bluuebunny/crossref_metadata_2025 huggingface dataset:
THE WEATHERING OF SCOTS PINE EPICUTICULAR WAX IN POLLUTED AND CLEAN AIR
Authors: CROSSLEY A. , FOWLER D.
Published: May 2006

Needle surfaces of Pinus sylvestris L. were examined at three sites, two in clean air (SO2 < 10 μg m−3) at Saltoun, (altitude 200 m) and Cairngorm (400 m) and one in polluted air (SO2 c 40 μg m−3) at Gorple (300 m). Needles one, two and (where available) three years old were sampled during the period July 1981 to March 1982. Needle longevity was greater at the two clean air sites where 50 % of two year old needles were present compared with only 10% at the polluted site.

The physical structure of epicuticular wax was assessed using scanning electron microscopy. The wax tubes shortened, thickened and fused into an amorphous surface ‘crust’ with time. The rate of this‘weathering’ declined logarithmically. A constant (k) was denned as the weathering constant for this process. Values of/? (months−1) differed significantly between sites (Saltoun 0.061 ±0.01, Cairngorm 0.084 + 0.012 and Gorple 0.154±0.013).

In addition to faster weathering, needles at the polluted site were heavily contaminated with particulate debris, much of which had the physical characteristics of pulverized fuel ash that is produced by large coal combustion sources. During‘weathering'the surface layer of tubular wax crystals show a marked increase in thickness from ∼ 130 nm for newly exposed needles to 220 nm after 30 months old. No significant inter‐site differences in the rate of change in tube width were noted.
MODERN POLLEN SPECTRA FROM THE WESTERN INTERIOR OF CANADA AND THE INTERPRETATION OF LATE QUATERNARY VEGETATION DEVELOPMENT
Authors: MACDONALD G. M. , RITCHIE J. C.
Published: May 2006

The pollen spectra obtained from 127 lake sediment surface samples from the western interior of Canada are examined. Principal components biplots and discriminant analysis are used to investigate the correspondence between modern pollen rain and major vegetation zones in the study area. It is demonstrated that the major vegetation zones in the western interior of Canada can be distinguished on the basis of their modern pollen rain. Principal components biplots and discriminant analysis are also used to compare late Quaternary fossil pollen assemblages from lakes located near the southern and northern periphery of the modern boreal forest with the modern pollen spectra. The results suggest that the late Pleistocene and early Holocene pollen spectra from the southern and northern periphery of the boreal forest lack modern analogues in the western interior of Canada. The northern and southern boundaries of the boreal forest were located north of their modern positions during the mid Holocene. Vegetation developed and responded to mid Holocene climatic change at different rates at the two sites. Modern vegetation conditions were established at both sites between 5000 B.P. to 3000 B.P. Vegetation has remained relatively stable during the last three thousand years.
PARTIAL RECOVERY IN PLASTIDS OF LEMNA AEQUINOCTIALIS WELWITSCH * 1073 TREATED WITH l‐METHIONINE OR l‐CYSTINE
Authors: MONSELISE EDNA BEN‐IZHAK , PORATH DAN , TAL MOSHE , ARZEE TOVA
Published: May 2006

When light‐grown plants of mutant 1073 of Lemna aequinoctialis Welwitsch were grown in a medium containing 31 μl‐cystine, the tubular clusters characteristic of this mutant disappeared in the mature fronds and chloroplasts and mitochondria appeared normal. l‐Methionine (2 μ) effected a similar but less dramatic change. In young fronds, however, 10% of chloroplasts when supplied with l‐cystine, and 50% when supplied with l‐methionine, still contained tubular clusters.

When l‐cystine was supplied to young fronds of the wild‐type strain 6746, chloroplasts were normal but contained much larger starch inclusions. Relative growth rates of both strains were improved by addition of l‐cystine or l‐methionine. In mutant fronds they attained values equivalent to wild‐type control. This partial recovery from ultrastructural defects was not matched by a physiological recovery, i.e. plants were still incapable of photosynthesis and ammonium ion uptake, as were mutant plants in control media.

Moreover when the partially recovered plants were tested for ammonium ion uptake, in the presence of either l‐methionine or l‐cystine, ammonium ions from plants moved out into the medium during the first 24 h, while increased ammonium uptake was detected with the wild strain.
REVERSAL BY PHENOLIC COMPOUNDS OF ABSCISIC ACID‐INDUCED INHIBITION OF IN VITRO ACTIVITY OF AMYLASE FROM SEEDS OF TRITICUM AESTIVUM L.
Authors: SHARMA SHASHI , SHARMA S. S. , RAI V. K.
Published: May 2006

Effects of abscisic acid and certain phenolic compounds have been studied, individually and in combination, on in vitro amylase activity from Triticum aestivum L. seeds. ABA suppressed the amylase activity, in vitro, while salicylic acid, cinnamic acid and ferulic acid applied alone promoted it; vanillic acid caused a slight inhibition. Irrespective of their individual effects, all the phenolic compounds studied reverted the inhibitory action of ABA on amylase activity. This behaviour suggests that phenolic compounds could have a role in regulating mobilization of carbohydrates through degradation of starch, and in turn some role in the regulation of seed germination.
THE POTENTIAL FOR EVOLUTION OF SALT (NaCl) TOLERANCE IN SEVEN GRASS SPECIES
Authors: ASHRAF M. , McNEILLY T. , BRADSHAW A. D.
Published: May 2006

The seedling root growth of Agrostis stolonifera L., Agrostis capillaris L., Holcus lanatus L., Lolium perenne L., Dactylis glomerata L., Festuca rubra L. and Puccinellia distorts (L.) Parl. was examined after 14 d of immersion in dilute nutrient solutions containing 0, 150, and 250 mol m−3 NaCl. Root growth of all species was significantly reduced by increasing NaCl concentration.

Samples of 10000 to 20000 seeds of each species were then screened for ability to root in solution cultures at NaCl concentrations which markedly inhibited root growth in the first experiment. Small numbers of individuals of all species rooted in these solutions and high and low selection lines were established based upon root length values.

Adult plants from these high and low selected lines were compared with an unselected sample for ability to root in a range of NaCl concentrations. The high line plants had significantly longer roots than the unselected plants in all species, and than the low selected line in all species except Agrostis capillaris. Low selected plants had significantly longer roots than unselected plants in Holcus lanatus, and Dactylis glomerata.

The pattern of response to selection showed no consistent relationship to the known ecology of the species examined, and suggests that variability in salt tolerance is widely present in species, but for other reasons salt tolerance does not always evolve in natural situations.
CUTICLE, CELL WALL ULTRASTRUCTURE AND DISEASE RESISTANCE IN MAIDENHAIR FERN
Authors: ARCHER K. J. , COLE A. L. J.
Published: May 2006

Light and scanning electron microscopy showed the pinnules of maidenhair fern, Adiantum raddianum var. raddianum (Hoshizaki), possess hydrophobic, crystalline deposits overlying a well developed cuticle on both abaxial and adaxial surfaces. In response to attempted infection by Botrytis cinerea (Pers. ex Fr.), browning, cell wall thickening and papilla formation occurred. Transmission electron microscopy revealed infection pegs are surrounded by electron‐dense papillae forming partial barriers to further colonization.
EFFECTS OF MYCORRHIZAL INFECTION ON PLANT GROWTH, NITROGEN AND PHOSPHORUS NUTRITION IN GLASSHOUSE‐GROWN ALLIUM CEPAL.
Authors: SMITH S. E. , JOHN B. J. ST. , SMITH F. A. , BROMLEY J.‐L.
Published: May 2006

Growth and rates of uptake of nitrogen and phosphorus (inflow) in Allium cepa L. were measured in three experiments. Effects of mycorrhizal infection (Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappe) and N and P fertilization were investigated. The experiments were carried out in a naturally‐lit glasshouse, so that seasonal variations in solar radiation influenced experimental results.

In all experiments, a large positive growth response to mycorrhizal infection was observed when soil P was low. However, at high soil P smaller growth responses to infection were observed, as expected. Infection was associated with increased inflow of P, at all levels of soil P, even when non‐mycorrhizal plants grew as well as or better than mycorrhizal plants. Lower P inflow was observed when infection was low and also at low irradiance in both mycorrhizal and non‐mycorrhizal plants. The results show that mycorrhizal fungi increase the rate at which P is absorbed from soil, even under conditions which precluded a positive growth response to infection.

In plants grown in spring and summer (two experiments), mycorrhizal infection was also associated with increased N inflow. N inflows in both mycorrhizal and non‐mycorrhizal plants were lower in a third experiment in late winter and mycorrhizal infection had little or no effect on N inflow in this experiment. Increased N supply increased the inflow of N, concentrations of N in plant tissues and plant growth except in plants that were severely P limited, and there was no evidence that mycorrhizal infection alleviated N stress in low N plants.

The results are discussed in relation to the environmental factors limiting plant growth, in particular nutrient uptake via and carbohydrate use by the fungal symbiont.
EFFECTS OF PHOTON IRRADIANCE ON THE GROWTH OF SHOOTS AND ROOTS, ON THE RATE OF INITIATION OF MYCORRHIZAL INFECTION AND ON THE GROWTH OF INFECTION UNITS IN TRIFOLIUM SUBTERRANEUM L.
Authors: TESTER M. , SMITH S. E. , SMITH F. A. , WALKER N. A.
Published: May 2006

The effects of photon irradiance on the growth of young plants (up to three weeks old) of Trifolium subterraneum L. and on the development of mycorrhizal root systems were studied with plants grown in a soil/sand mixture inoculated with Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe. Total plant growth was lower when photon irradiance was 100 μmol m−2 s−1, compared with 450 μmol m−2 s−1. Fresh weight of shoots was unaffected, but the fresh weight/dry weight ratio was increased at the lower irradiance in shoots, but not in roots. The main effect of decreased irradiance on the growth of the root system was a reduction in the numbers of first‐ and second‐order lateral roots initiated. The average rate of extension of axial and lateral roots was only slightly reduced. The fraction of the root length infected was lower at the lower irradiance, particularly in the first two weeks. Development of infection was analyzed in terms of the role of formation of mycorrhizal entry‐points (A) and the average rate of growth of infection units (B). Reduction in the fraction of the root length infected was found to be due to a reduction in A. B was remarkably constant at the two irradiances and in the different root subsystems. Thus both roots and infection units respond by making fewer units of unaltered rate of growth.
AXENIC SYNTHESIS OF ERICOID MYCORRHIZA IN VACCINIUM ANGUSTIFOLIUM AIT. BY OIDIODENDRON SPECIES
Authors: DALPÉ Y.
Published: May 2006

Oidiodendron griseum, O. cerealis, O. rhodogenum, O. tenuissimum and O. truncatum were tested for their endophytic ability on axenic seedlings of Vaccinium angustifolium grown on a synthetic nutrient medium. O. griseum, O. rhodogenum and O. cerealis produced typical intracellular hyphal coils characteristic of the ericoid infection. For these three species, the level of infection reached 9 to 21 % of the root cells after 60 d of incubation. O. truncation and O. tenuissimum did not infect the Vaccinium roots but the latter species stunted development of secondary roots and reduced the growth of the seedlings.
EFFECTS OF MONOVALENT AND DIVALENT CATIONS ON PHOSPHATE ABSORPTION BY BEECH MYCORRHIZAS
Authors: STRULLU D. G. , GRELLIER B. , GARREC J. P. , McCREADY C. C. , HARLEY J. L.
Published: May 2006

The rate of uptake of phosphate from dilute solutions of KH2PO4 by Fagus mycorrhizas was much increased if calcium or magnesium, as chlorides, was added to the solution but not if sodium or potassium was similarly added. No effect on the partition of phosphate between sheath and core was observed but increased uptake was associated with an increase in number and phosphate content of phosphatic (polyphosphate) granules. The P/Ca ratio of the granules was reduced in the presence of calcium and increased in the presence of magnesium. It is concluded that these divalent cations are incorporated into phosphatic granules and that their effect on phosphate uptake is related to the reduction in the soluble phosphate present in the cells rather than to their effects on the cell membranes.
FLANDRIAN ENVIRONMENTAL HISTORY OF THE ISLE OF MULL, SCOTLAND
Authors: LOWE J. J. , WALKER M. J. C.
Published: May 2006

Flandrian percentage pollen diagrams are presented from three sites in western and northern Mull, Inner Hebrides, Scotland, and these data are augmented by pollen concentration evidence from one of the sites. In general terms, the pattern of vegetational development is broadly similar to that found in a previous study in the uplands of south‐central Mull. However, differences in detail are apparent in the vegetational history of the northern and western parts of the island, particularly in the representation of Empetrum, Juniperus and Betula pollen in the early Flandrian deposits, and in the frequencies of Alnus and Quercus in the mid‐ and late‐Flandrian pollen records. These pollen‐stratigraphic contrasts between the three sites, and between these profiles and those from the more sheltered south‐central parts of the island can be attributed partly to differences in pollen recruitment processes and partly to variations in degree of exposure to prevailing winds.
TANSLEY REVIEW NO. 5 FRUCTANS AND THE METABOLISM OF SUCROSE IN VASCULAR PLANTS
Authors: POLLOCK C. J.
Published: May 2006

The occurrence, structure and metabolism of fructose polymers in tissues of vascular plants are discussed in relation to the metabolism of sucrose. Distinctions are made between long‐term and short‐term storage of such polymers and the regulatory mechanisms which govern accumulation are examined. The roles of various fructosyltransferases in the synthesis of the different fructan structures from sucrose are outlined. The potential selective advantages of the possession of fructan metabolism in different species are assessed with reference to possible roles as cryoprotectants, in osmotic control and as storage carbohydrates whose metabolism can continue at low temperatures (0 to 5°C). It is concluded that the complexity and variety of fructan structures and of the associated enzyme systems has resulted in an incomplete understanding of their physiology and biochemistry, but their significance as an alternative storage polysaccharide in both leaves and storage organs should not be underestimated.

Contents

I.
Introduction

II.
The structure of fructans in vascular plants: variations on a theme
2

III.
The enzymes of fructan synthesis: common elements and sources of structural diversity
5

IV.
The comparative biology of fructan metabolism: diversity in occurrence and function
11

V.
Concluding remarks
19

Acknowledgements
19

References
19
EARLY SENESCENCE OF THE ROOT CORTEX OF AGRICULTURAL GRASSES, AND OF WHEAT FOLLOWING ROOT AMPUTATION OR INFECTION BY THE TAKE‐ALL FUNGUS
Authors: KIRK J. JANE , DEACON J. W.
Published: May 2006

Nuclear fluorescence following acridine orange staining was used to assess patterns and rates of death of the root cortex (RCD) in Lolium perenne L., L.×hybridum Hausskn. and Dactylis glomerata L. grown in pathogen‐free soil in a glasshouse. The pattern of RCD was as previously described for cereals. The rate of RCD differed significantly between grasses and between cultivates of L. pefenne, but in most instances the cortex was anucleate, except for the innermost cell layer next to the endodermis, in 26 to 27 d old regions of seminal root axes. Root impedance caused by a nylon gauze barrier in soil significantly increased the rate of RCD in one tested cultivar of L. perenne.

RCD was more rapid in wheat than in grasses. In 8 d old regions of wheat seminal root axes the cortex contained only 54% of the nuclei initially present. Infection of wheat roots by the take‐all fungus, Gaeumannomyces graminis (Sacc.) Arx & Olivier var tritici Walker, caused vascular disruption followed by more rapid RCD than in uninfected roots. Similarly rapid RCD occurred in amputated roots, though in all instances the pattern of RCD was unchanged. The rate of RCD was slower in long than in short lengths of amputated root, perhaps because of remobilization of nutrients from dying cells.

Nuclei persisted for at least 10 d in the inner cortex of 2 cm lengths of young roots of wheat, barley and L. perenne buried in soil at 20 °C. The pattern of nuclear deletion from the root pieces was the same as in whole roots, and the rate of RCD was faster in wheat than in barley, as also found for roots attached to plants. All these results demonstrate a consistent pattern of cortical senescence in graminaceous roots and suggest that it is a programmed phenomenon.
RESPONSES OF THREE VESICULAR – ARBUSCULAR MYCORRHIZAL FUNGI AT FOUR SOIL TEMPERATURES AND THEIR EFFECTS ON COTTON GROWTH
Authors: SMITH G. S. , RONCADORI R. W.
Published: May 2006

The effects of four soil temperatures on growth of Stoneville 213 cotton (Gossypium hirsutum L.) and root colonization by three vesicular–arbuscular mycorrhizal fungi were tested in soil temperature tanks in the glasshouse. Growth responses in fresh and dry weights of shoots and plant height were linear for noninoculated plants, but nonlinear for plants mycorrhizal with Glomus intraradices Schenck & Smith, Glomus ambisporum Smith & Schenck, or Gigaspora margarita Becker & Hall at soil temperatures of 18, 24, 30 and 36 °C. Total length of root and length of mycorrhizal root were positively correlated and increased as soil temperatures increased. However, total root length was not significantly changed by soil temperature in nonmycorrhizal plants. At 18 °C, shoot and root growth were not improved by mycorrhizas and total root length was actually suppressed by the endophytes. At 24, 30, and 36 °C, mycorrhizas stimulated plant growth. Shoot dry weights were maximum at 30 °C on plants mycorrhizal with G. margarita and G. intraradicvs and at 36 °C on plants inoculated with G. ambisporutn. Percent root colonization by the endophytes was less than 10% at 18 °C and ranged from 57 to 80% at temperatures of 24 °C or higher. All mycorrhizal plants had increased leaf tissue concentrations of P, Cu, Zn, and Mn with concentrations of Cu, Zn, and Mn greatest in plants mycorrhizal with G. ambisporum. The three mycorrhizal fungi generally stimulated plant growth equally well at 24 and 30 °C and G. ambisporum was slightly more effective as a symbiont at 36 °C than either G. intraradices or G. margarita.
NICKEL INDUCED STIMULATION OF GROWTH, HETEROCYST DIFFERENTIATION, 14CO2 UPTAKE AND NITROGENASE ACTIVITY IN NOSTOC MUSCORUM
Authors: Rai L. C. , RAIZADA MEENA
Published: May 2006

Addition of nickel stimulates growth, heterocyst differentiation, 14CO2 uptake and nitrogenase activity in Nostnc muscorum. The significance of this observation is discussed.
CARBON NUTRITION AND THE REGULATION OF UPTAKE HYDROGENASE ACTIVITY IN FREE‐LIVING AND SYMBIOTIC ANABAENA CYCADEAE
Authors: KUMAR A. P. , PERRAJU B. T. V. V. , SINGH H. N.
Published: May 2006

Anabaena cycadeae was grown with N2 as nitrogen source, either photoautotrophically in light or with glucose as carbon source in darkness. The rate of growth was much slower in darkness but the heterocyst frequency was much the same; nitrogenase activity (on a chlorophyll basis) was about half that of light‐grown cells. Light‐grown organisms contained uptake hydrogenase activity but dark‐grown organisms did not. The addition of glucose to light‐grown organisms was followed by the disappearance of uptake hydrogenase activity over the following 48 hours and the disappearance was independent of light. Heterocyst frequency and nitrogenase activity were much less affected by glucose addition.

A. cycadeae growing symbiotically in cycad roots had much higher heterocyst frequency and nitrogenase activity than the free‐living form but no detectable uptake hydrogenase activity.

It is suggested that the rate of supply of carbohydrate to the heterocyst controls the development of uptake hydrogenase activity and that the absence of this activity in the symbiotic cyanobacteria indicates that the organisms in the cycad roots have an ample supply of carbohydrate.
EVENTS AT AND AROUND THE FIRST AND SECONDULMUSDECLINES: PALAEOECOLOGICAL INVESTIGATIONS IN CO. TYRONE, NORTHERN IRELAND
Authors: HIRONS KENNETH R. , EDWARDS KEVIN J.
Published: May 2006

Percentage and concentration pollen diagrams from the sediments of two adjacent inter‐drumlin hollow lakes near Dungannon, and in two cores from Lough Catherine, suggest that only small reductions in the pollen frequencies of trees such as pine and, at some sites, birch and oak, accompanied reducedUlmusat the elm decline in these parts of Co. Tyrone. They also confirm thatPteridium aquilinumcould sporulate and many herbs were able to flower more freely owing to an opening of the tree canopy. Seventeen radiocarbon dates provide chronologies for the sites and date the elm decline to between 5050 and 5375 B.P., the subsequent start of increased elm pollen percentages to between 5010 and 4850 B.P., and the beginning of a second decline in elm pollen to between 4330 and 4260 B.P. The initial decline in elm pollen values may have been caused by disease and this reduction was superimposed upon a background of small‐scale clearances which continued after a general elm regeneration. The question of a general similarity and causation of the second elm decline in Ireland and elsewhere is considered. Chemical, magnetic and pollen preservation data from the Co. Tyrone sites suggest episodes of erosion occurring at the first elm decline and others at the second elm decline.
ACCUMULATION OF PHOSPHORUS, DRY MATTER AND BETAINE DURING NaCl STRESS OF SPLIT‐ROOT CITRUS SEEDLINGS COLONIZED WITH VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI ON ZERO, ONE OR TWO HALVES
Authors: DUKE E. R. , JOHNSON C. R. , KOCH K. E.
Published: May 2006

Sodium chloride tolerance and phosphorus content were examined in split‐root Carrizo citrange seedlings [Poncirus trifoliata (L.) Raf. ×Citrus sinensis (L.) Osbeck] colonized with a vesicular‐arbuscular mycorrhizal fungus (Glomus intraradices Schenck & Smith) on zero, one or two root halves. Plants were treated with NaCl at 0, 25, 50 or 100 mM, and the degree of stress was measured as reduction of dry matter accumulation and rise in level of leaf proline‐betaine (stachydrine). Shoot and root dry weight production during this period decreased with increasing levels of salt. Absolute reductions were similar for plants inoculated on one vs two half‐root systems, but percentage decreases were less in the latter due to greater overall growth in all treatments. Betaine levels in leaf tissues were positively related to soil salt levels for each mycorrhizal treatment. Significant differences in betaine levels were also detected in plants with and without mycorrhizal fungi, and mean levels tended to be higher for those colonized on one vs two halves of their root system. In contrast, a half‐root system and its fungal symbiont supplied enough phosphorus to allow concentrations of leaf P to equal those of fully infected root systems, yet the two groups did not show equal growth under control conditions or percentage reductions with NaCl stress.
SYNTHESIZED ECTOMYCORRHIZAL ASSOCIATIONS Of SOME AUSTRALIAN HERBS AND SHRUBS
Authors: KOPE H. H. , WARCUP J. H.
Published: May 2006

The morphology and development of ectomycorrhizas formed by Pezisa whitei (Gilkey) Trappe, Labyrvnthomyces sp. (Ascomycetes) and Laccaria ohiensis (Mont.) Singer (Basidiomycete) on a range of hosts including Pultenaea obovata Benth., Gompholobium latifolium Sm. (shrubs) and Poranthera microphylla Brongn., Angianthus tomentosus Wendl., Waitssia citrina (Benth.) Steetz and Stvlidium gratninifolium Sw. ex Willd. (herbs) have been studied in a gnotobiotic system in a soil mix low in available phosphate.

The associations formed varied from mycorrhizas with well‐defined sheaths enclosing root apices on P. obovata and G. latifolium to less well‐defined ones on the herbs, where associations varied from partial sheathing of roots to discrete patches of fungal sheath to no sheath at all in the association A. tomentosus + P. whitei. A Hartig net was formed in most associations although L. ohiensis formed none with P. microphylla, A. tomentosus and W. citrina. The results showed that the form of a mycorrhiza depended on both partners, not on the fungus or higher plant alone.

All plant‐fungus combinations except for A. fomentosus + L. ohiensis showed a significant growth response compared with non‐inoculated plants, which indicated mycorrhizal effectiveness, irrespective of mycorrhizal form, in the growth conditions employed.
THE EFFECTS OF A POLYAMINE BIOSYNTHESIS INHIBITOR ON INFECTION OF VICIA FABA L. BY THE RUST FUNGUS, UROMYCES VICIAE‐FABAE (PERS.) SCHROET
Authors: WALTERS D. R.
Published: May 2006

The effects of the polyamine biosynthesis inhibitor, difluoromethylomithine (DFMO), on rust infection of the broad bean have been examined. DFMO was sprayed onto leaves at 0.025, 0.1 and 0.4 mM before and after inoculation. DFMO was also applied to leaf halves in order to examine the possible translocation of the inhibitor to untreated leaf halves (systemic treatment). DFMO gave good control of rust infection, irrespective of the treatment. DFMO applied after inoculation was more effective than a pre‐inoculatory treatment when used in non‐systemic tests. When used as a systemic treatment on leaf halves, pre‐inoculatory application of DFMO was more effective. DFMO did not affect plant growth or endogenous concentrations of poly amines. The possible use of DFMO in the control of a range of plant diseases is discussed.
ELECTROPHORETIC VARIATION IN TRIAZINE‐RESISTANT AND SUSCEPTIBLE POPULATIONS OF AMARANTHUS RETROFLEXUS L.
Authors: WARWICK S. I. , BLACK L. D.
Published: May 2006

Patterns of electrophoretic variation in seven enzyme systems were investigated in one triazine‐resistant and nine susceptible populations of Amaranthus retraflexus L. collected along an 800 km north‐south transect in southern Ontario, Canada. The resistant population occurs in a field in which continuous maize production and intensive use of atrazine had been combined over a 15–year period. The nine susceptible populations were collected from both waste ground and cultivated fields. One would expect the genetic make‐up of the triazine‐resistant population to be simpler than that of susceptible populations as a result of founder effects from a single or only a few resistant founder plants. Our results confirmed this prediction. The resistant population showed a marked reduction in genetic variation, as compared with susceptible populations. One enzyme, GDH, was monomorphic in all 10 populations, the other six enzymes (IDH, GOT, 6PGD, PGI, LAP and MDH) showed varying degrees of phenotypic polymorphism. The resistant population was variable for three of the seven enzyme systems examined. This was in contrast to the homogeneity observed in triazine‐resistant populations of Chenopodium album L. from Ontario. Differences in within‐population phenotypic polymorphism among the nine susceptible populations of A. rctroflexus were not correlated with habitat or latitude of collection sites.
THE EFFECTS OF SODIUM CHLORIDE ON GROWTH AND NITROGEN FIXATION IN CASUARINA OBESA MIQ.
Authors: REDDELL PAUL , FOSTER R. C. , BOWEN G. D.
Published: May 2006

Summary

In the field, nodulation of Casuarina obesa Miq. was found at sites with salinity levels up to 28 mg Cl−g−1soil. A subsequent glasshouse study examined effects of step‐wise additions of NaCl on plant growth and symbiotic nitrogen fixation in C. obesa seedlings nodulated by Frankia from two sources. Irrespective of Frankia source, plant growth declined above 0.15 mg NaCl g−1soil, but some growth still occurred at 15 mg NaCl g−1soil. Nitrogen fixation also decreased above 0.15 mg NaCl g−1soil, with total nodule weight being reduced at NaCl levels greater than 0.15 mg NaCl g−1soil for both Frankia sources. However, increasing NaCl markedly reduced the N fixed mg−1nodule weight for only one Frankia source: N fixed mg−1nodule was reduced by 60% at 1.5 mg NaCl g−1soil and inhibited at 15 mg NaCl g−1soil. Electron micrographs of the ‘effective’ nodules from the high‐salt treatment showed Frankia infected cells to have low (putative) Cl−levels when compared with adjacent uninfected cells.

At levels of 1.5 and 15 mg NaCl g−1soil both Na+and Cl−accumulated in shoots. Electron micrographs of shoots from the 15 mg NaCl g−1soil treatment showed Cl−to be concentrated in the intercellular spaces and in the hypodermal cells.

The success of plantings of salt tolerant Casuarinaceae such as C. obesa requires the selection of highly salt tolerant plant and Frankia genotypes.
COMPARISON OF YIELDS OF SEVERAL CULTIVARS OF FIELD‐GROWN SOYBEANS EXPOSED TO SIMULATED ACIDIC RAINFALLS
Authors: EVANS LANCE S. , LEWIN KEITH F. , OWEN ELIZABETH M. , SANTUCCI KAREN A.
Published: May 2006

Summary

Rainfall acidity response functions for crop yield and growth are necessary to predict the overall impacts on crop yields of ambient and/or anticipated levels of acidic rain. The experiment described herein was performed at Brookhaven National Laboratory to determine the effects of simulated rainfalls of pH 5.6, 4.4, 4.1 and 3.3 on seed yields of four cultivars of field grown soybeans. (Glycine max Merrill). Soybeans were chosen because previous results suggested that certain varieties of this crop are sensitive to rainfall acidity and because they are an economically important crop in the United States. Sixteen plots per treatment were used. Plants were grown using standard agronomic practices under automatically moveable rainfall exclusion shelters which minimized changes in the plants' microclimate. Soybeans of cv. Amsoy shielded from ambient rainfalls and exposed to simulated rainfalls of pH 4.4, 4.1 and 3.3 exhibited yields that were 11.5, 10.4 and 11.7%, respectively, below those of plants exposed to rain of pH 5.6. The comparable figures for other cultivars were as follows: Asgrow 3127– 14.5, 12.2 and 9.0%; Corsoy ‐ 13.7, 12.7 and 7.8 %; Hobbit ‐ 9.2, 6.2 and 16.6%. Most of the observed decreases in seed mass per plant and per unit area for these four cultivars appear to have resulted from a corresponding decrease in pod number per plant.
DEFORESTATION, CANNABIS CULTIVATION AND SCHWINGMOOR FORMATION AT CORS LLYN (LLYN MIRE), CENTRAL WALES
Authors: FRENCH C. N. , MOORE P. D.
Published: May 2006

Summary

Pollen and macrofossil diagrams from the schwingmoor sediments of Llyn Mire are presented. Prior to the formation of the schwingmoor, Cannabis sativa was cultivated around Llyn lake, first to the east and later to the west of the basin. Despite Cannabis cultivation so close to Llyn, there is no evidence to suggest that the lake was used for retting purposes.

A period of woodland clearance occurred immediately after the Cannabis cultivation and this process may have been responsible for the changes which led to schwingmoor formation in the basin. It is suggested that increased soil erosion into the lake, together with some eutrophication, encouraged the colonization of the lake surface by a floating mat of vegetation. The schwingmoor was formed in historic times by a floating carpet of such taxa as Carex rostrata, Sphagnum recurvum and Sphagnum section Subsecunda. The mat was initiated in the western part of the basin.

The use made of Cannabis/Humulus pollen density as a marker horizon in these studies demanded that these pollen taxa should be adequately separated, and the large numbers of grains of this type present in the sediments permitted the employment of numerical methods based on pore protrusion, which are described here.
REPAIR OF PHOTOINHIBITORY DAMAGE IN ANACYSTIS NIDULANS 625 (SYNECHOCOCCUS 6301): RELATION TO CATALYTIC CAPACITY FOR, AND ENERGY SUPPLY TO, PROTEIN SYNTHESIS, AND IMPLICATIONS FOR μmax AND THE EFFICIENCY OF LIGHT‐LIMITED GROWTH
Authors: RAVEN JOHN A. , SAMUELSSON GORAN
Published: May 2006

Summary

Previously published data on photoinhibition in Anacystis nidulans (Richt.) Drouet 625 (=Synechococcus Naeg. 6301) in the presence (gross rate) and absence (net rate) of an inhibitor of protein synthesis, and on the rate of repair of photoinhibitory damage, are analysed. The analysis makes assumptions about the relationship between changes in the efficiency of photosynthesis and changes in the number of undamaged photoreaction two reaction centres, the number of photoreaction centres of photoreaction two per unit cell volume, and the Mr of the photodamageable polypeptide associated with photoreaction two. With this background, the rate of protein synthesis (mol amino acid incorporated (m3 cell volume)−1 s−1) which is required to just balance the rate of protein destruction in gross photoinhibition, or to support the rate of protein synthesis in repair, is computed. The conclusions drawn from this analysis are:

(1) Repair of (gross) photodamage which is known to be submaximal requires rates of protein synthesis up to 1/10 of the rate of net protein synthesis at the μmax of Anacystis nidulans, and about 1/50 of the maximum possible capacity for protein synthesis deduced from the RNA content of Anacystis nidulans and the RNA‐based protein synthesis capacity of Escherichia coli.

(2) The rates of protein synthesis computed in (1) use up to 1/5 of the ATP production rate from oxidative phosphorylation in darkness and up to 1/10 of the ATP production rate (including photophosphorylation) at an incident photon flux density of 5 μmol photon (400 to 700nm)m−2 s−1

(3) Cells subject to photoinhibitory damage, and its repair, have an additional requirement for protein synthesis and ATP generation over cells not subject to photoinhibition. These additional requirements may limit both μmax and the efficiency of light‐limited growth.
THE DISTRIBUTION OF DRY MASS AND PHOSPHORUS IN AN EVERGREEN FYNBOS SHRUB SPECIES,LEUCOSPERMUM PARILE(SALISB. EX J. KNIGHT) SWEET (PROTEACEAE), AT DIFFERENT STAGES OF DEVELOPMENT
Authors: JONGENS‐ROBERTS S. M. , MITCHELL D. T.
Published: May 2006

Summary

The distribution of dry mass and phosphorus (P) in the proteoid shrub,Leucospermum parile(Salisb. ex J. Knight) Sweet, was determined at three stages of development following fire, over one year in coastal fynbos vegetation, South Africa. At the seedling stage, a mobilization of P was observed from the hypocotyl and cotyledons to the canopy (40% of total P). The numbers and dry mass of proteoid roots increased between eight and ten months after the fire when there was an apparent decline in total seedling P. The one‐ to two‐year‐old plants showed rapid vegetative growth, the leaves being the major storage organs for P. In the final stage of development (five‐ to six‐year‐old plants), flowering and seed production caused a reduction in P levels in the non‐reproductive parts of the plant and up to 20% of the total P accumulated in the inflorescences. There was a winter peak in root production and P content for one‐ to two‐year‐old plants which had root/shoot ratios of 0.77 and 0.48 respectively; the ratio fell to below 0.2 in the five‐ to six‐year‐old plants. The non‐mycorrhizal root systems ofL. parileare dominated by the tap root (up to 88% of total root) but the majority of the roots within the rhizosphere were from neighbouring species.
YIELD RESPONSE OF DAVIS SOYBEANS TO SIMULATED ACID RAIN AND GASEOUS POLLUTANTS IN THE FIELD
Authors: JOHNSTON J.WILLIAM , SHRINER D. S.
Published: May 2006

Summary

The yield response of soybeans (Glycine max (L.) Merr. cv. Davis) to simulated acid rain in the presence of ambient or less‐than‐ambient levels of gaseous pollution was determined in the field. Open‐top chambers were used to alter the levels of gaseous pollutants. An automatic rain simulation system was used to exclude ambient rain and apply rain simulants during natural rain events. These simulations mimicked natural rain events with respect to volume, duration, intensity and frequency. In addition, the intervals between simulated and natural rain events were the same, and therefore many of the potential experimental artifacts associated with scheduled rain simulant applications in earlier research were avoided. Variables measured in the experiment included seed, oil, and protein yield, stem weight, numbers of pods and seeds, and weight per seed. There were no statistically significant rain or chamber treatment effects on the measured variables except for weight per seed and protein yield. The presence of open‐top chambers, when compared with plots without chambers, caused yield variables to be reduced 15 to 20%. There was no evidence to suggest that the response to rain acidity was affected by exposure to ambient or less‐than‐ambient levels of gaseous pollution.
EMISSION OF ETHYLENE BY OAT PLANTS TREATED WITH OZONE AND SIMULATED ACID RAIN
Authors: PELL E. J. , PUENTE M.
Published: May 2006

Summary

Experiments were conducted to determine whether acidic rain either exacerbated or predisposed Avena sativa L. cv. ‘Ogle’ to ozone injury as measured by foliar emission of ethylene. Three sets of experiments were conducted. Experiment I: Plants were exposed to 588 μg m−3(0.30 ppm) ozone from 0830 to 1130 h. Plants were treated from 1300 to 1400 h with simulated acidic rain at pH 2.8, 3.8, 4.6 or 5.6. Experiment II: treatments were the same as in Experiment I except that only simulated acidic rain of pH 2.8 was utilized and larger numbers of plants per treatment were included. Experiment III: plants were treated with simulated acidic rain of pH 2.8 from 1500 to 1600 h followed by exposure to 588 μg m−3 ozone the next day (1200 to 1500 h). At the end of each experiment, ethylene emission was determined for a pooled sample of the first and second leaf of each plant. Seventy‐two hours after the experiment foliar injury was assessed. Acidic rain of pH 2.8 and 3.8 induced small lesions on the foliage but never induced increases in ethylene emission. Ozone induced flecking on the foliage and initiated significant increases in ethylene production. Ethylene emission was not affected by interactions between ozone and acidic rain in any of the experiments.
THE EFFECT OF AERATION ON COLONY DIAMETER, SPORANGIUM PRODUCTION AND ZOOSPORE GERMINATION OF PHYTOPHTHORA CINNAMOMI
Authors: DAVISON E. M. , TAY F. C. S.
Published: May 2006

Summary

The reduced aeration which occurs in waterlogged soil was simulated in the laboratory using O2/N2 gas mixtures, and its effects were studied on six isolates of Phytophthora cinnamomi Rands. Mycelial growth of five isolates grown on agar under a flowing atmosphere, and sporangium production by all of the isolates grown in bubbled liquid culture, were severely reduced under anaerobic conditions. Three of the isolates showed an increase in the number and rate of development of sporangia with increasing O2 concentration of the gas stream. The other isolates showed no increase in the number of sporangia formed at dissolved O., concentrations above 1.3 mgl−1. There was no effect of O2 concentration, either during growth (13.5 or 21% O2) or germination, on the proportion of zoospores that germinated on agar or on initial growth of germ tubes. However, after 19 h, the total length of germ tubes including branches increased with increasing O2 concentration during germination. The number of branches in 11 of the 12 combinations examined was also positively correlated with O2 concentration.
EFFECTS OF PHOSPHORUS ON THE FORMATION OF MYCORRHIZAS BY GIGASPORA CALOSPORA AND GLOMUS FASCICULATUM IN RELATION TO ROOT CARBOHYDRATES
Authors: THOMSON B. D. , Robson A. D. , ABBOTT L. K.
Published: May 2006

Summary

We compared the effects of phosphorus (P) supply on the formation of vesicular‐arbuscular (VA) mycorrhizas in Trifolium subterraneum L. by Gigaspora calospora (Nicol. & Gerd.) Gerd. and Glomus fasciculatum (Thaxter sensu Gerd.) Gerd & Trappe.

For both fungi, increasing the supply of P decreased the percentage of root length infected. At low P, this decrease was associated with a reduction in the growth of the fungi inside the root. At higher P, the growth of the fungi outside the root was also reduced. These detrimental effects of P on the growth of both mycorrhizal fungi were correlated with reductions in the concentrations of soluble carbohydrates in root extracts and root exudates but were not correlated with the concentrations of free amino‐nitrogen in extracts or exudates.

The percentage of root length infected by G. calospora was decreased to a greater extent than that of G. fasciculatum with increasing P supply. This could partially be explained by the lower concentrations of soluble carbohydrates in the roots of plants inoculated with G. calospora. Additionally, the percentage of root length infected by G. calospora appeared to be more sensitive to reductions in the supply of soluble carbohydrates than that of G. fasciculatum.

Growth responses to inoculation were dependent on the species of mycorrhizal fungus and the P level. Enhancements and depressions in the growth of tops could be explained in terms of increased and decreased P uptake.
ISOLATION AND STRUCTURAL CHARACTERIZATION OF SOIL‐Borne AUXILIARY CELLS OF GIGASPORA MARGARITA BECKER & HALL, A VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS
Authors: JABAJI‐HARE S. H. , PICHÉ Y. , FORTIN J. A.
Published: May 2006

Summary

Soil‐borne auxiliary cells of Gigaspora margarita Becker & Hall have been investigated with light and electron microscopy. The cell wall is composed of four prominent layers and autofluoresces intense yellow under blue light. Histochemically, it contains polysaccharides and lipids. The cytoplasm is composed of amorphous material, nuclei and a variety of osmiophilic granules. In old and moribund auxiliary cells and subtending hyphae, gram‐negative bacterium‐like structures (BLS), sometimes dividing, were colonizing the senescent cytoplasm. These BLS were surrounded by peripheral membranes and their cytoplasm was clearly differentiated into electron‐dense and transparent areas.
ULTRASTRUCTURAL STUDIES IN LICHENS
Authors: HONEGGER ROSMARIE
Published: May 2006

Summary

The mycobiont‐photobiont interface in examples of selected orders of ascolichens with trebouxioid photobionts was investigated by scanning (SEM) and transmission electron microscopy. Between 150 and 530 algal cell halves per species were examined by SEM in order to calculate the predominant type of interaction. Simple wall‐to‐wall apposition predominated in the calicialean Chaenotheca chrysocephala (Turner ex Ach.) Th.Fr. Prominent intracellular haustoria were observed in the majority of photobiont cells of Lecanorales with crustose, non‐stratified thalli [Lecanora conizaeoides Nyl. ex Crombie, L. chlarotera Nyl. and Lecidella euphorea (Flörke) Hertel]. Three different types of intraparietal haustoria were distinguished in lichens with stratified thalli. Intraparietal haustoria of type 1, consisting of a tiny infection plug formed by a tightly adhering hypha within the largely cellulosic photobiont cell wall were predominant in crustose species with stratified thallus [Rhizocarpon geographicum (L.)DC, Pertusaria amara (Ach.)Nyl.], but this haustorial type represents also a developmental stage in intraparietal haustoria of types 2 and 3. In the placodioid Lecanora muralis (Schreber)Rabenh. and in the squamules of Cladonia caespiticia (Pers.)Flörke, intraparietal haustoria of type 2 were seen in the majority of photobiont cells, or in ±50% of cell halves, respectively. These can be recognized as an intracellular protrusion formed by a tightly adhering hypha, the tiny infection plug being ensheathed by the algal cell wall. Intraparietal haustoria of type 3, the most highly evolved haustorial type occurring in lichens, was predominant in foliose Parmeliaceae [P. acetabulum (Necker)Duby, P. tiliacea (Hoffm.)Ach., Cetrelia olivetorum (Nyl.)Culb & C. Culb., Cetraria islandica (L.)Ach.], and in the fruticose Anaptychia ciliaris (L.)Körber, Alectoria ochroleuca (Hoffm.)Massal., Teloschistes flavicans (Swartz)Norman and T. capensis (L. Fil.)Malme. When fully developed the haustorial complex in intraparietal haustoria of type 3 was characteristically stalked owing to growth processes of the haustorium‐forming hypha which forms a tiny infection plug within the cell wall of the photobiont. All types of intraparietal haustoria were established exclusively between juvenile, differentiating partners (growing hyphal tips and algal autospores with not yet fully developed cell walls). Intraparietal haustoria of types 2 and 3 are probably restricted to evolved lichens, but structures resembling intraparietal haustoria of type 1 have also been observed in other symbiotic systems such as ectomycorrhizas.
THE EPIPHYLLOUS ALGAL COLONIZATION OF ELODEA CANADENSIS MICHX.: COMMUNITY STRUCTURE AND DEVELOPMENT
Authors: PATERSON D. M. , WRIGHT S. J. L.
Published: May 2006

Summary

The initiation and development of the epiphyllous algal community on the aquatic macrophyte Elodea canadensis Michx. were described using light and scanning electron microscopy (SEM). From initial discrete colonizing cells, a confluent matrix developed which included bacteria, algae, fungi, protozoa, mucilage and inorganic particles. The microtopography of the leaf surface affected'the initial colonization and influenced the growth of certain species. The tips, bases and edges of the leaves were the first areas to become colonized. As the age of the leaves increased, the density of the epiphyllon increased and the structure of the community changed. On young leaves, the Chlorophyta represented 80% of the community standing crop whilst on pre‐senescent leaves this proportion was reduced to 52%. The Bacillariophyta increased in proportional representation from 17% on young leaves to 47% on the older leaves.
THE EFFECTS OF TEMPERATURE AND MOISTURE ON DARK RESPIRATION IN THE FOLIOSE LICHEN UMBILICARIA ANTARCTICA
Authors: HARRISSON P. M. , WALTON D. W. H. , ROTHERY P.
Published: May 2006

Summary

The dark respiration of field‐fresh thalli of Umbilicaria antarctica Frey et Lamb is reported for temperatures from −5.5 to 19°C, and water contents from saturation to dryness. Detailed analysis of the respiratory response with changing water content has suggested that Michaelis‐Menten kinetics appear to provide a useful model. Q10 values are used to indicate possible ice formation in the thallus and water loss characteristics are explained in terms of thallus anatomy. The ecological implications of this approach are discussed.
THE DEVELOPMENT AND ULTRASTRUCTURE OF ECTOMYCORRHIZAS
Authors: DUDDRIDGE J. A.
Published: May 2006

Summary

An ultrastructural study was made of the interactions between Suillus grevillei (Klotzsch) Sing. and 11 species of ectomycorrhizal hosts in aseptic culture in the absence of glucose. No mycorrhizas were formed between S. grevillei and Betula pubescens Ehrh., Allocasuarina inophloia (F. Muell. & F. M. Bail.) L. Johnson, Picea sitchensis (Bong.) Carr., Picea abies (L.) Karst. Alnus glutinosa (L.) Gaertn. or Pinus nigra Arnold, although the fungus grew in the rhizosphere of some of these and in P. nigra it penetrated and killed adjacent epidermal cells. Mycorrhizas were formed with Larix kaempferi (Lamb.) Carr., Larix decidua Mill, Pinus sylvestris L. and Pseudotsuga menziesii (Mirb.) Franco. However, ultrastructural changes in the host‐fungus interface of associations with the latter two hosts suggest that in both cases the symbionts were not entirely compatible. The role of phenolic compounds in ectomycorrhizal compatibility and specificity is discussed.