ten presumptive secondary (minor) cyanobionts from Azolla were identified by genus and compared by morphology, binding to FITC‐conjugated lectins, and enzyme electrophoresis. Identification of allozymes was particularly helpful in differentiating among strains. Anabaena variabilis ATCC 24413 and Anabaena sp. PCC 7120 served as the free‐living control taxa. Based on morphological features, six strains identified as Anabaena and four as Nostoc. Those identified as Anabaena closely resembled one another morphologically and in general did not bind to lectins. In their banding patterns of 12 enzymes, five of the Anabaena cultures were identical to each other and to A. variabilis. No correlation was found between this group of cyanobaionts and any single Azolla host species. The Nostoc strains were each distinctive in appearance, and unrelated enzymatically. Cells of only one Nostoc, from India and judged to be an epiphyte rather than a symbiont, reacted with certain lectins (Canavalia, Erythrina, Phytolacca and Triticum). Culturable cyanobacteria from Azolla, previously asserted to be either Anabaena or Nostoc exclusively, have now been observed to belong to both genera.
The biology of mycorrhiza in the Ericaceae
Authors: SHAW G. , READ D. J.
Published: April 2006

Summary

The effects of the metals, iron and aluminium, on acid phosphatase (P‐NPPase) activity of the ericoid endophyte, Hymenoseyphus ericae (Read) Korf and Kernan were determined. The endophyte was grown in pure culture and then treated with Fe2+ and Al2−over a range of concentrations (0–1000mgl−1), and at two concentrations of inorganic phosphorus (20μ and 200 μM p). Activities of p‐NPPase were determined. Enzyme activity was greatly inhibited at the highest concentration of external P even in the absence of the metal ions. The presence of the metals in the low P treatment had effects determined by their concentration. At the highest concentration used, they precipitated products of acid phosphatase activity (p‐NP), and so invalidated the use of the assay at these metal levels. However, the assay could reliably be used over the concentration range 0–200 mg 1−1 Al2+ and 1–100 mg 1 −1 Fe2+, the upper concentrations in both cases being considerably above those normally found in soil solutions. Over these ranges the presence of Al3+ only slightly inhibited p‐NPPase activity, whereas there was a small increase of activity in the case of Fe2+. The results are discussed in relation to the role of ericoid mycorrhizal infection in the phosphorus nutrition of ericaceous plants in natural ecosystems.
Mycorrhizal synthesis in vitro between Glomus spp. and artificial seeds of alfalfa
Authors: STRULLU D. G. , ROMAND C. , CALLAC P. , TÉOULÉ E. , DEMARLY Y.
Published: April 2006

Summary

Artificial seeds of alfalfa (Medicago sativa L.), consisting of somatic embryos encased in a nutritive coating, were inoculated with Glomus. In vitro the fungus, regenerated from surface sterilized root fragments, formed typical vesicular‐arbuscular mycorrhizas.
Effect of nitrogen source on growth response to salinity stress in maize and wheat
Authors: LEWIS O. A. M. , LEIDI E. O. , LIPS S. H.
Published: April 2006

summary

The effect of ammonium and nitrate nutrition on maize and wheat grown hydroponically and salinity stressed was assessed from measurements of growth rate and gas exchange. In both maize and wheat the ammonium‐grown plains were much more sensitive to salinity toxicity than nitrate‐grown plants particularly when exposed to 60–80 mM salinity. Shoot growth was retarded to a far greater extent than root growth in salinity‐stressed plants of both wheat and maize with either nitrogen source.

There was no significant decrease of photosynthetic rate in salinity‐stressed plants of either species fed nitrate or ammonium, except in severely wilted plants of both species fed nitrate or ammonium at the highest (80 mM) salinity concentration. The same was true for stomatal conductance, transpiration rate and transpiration ratio (water use efficiency). In nitrate‐fed wheat, raising the calcium concentration from 2 to 12 mM in the presence of 60 mM salinity produced an 11% increase in growth. This effect is ascribed to improved nitrate uptake due to calcium protection of the nitrate transporter and was not evident in ammonium‐grown wheat. Possible reasons for the differential effects of ammonium and nitrate nutrition are discussed.
Sugar uptake and invertase activity in Dendrobium tissues
Authors: HEW C. S. , MAH T. C.
Published: April 2006

summary

Undifferentiated and differentiated tissues of Dendrobium exhibited no difference in their preference for sugars. The uptake of sugars was more rapid by undifferentiated tissue. Fructose provided the best carbon source for both tissues. Sucrose was hydrolysed before it was taken up, as the result of invertase activity. Both acid and alkaline invertase were present and invertase activity was detected in the soluble and cell wall fraction. There was a gradual increase in invertase activity of tissues grown in sucrose‐containing medium with time but not in tissues grown in fructose‐containing medium.
Ectomycorrhizal formation by micropropagated clones of Eucalyptus marginata inoculated with isolates of Pisolithus tinctorius
Authors: TONKIN C. M. , MALAJCZUK N. , McCOMB J. A.
Published: April 2006

summary

Eucalyptus marginata Donn ex Sm. and Pisolithus tinctorius (Pers.) Cok and Couch were co‐cultured to obtain ectomycorrhizal formation in vitro. One isolate of P. tinctorius formed mycorrhizas with aseptic seedlings of a juvenile clone derived from a 4‐month‐old seedling, and four clones derived from crowns of mature trees. A second P. tinctorius isolate formed mycorrhizas with only the clones from mature trees. Successful combinations resulted in formation of a mantle followed by a Hartig net and epidermal cell elongation. The fungal/seedlings or fungal/seedling clone combinations which did not produce ectomycorrhizal roots, were characterized by a mantle but lacked a Hartig net, and formed an abundance of polyphenols throughout the root. Genotype, maturity and fungal specificity are key factors influencing successful ectomycorrhizal formation on E. marginata by P. tinctorius in vitro.
Electrophoretic and immunological studies on acid phosphatase from a mycorrhizal fungus of Erica hispidula L.
Authors: STRAKER C. J. , GIANINAZZI‐PEARSON VIVIENNE , GIANINAZZI S. , CLEYET‐MAREL J.‐C. , BOUSQUET N.
Published: April 2006

summary

Wall‐bound acid phosphatases of an endomycorrhizal fungus of Erica hispidula L. were separated by PAGE, electrotransferred to nitrocellulose membranes and glycoprotein characteristics studied using Concanavalin A. An antiserum was raised against the major high‐molecular‐weight acid phosphatase and its specificity demonstrated by immunoblotting and ELISA. The antiserum reacted very little with protein extracts of other cellular fractions and was unable to bind to wall‐bound protein antigens of a mycorrhizal isolate from K. mauritanica. Ultrastructural localization of acid phosphatase by cytoenzymology and indirect immunogold labelling showed it to be almost exclusively associated with the fungal wall and septa of living hyphae, whilst in senescent hyphae it was also present within the disorganized cytoplasm.