bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EFFECT OF DESICCATION ON SUBSEQUENT ASSIMILATION AND RESPIRATION OF THE BRYOPHYTES ANOMODON VITICULOSUS AND PORELLA PLATYPHYLLA
Authors: HINSHIRI H. M. , PROCTOR M. C. F. 
Published: May 2006

Summary Anomodon viticulosus (Hedw.) Hook. & Tayl. and Porella platyphylla (L.) Lindb. show evidence of a consistent pattern in the course of net assimilation following moistening after various periods of desiccation. In the early stages of desiccation (up to 22 days at 50% RH in Anomodon viticulosus; up to 60 days in Porella platyphylla), recovery is rapid and apparently complete within c. 3–4 hours. After longer periods of desiccation the net assimilation rate is initially negative, but becomes positive after lengths of time increasing progressively to several days. This is partly a consequence of delayed (and probably incomplete) recovery of photosynthesis, and partly of an enhanced initial rate of respiration. After prolonged desiccation (more than 70 days) respiration in Anomodon viticulosus builds up to very high values over a period of about 24 hours following moistening and then falls to more normal levels, but subsequent recovery is problematical.
RAPID MEASUREMENTS OF RELATIVE TURGIDITY IN MAIZE (ZEA MAYS L.)
Authors: DOWNEY LLOYD A. , MILLER J. W. 
Published: May 2006

SummaryTwo rapid methods of assessing relative turgidity in maize are described. The first involved measuring the water uptake by discs of leaf tissue but omits the oven dry weight from the calculation. Where the position on the leaf was standardized, the relationship was linear (r = 0.99***) over a wider range than normally encountered in field conditions. The regression relationship held for plants grown under a wide variety of environmental conditions and at various stages of development.The second method utilized a series of photographic standards of plants at different relative turgidities. Relative turgidity could then be estimated visually by comparing the plant and the photographic standards.Accuracy with either method was similar to the experimental error of relative turgidity measured by normal means. Both offer a considerable saving in time, especially the photographic standard method which allows instantaneous readings to be made. This should permit field workers to assess rapidly the water status of their crop without the labour involved in conventional measurements.
MORPHOGENETIC STUDIES ON CULTURED MATURE ENDOSPERM OF CROTON BONPLANDIANUM
Authors: BHOJWANI S. S. , JOHRI B. M. 
Published: May 2006

SummaryThe mature endosperm of Croton bonplandianum proliferated profusely on White's medium (WM) + 2 ppm 2,4‐D + 5 ppm kinetin + 2500 ppm yeast extract. Association with the embryo was essential for initiation of proliferation of mature endosperm. Tracheidal cells usually differentiated. Twelve‐month‐old callus contained predominantly triploid and hexaploid cells. When the callus obtained on WM + 2,4‐D + kinetin + yeast extract was subcultured on WM triploid roots formed in 25% of the cultures. At 10−7 M, IBA, IAA, or NAA, in WM, promoted rooting; IBA was most effective. Attempts to induce shoot differentiation failed.
FUNGUS–ALGA ASSOCIATION IN LICHENS OF THE TELOSCHISTACEAE: AN ULTRASTRUCTURAL STUDY
Authors: GALUN MARGALITH , BEN‐SHAUL Y. , PARAN NAVAH 
Published: May 2006

SummaryThe ultrastructure of the physical contact between fungus and alga has been examined in six species of the lichen family Teloschistaceae. The relation between the fungus and living algal cells was found to be merely one of very close proximity of their cell walls. Only a few distorted algal cells were found to be intracellularly invaded by the fungus. The association between the symbionts was compared with that previously observed in lichens of the Lecanoraceae and Lecideaceae.
STELAR EVOLUTION IN VASCULAR PLANTS
Authors: SLADE BRENDA F. 
Published: May 2006

SummaryRecently Namboodiri and Beck (1968c) and Beck (1970) in proposing a new hypothesis of stelar evolution in the gymnosperms failed to mention its possible application to angiosperms. This paper, by showing the close similarity of the primary vasculature of gymnosperms with that of the ‘parastichous type’ (Philipson and Balfour, 1963) in dicotyledons, shows that the hypothesis applies equally to both groups. Brief reference is made to other instances of stelar structure where application of the leaf‐gap theory (Jeffrey, 1902, 1917) has failed. Here Namboodiri and Beck's new concept, that parenchymatous areas may arise having no association with leaf gaps, is most helpful.
CONTRIBUTIONS TO THE ECOLOGY OF BRACKEN (PTERIDIUM AQUILINUM)
Authors: WATT A. S. 
Published: May 2006

SummaryThe phenomena of change from the marginal belt to the hinterland on the acid sandy podsol of area E are regarded as symptoms of senescence (increase in age of the frond population and in patchiness: reduction in height and number of fronds, in size of plant and its rate of growth). They are considered in relation to causes, primary and secondary.The primary cause is the plant's reaction on itself: in the invading marginal plant increasing competition until the maximum number is reached (at 30–40 ft; 9–12 m) and reaction on the root and rhizome system through the amount and kind of litter. Once started a chain of reactions is set up in which frost and drought are important but secondary causes.Litter (s.l.) acts in two ways with opposing effects on the welfare of bracken but with no hard and fast line between them and the effect varying with the conditions. Litter (s.s. = the L layer) when abundant, as in the mid‐region of the marginal belt, means protection from winter frost and drought and by delaying emergence of the fronds reduces liability to spring frost and in its F and H forms induces a concentration of roots in them, a rise in the general level of the shoot system and greater vulnerability of the growing points to frost and drought. With age of the population the F and H layers increase relatively to the L (s.s.).Data on the vigour and vertical distribution of the rhizome system from an area (Blaxhall Heath) vacated by bracken and from the live bracken marginal to it show a similar robust but dead system in both, which in the latter has a younger, superficial, attenuated system, consisting mostly of intermediate and short shoots above it and lying almost wholly in the F layer. Details show that the process of degeneration has not only been checked but recently reversed.Response to fluctuations in weather show that the hinterland plant is not inherently weak, but its attainment of a size and vigour similar to that of the marginal plant depends on conditions enabling it to reach that status and to maintain it on the continued provision of open conditions with little competition.The interpretation of degeneration (regression) advanced here does not invoke the presence of a pathogen.The results are considered briefly in relation to the status of bracken in a man‐controlled environment.
A METHOD FOR THE GROWTH OF LARGE BATCHES OF PLANTS IN AN ASEPTIC ENVIRONMENT
Authors: WILDON D. C. , WONG DOREEN , BRYANT J. A. 
Published: May 2006

SummaryA method for growing large numbers of seedlings under aseptic conditions is described. The method makes use of peracetic acid for the initial sterilization of the seeds, followed by transfer of the seeds to a flexible film sterile isolator for germination and growth in an aseptic environment.
DISTRIBUTION OF THE LICHEN CHONDROPSIS SEMIVIRIDIS IN RELATION TO ITS HEAT AND DROUGHT RESISTANCE
Authors: ROGERS R. W. 
Published: May 2006

SummaryThe distribution of Chondropsis semiviridis (FvM. ex Nyl.) Nyl. was mapped for Australia. Studies in gas exchange physiology demonstrated that length of drought is likely to limit distribution of the species. Similarly, it is shown that sensitivity to heat when wet is likely to prevent the species from establishing in arid areas with a summer rainfall seasons The surge of respiration upon wetting of lichen thalli noted by other workers was so short for C. semiviridis that it could not affect the limits of its distribution.
FREEZING RESISTANCE OF RELICTS FROM THE ARCTO‐TERTIARY FLORA
Authors: SAKAI A. 
Published: May 2006

SummaryThe freezing resistance of winter twigs of genera which became extinct in Japan during Tertiary time, such as Sequoia, Metasequoia, Taxodium, Glyptostrobus, Pseudolarix, Keteleeria and Liquidambar, has been investigated. Except for Taiwania, Sequoia, Cunninghamia lanceolata, most of the genera were found to survive freezing down to – 20° to – 25°C, and Metasequoia and Taxodium to resist freezing down to – 25° to – 30°C. Most of the typical temperate deciduous genera native to Japan, such as Carpinus, Zerkova, Castanea, Acer and Cercidiphyllum, which lived together with the extinct genera during the Tertiary as common members of the Arcto‐Tertiary Forest, were also found to survive freezing down to –20° to – 25°C. From the standpoint of freezing resistance, it therefore seems likely that most of the Arcto‐Tertiary genera which became extinct in Japan could winter in the deciduous forests in Japan during late Tertiary time, unlike evergreen broad‐leafed trees and some conifers such as Taiwania, Sequoia and Cunninghamia lanceolata. To clarify the reason of their distinction from the standpoint of cold injury, a further study on their resistance to winter desiccation is required.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA
Authors: HOLLIGAN P. M. , JENNINGS D. H. 
Published: May 2006

SummaryCultures of Dendryphiella salina, grown in a liquid glucose‐tryptone medium, were transferred to a similar but more dilute medium until the mycelial soluble carbohydrates had been depleted. These so‐called starved cultures were then placed in various defined (regrowth) media, differing particularly with respect to concentrations of glucose and nitrate. The changes in mycelial carbohydrates, which occurred during starvation, and afterwards, in the regrowth media, were determined by gas chromatography.Mannitol and arabitol were the major products of glucose assimilation. When this sugar was depleted from the medium, mannitol was readily catabolized. By contrast, accumulation of arabitol continued for several hours after the exhaustion of substrate glucose and the maximum levels attained were dependent upon the nitrogen source.Microscopical observations on the mycelium during starvation and regrowth are reported. The results are discussed in relation to other studies on the growth of fungi in stirred liquid culture.
THE EFFECTS OF WATER STRESS ON NITROGEN‐FIXING ROOT NODULES
Authors: SPRENT JANET I. 
Published: May 2006

SummaryWater stress reduced nitrogen fixation of soybean plants grown in pots of sand. Provided that the nodules retained some activity, recovery on watering was normally complete in an hour. Using tritiated water (3HOH) it was confirmed that water could be withdrawn by nodules en route from the root to the shoot system.A field trial with Vicia faba showed a high degree of correlation between soil‐water content and nitrogen‐fixing activity. Slow natural drying over a 6‐week period resulted in progressive reduction of activity, which was restored by irrigation. Maximum nitrogen fixation occurred at about field capacity; above this, activity was reduced due to water logging. Under the conditions of the experiment, water supply was the major environmental factor affecting nitrogen fixation.It is suggested that water stress affects nodule activity directly, but that this effect may be aggravated by reduced supplies of photosynthate from wilted leaves.
THE EFFECT OF VESICULAR‐ARBUSCULAR MYCORRHIZAL ASSOCIATIONS ON GROWTH OF CEREALS
Authors: KHAN A. G. 
Published: May 2006

SummaryThe subsequent growth of maize seedlings which were already mycorrhizal when planted in the field was improved compared with non‐mycorrhizal controls. Mycorrhizal plants removed more phosphorus from the soil and had greater dry matter and phosphorus. There were positive correlations between spore number in the soil and mycorrhizal development, and between extent of root infection and increased growth. Root infection decreased with an increase in phosphorus level of the soil. The onset of the reproductive process in non‐mycorrhizal plants growing without added fertilizer was delayed and, even in those cases where ears did form, their quality was poor. Number of grains per ear and grain weight were increased almost twelve times by the fungus.
THE ACCUMULATION OF ZINC BY SUBCELLULAR FRACTIONS OF ROOTS OF AGROSTIS TENUIS SIBTH. IN RELATION TO ZINC TOLERANCE
Authors: TURNER R. G. , MARSHALL C. 
Published: May 2006

SummaryZinc tolerance in the grass, Agrostis tennis Sibth., was investigated by comparing the uptake of radiozinc by the cell wall and mitochondrial fractions from the roots of sixteen different populations. Large differences in tolerance between populations were found. There was a significant correlation between zinc accumulation by each subcellular fraction and the index of zinc tolerance but the cell wall fraction accumulated a greater quantity of zinc. There was no correlation between the nitrogen content of the cell wall fraction and zinc tolerance. The importance of metal accumulation by the cell wall fraction is discussed and it is suggested that it is a major feature of the mechanism of tolerance to heavy metals in A. tenuis.
AFTER‐EFFECTS OF NIGHT TEMPERATURES ON STOMATAL BEHAVIOUR AND PHOTOSYNTHESIS OF SORGHUM
Authors: PASTERNAK DOV , WILSON G. L. 
Published: May 2006

SummaryExposure of whole sorghum plants to cold (5° C) or hot (30° C) nights, or exposure of shoots only to a range of low night temperatures (5—15° C) reduced both the rate and extent of stomatal opening during the succeeding day. Photosynthesis was correspondingly reduced. The reduction in the rate of stomatal opening could be attributed to a development of water deficits in the leaves.
IDENTIFICATION OF ABSCISIC ACID IN YOUNG STEMS OF PINUS RADIATA D. DON
Authors: JENKINS P. A. , SHEPHERD K. R. 
Published: May 2006

SummaryAn inhibitor from Pinus radiata was separated using paper chromatography from an acidic ether fraction of a stem tissue extract. Using electrophoresis the inhibitory activity was resolved into two parts. One part remained at the origin. The second part behaved similarly to ABA, in electrophoresis and was investigated further.The inhibitor has similar properties to ABA in electrophoresis; TLC using a number of solvent systems; UV fluorescence spectra: UV absorption; ORD spectra and gas chromatography. Final proof of the identity of the natural inhibitor as ABA was obtained by gas chromatography‐mass spectrometry.
AGEING IN PLANT EMBRYOS
Authors: BERJAK PATRICIA , VILLIERS T. A. 
Published: May 2006

SummaryAn unusual pattern of senescence occurs in the root caps of embryos of Zea mays subjected to an artificial ageing treatment. After an initial reversal of membrane damage in the first stages of germination, precocious senescence was observed in the zone of differentiation of the root cap at the 48‐hour stage of germination. These senescent changes occurred suddenly, with apparently normal cells being found immediately adjacent to cells in which the entire protoplast had degenerated. Acid phosphatase activity was confined to lysosome‐like organelles in the still‐organized cells, but was distributed throughout the ground cytoplasm of the adjacent senescent cells. The degenerative changes appeared to progress from the outermost cells proximally towards the chronologically younger cells. Thus the precipitous senescent changes were probably caused by the release of hydrolases normally confined within lysosomes, and the precocious senescence was due to an acceleration of a genetically‐controlled process of ageing.
POLLEN TUBE GROWTH AND THE SITE OF THE INCOMPATIBILITY REACTION IN BRASSICA OLERACEA
Authors: OCKENDON D. J. 
Published: May 2006

SummaryUnpollinated, cross‐pollinated and self‐pollinated stigmas of Brussels sprouts and kale were examined in a scanning electron microscope as fresh uncoated specimens. The stigmatic papillae are closely appressed in young stigmas, but are held apart in the mature stigma by the swollen bases of the papilla cells. Some self‐pollen tubes show obvious signs of inhibition by being very short, or by coiling over the surface of the papilla without penetrating it. Other self‐pollen tubes appear to behave like cross‐pollen tubes by producing tubes which penetrate papillae directly. The implications of these observations for the identification of the site of the incompatibility reaction are discussed.
THE EFFECT OF PRE‐TREATMENT WITH GIBBERELLIC ACID ON THE DISTRIBUTION OF PHOTOSYNTHATE IN INTACT AND DISBUDDED PLANTS OF SOLANUM TUBEROSUM L.
Authors: BOOTH A. , LOVELL P. H. 
Published: May 2006

SummaryBefore tuberization, the radiocarbon from 14CO2 fixed by single leaves of Solanum tuberosum cv. Majestic was distributed fairly uniformly throughout the plant and treatment with gibberellic acid prior to 14CO2 fixation bad little effect on the distribution of labelled assimilates. After tuberization, the tubers imported the majority of the 14C supplied. Pretreatment with gibberellic acid greatly reduced accumulation of assimilate in, and growth of, tubers, particularly in the 7‐day period following pretreatment. This effect was manifest in plants from which all aerial shoot‐apices had been removed, suggesting that gibberellic acid acted directly on the tubers. The reduced import by tubers in gibberellic acid‐treated plants was associated with a substantial decrease in the ratio, 14C in the ethanol‐insoluble fraction to 14C in the ethanol‐soluble fraction. It is proposed that the main effect of gibberellic acid is to decrease starch accumulation and increase sugar levels in the tubers, and that these changes are associated with the characteristic‘growing‐out’ of the tubers and a ‘switching‐off’ of the tuber sink.
STOMATAL‐DIFFUSION RESISTANCE AND WATER POTENTIAL OF SOYBEAN AND SORGHUM LEAVES
Authors: TEARE I. D. , KANEMASU E. T. 
Published: May 2006

SummaryHourly trends in stomatal resistance and water potential of the upper leaves of sorghum and of soybean canopies (measured with diffusion porometer and thermocouple psychrometer) tended to parallel each other. Vertical profiles (both canopies) indicated that the stomatal resistance of the lower leaves usually was greater than that of the upper leaves. The position of minimum resistance varied with time of day. The profiles of temperature and water‐vapour pressure were consistent with the profile of canopy transpiration resistance. The upper sorghum leaves had a lower water potential than the lower leaves. In the morning a strong gradient of water potential existed from lower to upper leaves in plants in both canopies; in the afternoon the gradients continued in sorghum but disappeared in soybean plants.
THE PATTERN OF DISTRIBUTION OF AGROSTIS AND FESTUCA PLANTS OF VARIOUS GENOTYPES IN A SWARD
Authors: SMITH A. 
Published: May 2006

SummarySamples from a population of plants present in a grazed hill sward were isolated and grown as spaced individuals at a lowland site. The predominant taxa present were Agrostis, chiefly A. tenuis Sibth., and Festuca rubra L. Within each species, there was considerable variation between plants obtained from a relatively small area of sward. From an examination of morphological characters and tests of self‐ and cross‐compatibility among plants, an indication of the number of genotypes present was obtained. Eighty‐four putative genotypes of Agrostis and forty of Festuca were identified. A map is given showing the position of each putative genotype in the original population and the structure of Agrostis‐Festuca swards is discussed.
EFFECTS OF DAYLENGTH AND CHILLING ON THE RESPONSES OF DOUGLAS‐FIR (PSEUDOTSUGA MENZIESII (MIRB) FRANCO) SEEDLINGS TO ROOT DAMAGE AND STORAGE
Authors: LAVENDER D. P. , WAREING P. F. 
Published: May 2006

SummaryA series of experiments designed to identify the factors responsible for reduced seedling vigour and survival in Douglas‐fir seedlings following lifting and cool, dark storage in the fall, is described. Although pretreatment under short days leads to reduced root activity and less ability to regenerate new roots, this response does not account for the adverse effects of lifting and dark storage in the fall, since these latter effects are, in fact, greater after pretreatment with long days than short days. A period of chilling, following short‐day pretreatment, greatly increases the seedlings' resistance to the adverse effects of root damage and dark storage. The deleterious effects of dark storage can be greatly reduced by a daily exposure to several hours of low intensity illumination. The adverse effects of dark storage at cool temperatures appear to be exerted primarily through the roots, since maintenance of the roots at 15° C and of the shoots at 2° C largely removes the adverse effects of storage. The regeneration of roots by chilled seedlings is dependent on the presence of needles. If the needles are removed their effect on root regeneration cannot be replaced by application of naphthalene‐acetic acid, niacin or pyridoxine.
AGEING IN PLANT EMBRYOS
Authors: BERJAK PATRICIA , VILLIERS T. A. 
Published: May 2006

SummaryEmbryos of Zea mays that had lost viability were still able to continue certain metabolic processes. Radicle emergence and cell division did not occur, and mitochondria and plastids appeared to be degenerate. However, ER synthesis and delayed polysome formation occurred, 3‐uridine and 3H‐leucine were incorporated, and certain cells were able to take up 3H‐thymidine. From the sequence of events, it is concluded that loss of viability was due to general damage to macromolecules, including nucleic acids, membrane components, and enzymes.
AGEING IN PLANT EMBRYOS
Authors: BERJAK PATRICIA , VILLIERS T. A. 
Published: May 2006

SummaryFollowing an accelerated ageing treatment, the radical cells of non‐viable embryos of Zea mays were found to be disorganized. Organelles were swollen and did not differentiate into functional structures. During inhibition the cells deteriorated progressively and their cytoplasm lysed. Acid phosphatase activity, normally confined to lysosomal vacuoles, spread to the cytoplasm during inhibition, and this was presumed to indicate general release of hydrolytic enzymes. Loss of viability is considered to be a consequence of the deterioration of membrane systems.
FEATURES OF MYCORRHIZAL INFECTION IN SOME MALAYAN ORCHIDS
Authors: HADLEY G. , WILLIAMSON B. 
Published: May 2006

SummaryIn the roots of most species of terrestrial and epiphytic Malayan orchids examined, mycorrhizal infection was spasmodic and confined to a small proportion of the root cortex cells. Only a few terrestrial species exhibited the pattern of dense infection seen in north temperate orchids. Chlorophyllous tissue in the roots of some terrestrial and epiphytic species was invaded and cytological changes, including fragmentation and disappearance of the chloroplasts, occurred in some instances.Measurements of host cell nuclei indicated that nuclear hypertrophy occurred not only in infected cells but also in many non‐infected cells localized around pockets of infection.