bluuebunny/crossref_metadata_2025_split huggingface dataset:
CELL DIVISION AND WALL STRUCTURE IN MICROSPORA
Authors: PICKETT‐HEAPS IEREMY 
Published: May 2006

SUMMARYCell division and wall structure are described for Microspora. Persistent centrioles replicate at prophase and establish the poles of metaphase spindles. Microtubules penetrate the nucleus at prometaphase, and during metaphase and anaphase, the nuclear envelope although vesiculated, remains around the spindle. Kinetochores are present. The orientation of the metaphase spindle is highly variable; anaphase elongation of the skew spindle causes it to become bent and twisted. After telophase, daughter nuclei come together in the middle of the cell. The centrioles migrate around the nuclei to the plane of cytokinesis established by a typical phycoplast of microtubules. Both imagination of the outer membrane and a cell plate probably contribute to cross wall formation. These results establish an affinity of Microspora with certain Ulotrichalean algae (e.g. Ulothrix and Stigeoclonium), but not others (Klebsormidium).The characteristic H‐shaped wall segments arise from two separate phases of wall secretion. During interphase, cell expansion is accommodated by the interlocking H‐shaped segments moving apart; concurrently, a new cylindrical wall is secreted inside these segments. Then during cytokinesis, the newly formed cross wall turns this cylinder into the typical wall segment. This pattern of wall secretion may be common in the Ulotrichales (and other algae) and it may have been derived by the acquisition of the filamentous habit from primitive unicellular ancestors. A scheme showing how this evolution could have occurred is proposed.
DO COLEOPTILE TIPS PRODUCE AUXIN?
Authors: SHELDRAKE A. R. 
Published: May 2006

SUMMARYA re‐examination of the evidence for auxin production by coleoptile tips reveals that it is not conclusive and that several important problems remain unresolved. The possibility that auxin and auxin precursors move acropetally in the xylem was tested by analysing guttation fluid from intact coleoptiles, decapitated coleoptiles and primary leaves of Avena sativa. In all cases two zones of auxin activity were detected on chromatograms of the acidic ether‐soluble fraction, one of which corresponded to the RF of indol‐3‐yl acetic acid (IAA). Similar auxin activity was found in guttation fluid from seedlings of Zea mays, Triticum aestivum and Hordeum vulgare. Evidence that guttation fluid also contains alkali‐labile auxin complexes was obtained. Experiments on the movement of dyes and radioactive IAA introduced into the xylem of transpiring or guttating coleoptiles showed that these substances accumulate at the tip of the coleoptile, or at the apical region of decapitated coleoptiles. The hypothesis that IAA and‘inactive auxins move acropetally in the xylem from the seed to the coleoptile tip where they accumulate and where the ‘inactive auxins’ can be converted to IAA is shown to be consistent with the classical work on coleoptiles; it can also explain the autonomous curvature of coleoptiles and the influence of the roots on the auxin content of coleoptile tips. An analogous accumulation of auxin probably occurs at the tips of primary leaves. The anomalous auxin economy of coleoptile tips is discussed.
RNA METABOLISM IN DEVELOPING COTYLEDONS OF PHASEOLUS VULGARIS*
Authors: WALBOT VIRGINIA 
Published: May 2006

SUMMARYRNA metabolism in the cotyledons of Phaseolus vulgaris L., cv. Taylor's Horticultural, has been examined as well as the composition of the RNA synthesized during embryogeny and germination. The cotyledons cease RNA synthesis during maturation at the onset of dehydration. During germination RNA synthesis resumes; however, organellar rRNA is the major class of RNA synthesized. The total RNA content of the cotyledons doubles during the first 3 days of germination and then declines as the cotyledons senesce. RNA synthesis is restricted to periods of near normal water content.
THE GROWTH OF BARLEY MUTANTS AT THE XAN‐B AND XAN‐C LOCI IN THE PRESENCE OF SUCROSE OR l‐LEUCINE IN THE GROWTH MEDIUM
Authors: LAND J. B. , NORTON G. 
Published: May 2006

SUMMARYThe effects of additions of leucine or sucrose to the medium on which chlorotic barley mutant seedlings developed were examined and compared with those of corresponding green segregants. These additions often raised their fresh weight to that of the green segregants grown on basal medium; their protein content was also higher. Although the chlorophyll content of the mutants Xan‐b15,18 and Xan‐c23 was increased, it remained substantially below that of the green segregants; that of the mutants Xan‐b22 and Xan‐b54 did not increase.In addition to these abnormal growth characteristics, the soluble amino acid pools of the mutants grown on all media and of green segregants grown on leucine medium showed characteristics of chlorotic growth with high levels of aspartic acid and asparagine; these levels were less marked in the mutants which responded to sucrose supplementation.Levels of ribulose‐1,5‐diphosphate carboxylase remained substantially below those of the green segregants irrespective of the medium supplementation. It was concluded that while these Xantha mutants of barley responded to leucine and sucrose supplementation, this response was different from the pattern associated with strictly auxotrophic growth.
ASYMBIOTIC GERMINATION OF ORCHID SEEDS ON CARBOHYDRAES OF FUNGAL ORIGIN
Authors: SMITH S. E. 
Published: May 2006

SUMMARYAsymbiotic germination of two orchid species on sugars found in orchid mycorrhizal fungi was studied. Trehalose and glucose both provided a satisfactory carbon source for growth of non‐photosynthetic orchid protocorms while mannitol did not.
UPTAKE OF SUGARS BY EPICHLOE TYPHINA (PERS. EX FR.) TUL. IN CULTURE AND FROM ITS HOST, AGROSTIS STOLONIFERA L.
Authors: THROWER L. B. , LEWIS D. H. 
Published: May 2006

SUMMARY Epichloe typhina forms an intercellular systemic mycelium within its host, Agrostis stolonifera, and a stroma (upon which conidia and perithecia are produced) at the junction of the lamina and sheath of the flag leaf where association between the stroma and vascular tissue of the host is close. There is movement of labelled photosynthate to the stroma from other parts of the shoot. Movement through the systemic mycelium appears to be slight and most probably occurs through the host vascular tissue with subsequent uptake of photosynthate by the stroma.The principal carbohydrate acquired from the host is sucrose, and there is concomitant transformation to mannitol and trehalose by the fungus.
MULTIPERFORATE SEPTA IN LICHENS
Authors: WETMORE CLIFFORD M. 
Published: May 2006

SUMMARYAscomycetes usually have only one pore in the hyphal septum. This paper reports the first observation of multiperforate septa in lichen fungi using the electron microscope. Multi‐perforate septa are reported in Peltigera, Peltula and Hydrothyria. The extra pores probably facilitate intercellular transport of nutrients and water within the thallus. Previous reports of multiperforate septa in other lichen genera using the light microscope need to be verified by electron microscope studies.
THE CONSTRUCTION AND OPERATION OF A DEW‐SIMULATION CHAMBER
Authors: CLIFFORD BRIAN C. 
Published: May 2006

SUMMARYA variable dew‐point chamber which simulates dew fall on plant parts within a temperature range of 1–35° C is described, with technical data on construction and performance. Although designed to obtain uniform infections of cereal leaves following their inoculation with rust uredospores in a settling tower, possible wider uses of the apparatus in biological research are discussed.
THE ROLE OF TAXIMETRICS IN ANGIOSPERM TAXONOMY I. EMPIRICAL COMPARISONS OF METHODS USING CROTALARIA L.
Authors: BISBY F. A. 
Published: May 2006

SUMMARYTwo hundred and seventy‐three African species of Crotalaria L. (Leguminosae) were subjected to three taximetric procedures: single‐link clustering, with subgraph representation; principal co‐ordinate analysis; and median clustering. The classifications suggested by these methods were compared with each other, compared with a contemporary orthodox classification by Polhill and checked against the original plant material to see if the groupings were recognizable notwithstanding any similarity with Polhill's classification. Above the species level Crotalaria presents classification problems in size and complexity not uncommon for the angiopersms.The results of single‐link clustering suggest a classification close to Polhill's. In one case, where selected characters had been used, much of the correspondence is exact and of the few discrepancies some reveal possible improvements to the classification and others were caused by external factors. The principal co‐ordinate analysis results are difficult to interpret, suggest some unrecognizable groupings and only vaguely resemble Polhill's arrangement. The median clustering results suggest a tidy‐looking classification which, on investigation, proves largely spurious.The single‐link and principal co‐ordinate analysis were used to process two different sets of data. One set consisted of data for characters chosen mainly from the other set, selected for high intercorrelations using the information contribution measure. For both methods data for the selected character set gave more useful results.These findings favour the use of single‐link clustering for classifying angiosperms above the species level. They are a variance with the conclusions of some earlier empirical comparisons using angiosperms, but lend support to a number of theoretical arguments for preferring the single‐link procedure.
MYCORRHIZAS OF THE LILIIFLORAE I. MORPHOGENESIS OF ENDYMION NON‐SCRIPTUS (L.) GARCKE AND ITS MYCORRHIZAS IN NATURE
Authors: DAFT M. J. , CHILVERS M. T. , NICOLSON T. H. 
Published: May 2006

SUMMARYBluebell [Endymion non‐scriptus (L.) Garcke] annually produces a new root system that becomes mycorrhizal very quickly after the roots emerge from the bulb. Morphogenesis of the mycorrhizas is rapid during the autumn and cold winter periods whilst the host is subterranean. Infection is restricted to roots free in the soil and never extends to the root tissues enclosed within the bulb. Environmental conditions alter the rates of host and mycorrhizal development. On the basis of spore and mycelial characters, five species of endophytes were identified. The importance of mycorrhizas to the bluebell and other members of the Liliiflorae is discussed.
THE GENECOLOGY OF LAWN WEEDS. IV. ADAPTIVE SIGNIFICANCE OF VARIATION IN BELLIS PERENNIS L. AS REVEALED IN A TRANSPLANT EXPERIMENT
Authors: WARWICK S. I. , BRIGGS D. 
Published: May 2006

SUMMARYIn order to study the adaptive significance of variation in Bellis perennis L., an experiment was carried out in which plants from 19 populations – drawn from four habitat groups (I, lawns; II, grazed areas; III, seasonally mown and/or grazed areas; and IV, areas not seasonally reduced in height by grazing and/or mowing) ‐ were transplanted into a lawn subjected to regular mowing. Vegetative growth (as revealed by increment of plant width, dry wt and number of rosettes) and reproduction (as estimated by the number of capitula which survived mowing and produced fruit) were investigated over a 17 month period. As most plants in the experiment grew successfully and approximately 60 % of the 95 individuals (including plants from all four habitat groups) produced fruiting capitula, there was no evidence of distinct ‘races’ of B. perennis in the regularly defoliated habitats of lawn and pasture studied. However, the more successful plants, in terms of numbers of fruiting capitula, were found in samples collected from lawns and Port Meadow: pasture. Four individuals (three from lawns and one from Port Meadow) yielded approximately 50% of all the capitula which fruited. Within ‘successful’ populations there were plants which produced few or no fruiting capitula. Various hypotheses are presented to account for population variation.Estimates of coefficients of selection, comparing different features of growth and reproduction, may yield different values. For example, even though different individuals are apparently equally successful in vegetative growth under experimental conditions, i.e. with coefficients of selection of 0, a comparison of reproductive success for the same plants may give a value of 10.
THE GENECOLOGY OF LAWN WEEDS. V. THE ADAPTIVE SIGNIFICANCE OF DIFFERENT GROWTH HABIT IN LAWN AND ROADSIDE POPULATIONS OF PLANTAGO MAJOR L.
Authors: WARWICK S. I. , BRIGGS D. 
Published: May 2006

SUMMARYThe differential responses of two genetically‐determined growth forms of Plantago major L. ‐prostrate plants from lawns and erect plants from roadsides ‐ were studied in experiments involving clipping and reciprocal transplants.Under a regime of clipping at 2 cm above soil level in a pot experiment, plants from roadsides were severely damaged and all reproductive structures were lost, whereas plants from lawns were able to produce several thousand seeds per plant. In a reciprocal transplant experiment of ‘mown’ and ‘tall grass’ plots, a small number of erect inflorescences of the roadside plants survived mowing and were able to produce a minute quantity of seed. Lawn plants in mown plots produced significantly more seeds. In the tall grass plots, the roadside plants exhibited significantly greater vegetative and reproductive dry wt than lawn plants.Estimates of coefficients of selection were calculated for both experiments. Although values varied with different estimates of performance, in general: (1) selection against the roadside plants in the clipping treatment of the pot experiment and in the mown plots of the reciprocal transplant experiment was high (c.s. values based on reproductive features ranged from 078 to 1 00); and (2) coefficients of selection against lawn plants in the control of the pot experiment and in the tall grass plots of the reciprocal transplant experiment were also high (c.s. values in the reciprocal transplant experiment ranged from 0‐74 to 0‐77).Plants from lawns flowered significantly earlier than those from roadsides, and both lawn and roadside plants flowered significantly later in tall grass plots than in mown plots.Some problems and advantages of reciprocal transplant experiments are discussed.Our experiments provide strong evidence that differences in growth habit in Plantago major are of adaptive significance.
THE ENERGETICS OF FRESHWATER ALGAE; ENERGY REQUIREMENTS FOR BIOSYNTHESIS AND VOLUME REGULATION
Authors: RAVEN JOHN A. 
Published: May 2006

SUMMARYFreshwater algae have an intracellular osmolarity in excess of that of the medium. The tendency for water to enter the cells is resisted, in cells with a mechanically functional cell wall, by the ability of the wall to withstand a turgor pressure equivalent to the intracellular osmolarity; in cells lacking such a mechanically functional wall the water which enters is expelled by a contractile vacuole (or its functional equivalent). A comparison of the energy costs of cell volume regulation by these two mechanisms has been carried out making energy costings based on the minimum thermodynamic requirement and on plausible mechanisms for the two processes (wall synthesis and contractile vacuole function). This analysis yielded the following conclusions.(1) Wall synthesis is a ‘growth’ process, while contractile vacuole operation is a’maintenance’process; other things being equal, a cell wall is a preferable mechanism of volume regulation in non‐growing cells.(2) For a 5 μm radius cell with a specific growth rate of 8 × 10−6 s−1 and a 10 μm radius cell with a rate of 4 × 10−6 s−1 the energy input rate for contractile vacuole operation is considerably lower than for wall synthesis on the basis of minimum thermodynamic requirement; the plausible mechanism approach makes the two energy costs quite similar. Decreased growth rates favours the wall over the contractile vacuole mechanism.(3) Increased cell size (10 μm radius rather than 5 μm) has similar effects on the energy costs of both volume regulation mechanisms, provided a (cell organic weight)−0.32 dependence of intrinsic growth rate is incorporated into the computations.(4) Increased intracellular osmolarity (at constant extracellular osmolarity) causes a directly proportional increase in energy input rate for the cell wall mechanism, and a more than proportional increase in energy cost for the contractile vacuole mechanism.(5) A non‐spherical shape increases the energy cost (at constant cell volume) for both the cell wall and the contractile vacuole mechanisms.These conclusions may be used in the interpretation of such phenomena as the lower osmolarity of wall‐less than walled cells and the tendency for the resting stages of normally wall‐less and flagellate cells to have walls. It appears that the majority of freshwater algae have genetic capabilities to produce both walls and contractile vacuoles for cell volume regulation (e.g, the production of walled cysts by organisms which are normally flagellate, and the production of wall‐less motile spores and gametes by normally walled organisms).
THE IMPORTANCE OF QUANTITATIVE ANATOMY IN THE INTERPRETATION OF WHOLE LEAF BIOCHEMISTRY IN SPECIES OF TRITICUM, HORDEUM AND AVENA
Authors: JELLINGS A. J. , LEECH RACHEL M. 
Published: May 2006

SUMMARYThe quantitative internal leaf architecture of the first leaves of several cereals, including species of Triticum, Hordeum and Avena, is described. In all the species only between 50 and 60% of the cells are mesophyll cells, 30 to 40% are vascular cells and 10% epidermal cells. Interspecific differences were identified in cell density and in the amount and distribution of non‐cellular space. In Triticum monococcum and Triticum aestivum the cell densities were 394 × 103 cm−2 and 124 × 103 cm−2 and non‐cellular space 20 and 24% respectively. The implications of these findings in the interpretation of leaf biochemistry are discussed.
GROWTH OF SITKA SPRUCE SEEDLINGS WITH ROOTS DIVIDED BETWEEN SOILS OF UNEQUAL MATRIC POTENTIAL
Authors: COUTTS M. P. 
Published: May 2006

SUMMARYPost‐dormant seedlings with dormant roots were grown with their roots divided between two containers of loam or peat soil corresponding to wet/wet, dry/dry and wet/dry; the soil matric potentials were: loam, minus 6 kPa (wet) and minus 60 kPa (dry); peat, minus 5 kPa (wet) and minus 30 kPa (dry). In both soils the wet/dry treatment had little effect on leaf water potential, or on total plant growth compared with the wet/wet, but produced very uneven root development. Most growth of primary and woody roots occurred in the wet soil. Water supplied to one‐half of the root system did not increase growth of the half in dry soil, compared with the dry/dry treatment. Fewer roots emerged from dormancy in the dry than in the wet soil and at any one time, fewer roots were growing in the dry soil. The extension of main root axes in the dry soil was only slightly slower than in the wet soil. However, in the dry soil some roots were dying while others were extending and at the final harvest no increase was recorded in total root length.When both halves of the root system were in dry soil, leaf water potential was slightly reduced and shoot and root growth were significantly reduced compared with the wet/wet treatment.Soil adhered strongly to roots grown in the dry soil and the significance of this in plant water relations is discussed.
THE DISTRIBUTION OF CARBON AND THE DEMAND OF THE FUNGAL SYMBIONT IN LEEK PLANTS WITH VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: SNELLGROVE R. C. , SPLITTSTOESSER W. E. , STRIBLEY D. P. , TINKER P. B. 
Published: May 2006

SUMMARYLeek plants (Allium porrum) were grown on partially sterilized soil either inoculated (M) or not (NM) with the vesicular‐arbuscular mycorrhizal fungus, Glomus mosseae. They were pulse‐fed with 14CO2 in an apparatus which allowed CO2 subsequently respired either by the shoots or by the roots plus soil to be separately monitored. There were three experiments. In two, plants were harvested 48 h after labelling and in the third after 214 h. At harvest, the distribution of 14C between shoot, root, soil organic matter and root washings was measured.Similar growth curves for M and NM plants were obtained by supplying extra phosphorus to the latter, so that C distributions for both treatments could be compared directly. In all three experiments, about 7 % more of the total fixed C was translocated from shoot to root in M plants compared to NM plants. In the third experiment, this extra translocate could be accounted for by increased root respiration plus increased loss of C to the soil but, despite this drain, M and NM plants had equal rates of C assimilation per unit of leaf area. However, shoots of M plants had a lower content of dry matter and hence higher assimilation rates expressed on a dry matter basis.Increased hydration is suggested as a mechanism whereby leaf area and hence C assimilation increases in mycorrhizal plants and which offsets the effects of the drain imposed by the mycorrhizas.
SPATIAL STRUCTURE OF A POPULATION OF TRICHOLOMOPSIS PLATYPHYLLA IN A WOODLAND SITE
Authors: THOMPSON WENDY , RAYNER A. D. M. 
Published: May 2006

SUMMARYIsolates of the mycelial cord‐forming agaric, Tricholomopsis platyphylla, were obtained from an oak stand and their mating and mycelial interactions studied. The fungus was found to have tetrapolar incompatibility and genetically different dikaryons were strongly mutually antagonistic in culture. On the basis of such antagonism, 22 mycelial types, each comprising from one to 15 isolates were identified amongst a random sample of 113 dikaryotic mycelial isolates from an area of 20·8 ha. Isolates belonging to the same mycelial type were frequently found in close proximity in areas from which other types were excluded. However, some were from samples as much as 150 m apart and separated by areas occupied by other mycelial types. The likely origin of this distribution is discussed in relation to the pattern of dispersal, establishment and spread of this saprophytic fungus in a woodland habitat.
THE INFLUENCE OF soil AERATION ON THE EFFICIENCY OF VESICULAR–ARBUSCULAR MYCORRHIZAS
Authors: SAIF S. R. 
Published: May 2006

SummaryLow concentrations of soil CO2 increased but higher concentrations of CO2 decreased the dry matter of mycorrhizal and non‐mycorrhizal plants of Eupatorium odoratum L. Dry matter of Guizotia abyssinica (L.f.) Cass. decreased linearly with increasing CO2. Shoot dry weight of Sorghum tricolor (L.) Moench was unaffected by increasing soil CO2. Inoculation with Glomus macrocarpum increased the dry matter of E. odoratum and Guizotia abyssinica significantly at all CO2 concentrations. Mycorrhizal plants were more sensitive to soil CO2 than were the non‐mycorrhizal plants. Carbon dioxide at concentrations up to 8% had little effect on mineral uptake (except N) by E. odoratum but 16% CO2 decreased the mineral uptake significantly. Mineral uptake by Guizotia abyssinica decreased but the mineral concentration in the plant increased with rising CO2. The mineral uptake and concentration in 5. bicolor showed variable response to soil CO2. The efficiency of the mycorrhizal fungus Glomus macrocarpum in enhancing growth of its hosts was more affected by soil CO2 than was its development in roots.