bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENT OF CHLOROPLASTS FROM AMYLOPLASTS IN POTATO TUBER DISCS
Authors: ANSTIS P. J. P. , NORTHCOTE D. H.
Published: May 2006

White potato tuber tissues (Solarium tuberosum, vars. King Edward and Craigs Royal), contained carotenoids but did not contain either protochlorophyll or chlorophyll. On illumination of tuber discs, the accumulation of chlorophyll a and chlorophyll b began simultaneously after 19 hours and continued for 3 weeks. This greening process was associated with a synthesis of galactolipids.

Light of intensity 750 1× was sufficient to induce maximum greening and to cause greening throughout the disc. Blue light was more effective than orange or green light.

Chlorophyll accumulation in tuber discs was inhibited by cycloheximide, chloramphenicol, lincomycin, δ‐aminolaevulinic acid, benzyladenine, and high concentrations of sodium arsenate and potassium cyanide. It was unaffected by 2,4‐D, laevulinic acid and malonic acid. When green discs were returned to darkness, the total chlorophyll content remained constant over a period of 7 days but the ratio of chlorophyll a to chlorophyll b decreased.

These results are discussed in terms of the control mechanisms and differentiation processes involved in the development of chloroplasts from amyloplasts.
NITROGEN METABOLISM OF HALOPHYTES II. NITRATE AVAILABILITY AND UTILIZATION
Authors: STEWART G. R. , LEE J. A. , OREBAMJO T. O.
Published: May 2006

The availability and utilization of nitrate by salt‐marsh plants has been studied. All the species examined are able to assimilate nitrate, which appears to be the most important form of nitrogen available on the marsh. Species, from the strand line and lower marsh have higher nitrogen contents and nitrate reductase levels, than those from the upper marsh. Competition between species for nitrate is more important in the upper than lower marsh, because of low nitrate supply. Species such as Armeria maritima, Glaux maritima, Limonium vulgare and Triglochin maritima are able to compete more effectively for nitrate in the upper marsh than Puccinellia maritima, Salicornia europaea, Suaeda maritima, Spergularia media and Spartina×anglica. The results indicate there is an increase in nitrogen supply down the marsh, which may be associated with the input of nitrate during tidal innundation.
THE INFLUENCE OF LIGHT AND WATER DEFICIT UPON DIFFUSIVE RESISTANCE OF LEAVES OF VICIA FABA L.
Authors: KASSAM A. H.
Published: May 2006

The resistance of the upper (ru) and lower (r1,) surface of the leaf to diffusion of water vapour in Vicia faba was influenced differently by light and water deficit. ru saturated at about 100 Wm‐2 while r1, saturated at about 13 Wm‐2. At a given light intensity r1, was always smaller than r1. The difference in the density of stomata between the two surfaces of the leaf alone does not explain the magnitude of the difference between ru and r1, for V. faba and other species. Impressions of the stomata of the two surfaces at different light intensities indicated that the stomata on the lower surface were more widely open than those of the upper surface.

When stomatal response to light was not saturated, increase in leaf‐water deficit was accompanied by increase in ra and r1. Under saturating light intensities however r1, increase in leaf‐water deficit did not affect ru and r1, until leaves were flaccid and pressure potential close to zero; although the stomata on the upper surface closed at slightly higher water potentials than those of the lower surface. A dry treatment lasting 2 days, at the end of which the leaf was flaccid, affected the subsequent performance of the stomata while the leaf‐water deficit had been eliminated. This after‐effect was much greater on ru than on r1, and a complete recovery of the stomata on the upper surface took more than 2 days.

Larger differences between ru and r1, values are associated with larger lower to upper stomatal density ratios in a number of species. However r1, the ratios of ru/r1, are much larger than the corresponding stomatal density ratios. It appears that in V. faba, and in a number of other species, the stomata of the lower surface are more widely open that those of the upper surface either at equal light intensity or when leaves are illuminated from above.
COMMENTS ON THE USE OF REGRESSION ANALYSIS FOR THE STUDY OF PLANT GROWTH
Authors: NICHOLLS A. O. , CALDER D. M.
Published: May 2006

The adaptations of plants to environment can take many morphological and physiological forms. The rate at which new plant material is accumulated is an integrated measure of plant response to environment and is a useful character when comparing either genetic differences between populations or effects of different environmental conditions on populations.

Several approaches have been made to the study of quantitative plant growth. With frequent harvesting, regression analysis provides a powerful tool in describing the relationship of total weight with time. In this paper we have adopted procedures outlined by Draper and Smith (1966) and applied regression analysis to two sets of data from our programme on Atriplex. These demonstrate ways in which appropriate polynomial regression equations can be objectively applied to the total weight‐time relationship. Implications of fitting an inappropriate regression equation and the problems of extrapolation are also discussed.
LINKS BETWEEN ROOTS BY HYPHAE OF VESICULAR–ARBUSCULAR MYCORRHIZAS
Authors: HEAP ALISON J. , NEWMAN E.I.
Published: May 2006

Using a buried slide technique, hyphal connections are shown to exist between different roots on one plant, Lolium perenne L., and also between two roots of different species L. perenne and Plantago lanceolata L. These two species are commonly found together in permanent pasture.
THE INFLUENCE OF VESICULAR‐ARBUSCULAR MYCORRHIZAS ON PHOSPHORUS TRANSFER BETWEEN PLANTS
Authors: HEAP ALISON J. , NEWMAN E. I.
Published: May 2006

In six experiments Lolium perenne L. and Plantago lanceolata L. were grown together in pots. Two experiments also included L. perenne alone, P. lanceolata alone, or L. perenne + Trifolium repens L. In five of the experiments prior sterilization of the soil followed by reinoculation was used to obtain two treatments, one having plants infected with vesicular‐arbuscular mycorrhiza, the other non‐mycorrhizal. The shoots of some plants in each pot (‘donors’) were injected with 32P. After a week these shoots were removed, and after a further week the remaining plants (‘receivers’) were harvested and their 32P content determined.

In all experiments and species‐combinations there was some 32P transfer to the shoots of both mycorrhizal and non‐mycorrhizal receiver plants. The amount of transfer in mycorrhizal treatments was 2 to 8‐fold greater than in non‐mycorrhizal treatments, except in one experiment where mycorrhizal infection was very low. There was no clear difference between the different species combinations in the amount by which phosphorus transfer was enhanced by mycorrhizas. These results show that mycorrhizas can increase phosphorus transport between plants, but do not show whether there is direct transport from one root to another via interconnecting hyphae or whether the phosphorus must leave the donor root before being taken up by mycorrhizal hyphae.
THE HOST‐PARASITE RELATIONSHIP BETWEEN ZIZANIA CADUCIFLORA TURCZ. AND USTILAGO ESCULENTA P. HENN. IV. GROWTH SUBSTANCES IN THE HOST‐PARASITE COMBINATION
Authors: CHAN YUK‐SIM , THROWER L. B.
Published: May 2006

The mycelial and sporidial stages of Ustilago esculenta could synthesize IAA in vitro, especially if the medium contained tryptophan. Extract from culms of its host, Zizania caduciflora, contained tryptophan and was a suitable medium for the production of IAA. Significant levels of IAA occurred in non‐sporulating and sporulating culms. The culms also contained three cytokinins (presumed to be zeatin and zeatin riboside with one unidentified). Total amounts of cytokinins were (kinetin equivalents): unswollen culm, 8·5 μg 100 g‐1; non‐sporulating culm, 11·9 μg 100 g‐1; sporulating culm, 1·3 μg 100 g fresh wt‐1. U. esculenta was able to produce zeatin in culture but the other cytokinins originated from the host or host‐parasite combination. A possible sequence of events is proposed to explain the formation of gau sun from the flowering culm.
THE RESOURCE COSTS OF GENDER AND MATERNAL SUPPORT IN AN ANDROMONOECIOUS UMBELLIFER, SMYRNIUM OLUSATRUM L.
Authors: DOUST J. LOVETT , HARPER J. L.
Published: May 2006

In hermaphrodite flowers the various organs are potentially in competition with each other for resources translocated via the peduncle. It is an interesting question to ask: in what proportions does a plant with hermaphrodite flowers allocate various potentially limiting resources between these potentially ‘competing’ organs – between sporophylls and organs of attraction (petals, nectaries) and between stamens and pistils? The question becomes even more interesting in an andromonoecious species in which the plant supplies resources to both male and hermaphrodite (perfect) flowers.

In the biennial andromonoecious umbellifer Smyrnium olusatrum L. a constant ratio of one hermaphrodite flower to four staminate flowers was found to be maintained despite a fivefold range in both total flower number and total plant dry wt produced by surgery and nutrient depletion.

The allocation of nitrogen, phosphorus and potassium in floral organs was studied in S. olusatrum that had received various experimental treatments.

The ratio of resource allocated to sporophylls and to ancillary attractive organs was found to remain relatively constant whereas the allocation to the two types of attractive organs (petals and stylopodia) tended to vary with the experimental manipulations. The relative allocation of nutrient resources to male and female activities was scarcely altered by the treatments. Before fertilization plants distributed a greater (c. fivefold) proportion of phosphorus to male than to female organs. However, the cost of placental support of developing embryos reversed the ratio such that at seed maturity a greater proportion of phosphorus (c. × 2) had been allocated to seed than to stamens.
HIGH TEMPERATURE‐INDUCED INACTIVATION OF SPOROPHYTIC SELF‐INCOMPATIBILITY IN IPOMOEA FISTULOSA
Authors: PRABHA KIRAN , SOOD RENUKA , GUPTA SHRISH C.
Published: May 2006

Hot water treatments (50–55 °C) given to the stigmatic ends of excised pistils, just before pollination, overcame the self‐incompatibility barrier in Ipomoea fistulosa, a species with sporophytic self‐incompatible system. The minimal dose for inactivation of this barrier is treatment at 50 °C for 2 min but the optimum response is after 6 to 8 min. On increasing the temperature to 55 °C the optimum response is achieved in a shorter time. The changed, compatible behaviour, is reversed if pollination of the stigma is delayed for a day after the heat treatment. The rate of recovery of self‐incompatibility depends on the initial heat treatment given to the stigma.
EXPERIMENTAL ANALYSIS OF FLUORIDE SUSCEPTIBILITY OF GRAPE VINE (VITIS VINIFERA L.): FOLIAR FLUORIDE ACCUMULATION IN RELATION TO AMBIENT CONCENTRATION AND WIND SPEED
Authors: DOLEY D.
Published: May 2006

Summary

Three cultivars of Vitis vinifera L. (Chardonnay, Gordo and Traminer) were exposed to ambient gaseous fluoride concentrations of 0.37 to 6.0 μg F m−3 for 60 to 159 d during four successive growing seasons. In two growing seasons plants were fumigated for either 4 or 24 h d−1. The rate of accumulation of fluoride by leaves of each variety was independent of the presence or absence of visible injury. Within the range of conditions tested, fluoride accumulation was best described as the product of an accumulation coefficient characteristic of the variety, ambient fluoride concentration, duration of exposure, and wind speed at the top of the plant canopy. Leaves exposed to fluoride for 4 h d−1 accumulated fluoride more rapidly with respect to the dose (ambient concentration × exposure time) than did leaves exposed for 24 h d−1. The application of the findings to the study of fluoride accumulation in the field is discussed.
QUANTITATIVE DETERMINATION OF SIEVE‐TUBE DIMENSIONS IN RICINUS, CUCUMIS AND MUSA
Authors: MILBURN J. A. , KALLARACKAL J.
Published: May 2006

Summary

The percentage cross‐sectional area of sieve tubes in the phloem of Ricinus communis L. var. Gibsonii, Cucumis myriocarpus Naud. and Musa sp. L. (cv. Williams) was determined from thin serial sections stained for callose fluorescence. A new maceration method was developed to measure the percentage cross‐sectional area as well as the dimensions of a large number of sieve‐tube members in Ricinus.

Determinations of the proportion of sieve tubes in the phloem showed that this varied in different plants, and also in different parts of the same plant. Except in Cucumis, the petiole showed a much higher proportion when compared with stem and fruit stalk. The measurements of the diameter and length of sieve tube members in Ricinus revealed interesting distribution patterns.
A THERMOGRADIENT BAR APPARATUS FOR THE STUDY OF THE GERMINATION REQUIREMENTS OF BURIED SEEDS IN SITU
Authors: THOMPSON K. , WHATLEY J. C.
Published: May 2006

Summary

An apparatus is described which enables a layer of soil, containing naturally‐buried seeds, to be subjected to controlled temperature fluctuations over the range 5 to 30 °C, in the presence or absence of light. Results obtained from the use of this apparatus are presented for 14 species, all common constituents of the buried seed bank and nearly all weeds of arable land or pasture. At least partial inhibition of germination by darkness was found in all 14 species and stimulation of germination by temperature fluctuations in all but one. In some cases germination was inhibited by very large fluctuations.

There was some evidence that a requirement for temperature fluctuations may be induced by burial. The ecological significance of the results and the limitations of the thermogradient apparatus are discussed and some further applications of the apparatus are suggested.
GENECOLOGICAL STUDIES OF URTICA DIOICA L, II, PATTERNS OF VARIATION AT WICKEN FEN, CAMBRIDGESHIRE, ENGLAND
Authors: POLLARD A. J. , BRIGGS D.
Published: May 2006

Summary

An extreme genetic variant of Urtica dioica L. (stinging nettle), differing from the common plant in its paucity of stinging hairs, tall unbranched growth form, long narrow leaves and late flowering, occurs in large numbers at Wicken Fen, Cambridgeshire, England. Evidence from experimental cultivation of plants collected as adults and as seed along a transect across and beyond the boundaries of Wicken Sedge Fen suggests that:

Significant gene flow into the Sedge Fen occurs by both seed and pollen transport.

Pollen flow has significant within‐population effects also, acting to even out variation expressed in the adult generation.

Patterns of variability in adults do not indicate that natural selection is acting to limit the range of variability contained in the seed population.

Selection may, however, be occurring, since for this long‐lived perennial, patterns of variability may be more related to historical factors than to current ones.
MEMBRANE POTENTIAL COMPONENTS OF THE MARINE FUNGUS DENDRYPHIELLA SALINA (SUTH.) PUGH ET NICOT. POSSIBLE INVOLVEMENT OF CALMODULIN IN ELECTROPHYSIOLOGY AND GROWTH
Authors: BROWNLEE C.
Published: May 2006

Summary

Dendryphiella salina has membrane potentials of around −250 mV. Inhibition of respiration produced large, rapid and reversible depolarizations, which suggests the presence of an electrogenic pump. The Ca2+‐calmodulin inhibitor trifluoperazine in the micromolar range reversibly depolarized the membrane potential and irreversibly (or only slowly reversibly) decreased membrane conductance. Trifluoperazine inhibited hyphal extension but did not alter branching, although branching was stimulated at the hyphal tips following removal of the inhibitor.
THE RESPONSES OF SIX BROADLEAVED TREES DURING LONG‐TERM EXPOSURE TO SO2 AND NO2
Authors: FREER‐SMITH P. H.
Published: May 2006

Summary

In three experiments young trees were exposed to SO2 and NO2, singly and in mixtures, at concentrations of 110 nl l−1 or 100 nl l−1 for 5 d each week, and their growth was compared with that in clean air.

Exposure of Populus nigra during the summer and autumn (11/6/80 to 12/11/80) showed that greater than additive and additive growth inhibitions occurred in SO2 and NO2 during the growing season. Exposure to SO2 during dormancy (29/1/81 to 9/4/81) delayed leaf growth in the following spring, but the presence of NO2 did not influence this effect. Detailed observations of a few plants of six species during summer and winter fumigation (23/3/81 to 17/5/82) confirmed that the responses were influenced by season, and showed that pollutant effects can change during continuous exposures. In SO2 the growth effects did not occur to Tilia cordata, Malus domestica, Betula pendula and P. nigra until the second year of exposure, but in Betula pubescens and Alnus incana decreases of dry weight occurred in the first year. Nitrogen dioxide alone initially stimulated the shoot growth of T. cordata, B. pendula and A. incana, but these effects were lost for T. cordate and B. pendula in the second season of exposure. Inhibitory effects on a number of parameters developed more rapidly in SO2+ NO2 mixtures than in SO2 alone. In most instances the nature of these responses altered after overwintering, with the damage done by SO2 becoming more marked and the beneficial effects of NO2 being lost.

The responses to SO2 and NO2, were variable, depending on species, on the duration of exposure and the time of year. Sequential observations of the shoots suggested that the physiology of growth influenced pollution sensitivity. Foliar blemish, senescence and abscission were the main symptoms of injury in SO2 and SO2+ NO2, and the severity of these effects was well correlated with the magnitude of the decreases in dry weight.
THE POSSIBILITY OF CELL PLATE‐INDUCED PLASTID DIVISION IN A FLOWERING PLANT
Authors: STAFF I. A. , PARTHASARATHY M. V.
Published: May 2006

Summary

Plastid division, presumably caused by constriction by a developing cell plate, is described as seen once in a seedling root ofXanthorrhoea thorntoniiR. Tate (Monocotyledonae). Such a method of plastid division for a higher plant is novel, and may be caused either by an anomalous or a normal cell division. Similar types of plastid division have been observed in the green algae, bryophytes and lycopods with low numbers of plastids, so that it is possible that the occurrence of such a phenomenon is a rare but natural event in angiosperms. If constriction in an abnormal position of the plastid is forced by the cell wall, then heredity of the plastid derivatives may be perturbed. The involvement of the developing cell plate as an agent that might sometimes cause ‘sister’ plastids of a plastid division to go to different cells is a possibility that has, in the past, been overlooked for angiosperms.
THE EFFECT OF GREENING ON FLAVOUR PRODUCTION IN CELERY TISSUE CULTURES
Authors: WATTS M. J. , GALPIN I. J. , COLLIN H. A.
Published: May 2006

Summary

The relationship between greening and production of flavour compounds was investigated in blanched and green young (10‐week) and mature (20‐week) celery plants, and in colourless and green celery cell suspensions. In the young plants the concentrations of limonene and other terpenoids increased in the petiole and leaf‐extract as the level of chlorophyll increased. In the cell cultures, greening was induced by transferring cells to a medium where 2,4‐dichlorophenoxyacetic acid (2,4‐D) was replaced by 3,5‐dichlorophenoxyacetic acid (3,5‐D). During the first subculture, phthalides were produced in the growth phase, but were present in trace amounts only in the second and third subculture. Limonene, however, increased after the first subculture and during the growth phase of the third subculture was comparable to the levels in the young celery plant. Greening and aggregation of the cells had also increased by the third subculture in the 3,5‐D‐containing medium. It was suggested that phthalide production was stimulated by the transfer from a 2,4‐D‐ to a 3,5‐D‐containing medium, but as the level of aggregation and greening increased in the culture, phthalide production was reduced and limonene production increased. Electron and light microscope pictures showed that, despite the greening and aggregation, there was no chloroplast formation or cell differentiation in the cultures incubated with 3,5‐D. The role of greening in stimulating the formation of celery flavour compounds in tissue cultures is discussed.
AN ENDOMYCORRHIZA‐ECTOMYCORRHIZA SUCCESSION ASSOCIATED WITH ENHANCED GROWTH OF EUCALYPTUS DUMOSA SEEDLINGS PLANTED IN A CALCAREOUS SOIL
Authors: LAPEYRIE F. F. , CHILVERS G. A.
Published: May 2006

Summary

Seedlings of Eucalyptus dumosa A. Cunn. ex Schau., derived from a parent tree growing in a patch of calcareous soil, grew very poorly or not at all in that same soil unless they had formed abundant mycorrhizas. Other seedlings of that tree, planted in non‐calcareous soil from the same locality, grew well with negligible mycorrhizas. Similar results were obtained using synthetic calcareous and non‐calcareous potting mixtures. E. dumosa appears therefore to be primarily a calcifuge species, which becomes secondarily or facultatively calcicole as a consequence of mycorrhiza formation. Inflow of calcium into the seedlings with many mycorrhizas was the same as that into seedlings with few, but phosphorus inflow was greater into the mycorrhizal system. Mycorrhizas were presumably more effective at mobilizing and accumulating phosphate from insoluble calcium phosphates in the calcareous substrates than were uninfected roots.

Early infection of the seedlings was almost entirely by VA endomycorrhizal fungi, in contrast to the ectomycorrhizal fungi which are usual in eucalypts. Most of the growth stimulus seemed to be associated with these early endomycorrhizas. Ectomycorrhizas formed later and tended to replace the endomycorrhizas. The ectomycorrhizas which succeeded the endomycorrhizas in inoculated pots were of a different type (hyaline) from those (black) which developed spontaneously, presumably from airborne spores, on uninfected roots in uninoculated pots.
PHOTOSYNTHESIS BYFONTINALIS ANTIPYRETICA
Authors: MABERLY S. C.
Published: May 2006

Summary

Rates of net photosynthesis of the aquatic mossFontinalis antipyreticaHedw. were measured at seven levels of photon irradiance and five or six concentrations of CO2at the ambient temperature of the collection site, Esthwaite Water, in four months during a year. The effect of each factor on rates was assessed by fitting the data to models using non‐linear and linear regressions. There was no evidence for photoinhibition. The light compensation point was generally low compared with published values. The CO2compensation point was similar to that of C3plants. The slope of photosynthesisvsCO2concentration increased linearly with temperature in a manner consistent with the effects of boundary‐layer resistance. Other estimated and calculated variables are presented and discussed. Rates of saturated gross photosynthesis, compensation points and indices of degree of saturation varied with the level of the second factor. The results emphasize the interaction between photon irradiance, CO2concentration and temperature and the necessity of taking all these into account when studying the effect of one of these factors on photosynthesis.
PHOTOSYNTHESIS BY FONTINALIS ANTIPYRETICA
Authors: MABERLY S. C.
Published: May 2006

Summary

Environmental variables in the North Bay of Esthwaite Water, where the aquatic moss Fontinalis antipyretica Hedw. grows, were measured over a year. Steep depth profiles often existed in the water column of about 1 m, with lower pH and higher alkalinity 01m above the sediment where F. antipyretica was found. Consequently, CO2 concentration was higher at depth than at the surface. The North Bay generally had higher CO2 concentrations than the centre of the lake. The survival of F. antipyretica in this productive lake probably results partly from these elevated concentrations of CO2.

Nutrient limitation of production was discounted since tissue levels of phosphorus and nitrogen were about six and four times greater respectively than suggested limiting levels of these nutrients. Rates of photosynthesis, respiration and production were calculated from the field data and the previously‐determined measurements of the effect of photon irradiance, CO2 concentration and temperature on photosynthesis. In all the four months studied, no single factor appeared to be predominantly limiting. Calculations suggested that in November, photon irradiance and in March, temperature were the major factors limiting production, both as a result of physical conditions. In August, low CO2 concentration, caused by the activity of dense phytoplankton, was the major factor limiting production.
PHYTOCHROME REGULATION OF EXTRACTABLE CYTOCHROME OXIDASE ACTIVITY DURING EARLY GERMINATION OF BROMUS STERILIS L. AND LACTUCA SATIVA L. CV. GRAND RAPIDS SEEDS
Authors: HILTON J. R. , OWEN P. D.
Published: May 2006

Summary

Phytochrome‐induced changes in the activity of cytochrome oxidase, the respiratory enzyme involved in the terminal oxidation of substrates of the tricarboxylic acid cycle, have been detected during the early stages of germination prior to radicle protrusion. Photoreversible changes in extractable enzyme activity have been demonstrated in the seeds of two species; Lactuca sativa, in which germination is promoted by Pfr, and Bromus sterilis, in which germination is inhibited by Pfr.
RESPONSES OF RADISH CULTIVARS TO LONG‐TERM AND SHORT‐TERM EXPOSURES TO SULPHUR DIOXIDE, NITROGEN DIOXIDE, AND THEIR MIXTURE
Authors: GOKZIK S. , ASHMORE M. R. , BELLF J. N. B.
Published: May 2006

Summary

Six cultivars of Raphanus sativus L. were fumigated continuously with 400 fig m−3 sulphur dioxide (SO2) or nitrogen dioxide (NO2), or their mixture at 400 fig m−3 for each gas, for 20 d, after which plants were exchanged between treatments and subjected to 3 h fumigations with higher concentrations of the same gases. SO2 reduced hypocotyl dry weight in three cultivars, while NO2 had no significant effect; large reductions in hypocotyl dry weight occurred in all six cultivars in the gas mixture. All long term fumigation treatments tended to reduce the amount of leaf injury caused by subsequent exposure to a mixture of 1300 fig m−3 SO2 and 950 fig m−3 NO2 for 3 h. Long‐term fumigation with NO2 alone tended to increase the amount of leaf injury caused by subsequent exposure to SO2 alone. A decrease in 35SO2 uptake was found in plants which had been given long‐term fumigation with SO2 or with SO2+ NO2.
STUDIES ON THE MYCORRHIZAS OF PINU SYLVESTRIS L. PRODUCED IN VITRO WITH THE BASIDIOMYCETE SUILLUS VARIEGATUS (SW. ex Fr.) O. KUNTZE
Authors: WARMBRODT R. D. , ESCHRICH W.
Published: May 2006

Summary

Ectomycorrhizas of Pinus sylvestris L. synthesized in vitro with Suillus variegatus (Sw. EX Fr.) O. Kuntze were studied by light and electron microscopy. Approximately two months following innoculation of germinated seedlings of Pinus sylvestris with the fungus, the host showed well‐developed ectomycorrhizas each consisting of a fungal mantle, tannin layer and Hartig net region surrounding the endodermis and root vascular cylinder. The mantle formed by the mycosymbiont was 3 to 10 hyphae deep and covered the root tip completely but did not invade the cells of the apical meristem. The tannin layer consisted of dead host cells, apparently derivatives of the root cap, containing electron‐dense deposits. Fungal cells which did not differ in appearance from those forming the mantle and the Hartig net were appressed to the tannin layer, partly embedded in an electron‐dense mucilaginous substance. The fungal hyphae in the Hartig net region were up to several cells in thickness but did not penetrate the protoplasts of the root cortex cells nor the intercellular spaces beyond the endodermis. The presence of plasmodesmata in the cell walls not separated by the fungal hyphae indicated that symplastic continuity of the root cells in the Hartig net region was not completely disrupted. The ultrastructure of the various cells of the mycorrhizas plus examination of free‐hand sections indicate that the mycorrhizas, at the time of fixation, were viable associations. The structure of the mycorrhizas produced in vitro is compared and discussed with respect to naturally occurring mycorrhizas on the same host species.
THE GENESIS OF SIZE HIERARCHIES IN SEEDLING POPULATIONS OF IMPATIENS CAPENSIS MEERB.
Authors: WALLRE D. M.
Published: May 2006

Summary

In 1978 and 1980 I planted 660 and 900 seeds of Impatiens capensis Meerb. at four densities in the greenhouse to examine how variation in plant performance is generated. I noted seed weight, seed type (cleistogamous or chasmogamous), maternal parent, and population of origin, and monitored emergence date, cotyledon area, the biomass of competitors within the same flat, and the final size reached by the seedlings after 63 to 80 d of growth. Larger seeds tended to germinate sooner, as did seeds derived from chasmogamous flowers. Seeds from northern populations took longer to germinate. Seeds from different maternal parents also germinated at different rates. Cotyledon area strongly depended on seed weight, and, to a lesser extent, germination date. Maternal parent and seed type significantly affected cotyledon area in 1980.

Plant density and cotyledon area influenced final size the most, but almost every factor proved to be statistically significant. As expected, earlier emerging seedlings with larger cotyledons growing at the lowest density grew into the largest plants. I applied path analysis to summarize the interactions among the continuous variables and to disentangle direct from indirect causal effects. This technique revealed that seed weight enhanced performance primarily through its effects on emergence date and cotyledon area. Chasmogamous seedlings outperformed cleistogamous seedlings, and their advantage was expressed during most phases of growth. Together, the predictor variables accounted for over four‐fifths of the total variation in final size.

The inequality of plant sizes, as measured by the Gini coefficient, increased appreciably during the course of the experiment. There was no simple relation to density, however, suggesting that both intrinsic differences in growth rate, and competitive dominance and supression fuel the establishment of size hierarchies.
ON THE OCCURRENCE OF BRANCHED AND SWOLLEN RHIZOIDS IN BRITISH HEPATICS: THEIR RELATIONSHIPS WITH THE SUBSTRATUM AND ASSOCIATIONS WITH FUNGI
Authors: POCOCK K. , DUCKETT J. G.
Published: May 2006

Summary

The occurrence of branched and swollen rhizoids was investigated in 72–5 % of British hepatics (206 of the 284 species). Branched rhizoids are widespread in the Jungermanniales (100 of the 169 species) but are restricted to the Metzgeriineae in the Metzgeriales. They were not detected in the Marchantiidae. Terminal swellings, particularly well developed in the Lepidoziineae and Cephaloziineae, were found in 33 species in the Jungermanniales.

Rhizoid branching is associated with contact with a range of substrata whereas swollen rhizoids, exclusive to species growing on peat and rotten wood, are always associated with fungal hyphae. In some species, the hyphae probably derive from the fungal zone in the stem of the hepatic but, in others, they more likely come from repeated external invasions. The function of branched rhizoids is almost certainly anchorage whereas the swollen tips may well be absorbtive, probably involving the fungus as an intermediary.

Branched and swollen rhizoids are particularly prominent on flagellar shoots but are most developed on leafless underground stems. These hitherto undescribed subterranean axes which extend to depths of up to 20 cm in several members of the Lepidoziaceae and Cephaloziaceae may be important organs of perennation enabling plants to survive drought and fire.
THE ELM DECLINE AT PAWLAW MIRE: AN ANTHROPOGENIC INTERPRETATION
Authors: STURLUDOTTIR SIGRUN A. , TURNER JUDITH
Published: May 2006

Summary

A fine‐resolution pollen diagram has been prepared from across the elm decline at Pawpaw Mire, 462 m OD, in the northern Pennies of England. It covers 25 cm with 01 cm thick samples at intervals varying from 08 to 01 cm in different parts of the diagram. It is estimated that each sample contains the pollen produced during an average of one to two seasons. There is evidence that the woodland vegetation was being managed by the local mesolithic population throughout the four centuries or so represented and although other factors may have contributed, the elm decline at this site can be explained satisfactorily in terms of the cumulative effect of this mesolithic activity on the soils of the area.
LEAF DIFFUSIVE RESISTANCE AND WATER ECONOMY IN CARBON DIOXIDE‐ENRICHED RICE PLANTS
Authors: KHAN M. A. H. , MADSEN A.
Published: May 2006

The leaf diffusive resistance to the transfer of water vapour and CO2 exchange in rice plants (Oryza sativa L., ev. IR‐20) measured from the late vegetative stage to maturity, varied in response to differing CO2 enrichments. The leaf diffusive resistance of plants treated with 900 μ11−l CO2 ranged from one‐half to twice that of the control plants (330μl l−1 CO2).This difference was more pronounced during the heading and ripening stages. In plants treated with 600 μ1 −1 CO2, the diffusive resistances appeared to be smaller than in the control plants for most of the day. In the diurnal cycles, resistances were highest during the early morning and before sunset, the maximum again occurring in the plants treated with 900μ11 −1 CO2.

The rate of transpiration was inversely related to the diffusive resistance, and was 20 to 100% lower in the plants treated with 900 μ1 1−1 CO2 than in the controls, both in the seasonal and diurnal cycles. In plants treated with 600 μ1 1−1 CO2, the rate of transpiration was lower than in the controls in the morning but distinctly higher during the afternoon. However, the integrated total daily transpiration in 600 μ1 1−1 CO2 did not exceed that of the controls. In all cases, CO2‐treated plants, through their increased biomass production and economic yield, appeared to have a higher water use efficiency than the control plants.
DEPRESSION OF GROWTH AND YIELD IN WINTER BARLEY EXPOSED TO SULPHUR DIOXIDE IN THE FIELD
Authors: BAKER C. K. , COLLS J. J. , FULLWOOD A. E. , SEATON G. G. R.
Published: May 2006

A field exposure system designed for the controlled release of sulphur dioxide (SO2) was used in two contrasting seasons to expose commercial crops of winter bailey (Hordeum vulgare L.) to SO2 concentrations ranging from 40 to 200 ppb [parts per billion (109) by volume] above ambient. During winter and early spring, growth of the plants was depressed at high SO2 concentrations but later recovered; in spring and summer, low concentrations stimulated growth above that of controls, but there was no corresponding increase in grain yield. Yield depression is discussed in relation to SO2 concentration and dose.
STRUCTURAL ASPECTS OF THE PRIMARY TISSUES OF THE CUCURBITA PEPO L. ROOT WITH SPECIAL REFERENCE TO THE PHLOEM
Authors: WARMBRODT ROBERT D.
Published: May 2006

Summary

The primary phloem and associated tissues in the root of Cucurbita pepo L. were examined by light and transmission electron microscopy to provide information on the feasibility of symplastic transport from the sieve‐tube members to the cortex in this organ. The structure, distribution and frequency of cytoplasmic connections between the various cell types of the root are reported as well as the cytological characteristics of the various cells. The protoplasts of contiguous cells of the root are joined by various numbers of cytoplasmic connections: plasmodesmata (simple and branched) between parenchymatous elements; pore‐plasmodesmata between sieve‐tube members and parenchymatous elements (companion, phloem parenchyma or pericycle cells in the Cucurbita root); and sieve‐area pores between contiguous sieve elements. The plasmodesmata associated with secondary‐ and tertiary‐state endodermal cells are not constricted by the suberin lamellae. Differences in the frequency of cytoplasmic connections between the various cell types of the primary phloem, pericycle and ground tissue do occur with the highest frequency between sieve‐tube members and companion cells. The results indicate that the structure of the C. pepo root may be compatible with a symplastic pathway of phloem unloading and transport to the cells of the ground tissue.
POPULATION COMPOSITION, GENDER SPECIALIZATION, AND THE ADAPTIVE SIGNIFICANCE OF DISTYLY IN LINUM PERENNE (LINACEAE)
Authors: NICHOLLS MARC S.
Published: May 2006

Summary

Spatial distribution, pollen‐flow and the factors affecting seed‐set were studied for a population of the distylous perennial Linum perenne L. during a single season. The morphs were spatially segregated at the site. Stigmatic pollen loads on long‐style plants comprised 27 to 51 % legitimate pollen and on short‐style plants 0 to 46% legitimate pollen. Most flowers received more legitimate pollen grains than the number theoretically required to fertilize the corresponding number of ovules. Intraflower pollinations accounted for a large proportion of individual stigma loads. There was a weak negative correlation between the distance of the nearest legitimate neighbour and the number of legitimate pollen grains recorded on the stigma. No relationship was established between either the proximity or proportion of legitimate neighbours and seed‐set. Long‐style plants produced less pollen and matured more seeds than short‐style plants. It is suggested that, in the population studied, paternal (pollen) and maternal (seed) investment are unequally divided between the morphs. This may be a common theme associated with heterostyly in plants.
THLASPI CAERULESCENS J. & C. PRESL. (T. ALPESTRE L.) IN BRITAIN
Authors: INGROUILLE M. J. , SMIRNOFF N.
Published: May 2006

Summary

Thlaspi caerulescens J. & C. Presl. (T. alpestre L.) has a restricted and disjunct distribution in Britain. Both on natural and mine sites it is confined to soils contaminated by lead and zinc. Morphological variation occurs both regionally and locally but there is no support from a taxometric cluster analysis for the taxonomic recognition of variants. In experiment the index of zinc tolerance of plants raised from seed was positively correlated with the concentration of zinc in the soils from which the seed parents originated. The distribution of T. caerulescens is discussed in relation to morphological and physiological variation between populations.
PHOTOSYNTHESIS IN VIVO CAN BE LIMITED BY PHOSPHATE SUPPLY
Authors: SIVAK MIRTA N. , WALKER DAVID A.
Published: May 2006

Summary

Measurements of photosynthetic CO2 and O2 exchange, and associated chlorophyll fluorescence were made on leaves (from plants grown in complete nutrient medium) while the internal inorganic phosphate concentration was increased or decreased by feeding solutions through the vascular tissue. The data indicate that orthophosphate supply to the chloroplast can, in some circumstances, become the process that limits photosynthesis in vivo.
INDUCTION AND LOSS OF CADMIUM TOLERANCE IN HOLCUS LANATUS L. AND OTHER GRASSES
Authors: BAKER A. J. M. , GRANT C. J. , MARTIN M. H. , SHAW S. C. , WHITEBROOK J.
Published: May 2006

Summary

This paper reports the results of an experimental study of Cd tolerance in the grass Holcus lanatus L. The responses of plants from a site aerially contaminated with Cd have been compared with those of plants from metalliferous mine sites and uncontaminated sites, using a range of soil treatments and pretreatments to assess the extent to which Cd tolerance can be affected. Responses in H. lanatus have been compared with those for three other grasses, Agrostis capillaris L., Deschampsia cespitosa (L.) Beauv. and Festuca rubra L., collected from the same sites and propagated as clones on their original soil and uncontaminated soil for three years prior to tolerance testing. Overall, a 13% drop in mean tolerance index was observed; even non‐tolerant clones showed a loss of tolerance when grown in John Innes Potting Compost. These results suggest that H. lanatus is capable of greater phenotypic adjustment than A. capillaris, D. cespitosa and F. rubra and that Cd tolerance in this species can also be partially induced de novo in clones from uncontaminated sites. In H. lanatus there is also an indication that the clones from mines are more stable in their Cd tolerance than that from the aerially polluted site. The possible evolutionary significance of these observations is discussed.
Research for Democracy: Linking Community Organizing and Research to Leverage Blight Policy
Authors: Shlay Anne B. , Whitman Gordon
Published: May 2006

Urban scholarship has focused on the role of power and politics in fostering uneven development, showing that urban patterns are not inevitable but controllable. Yet shifting power from one group to another is easier said than done. How may community organizations acquire leverage that permits them to alter political decision making around space and urban development? This article describes a collaboration in Philadelphia between a citywide faith‐based coalition and a university policy research center. Called “Research for Democracy,” this collaboration combined research and organizing sophistication to successfully reshape citywide policy around neighborhood blight. Research for Democracy became a collaboration where community leaders' experiences were voiced in the collective research experience. This helped to reinforce alternative views on blight and break down the third dimension of power—the ability to shape the conceptions and ideas of the powerless. Armed with research ammunition that mirrored people's shared experiences, organizers strategically worked with other political actors to reshape the policy agenda around blight and break down the second dimension of power—policy agenda setting. As a consequence, Philadelphia's blight policy was broadened to include money for neighborhood stabilization, acquisition, and improvements, not solely demolition as was originally proposed.
Echocardiographic Follow‐Up of Patients with Takayasu's Arteritis: Five‐Year Survival
Authors: Soto María Elena , Espinola‐Zavaleta Nilda , Ramirez‐Quito Oscar , Reyes Pedro A.
Published: May 2006

Takayasu's arteritis (TA) is a primary vasculitis that causes stenosis or occlusion, rarely aneurysm and distal ischemia. This study was undertaken to examine cardiovascular damage using echocardiography and determine the causes of morbid‐mortality in Mexican Mestizo patients with TA. Seventy‐six patients were studied by transthoracic echocardiography. Left ventricular diameters, parietal thickness, systolic function, and wall motion were analyzed, also, valvular lesions and aorta features were assessed. Thickness of the interventricular septum was 12 mm ± 3 (8–19), and that of posterior wall was 12 mm ± 2 (9–18). The average left ventricular diastolic diameter was 47 mm ± 7 (33–68) and the left ventricular systolic diameter 32 mm ± 8 (16–64). The left ventricular ejection fraction was of 57 ± 11%. Left ventricular concentric hypertrophy was found in 28 (50%) of the 56 hypertensive patients. The five‐year survival of patients with left ventricular concentric hypertrophy was 80%, compared to 95% in patients without hypertrophy (P = 0.00). Abnormal wall motion was found in 15 patients. Thirty‐one patients had aortic regurgitation, 19 had mitral regurgitation, 13 had tricuspid regurgitation, and 10 and pulmonary hypertension. Six patients had aneurysms of ascending aorta and 7 stenosis of descending aorta. Thirteen of 76 patients died (17%), 85% were hypertensive, and 9% also had acute myocardial infarction (AMI). Echocardiography, a noninvasive technique, shows a great utility in detection and follow‐up of cardiovascular manifestations in patients with TA. New techniques, more sensitive toward detecting the early stages of left ventricular dysfunction, are promising to limit left ventricular hypertrophy development.
Psychosocial Outcomes and Drug Attributes Affecting Treatment Choice in Men Receiving Sildenafil Citrate and Tadalafil for the Treatment of Erectile Dysfunction: Results of a Multicenter, Randomized, Open-Label, Crossover Study
Authors: Dean John , Hackett Geoffrey I. , Gentile Vincezo , Pirozzi-Farina Furio , Rosen Raymond C. , Zhao Yanli , Warner Margaret R. , Beardsworth Anthony
Published: May 2006

Introduction

Although sildenafil citrate (sildenafil) and tadalafil are efficacious and well-tolerated treatments for erectile dysfunction (ED), preference studies have shown that patients may favor one medication over the other.

Aim

To determine whether psychosocial outcomes differed when men with ED received tadalafil compared with sildenafil.

Main Outcome Measures

Measures included a treatment preference question, Psychological and Interpersonal Relationship Scales (PAIRS), and Drug Attribute Questionnaire.

Methods

Randomized, open-label, crossover study. After a 4-week baseline, men with ED (N = 367; mean age = 54 years; naïve to type 5 phosphodiesterase inhibitor therapy) were randomized: tadalafil for 12 weeks then sildenafil for 12 weeks or vice versa (8-week dose optimization/4-week assessment phases). During dose optimization, patients started with 10 mg tadalafil, or 25 or 50 mg sildenafil and could titrate to their optimal dose (10 or 20 mg tadalafil; 25, 50, or 100 mg sildenafil). Medications were taken as needed. Patients completing both 12-week periods chose which medication to continue during an 8-week extension.

Results

Of 291 men completing both treatment periods, 71% (N = 206) chose tadalafil and 29% (N = 85) chose sildenafil (P < 0.001) for the 8-week extension. When taking tadalafil compared with sildenafil men had higher mean endpoint scores on PAIRS Sexual Self-Confidence (tadalafil = 2.91 vs. sildenafil = 2.75; P < 0.001) and Spontaneity (tadalafil = 3.32 vs. sildenafil = 3.17; P < 0.001) Domains and a lower mean endpoint score on Time Concerns Domain (tadalafil = 2.2 vs. sildenafil = 2.59; P < 0.001). The two most frequently chosen drug attributes to explain treatment preference were ability to get an erection long after taking the medication and firmness of erections. Tadalafil and sildenafil were well tolerated with 12 (3.3%) patients discontinuing for an adverse event.

Conclusions

As measured with PAIRS, men with ED had higher sexual self-confidence and spontaneity and less time concerns related to sexual encounters when treated with tadalafil compared with sildenafil. These psychosocial outcomes may help explain why more men (71%) preferred tadalafil for the treatment of ED in this clinical trial.
Helium pre-enrichment in the first stars
Authors: Chuzhoy Leonid
Published: May 2006

We show that element diffusion can produce large fluctuations in the initial helium abundance of stars. Diffusion time-scale, which in stellar cores is much larger than the Hubble time, can fall below 108 yr in the neutral gas clouds of stellar mass, dominated by collisionless dark matter or with dynamically important radiation or magnetic pressure. Helium diffusion may therefore explain the recent observations of globular clusters, which are inconsistent with initially homogeneous helium distribution.