bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE
Authors: BRADLEY R. , BURT A. J. , READ D. J. 
Published: May 2006

SUMMARYPlants with ericoid mycorrhizas successfully colonize acidic soils containing high levels of heavy metals. While mycorrhizal infection normally enhances uptake of mineral elements, such a function in metalliferous soils would be disadvantageous. The role of infection in heavy metal tolerance was therefore investigated in three ericaceous species. Plants of Calluna vulgaris, Vaccinium macrocarpon and Rhododendron ponticum were grown in the mycorrhizal and non‐mycorrhizal conditions in sand containing a dilute nutrient solution supplemented with Cu or Zn at 0, 10, 25, 50 and 75 and 0, 25, 50, 100, 150 mg−1 respectively. Fungal endophytes isolated from these host plants were also grown in pure culture over a wide range of concentrations of both metals. Mycorrhizal plants showed some growth in all metal treatments, whereas non‐mycorrhizal plants failed to grow in all but the lowest metal levels. The endophytes all grew vigorously up to 75 mg Cu 1−1 and 150 mg Zn 1−1. In all but one case, the mycorrhizal plants had a significantly lower concentration of metal in their shoots. Concentrations of metal in roots were higher in mycorrhizal plants. It is proposed that the hyphal complexes of the endophyte provide adsorptive surfaces within the cortical cells of the host roots, thus facilitating exclusion of metals from the shoot and avoidance of metal toxicity. The ecological significance of these observations is discussed.
EFFECT OF REDUCED SOIL MOISTURE AVAILABILITY ON LEAF MORPHOLOGY AND IN VITRO DRY MATTER DIGESTIBILITY OF FESTUCA ARUNDINACEA GENOTYPES WITH CONTRASTING LEAF TENSILE STRENGTH
Authors: SILCOCK R. G. , WILSON D. 
Published: May 2006

SUMMARYTwelve genotypes of Festuca arundinacea Schreb. differing in leaf size and leaf tensile strength were grown in pots with either adequate or very restricted watering. When leaves expanded under moisture stress their length, width, specific leaf area (SLA) and tensile strength were reduced but leaf dry wt was unaffected. However, the reduction in SLA was inversely proportional to original leaf strength. Leaf tensile strength was directly related to leaf length, SLA and mesophyll cell wall thickness. In vitro dry matter digestibility was inversely related to leaf strength but was not consistently reduced by moisture stress. However, in genotypes where moisture stress markedly reduced leaf strength, digestibility was increased. The results are discussed in relation to possible improvements in plant growth under moisture stress in the field and the usefulness of leaf tensile strength as a selection criterion in plant breeding programmes.
COMPETITION FOR POLLINATORS IN THE ECOLOGY OF CENTAUREA SCABIOSA L. AND CENTAUREA NIGRA L.
Authors: LACK ANDREW J. 
Published: May 2006

SUMMARYObservations are presented on: (a) the numbers of insects foraging on Centaurea scabiosa and Centaurea nigra per available capitulum of each species; (b) the numbers of insect visits to each capitulum of C. scabiosa and C. nigra in 30 min intervals; (c) the numbers of insect visits to rayed capitula compared with ray less capitula; (d) the number of successful pollinations. The study was carried out on the Devil's Ditch, Cambridgeshire where C. nigra is rayless, and on Hod Hill, Dorset where C. nigra is rayed, with a few results from a garden trial set out in the Cambridge Botanic Garden.In the counts of insects in each area of the Devil's Ditch the numbers recorded feeding on each Centaurea species per capitulum were approximately proportional to the nectar reward of each species.On Hod Hill the number of insect visits to C. nigra plants from which rays had been removed was half to three‐quarters of the number of visits to rayed capitula. This is very similar to the difference on the Devil's Ditch between the number of visits to C. scabiosa (rayed) and C. nigra (rayless), and this difference may therefore be a result simply of the possession of ray florets in C. scabiosa but not in C. nigra. The difference between the two species on Hod Hill was greater (C. scabiosa receiving two to three times as many visits as C. nigra) although C. nigra possesses ray florets and therefore resembles C. scabiosa. Some bees were observed visiting C. scabiosa selectively on Hod Hill but none did so on the Devil's Ditch.On the Devil's Ditch both species had similar numbers of styles successfully fertilized on nearly all dates. Hod Hill on most dates a similar number of styles was fertilized in each species, but on a few dates C. scabiosa had more successful fertilizations than C. nigra. It is concluded that competition for pollinators is not a strong selective factor in Centaurea on the Devil's Ditch but may be a factor promoting the later flowering and the possession of ray florets in C. nigra on Hod Hill. Competition for pollinators may have been more important as a selection pressure in the past when less suitable habitat was available.
THE EFFECT OF TEMPERATURE ON PHYTOCHROME CONTROLLED HYPOCOTYL EXTENSION IN SINAPIS ALBA L.
Authors: WALL J. K. , JOHNSON C. B. 
Published: May 2006

SUMMARYThe effect of temperature on phytochrome control of hypocotyl elongation has been investigated using light‐grown seedlings of Sinapis alba. Temperature markedly affects the way in which these seedlings respond to both light quality and light quantity. The strong fluence rate dependence observed at 25 °C is not present at 10 °C and it is suggested that under conditions prevailing in the seedlings’natural environment phytochrome will measure only light quality.
STIMULATION AND INHIBITION BY BICARBONATE OF STOMATAL OPENING IN EPIDERMAL STRIPS OF COMMELINA BENGHALENSIS
Authors: MRINALINI T. , LATHA Y. K. , RAGHAVENDRA A. S. , DAS V. S. R. 
Published: May 2006

SUMMARYThe effect of 0 to 100μM bicarbonate on stomatal opening in epidermal strips of Commelina benghalensis was examined in the presence or absence of fusicoccin in light or darkness. Low concentrations of bicarbonate (up to 10 μM in the absence and 25 μM in presence of fusicoccin) stimulated stomatal opening while higher concentrations inhibited. The enhancement of opening by low concentrations of bicarbonate and phosphoenol pyruvate (PEP), and prevention of bicarbonate stimulation by malate or oxaloacetate suggested PEP carboxylase as a CO2 sensor in the guard cells. However, the inhibition of PEP carboxylase did not completely suppress the opening caused by fusicoccin. The action of fusicoccin therefore appears to involve a site other than CO2 fixation, presumably through the stimulation of proton excretion.
ECTOMYCORRHIZA FORMATION IN EUCALYPTUS
Authors: MALAJCZUK NICHOLAS , MOLINA RANDY , TRAPPE JAMES M. 
Published: May 2006

SUMMARYEctomycorrhiza formation by 11, geographically distinct Eucalyptus species and Pinus radiata with 23 diverse ectomycorrhizal fungi was examined in pure culture syntheses. Few differences occurred between the Eucalyptus species in their ability to form ectomycorrhizas with several fungi, thus indicating no evidence for host‐fungus specificity within Eucalyptus. Pinus radiata and most Eucalyptus species formed ectomycorrhizas in common with several broad‐host‐ranging fungi. However, fungus species which are known to associate exclusively with members of the Pinaceae, e.g. Suillus and Rhizopogon species, did not form ectomycorrhizas with any Eucalyptus species and vice versa. Possible incompatibility between several host‐fungus combinations was characterized by host accumulation of phenolic compounds in epidermal and cortical cells. These results are discussed relevant to better understanding degrees and processes of ectomycorrhiza host‐fungus specificity and compatibility and to practical considerations in reforestation of exotic plantations.
FINE STRUCTURE OF THE ENDOTHECIUM AND DEVELOPING XYLEM IN PHASEOLUS VULGARIS
Authors: WHATLEY JEAN M. 
Published: May 2006

SUMMARYDifferentially thickened wall bars are formed in cells of the anther endothecium as well as in the xylem. In Phaseolus vulgaris both types of wall bar appear to be lignified. As thickening takes place, Golgi bodies become numerous, endoplasmic reticulum proliferates and both types of organelle occupy characteristic sites within the cell. Thickening begins at an early stage of xylem development but in the endothecium it is long delayed. Subsequent loss of cytoplasm is associated with increasing vacuolation of xylem elements, but may be associated with plasmolysis in the endothecium.
POLLINATION ECOLOGY OF STERNBERGIA CLUSIANA (KER‐GAWLER) SPRENG. (AMARYLLIDACEAE)
Authors: DAFNI AMOTS , WERKER ELLA 
Published: May 2006

SUMMARY Sternbergia clusiana is pollinated by two main types of pollinators, Apis mellifera and various Syrphidae. The honey bees collect nectar and pollen from the shorter inner whorl of stamens and from the lowermost part of the funnel‐shaped perianth tube. The hover flies visit mainly the appendages on the outer perigone and the longer stamen whorl. These appendages were found to secrete a sugar solution as well as polysaccharides and lipids. The latter probably attract the flies.It is suggested that each pollinator is attracted by a different nectary type and that the modes of pollination prevent competition between the different pollinators and are to be interpreted as maximizing the floral attraction in the harsh season of flowering (September to December).
NITROGEN METABOLISM OF HALOPHYTES.
Authors: AHMAD I. , LARHER F. , MANN A. F. , McNALLY S. F. , STEWART G. R. 
Published: May 2006

SummaryIon‐exchange chromatography on DEAE‐Sephacel revealed the presence of two forms of glutamine synthestase (GSI and GSII) in leaf tissue and one form in root tissue of the angiosperm halophyte, Triglochin maritima. The chromatographic characteristics of GSI and the root enzyme were similar but there were differences in their stability, GSI being considerably more stable than the root enzyme. The characteristics of GSI and GSII exhibited some differences, GSII showed negative cooperativity with respect to glutamate and had a pH optimum of 8−0 compared with 7.2 for GSI. GSI was found to be unstable, particularly in the presence of inorganic salts. Compounds such as glycine betaine, proline and sorbitol, which are thought to function as compatible osmotic solutes in halophytes, were found to stabilize GSII.
AN ELECTRON PARAMAGNETIC RESONANCE (EPR) STUDY OF THE UPTAKE OF VANADYL BY WHEAT PLANTS
Authors: McPHAIL D. B. , LINEHAN D. J. , GOODMAN B. A. 
Published: May 2006

SummaryElectron paramagnetic resonance (EPR) spectroscopy has been used to monitor, in vivo, the uptake of the vanadyl ion by wheat plants. The use of high levels of vanadyl ion produced, in the plant, high molecular weight complexes with EPR parameters similar to those obtained from cellulose–vanadyl derivatives. With lower vanadyl concentration, low molecular weight complexes were observed and interpreted as arising from vanadyl‐amino acid complexes. Low molecular weight complexes with similar parameters were obtained from root washings.
PHOTOSYNTHESIS IN DESICCATED SHOOTS OF POLYTRICHUM
Authors: PENNY M. G. , BAYFIELD N. G. 
Published: May 2006

SummaryThe desiccation responses of four species of Polytrichum were examined. The relationship between CO2 assimilation and shoot water content was similar in Polytrichum commune and Polytrichum piliferum, the species most dissimilar in ecological requirements. There were, however, considerable differences between species in recovery following various desiccation treatments.Continuous desiccation was found to be more damaging than the same total period of desiccation interrupted by periods of wetting. Polytrichum piliferum was least affected by any of the desiccation treatments. Desiccation to 76 % r.h. was found to suppress the photosynthetic rate of both Polytrichum commune and Polytrichum piliferum after rewetting more than treatment at 55% or 90% r.h. Subsequent recovery was generally better following the 90% r.h. treatment.Slow desiccation of Polytrichum commune was substantially less damaging than rapid drying.
ULTRASTRUCTURAL ASPECTS OF ENDOMYCORRHIZA IN THE ERICACEAE
Authors: BONFANTE‐FASOLO P. , GIANINAZZI‐PEARSON V. 
Published: May 2006

SummaryThe ultrastructural features of the dissociated mycorrhizal symbionts Pezizella ericae Read and Calluna vulgaris L. Hull, grown in pure culture, and of the modifications occurring in both fungus and root cells during their reassociation in axenic culture have been studied in detail. Growing (apical/subapical and vacuolated zones) and non‐growing (ageing zone) regions can be distinguished in colony margins of Pezizella ericae in pure culture. In axenic mycorrhiza cultures the general morphology of the fungus remains the same with living hyphae closely resembling those in the active growing region. However, the external hyphae around roots develop an abundant fibrillar sheath which has a polysaccharide‐protein composition and the possibility that this may play a role in recognition and adhesion phenomena in ericoid mycorrhizae is discussed.Metachromatic vacuolar granules, which are very common in pure cultures of Pezizella ericae, are often present in external hyphae around axenic mycorrhizal roots but are very rarely observed in intracellular fungal hyphae. The general ultrastructural organization of these axenically produced ericoid mycorrhizae is compared to that reported for natural infections in several ericaceous species.
ESTABLISHMENT AND DEVELOPMENT OF A POPULATION OF ORCHIS SIMIA LAMK. IN THE NETHERLANDS, 1972 TO 1981
Authors: WILLEMS J. H. 
Published: May 2006

SummaryObservations in chalk grassland in South Limburg, Netherlands, were made over a 10‐year period on the development of a population of Orchis simia which probably originated from a single individual.The original plant (‘mother plant’) flowered for 10 successive years and, in years when the inflorescence was not damaged by grazing animals, produced viable seed. The species is clearly self‐compatible.Juvenile plants with only one or two narrow leaves were found for the first time 4 years after the mother plant had flowered. Thereafter, recruitment to the population occurred annually, but the number of new plants in any one year was low (5 to 13). Some juvenile plants flowered 3 years after appearing above ground, while others have still to flower after 6 years above ground. Only those plants which had developed four or five leaves in the rosette with a minimum leaf area of more than 60 cm2 flowered.The height of the flowering stem and number of flowers on the inflorescence at the mother plant varied considerably from year to year but in every year it was more vigorous than the juvenile plants. New plants were also developed by vegetative means, but this method of reproduction is considered to be unimportant compared with spread by means of seeds.
BRANCHING PATTERNS OFLINDERA BENZOINBENEATH GAPS AND CLOSED CANOPIES
Authors: VERES JOHN S. , PICKETT S. T. A. 
Published: May 2006

SummaryLindera benzoin, a major forest shrub in central New Jersey, was studied in order to determine whether branching and biomass allocation differ between plants growing under open and closed canopies. Higher bifurcation ratios (ratio of numbers of distal to proximal branches) of open canopy plants combined with large interbranch distances, long internodes and large branch angles to the horizontal reveal a branching pattern very different from that of closed canopy plants. Plants under closed canopies possessed a higher proportion of leaf to total biomass.The ratio of overlapping leaf area to total leaf area did not differ between subsamples of the two groups, possibly due to small sample sizes. Leaf area, leaf biomass and branch biomass, for developmentally equivalent third order samples, were found to be greater in the open canopy group. The high productivity ofLinderain gaps, its branching characteristics, including, e.g. spiral leaf insertion and short interbranch distance, and a failure to adjust allocation in shady habitats as do some species, suggest that it is basically a multilayer plant that can effectively change branch presentation and leaf orientation in shady habitats. Thus,Linderamay be particularly well suited to exploiting both the small gaps and closed canopy matrix of old growth forests.
REGULATION OF SEED‐GERMINATION TIMING BY MOIST CHILLING IN WESTERN HEMLOCK
Authors: CAMPBELL ROBERT K. , RITLAND STANLEY M. 
Published: May 2006

SUMMARYExistence of a natural system is proposed, in which duration of winter chilling of seeds of western hemlock, Tsuga heterophylla (Raf.) Sarg., regulates timing of germination in spring. Seeds from 12 populations (from Oregon and Washington, U.S.A.) were germinated in 12 combinations of three chilling durations and four germination temperatures. Embryo development rates, calculated as 100/Y where Y= days to 50% germination, increased directly with temperature, and the relation could be described by an empirical logistic equation. Chilling increased embryo developmental rates at all germination termperatures, altering coefficients in the equation and the shape of the resulting temperature‐response curve. Each population, deviated slightly from the average curve for each chilling duration. Population deviations were described by a complex cline based on latitude, elevation, and distance from the ocean of the parent tree. Results are discussed as being consistent with Levins' dormancy‐strategy hypothesis.
RESPONSES OF SIX SPECIES OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI AND THEIR EFFECTS ON SOYBEAN AT FOUR SOIL TEMPERATURES
Authors: SCHENCK N. C. , SMITH GEORGE S. 
Published: May 2006

SUMMARYThe effects of four soil temperatures on colonization of soybean roots, sporulation and enhancement of plant growth by six species of vesicular‐arbuscular (VA) mycorrhizal fungi were tested. The mean values for all fungus and plant variates in three tests were generally greatest at 30 °C and lowest at 18 °C. Four fungus species, Glomus claroideum, Glomus clarum, Gigaspora pellucida, and Gigaspora gregaria, produced the greatest number of spores per gramme of colonized root at 24 °C, while Glomus mosseae and Acaulospora laevis reached their maximum at 30 °C. Gigaspora gregaria had its maximum percentage of root colonization at 36 °C, Glomus mosseae reached its maximum at 24 °C, while all other species had maximum root colonization at 30 °C. Glomus claroideum and Acaulospora laevis were the only species which had maximum root colonization and sporulation occurring at the same temperature, 30 °C. Spore diameter was generally less at 30 than 24 °C, but this varied with fungus species and test. Soybean flower numbers, pod set and seed yield varied considerably in the three tests, but plant height was little affected by soil temperature or by fungus species. Generally, plants colonized with Glomus mosseae had an increased plant response and those colonized with Acaulospora laevis had a depressed plant response. There was considerable variation in plant response to various combinations of temperature and fungus species, with both growth stimulatory and growth repressive effects occurring.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: METCALF E. , JENNINGS D. H. 
Published: May 2006

SUMMARYThe effect of 3‐O‐methyl glucose on the carbohydrate metabolism of, and loss of 14C‐labelled compounds from, mycelium of Dendryphiella salina pretreated with [U‐14C]mannitol was investigated. Though concentrations of mycelial glycerol were higher than previously reported, the results for other internal carbohydrates were generally similar. In particular, the sugar reduced the concentration of mannitol. Loss of radioactivity into the medium was increased by 3‐O‐methyl glucose. The pattern of loss cannot yet be explained but since there was no loss of labelled mannitol or arabitol, unspecific membrane damage seems unlikely.
SEQUENTIAL ANALYSIS OF PLANT GROWTH
Authors: JOLLIFFE P. A. , EATON G. W. , DOUST J. LOVETT 
Published: May 2006

SUMMARYPlant growth analysis, demographic analysis and yield component analysis are three procedures used to study relationships underlying plant growth and development. Previously, it has been shown that demographic analysis is qualitatively different from plant growth analysis. This paper demonstrates how plant growth analysis and yield component analysis can be merged into a composite procedure, sequential plant growth analysis. The composite approach treats some of the traditional indices of plant growth, including leaf area ratio, leaf area index, unit leaf rate, relative growth rate, crop growth rate and harvest index, as yield components. Regression analysis is used to assess quantitatively the contributions of individual yield components to variations in growth and yield. Fitted curves and trends in coefficients of determination are both used to follow the time course of relationships during development. A study of vegetative growth in bean plants is used to illustrate the composite procedure.
THE DEVELOPMENT OF ENDOMYCORRHIZAL ROOT SYSTEMS
Authors: BUWALDA J. G. , ROSS G. J. S. , STRIBLEY D. P. , TINKER P. B. 
Published: May 2006

SummaryA model of infection of roots by vesicular–arbuscular mycorrhizas, presented earlier (Buwalda et al., 1982), is used to study the effects of phosphorus on the spread of infection in root systems. Two hosts, with contrasting responses to mycorrhizal infection (wheat and leek), were grown at a range of phosphorus levels, and sequential measurements of growth and concentrations of phosphorus in plants, and infection of roots, were made. Increasing levels of phosphorus in the soil increased concentrations of phosphorus in the plants and reduced the percentage of root length infected in both hosts, but the effect was greater in wheat. Fitting the model showed that the inherent rate of spread of the fungus was not significantly altered by applications of phosphorus. However, the maximum proportion of the root system which could become infected was reduced, especially in wheat. Some implications of this finding on our understanding of the mycorrhizal symbiosis are discussed.
ASULAM RESISTANCE IN EMBRYOIDS OF CELERY TISSUE CULTURES
Authors: MERRICK M. M. A. , COLLIN H. A. 
Published: May 2006

SummaryEmbryogenic cell suspensions were filtered and the globular embryoids and embryogenic aggregates exposed to the herbicide Asulam at a concentration of 8 × 10−5 M in liquid culture for 1 week; the suspension was then plated in an Asulam‐free agar medium. The surviving embryoids were allowed to develop into plants which eventually flowered and the seed was collected. Cultures were also re‐initiated from the young plants and tested for the presence of Asulam resistance. Undifferentiated and differentiated cell lines were isolated from the selected plantlets and both were shown to be resistant to Asulam. Since the plants did not set viable seed it was not possible to test the progeny. However, the presence of resistance in the tissue cultures derived from the plants developed from selected embryoids suggested the selection procedure involving embryoids, rather than undifferentiated cells, was successful in producing a source of Asulam resistance which was possibly due to a mutation.
MYCORRHIZAL SYNTHESIS BETWEEN CISTACEAE AND TUBERACEAE
Authors: GIOVANNETTI G. , FONTANA A. 
Published: May 2006

SUMMARY Cistus incanus ssp. incanus was tested with six Tuber species to prove its ectomycorrhizal development; the same was done with Tuber melanosporum and five Cistus species. Cistus incanus L. ssp. incanus formed ectomycorrhizas with Tuber albidum Pico, T. brumale Vitt., T. aestivum Vitt. and T. rufum Pico. The five Cistus species (Cistus albidus L., C. laurifolius L., C. salvifolius L., C. crispus L. and C. monspeliensis L.) developed ectomycorrhizas with Tuber melanosporum Vitt. These Cistaceae may be used as shrubby plants and as colonizers in truffle cultivations; the variety of their environmental and ecological requirements is such that it would be possible to increase the types of soil and number of places where truffles can be grown.