bluuebunny/crossref_metadata_2025 huggingface dataset:
BRANCHING PATTERNS IN FOREST SHRUBS AND UNDERSTORY TREES IN RELATION TO HABITAT
Authors: PICKETT S. T. A. , KEMPF J. S.
Published: May 2006

We investigated the branching and leaf display of dominant forest shrubs and understory trees in central New Jersey to determine (1) whether branching differentiation occurs in shrubs which reach optimum development in different successional environments, (2) the contrast in branching of small trees between field and forest and (3) the nature of within‐crown branching plasticity in a mature canopy tree. We discovered that shrubs do not differ in gross branching structure (ratio of terminal to supporting branches) and propose that branch angle, length and alteration of leaf orientation may be significant display characters. Small trees exhibit markedly variable response to open ν. closed habitats, confirming the expected increase in branching ratio in open environments. Within, but not outside, the forest, earlier successional species were more variable in branching. A single canopy tree crown also demonstrated alteration of leaf display components, including increased length and wider angle of branches, but not branch ratio in the shaded, lower crown. We suggest some of the fine‐scale morphological traits of shrub branching which may be important in determining their leaf display. Finally, we discuss differences in shrub and tree habit, such as cloning and the presumably reduced costs of support in shrubs, which may explain the failure of shrubs to exploit the same component of branching strategy as trees.
THE EFFECT OF FESTUCA RUBRA ON SIZE, LEAF DEMOGRAPHY AND REPRODUCTIVE CAPACITY OF VULPIA FASCICULATA
Authors: ROGERS R. W.
Published: May 2006

The effect of a perennating population of Festuca rubra on a population of Vulpia fasciculate, in which a second generation was grown using seeds produced by the first, was observed over 2 years. After one season, there was no apparent effect of F. rubra on performance of V. fasciculata as measured by leaf number, total length of leaf produced, number of seeds produced, dry wt of individuals, and dry wt of propagules. Within V. fasciculata populations, it was possible to follow life histories of individual plants and their leaves. Plants which germinated later remained smaller than early germinants, additional nutrients exaggerating this effect. Sixty seven per cent of the variance in total length of leaf produced by a plant in its life could be accounted for in terms of leaf number. It appears that counting leaf number, or measuring length of leaf produced, is a suitable method for studying interactions between grasses and the manner in which these change with time without the need for destructive harvesting. After a second year of growth and interaction, F. rubra severely reduced the dry wt and percentage of V. fasciculata plants able to flower. This was probably due to root interaction and not to exhaustion of nutrient reserves in the seed.
BORON, LIGNIFICATION AND THE ORIGIN OF VASCULAR PLANTS‐A UNIFIED HYPOTHESIS
Authors: LEWIS D. H.
Published: May 2006

It is proposed that the development of an essential role for boron was a prerequisite for the evolution of vascular from prevascular plants since there is a prima jade case that a primary role of boron concerns the biosynthesis of lignin and, in conjunction with auxin, differentiation of xylem. In particular, a potential role for borate in regulating the hydroxylase and oxidase activities of the phenolases involved in the biosynthesis of caffeic and hydroxyferulic acids is suggested. The origin of this role for boron depended on the selection of sucrose in the Chlorophyta as a mobile and storage carbohydrate since, compared with the acyclic sugar alcohols accumulated in other algal groups, sucrose forms only a very weak complex with borate. It is argued that only when borate was not sequestered by complexing with other carbohydrates did the way become clear for it to acquire an essential role. This acquisition catalysed the evolutionary dichotomy between non‐lignified and lignified photosynthetic land‐plants, the bryophytes and tracheophytes. Boron subsequently became involved in two other requirements for success on land ‐ the exploitation of soil for anchorage, water and minerals, and the emancipation of fertilization from external water‐since this element is required for development of adventitious roots (again in conjunction with plant hormones) and, in angiosperms, for germination of pollen.
THE ROLE OF LEAVES IN AUXIN AND BORON‐DEPENDENT ROOTING OF STEM CUTTINGS OF PHASEOLUS AUREUS ROXB.
Authors: MIDDLETON W. , JARVIS B. C. , BOOTH A.
Published: May 2006

The promotion of rooting of cuttings of Phaseolus aureus by indolebutyric acid (IBA) occurs only when leaves are present. IBA may have some direct action on root initiation in the hypocotyl but its main action is in the leaves where it leads to an early increase in free sugars. A later increase in sugars in the hypocotyl is largely dependent on exogenous boron which is essential for root development in cuttings of light‐grown material. IBA also stimulates and boron promotes the accumulation of l4C in hypocotyls when [l4C]sucrose is applied to the leaves. These events occur before roots develop on the hypocotyl. Illumination of the leaves of cuttings during the rooting treatment (IBA for 1 day, followed by boron for 6 days) is beneficial for root development. A progressive loss of response to IBA and boron by cuttings aged in water prior to the rooting treatment is greater in cuttings with leaves in the light during the period of ageing than with leaves in darkness. Possible roles of leaves, auxin and boron in rooting are discussed.
DISTRIBUTION OF ATPASE IN CELLS OF SALICORNIA PACIFIC A VAR. UTAHENSIS AS DETERMINED BY LEAD PHOSPHATE PRECIPITATION AND X‐RAY MICROANALYSIS
Authors: WEBER D.J. , HESS W. M. , KIM CHONG KYUN
Published: May 2006

Salicornia pacifica stem tissues were treated with ATP, Ca(NO3)2 and Pb(NO3)2 to localize ATPase. ATPase activity was present along the plasma membranes and in the cytoplasm of the cortical palisade, inner cortex and vascular cells of young shoots. ATPase was also present in the plasma membranes of tracheids which are present in the palisade region. Ouabain did not inhibit ATPase, but NaF‐, crown ethers, and N.N′‐dicyclohexyl carbodiimide (DCCD) did so in vitro. Only DCCD significantly inhibited (82 %) ATPase in tissues processed for electron microscopy. Energy dispersive microanalysis was used to verify that the precipitates were Pb phosphate.
THE KINETICS OF REHYDRATION OF DETACHED SUNFLOWER LEAVES FOLLOWING SUBSTANTIAL WATER LOSS
Authors: CRUIZIAT P. , TYREE M. T. , BODET C. , LoGULLO M. A.
Published: May 2006

The rate of rehydration of sunflower (Helianthus annuus L.) leaves was measured after dehydration (in air or in a pressure bomb) down to a relative water content of about 89 %. The results, when plotted as the log of the rate of rehydration (mg min‐1) against time, displayed an unusual shoulder in which a phase with a long half time was succeeded by a phase with a short half time. The rehydration kinetics can be explained by two cellular compartments in series in which the bulk elastic modulus increases substantially during rehydration. The first compartment might be associated with the phloem and bundle sheath cells. Water rehydrating the second compartment, consisting of the remainder of the leaf cells, must pass through the first compartment by a transcellular pathway.
VISUALIZATION OF PHOSPHATE ACCUMULATION IN BEECH MYCORRHIZAS
Authors: Chilvers G. A. , Harley J. L.
Published: May 2006

Histochemically monitored uptake experiments, using strips of fungal sheath dissected from beech (Fagus sylvatica) mycorrhizas and incubated in phosphate solutions under a range of conditions, show that accumulation of phosphate is closely paralleled by increases in the number and size of polyphosphate‐containing metachromatic granules, suggesting that these granules represent a major pool of storage phosphate.
SEASONAL CHANGE IN THE PATTERN OF NET CO2 EXCHANGE IN UMBILICARIA LICHENS
Authors: LARSON D.W.
Published: May 2006

The response of net photosynthesis and respiration in five species of Umbilicaria to thallus moisture content at three temperatures (0, 14, 28 °C) and four light intensities (0, 100, 330, 700 μmol m‐2 s‐1) was studied in collections made in summer and winter.

The pattern of response to these variables suggests that each species is uniquely adapted to the cliff environments in which they grow. A simple model suggests further that each species can maintain a positive energy balance provided that its distribution does not extend to sites with temperatures in excess of certain values.

None of the species show photosynthetic acclimation to temperature, yet they all exhibit large seasonal changes in their response structures. The significance of such patterns is discussed.
THE PLASMALEMMA STRUCTURE IN THE PHYCOBIONT TREBOUXIA AT DIFFERENT STAGES OF HUMIDITY OF A LICHEN THALLUS
Authors: Peveling E. , Robenek H.
Published: May 2006

Using the freeze‐fracture technique, the plasmalemma structure of the phycobiont Trebouxia was observed to depend on the hydration of the thallus. The EF and PF fracture faces showed characteristic ridges and corresponding grooves as well as intramembranous particles found in plasmalemma membranes. After prolonged drying of the thallus, the particles were reduced in both number and size and they became reorganized after moistening for a few hours. The ridges appear most distinct and close in dry stages while they are almost completely overlayed by particles in moist thalli. The possible significance of the findings is discussed.
THE EFFECTS OF STARVATION ON THE SYMBIOTIC CHLOROPLASTS IN ELYSI A VIRIDIS: A FINE STRUCTURAL STUDY
Authors: Hawes C. R. , Cobb A. H.
Published: May 2006

An ultrastructural approach was used to study the effects of light and dark starvation on chloroplasts symbiotic in the mollusc Elysia viridis.

Starvation for 27 days in a 16 h light/8 h dark photoperiod resulted in loss of starch grains and a gradual disintegration of the chloroplasts by a progressive increase in the inter‐thylakoid spaces, resulting in the separation and degeneration of the photosynthetic membranes. To account for these observations a process of photodestruction is suggested.

Chloroplasts in animals starved in total darkness for a corresponding period remained relatively intact, and showed a marked increase in the number of plastoglobuli per chloroplast. This increase in plastoglobuli may be a result of the normal ageing process of chloroplasts with a redundant photosynthetic apparatus.
EVOLUTIONARY IMPLICATIONS OF THE DISTRIBUTION AND ECOLOGY OF THE TROPICAL CONIFER AGATHIS
Authors: WHITMORE T. C. , PAGE C. N.
Published: May 2006

Agathis is one of two genera of a taxonomically isolated southern hemisphere conifer family, Araucariaceae. The geographical range and ecological niches of the thirteen species are briefly described. On the Gondwanic fragments of north Queensland and New Caledonia there are respectively three and five sympatric species mostly with a different habitat. Elsewhere, from New Zealand and Fiji west throughout the Malay archipelago to Sumatra, the species are (with one minor exception) allopatric and all show ecotypic differentiation. In Malesia Agathis only dominates and regenerates in situ in forests on poor sites but in Melanesia it is not restricted in this way. The hypothesis is put forward that Agathis has expanded its range from these two Gondwanic centres and is most successful in competition with angiosperms in relatively species‐poor forests.
THE RELATIONSHIP OF MYCORRHIZAL INFECTION TO PHOSPHORUS‐INDUCED COPPER DEFICIENCY IN SOUR ORANGE SEEDLINGS*
Authors: TIMMER L. W. , LEYDEN R. F.
Published: May 2006

In an initial experiment, inoculation of sour orange (Citrus aurantium L.) seedlings in sand with Glomus fasciculatus greatly increased growth with or without fertilization with P or Cu. Application of P or Cu to non‐mycorrhizal seedlings in sand did not stimulate growth. Application of P to non‐mycorrhizal seedlings in a sandy loam soil increased growth, but induced Cu deficiency symptoms and reduced foliar Cu concentrations. Application of P to mycorrhizal seedlings did not induce Cu deficiency symptoms, but reduced foliar Cu concentrations slightly. In a complete factorial experiment, sour orange seedlings in the sandy loam soil, were inoculated with G. fasciculatus or not inoculated, fertilized with 5 levels of P from 0 to 800 mg P 1‐1 of soil and 3 levels of Cu from 0 to 8.6 mg 1‐1. Non‐mycorrhizal seedlings, which received no Cu, developed copper deficiency symptoms which were most severe at 200 mg P 1‐1. Copper deficiency symptoms did not appear on the seedlings receiving no P because seedlings failed to grow. Deficiency symptoms disappeared and foliar Cu concentrations increased when seedlings were fertilized with P at 800 mg 1‐1 probably because the high rates of P decreased the pH making Cu more soluble. On seedlings inoculated with G. fasciculatus and not fertilized with Cu, increasing rates of P decreased percentage mycorrhizal infection, the number of chlamydospores per g of soil, and the foliar Cu concentrations. Copper deficiency symptoms occurred only at 800 mg P 1‐1 and were mild. No Cu deficiency symptoms occurred and foliar Cu concentrations were in the optimum range where Cu was applied. Apparently, P induces Cu deficiency by stimulating growth of non‐mycorrhizal seedlings until Cu becomes the limiting nutrient, whereas, P‐induced Cu deficiency appears to be due to P inhibition of mycorrhizal development on seedlings inoculated with G. fasciculatus.
EFFECT OF VESICULAR‐ARBUSCULAR MYCORRHIZA ON CITRUS JAMBHIRI WATER RELATIONS
Authors: LEVY YOSEPH , KRIKUN JAMES
Published: May 2006

Recovery from water stress was studied on similarly sized VA mycorrhizal and non‐mycorrhizal rough lemon seedlings (Citrus jambhiri Lush). VA mycorrhiza affected stomatal conductance, photosynthesis and proline accumulation, but not leaf water potential, suggesting that most of the effect of the mycorrhizal association is on stomatal regulation rather than on root resistance.
EFFECTS OF AMMONIUM AND NITRATE IONS ON MYCORRHIZAL INFECTION, NODULATION AND GROWTH OFTRIFOLIUM SUBTERRANEUM
Authors: CHAMBERS C. A. , SMITH S. E. , SMITH F. A.
Published: May 2006

Addition of combined nitrogen decreases vesicular‐arbuscular mycorrhizal development in youngT. subterraneumplants. Ammonium ions, added as (NH4)2SO4, are more effective than nitrate ions, added as NaNO3. Addition of Na2SO4as a control treatment also decreases infection, suggesting a less specific ‘salt effect’ underlying the responses to combined nitrogen. Inhibition of nodulation and nitrogenase activity occurs (as is normal) in the presence of combined nitrogen.

These effects have been studied as a function of time (10 to 30 days), using a range of external concentrations. Different methods of application (surface addition versus mixing throughout the soil) have been tested. Effects on the levels of N, K+and Na+in the plants have also been determined.

The results are discussed in relation to the effects of ammonium nitrogen and nitrate nitrogen on the mineral nutrition of plants, especially within the context of the influence of vesicular‐arbuscular mycorrhizas on plant growth.
THE EFFECT OF COPPER ON NITROGEN FIXATION IN SUBTERRANEAN CLOVER (TRIFOLIUM SUBTERRANEUM)
Authors: SNOWBALL K. , ROBSON A. D. , LONERAGAN J. F.
Published: May 2006

Copper deficiency decreased nitrogen fixation in subterranean clover. Three lines of evidence support this conclusion. Firstly, while both copper and nitrogen application increased the growth of the legume the interaction between copper and nitrogen on growth was negative. Secondly, the application of copper increased the concentrations of both total and protein nitrogen in the plant. Lastly, nitrogen fixation as measured by the acetylene reduction assay increased with copper application to the soil.
HEAVY METAL CO‐TOLERANCE IN A COPPER‐TOLERANT POPULATION OF THE MARINE FOULING ALGA, ECTOCARPUS SILICULOSUS (DILLW.) LYNGBYE
Authors: HALL A.
Published: May 2006

The growth of individuals from a copper‐tolerant and a non‐tolerant population of Ectocarpus siliculosus (Dillw.) Lyngbye, in media containing copper (0.10 mg 1‐1), cobalt (0.10 mg 1‐1), zinc (0.25 mg 1‐1) or cadmium (1.50 mg 1‐1) was measured using a wet wt method. The copper‐tolerant population was found to have an increased tolerance to cobalt and zinc, in addition to a high tolerance to copper. It is believed that the copper tolerance mechanisms, or other physiological processes, typical of the fouling population, are the basis of this co‐tolerance. The importance of a general tolerance to heavy metals in a major fouling alga is noted.
A GENECOLOGICAL STUDY OF PUCCINELLIA MARITIMA HUDS. (PARL.) I. VARIATION ESTIMATED FROM SINGLE‐PLANT SAMPLES FROM BRITISH POPULATIONS
Authors: GRAY A. J. , SCOTT R.
Published: May 2006

By means of a replicated clone trial of 56 plants taken at random from six geographical regions a preliminary assessment was made of variation in Puccinellia maritima (Huds.) Parl., the predominant grass species on British salt marshes. We found significant differences between genotypes in the mean values for 19 morphological and flowering characters. The variation between genotypes was further examined using a correlation matrix of these values (plus seed weight). The first three principal components extracted from the matrix defined variation trends in vegetative biotype, yield, and reproductive strategy respectively. Graphic representations revealed that variation on the vegetative biotype component, a measure of tillering rate, overall plant leaf size, and the tendency to produce either a few large or many small tillers, was associated with variation in growth habit (erectness) and that genotypes originally collected from grazed salt marshes tended to be fast‐tillering, small, short‐leaved, and prostrate. Variation in yield (dry‐matter production) appeared to be related to the soil nutrient status of the site of collection, the relatively high yielding genotypes generally coming from mature marshes at higher elevations. There is no evidence of an effect of grazing on the reproductive strategy component, which measured the relative allocation of resources to flowering or vegetative tillers, but, probably through its association with date of ear emergence, variation on this component had an apparently regional basis.

Estimates of genetic coefficients of variation and heritability suggested that much of the variation was genetically controlled and indicated, for example, that date of ear emergence was genetically more variable and had a higher heritability than date of anthesis. These results indicated that, in future trials, measurement on only three occasions of only eight characters would provide a reasonable estimate of the variation within and between populations of the species.
TRANSLOCATION OF SULPHITE IN VICIA FABA L.
Authors: GARSED S. G. , MOCHRIE ANNE
Published: May 2006

Summary

The translocation of radioctivity was studied quantitatively and qualitatively after application of droplets containing Na235SO2 to leaves of Vicia faba L. and using the aphid species Megoura viciae Buckt. to tap sieve elements in the atexn. Concentrations of 4 and 8 mM Nag235SO2 were chosen after studying the effects of a range of sulhite concentrations on 14CO2 fixation.

Extracts of leaves contained 35S‐labelled sulphite, sulphate and organic material. Only sulphite and sulphate were labelled in honeydew. The aphids contained sulphate and soluble organic compounds, but no sulphite. Extracts of aphids contained more radioactivity 0.5 h after application of Na235SO2 to the source leaf than after 24 h. It is concluded that incompletely oridized sulphur compounds can be translocated, and the results are discussed with reference to the uptake of the atmospheric pollutant sulphur dioxide and its effects on plant growth and development.
ROOT SIZE, ROOT HAIRS AND MYCORRHIZAL INFECTION: A RE‐EXAMINATION OF BAYLIS'S HYPOTHESIS WITH TROPICAL TREES
Authors: JOHN T.V. St
Published: May 2006

Summary

A series of 89 Brazilian forest species, for which root characteristics and VA mycorrhizal condition were known, was used to test an aspect of Baylis's magnolioid root hypothesis. A non‐parametric statistical test showed a significant association between magnolioid root characteristics and VA infection.
AN EVALUATION OF TECHNIQUES FOR MEASURING VESICULAR ARBUSCULAR MYCORRHIZAL INFECTION IN ROOTS
Authors: GIOVANNETTI M. , MOSSE B.
Published: May 2006

Summary

Assessment of infection is an essential part of many studies involving VA mycorrhiza. A summary is given of the range of techniques that have been used. We calculated the standard error of four methods of assessment based on observations of stained root samples either randomly arranged in a petri dish or mounted on microscope slides. The methods are based on presence or absence of infection at root/grid intersect points, on a visual estimate of percentage cortex occupied by fungus or on estimates of length, or presence or absence of infection in root pieces mounted on slides. The number of replicate observations required for a given standard error % infection can be read from the curves provided. The advantages of the different methods of assessment are discussed and reasons given why they all probably overestimate the true values.
THE USE OF POLLEN ISOENZYMES AS AN AID TO THE BREEDING OF FIELD BEANS (VICIA FABA L.)
Authors: GATES P. , BOULTER D.
Published: May 2006

summary

Non‐specific esterase and glutamate‐oxaloacetate transaminase isoenzymes, extracted from pollen and separated by electrophoresis on acrylamide gel, have been used to identify inbred lines and to measure crossing between them. Isoenzyme patterns were genotype‐specific and were not affected by a range of environmental variables or by prolonged storage of pollen at low temperature.
SOME GENERAL OBSERVATIONS ON ZOOSPORES OF THE CHYTRID RHIZOPHYDIUM PLANKTONICUM CANTER EMEND.
Authors: CANTER HILDA M. , JAWORSKI G. H. M.
Published: May 2006

Summary

General microscopic observations of zoospores of the chytrid Rhizophydium planktonicum Canter emend, contained within a small glass chamber, have shown that they have strong reactions to visible light. There appears to exist a threshold level of dim light below which zoospores will eventually enter what is termed the ‘state of quiescence’ and above which they will continue to maintain active swimming. Alternations between these two states can he manipulated with ease under the microscope. Free swimming zoospores after a period in dim light or darkness and quiescent zoospores both respond to sudden exposure to bright light.

The concentration of zoospores into aggregates of individuals circling at the upper and or lower surfaces of a chamber is recorded. As viewed from above, those uppermost circle in a clockwise direction while those below go round counter‐clockwise.

Adherence between zoospores as swimming individuals or in the encysted state has been seen but there is no evidence of any fusion taking place. A specially adapted channel image intensifier made possible the examination of material under infra‐red.
PHOTOREVERSIBLE CONTROL OF HETEROPHYLLY IN HIPPURIS VULGARIS L.
Authors: Bodkin P. C. , Spence D. H. N. , Weeks D. C.
Published: May 2006

summary

The freshwater macrophyte Hippuris vulgaris exhibits heterophylly. During July and August aerial‐type leaves occur even on immersed shoots down to a depth of 15 m in two clear‐water limestone lochs in Scotland. Complementary field and laboratory data indicate that a high intensity photoperiod and temperatures above 10°C are prerequisites for aerial‐type leaf production on submerged shoots. In these conditions, regular injections of additional sucrose, the natural photosynthate, at 05 mol kg−1 fresh weight will not induce the aerial‐type leaf. There is relatively little attenuation of blue light with depth in these lakes and additional blue light just after the photoperiod does not induce the aerial‐type leaf. There is no evidence for an ontogenetic or circadian photoperiodic requirement for the production of aerial‐type leaves, or that heterophylly is mediated by ethylene.

However, a low ratio of red (R 660 run) to far red (FR 730 run) light throughout, or very dimly for a brief period just after, the photoperiod treatment regularly induces aerial leaf formation on submerged shoots of any length. A similar low R/FR ratio is found naturally in these lakes in summer at depths where submerged aerial leaves occur. Selective attenuation of far red by lakewaters raises the R/FR ratio steeply with increasing depth. At R/FR ratios above a critical range, which is similar in field and laboratory, aerial leaf formation is inhibited and only submerged‐type leaves are formed. Simply by changing the R/FR ratio, either during or briefly after the photoperiod, transitions between submerged and aerial‐type leaves are repeatedly reversible, implying direct phytochrome control.
NEW EVIDENCE CONCERNING THE ORIGIN OF INLAND RADIATE GROUNDSEL, S. VULGARIS L. VAR. HIBERNICUS SYME
Authors: INGRAM RUTH , WEIR JACQUELINE , ABBOTT RICHARD J.
Published: May 2006

summary

Triploid hybrids 5. vulgaris L.×S. squalidus L. were synthesized, frequently using a diverse array of radiate and non‐radiate plants of S. vulgaris as the female parent. All hybrids have so far proved sterile when selfed. By backcrossing one hybrid (S. vulgaris L. var. vulgaris×S. squalidus L.) to the female parent, and then selfing the products, several fertile radiate individuals were formed that were tetraploid and resembled S. vulgaris L. var. hibernicus Syme. The implication of these results for the possibility of introgression occurring between S. vulgaris and S. squalidus in the wild is discussed.
THE VEGETATION OF THE SUMMIT ZONE OF MOUNT KINABALU
Authors: SMITH J. M. B.
Published: May 2006

Summary

The summit zone of Mt Kinabalu (4101 m) largely comprises exposed rock, but nevertheless includes in its flora plants with various and geographically distant affinities. The vegetation of the zone has not hitherto been adequately described. Eighty‐three plots with 98 vascular plant species were studied. Vegetation types recognized are upper mountain forest (3260 to 3550 m), summit scrub (3720 to 3950 m), sayat‐sayat scrub (3300 to 3800 m), summit heath (3850 to 4020m), three depauperate crevice communities (together 3330 to 4040m), seepage fens (3320 to 3590 m) and sandy depressions (3500 to 4040 m). All except upper mountain forest and the crevice communities are very local in distribution, and none are anthropogenic. Ecological controls are suggested. Disturbed vegetation along the summit path is also described, and alien species are listed. Comparison is made between the vegetation of Mt Kinabalu and; of mountains in New Guinea.
STRUCTURAL STUDIES ON HEALTHY AND NECROTIC YOUNG EPIDERMAL CELLS OF GROWING POTATO SPROUTS
Authors: LYSHEDE OLE B.
Published: May 2006

Summary

A structural study of pre‐emergence growth stages of potato sprouts is described. Dormant cells contain concentric endoplasmic reticulum. No differences are to be found in the palisade‐like epidermal cells of sprouts at different growth stages. The cells are filled with ribosomes and contain an abundance of other organelles. The thickish outer wall is covered by a thin electron‐dense cuticle.

Necrotic epidermal and subepidermal cells were frequently observed. The walls of such cells appear to have decomposed, followed by extrusion to the plant surface of disintegrating cytoplasm that spreads over large areas. The type of necrosis investigated here is believed to be identical to one due to calcium deficiency, described by several previous authors. Its possible pathological aspects are briefly discussed.
OBSERVATIONS ON THE MECHANISM OF CHLOROPLAST DIVISION IN HIGHER PLANTS
Authors: LEECH RACHEL M. , THOMSON W. W. , PLATT‐ALOIA K. A.
Published: May 2006

The sequence of changes in membranes that occur during the division of young green chloroplasts is described from observations in the electron microscope of thin sections of leaf tissue of Triticitm aestivum var. Maris Dove, Atriplex semibaccata R.Br. and Sesamum indicum var. glauca. Comparative observations of the morphological forms of dividing chloroplasts present in suspensions from young wheat leaves were made using phase contrast and Nomarski interference optics and from thin sections. The isthmus region of the dividing chloroplasts has a similar form in all three species and fuzzy plaques of electron opaque material and some invaginations in the isthmus were frequently observed. The significance of these fuzzy plaques is discussed and a possible mechanism for chloroplast division suggested.
CHARACTERIZATION OF EXTRANEOUS PARTICLES LOCATED ON THE LEAF SURFACE OF SEVERAL PLANT SPECIES
Authors: BAKER E. A. , JEFFREE C. E.
Published: May 2006

Microscopic particles, distributed randomly over the leaf surfaces of several plant species, are identified as artefacts arising from contamination by populations of adult whitefly (Trialeurodes vaporarium). The larger particles are shown to be whitefly eggs contained within a capsule. The smaller particles, in the form of grooved ribbons or coils;, form part of a waxy secretion covering the eggs and the whole surface of the adult insect. The waxy material was composed predominantly of glyceryldioctadecenylhexadecanoate.
PALAEOBOTANY AND PLEISTOCENE STRATIGRAPHY IN BRITAIN
Authors: WEST R. G.
Published: May 2006

The history of the application of palaeobotany to the development of Pleistocene stratigraphy in Britain is reviewed. Problems arising in the interpretation of pollen assemblages are discussed from palaeobotanical and stratigraphical points of view. Problems of correlation and nomenclature are also discussed.
INHIBITION OF GROWTH OF ECTOMYCORRHIZAL FUNGI IN CULTURE BY PHOSPHATE
Authors: GILTRAP N. J. , LEWIS D. H.
Published: May 2006

The influence of pH on the growth of, and carbohydrate utilization by, three ectomycorrhizal fungi in culture was assessed by growing them on glucose, sucrose and raffinose in the presence and absence of 0‐05 M phosphate buffer and 0‐05 M 2‐(N‐morpholino) ethane‐sulphonic acid buffer (MES). This concentration of phosphate significantly inhibited growth of Cenococcum geophilwn and Rhizopogon roseolus on all carbon sources. Suillus bovinus was more tolerant, exhibiting uninhibited growth on glucose, though adaptive growth on both sucrose and raffinose was significantly less in phosphate buffer than in the other two systems. MES had a superior buffering capacity and was less inhibitory to growth of the three fungi than phosphate buffer. The growth of C. geophilum on all carbon sources was uninhibited in MES, although this buffer significantly inhibited adaptive growth by the other two species on sucrose and raffinose, possibly by inhibiting induction or activity of invertase. The use of phosphate buffers by several workers in tests of carbohydrate utilization by ectomycorrhizal fungi will undoubtedly have affected their growth. This may, to some extent, explain differences in patterns of utilization of carbon between isolates of the same species which have been reported by different investigators. These have previously been attributed to variability between strains in utilization of carbohydrate rather than in sensitivity to phosphate. Possible ways by which phosphate inhibits growth are discussed.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA XII. FIELD INOCULATION RESPONSES OF BARLEY AT TWO SOIL P LEVELS
Authors: CLARKE C. , MOSSE B.
Published: May 2006

The results are described of a field experiment in which barley was inoculated in the field by‐placing 20 g of soil containing infected roots below each sowing position. Three VA endophytes were used as inoculants and half the plots were given phosphate before sowing. Growth and infection were recorded twice during the experiment and at harvest. In the plots without added phosphate the fresh wt of ears was doubled by inoculation to approximately 100 gm‐2irrespective of endophytes. Added phosphate increased this more than inoculation and weight of ears rose to 200 to 300 gm‐2. With one inoculant dry wt of ears was 35% greater than with phosphate only, but with the other two it was marginally less. The results are discussed in relation to other experiments with barley and to the levels of infection throughout the experiment.
INTERACTION BETWEEN BEIJERINCKIA MOBILIS, ASPERGILLUS NIGER AND GLOMUS FASCICULATUS AND THEIR EFFECTS ON GROWTH OF ONION
Authors: MANJUNATH A. , MOHAN R. , BAGYARAJ D. J.
Published: May 2006

Effect of inoculation with Gloms fasciculatus, Beijerinckia mobilis and Aspergillus niger, singly and in combination, on growth and nitrogen and phosphorus content of onion was studied. Inoculation with G. fasciculatus or B. mobilis increased the dry wt and nitrogen content of the plant. A. niger inoculation had no significant influence on plant growth. B. mobilis inoculation stimulated the sporulation by VA mycorrhizas. Synergistic beneficial effect due to inoculation with all the three organisms was observed.
STUDIES OF THE AZOLLA PINNATA‐ANABAENA AZOLLAE SYMBIOSIS: GROWTH AND NITROGEN FIXATION
Authors: TUNG H. F. , SHEN T. C.
Published: May 2006

Azolla pinnata grown in a standard medium and on floodwater under the high light (30 to 120 klx) and high temperature (26 to 35°C) conditions of Malaysia doubled its fresh wt in about 3 and 5 days respectively. The main factor limiting growth and acetylene reduction activity (ARA) of the A. pinnata‐Anabaena assollae symbiotic association on floodwater was phosphorus. Addition of phosphorus (P) to P‐deficient Azolla in floodwater resulted in an immediate increase in ARA followed by an increase in the growth rate. Minus P treatment caused a 50% reduction of ARA but had little effect on the growth rate of Azolla in the first week. Continued culture of Azolla in the minus P medium caused a significant reduction in growth rate, ARA, and the formation of anthocyanin pigment in the fern. Subsequent transfer into a standard medium did not restore its ARA. Full sunlight also reduced the growth and ARA of Azolla, and P modified the response of Azolla to light.
THE STRUCTURE OF THE SPORES OF GIGASPORA MARGARITA. I. THE DORMANT SPORE
Authors: SWARD R. J.
Published: May 2006

Histochemical tests, light and electron microscopy have been used to investigate the structure of the dormant spore of Gigaspora margarita (Endogonaceae). There is a plug in the neck of the mature spore consisting of a dense matrix of highly osmiophilic material bounded by wall‐like depositions. The complex spore wall is composed of four prominent layers, an inner and outer layer that contain polysaccharide, protein and lipid; a laminated chitinous layer and an ill‐defined‘cementing’layer.

The cytoplasm is composed of amorphous material and a variety of granules and particles that form a fine network between large oil droplets. In certain areas the cytoplasm is concentrated and forms two dense regions named the 'synthesizing’and‘nuclear’centres which contain different proportions of various organelles. Two unusual types of organelles found in the cytoplasm of G. margarita spores have been previously described in honey‐coloured, sessile spores of Acaulospora laevis.
THE INFLUENCE OF LIGHT REGIMES DURING FLORAL DEVELOPMENT ON APOMICTIC SEED PRODUCTION AND ON VARIABILITY IN RESULTING SEEDLING PROGENIES OF POA AMPLA AND P. PRATENSIS
Authors: WILLIAMSON CYNTHIA J.
Published: May 2006

The influence of five light regimes during the period just prior to ear emergence until anthesis on Poa ampla, three P. pratensis biotypes and on the seedling progenies of an incomplete diallel cross between them, was examined. Both photoperiod and total irradiance affected seedling characters, their variances and dispersions, but the direction and magnitude of response differed between biotypes of P. pratensis. Results from P. ampla indicated that a higher proportion of amphimictic seed matured after 10‐h photoperiodic treatments than after 20‐h treatments. Biotypes differed in their response to light regimes in the period before and after ear emergence. The pollen parent and the interaction between pollen parent and light regime also affected seedling characters and their variances. Canonical analyses of discriminance were used to investigate interactions between seed parents, pollen parents and light regimes. The results are disussed in relation to different stages in apomictic seed production.
FLORISTIC DIVERSITY IN RELATION TO SOIL CHARACTERISTICS IN A LEAD MINING COMPLEX IN THE PENNINES, ENGLAND
Authors: CLARK R. K. , CLARK S. C.
Published: May 2006

Adjacent species‐rich and species‐poor areas of a limestone outcrop were investigated in a heavy metal mining complex on Grassington Moor, Yorkshire, England, to determine reasons for the differences in their floras. Levels of soil lead, zinc, nitrogen, phosphorus and potassium were determined and the activities of the enzymes urease, acid phosphatase and dehydrogenase in the soil were measured. Soil respiration rates were also determined. The percentages of the variation in species‐density accounted for by each factor were determined using a step‐wise multiple regression technique. Binding of lead in organic forms resulting in low levels of available lead, together with higher levels of the major plant nutrients, were probably the main factors enabling a species‐rich community to occur on one part of the outcrop. Possible ways in which the differences in habitat became established are discussed.
REVERSIBLE EFFECTS OF FARNESOL ON COMMELINA COMMUNIS L.
Authors: MALLOCH K. R. , FENTON R.
Published: May 2006

The application of farnesol to isolated epidermis of Commelina causes stomatal closure and death of guard cells. Experiments are reported in which the toxic effects were reduced by manipulation of the assay conditions. Reversible stomatal closure by farnesol was observed in intact plants. These results are discussed in relation to similar physiological effects in Sorghum and the possible role of farnesol as an endogenous antitranspirant.
THE ACID INVERTASES OF THE DEVELOPING THIRD LEAF OF OAT
Authors: GREENLAND A. J. , LEWIS D. H.
Published: May 2006

Soluble acid invertases, obtained from the developing third leaf of oat, were fractionated by gel filtration and ion‐exchange chromatography. Gel filtration separated two peaks. Isoenzyme II (85 × 103 daltons) was the dominant form in the non‐emerged leaf but decreased in activity after leaf emergence. The activity of isoenzyme I (143 × 103 daltons) remained constant throughout leaf development and was dominant in mature tissues. Ion‐exchange chromatography separated two discrete peaks (A and B) and a composite peak (C), comprised several isoenzymes. The activities associated with A, B and C varied considerably during leaf development. One or more of the isoenzymes of invertase in peak C was the predominant invertase at all stages of leaf development. These observations are discussed in relation to the role and control of synthesis of invertases during development.
MYCORRHIZAL INFECTION AND GROWTH OF TRIFOLIUM SUBTERRANEUM: COMPARISON OF NATURAL AND ARTIFICIAL INOCULA
Authors: SMITH F. A. , SMITH S. E.
Published: May 2006

Mycorrhizal infection and growth of Trifolium subterraneum have been measured, using plants grown in soil/sand mixtures containing natural inoculum, and plants grown in sterilized soil/sand mixtures to which mycorrhizal T. subterraneum roots were added as an artificial inoculum. As control treatments, plants have been grown in sterilized soil/sand mixtures without the addition of roots, or in soil/sand mixtures with the addition of non‐mycorrhizal roots.

In one experiment, the two methods of inoculation resulted in similar increases in leaf numbers and in weight. In the second experiment, the growth responses of plants artificially inoculated were less than those of plants with natural inoculum and this was related to delayed mycorrhizal infection. In the third experiment, mycorrhizal infection was again delayed when artificial inoculum was used: this experiment was terminated before increases in weight occurred. The extent and location of mycorrhizal infection from artificial inoculum depended on the location (in the pots) of the added inoculum. The advantages and disadvantages of these two methods of studying mycorrhizal infection are assessed in relation to the different aims of investigations of the mycorrhizal symbiosis.
TRANSLOCATION AND TRANSFER OF NUTRIENTS IN VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: COOPER KAREN M. , TINKER P. B.
Published: May 2006

This paper reports the effects of environmental variables on the movement of phosphate by external hyphae of the mycorrhizal fungus Glomus mosseae, infecting Trifolium repens (white clover), across a barrier in soil‐agar/agar split‐plate cultures. Increasing the transpiration rate of the host increased the total P translocated by the fungus: the maximum rate obtained at full transpiration was 2·3 times that at low transpiration. Temperature also affected P transport, which was at a maximum at 15 to 25°C, but at 5°C only a small amount of P was transported. The maximum P flux in the hyphae, calculated for 20 to 25°C and a moderate host transpiration rate, was 2 × 10‐9 mol cm‐2 s‐1. A cytoplasmic streaming inhibitor (cytochalasin B) prevented detectable movement of P across the barrier by the fungus and consequently had inhibited either the uptake or translocation of P by the fungus. Osmotic potentials of 1 or 2 bars in the medium from which 32P was being absorbed did not appreciably alter the rate of transport of P.

The results support the general conclusion that translocation of P in the hyphae occurs normally by protoplasmic streaming but there may also be a‘bulk flow’of hyphal contents under a water potential gradient.
OBSERVATIONS ON THE MYCORRHIZAL STATUS OF SOME ALPINE PLANT COMMUNITIES
Authors: READ D. J. , HASELWANDTER K.
Published: May 2006

In some Austrian alpine plant communities, levels of vesicular‐arbuscular mycorrhizal infection are highest in closed herb‐rich communities of intermediate altitudes (1900 to 2500 m). In fertilized hay meadows of lower altitudes (1600 m) and in the nival zone above 3000 m, endogonaceous infection is light. In the latter, it is mainly by the fine endophyte, Glomus tenuis. Many plants throughout the altitudinal range of the survey are infected with dark septate hyphae and, in the Cyperaceae, this is the dominant infection. Ectomycorrhizas occur on some herbaceous species as well as on Salix up to 2500 m. The possible significance of the infection patterns is discussed.
CARBON DIOXIDE EXCHANGE IN LICHENS: RESISTANCES TO CO2 UPTAKE AT DIFFERENT THALLUS WATER CONTENTS
Authors: SNELGAR W. P. , GREEN T. G. A. , WILKINS A. L.
Published: May 2006

Carbon dioxide resistance and water content curves are presented for Pseudocyphellaria amphisticta, P. homoeophylla, P. billardierii, P. colensoi, Sticta latifrons and Peltigera dolichorhiza. In all cases the curves are triphasic with a high resistance at low and high water contents and a low resistance at intermediate water contents. The exact water contents at which these changes in resistance occur, and the rate at which the resistance increases at the higher water contents, appear to be species specific. The depressed NAR often found at higher water contents is shown to be caused in part by the increased resistance since it occurs under conditions where there are no changes in respiratory rate. The increase in resistance at higher water contents is suggested to be a result of water on the lower cortex.
VARIABILITY IN THE RESISTANCE OF SODIUM CHLORIDE SALINITY WITHIN RICE (ORYZA SATIVA L.) VARIETIES
Authors: FLOWERS T. J. , YEO A. R.
Published: May 2006

Varieties of rice differ in their resistance to sodium chloride salinity. Within varieties, which are not homozygous lines, there is very high variability in sodium uptake and in survival under saline conditions by the individual plants. This is in contrast with the relative uniformity in (for example) potassium uptake, dry wt and transpiration rate.

There is a negative correlation between sodium (and chloride) accumulation by individual plants and their survival in saline conditions, demonstrating that variability amongst individuals fits the same pattern as has become generalized for varietal differences in glycophyte species. Possible reasons for this variability in sodium and chloride uptake within varieties, and its relevance to selecting salt‐resistant varieties of rice, are discussed.
ANATOMICAL VARIATION ALONG THE LENGTH OF THE ZEA MA YS LEAF IN RELATION TO PHOTOSYNTHESIS
Authors: MIRANDA VALENTINE , BAKER NEIL R. , LONG STEPHEN P.
Published: May 2006

Anatomical features of the leaf, related to C4 photosynthetic activity, were examined along the length of the second leaf of 7‐day‐old plants grown under a diurnal light regime. Changes of significance to photosynthetic activity were observed in cuticle thickness, stomatal size and frequency, mesophyll anatomy and interveinal distance. Anatomical changes within the basal 3 cm of the leaf were attributable to development. Above this region, variation in some anatomical characteristics, notably stomatal frequency and interveinal distance, could only be attributed to ontogenetic differences between parts of the leaf.
THE SEPARATION, IDENTIFICATION AND QUANTITATIVE DETERMINATION OF PHOTOPIGMENTS FROM THE SIPHONACEOUS MARINE ALGA CODIUM FRAGILE
Authors: BENSON ERICA E. , COBB A. H.
Published: May 2006

The photopigments of the Siphonaceous marine alga Codium fragile have been quantitatively determined using thin layer chromatography (TLC). Codium fragile fronds contain a unique spectrum of carotenoids, notable by the absence of β‐carotene, and the presence of a‐ and e‐carotenes, siphonoxanthin, siphonein, neoxanthin and violaxanthin. The carotenes are present in low concentrations whereas siphonoxanthin and its ester siphonein account for as much as 60% of the total carotenoids present. The significance of these findings is discussed in relation to the habitat of this alga.
ULTRASTRUCTURAL AND ULTRACYTOCHEMICAL FEATURES OF A GLOMUS TENUIS MYCORRHIZA
Authors: GIANINAZZI‐PEARSON V. , MORANDI D. , DEXHEIMER J. , GIANINAZZI S.
Published: May 2006

The ultrastructural organization and some cytochemical features (protein and polysaccharide distribution) of the mycorrhiza formed by Glomus tenuis in raspberry roots have been investigated. Certain aspects of the fine mycorrhizal endophyte (smaller hyphae, thinner walls, distinct two‐layered wall structure following the PATAg test for polysaccharides, complete absence of septa) distinguish it from the coarse vesicular–arbuscular mycorrhizal fungi. The modifications occurring in the host‐fungus interface during Glomus tenuis mycorrhiza development are however very similar to those that have been described in several mycorrhizae formed by coarse vesicular‐arbuscular endophytes.
CYTOPLASMIC PHENOLS AND POLYSACCHARIDES IN ECTOMYCORRHIZAL AND NON‐MYCORRHIZAL SHORT ROOTS OF PINE
Authors: PICHÉ YVES , FORTIN J. ANDRE , LAFONTAINE JEAN G.
Published: May 2006

Pinus strobus seedlings were cultivated in growth pouches and inoculated with Pisolithus tinctorius. Semi‐thin sections of mycorrhizal and uninoculated short roots and long roots were stained with toluidine blue and periodic acid Schiff's reagent for phenolic and polysaccharidic intracytoplasmic substances respectively.

No obvious difference in intracytoplasmic contents of phenolic substances was observed between ectomycorrhizal and uninoculated short roots. However, the phenolic content of the cortical cells of the long roots was much lower than that of both mycorrhizal and uninoculated short roots.

Starch grains were not observed in cortical cells of either mycorrhizal or uninoculated short roots but were abundant both in the cortex and the stele of long roots and in the stele of short roots. The absence of starch synthesis in the cortical cells of potentially ectomycorrhizal short roots should be taken into account when explaining the accumulation of soluble sugars as a prerequisite for ectomycorrhizal formation.