bluuebunny/crossref_metadata_2025_split huggingface dataset:
ULTRASTRUCTURAL STUDIES IN THE BROWN ALGA ECTOCARPUS IN CULTURE: AUTOLYSIS*
Authors: OLIVEIRA LUIS , BISALPUTRA THANA 
Published: May 2006

SUMMARYDuring autolysis of senescent cells of the brown alga Ectocarpus the disintegration of nuclei, endoplasmic reticulum, and Golgi apparatus is completed. Degenerating mitochondria and plastids remain as the only recognizable organelles. Results from ultrastructural study in correlation with cytochemical localization of acid phosphatase indicate that lysosomal compartmentation no longer exists because the acid phosphatase reaction becomes distributed throughout the remainder of the cytoplasm and is also shown by the disintegrating plasmodesmata. Aspects of cell wall breakdown are described and related to knowledge of the chemistry of the cell wall.
CONTROL OF RESPIRATION OF BEECH MYCORRHIZAS DURING AGEING
Authors: HARLEY J. L. , McCREADY C. C. , WEDDING R. T. 
Published: May 2006

SUMMARYA detailed examination was made of the effects of potassium phosphate, 2,4‐DNP, KCN, and mCLAM on the respiration of beech mycorrhizas during ageing. Samples were taken on nine occasions during the year and aged for 9 days. Previous results were confirmed and it was shown that the cyanide‐insensitive pathway of oxygen uptake failed to develop fully if respiration was uncoupled. The application of cyanide seemed to allow phosphorylation to proceed at site 1 and in its presence the cyanide‐insensitive pathway could develop. Cyanide and DNP applied together caused considerable inhibition presumably owing to the small development of the cyanide‐insensitive pathway. The further addition of mCLAM gave additional inhibition. mCLAM appeared also to act as if it uncoupled phosphorylation from respiration, in addition to acting as an inhibitor of the cyanide‐insensitive pathway. It is suggested, since mCLAM does not uncouple mitochondrial oxygen uptake, that it is converted in the tissue to an uncoupling compound. The significance of the control of the insensitive pathway by phosphorylation or ATP level in the tissue is discussed.
THE LATE QUATERNARY HISTORY OF THE DIATOM FLORA OF LLYN CLYD AND LLYN GLAS, TWO SMALL OLIGOTROPHIC HIGH MOUNTAIN TARNS IN SNOWDONIA (WALES)
Authors: EVANS G. H. , WALKER R. 
Published: May 2006

SUMMARYThree cores were taken from the deposits of Llyn Clyd and two cores from Llyn Glas, using a Mackereth corer. Samples taken at approximately 10 cm intervals have been analysed for pollen and diatoms. Pollen analysis has been used as a means for correlating deposits in the two tarns. The data show that changes have occurred in the diatom flora of both tarns but these changes are less pronounced than in some lowland bodies of water. Llyn Glas appears to have had more stable conditions throughout its development than Llyn Clyd.
STUDIES IN FESTUCA. 11. INTERRELATIONSHIPS OF SOME PUTATIVE DIPLOID ANCESTORS OF THE POLYPLOID BROAD‐LEAVED FESCUES
Authors: BORRILL MARTIN , KIRBY MADELEINE , MORGAN W. GARETH 
Published: May 2006

SUMMARYThe relationships of six diploid Festuca species were studied: Section Montanae: F. donax, drymeja, altissimaScariosae: F. scariosaBovinae: F. pratensisOvinae: F. polesica.The criteria used were ability to hybridize, and fertility and meiotic chromosome pairing in the F1 hybrids. The closest affinity discovered was amongst the species within Section Montanae, there was also a strong affinity between these and F. scariosa, and a weak link with F. pratensis and F. polesica. The results are briefly discussed from the standpoint of species‐relationships in Festuca and Lolium.
ON THE THEORY OF EXPLOSIVELY DISPERSED SEEDS
Authors: BEER TOM , SWAINE M.D. 
Published: May 2006

SUMMARYWe calculate the theoretical distribution of seed numbers (a probability density function) that would be expected on the ground around a parent plant that disperses its seeds explosively. The initial velocity of the projected seed, and its air resistance are shown to have considerable influence on the maximum dispersal distance, as well as on the angle (the optimum angle of projection) which attains in. All other angles give rise to lesser dispersal distances and their relative frequencies contribute to the shape of the probability density function. The height of release has little influence on the maximum distance, but radically affects the shape of the probability density function. Some practical consequences and biological implications of these results are discussed.
EXPLOSIVE SEED DISPERSAL IN HURA CREPITANS L. (EUPHORBIACEAE)
Authors: SWAINE M. D. , BEER TOM 
Published: May 2006

SUMMARYMethods are described for measuring the initial velocity, angular velocity, projection angle and air resistance coefficient of explosively dispersed seeds of Hura crepitans. The methods are generally applicable to any explosively dispersed seeds. In Hura the initial velocities were normally distributed about a mean of 43 ms−1 and in one case exceeded 70 m s−1. Although projection angles are not constant, the mean of 34° above horizontal lies close to the optimum for maximum dispersal, and the frequency of angles less than 0° or more than 50° are negligible. Angular velocities are high, attaining at least 15,000 rpm in one case. The resistance coefficient could not be measured precisely, but was probably between 0.087 and 0.118 m−1. The maximum dispersal distance recorded was 45 m from the parent tree, with a marked modal dispersal distance at about 30 m. The ecological implications of explosive dispersal are briefly discussed.
INFLUENCE OF MYCORRHIZAL INFECTION ON COMPETITION FOR PHOSPHORUS AND POTASSIUM BY TWO GRASSES
Authors: FITTER A. H. 
Published: May 2006

Summary Lolium perenne L. and Holcus lanatus L. were grown together in 125‐mm pots in a factorial experiment combining mycorrhizal infection and root competition. Both root competition and mycorrhizal infection gave a slight advantage to H. lanatus but, in combination, these produced considerable suppression of Lolium perenne. Root length of L. perenne was reduced by mycorrhizal infection, which was itself increased by competition. The competitive effects can be explained solely in terms of mycorrhizal infection.
THE EFFECT OF TIME OF EXPOSURE TO SULPHUR DIOXIDE ON POTASSIUM LOSS FROM AND PHOTOSYNTHESIS IN THE LICHEN, CLADINA RANGIFERINA (L.) HARM.
Authors: TOMASSINI F. D. , LAVOIE P. , PUCKETT K. J. , NIEBOER E. , RICHARDSON D. H. S. 
Published: May 2006

SummarySamples of the lichen, Cladina rangiferina, were exposed to various concentrations of aqueous SO4 for 10 min, and 0.5, 1, 3, 6 and 12 h. K+‐efflux curves (K+ release versus ppm SO2(wt/wt, aqueous)) were constructed for each exposure period. In separate experiments, the photosynthetic 14C fixation rates were measured after the SO2 exposures. Plots of % total 14C fixation v. ppm SO2 (wt/wt, aqueous) were found to be linear for the 3 h and 6 h exposure periods, while plots of log (% total 14C fixation) v. ppm SO2 (wt/wt, aqueous) were linear for shorter exposures (10 min, 0.5 and 1 h). Threshold SO2 concentrations for each exposure time were evaluated by extrapolating the K+‐efflux curves, or their linear transformations, to zero K+ release. Similarly, the threshold SO2 concentrations that did not cause a reduction in 14C fixation (relative to control samples not exposed to SO2) were determined by extrapolation of the linear relationships mentioned. The threshold values obtained from the K+‐efflux data were in good agreement with those evaluated from fixation rates. Aqueous threshold SO2 concentrations were converted to gaseous threshold values by an experimentally verified relationship. The resulting gaseous SO2 threshold concentrations, (SO2)g** in units of ppm(v/v) in air, were related to the exposure time in hours, t, through the following rectangular hyperbolic function: (SO2)g**=1.5 t−0.62. Notwithstanding the uncertainties involved, extrapolation of this expression to exposure times considerably longer than the experimental range yielded threshold values for 6 months and 1 year in good agreement with mean SO2 levels known from mapping studies to affect detrimentally sensitive lichen species.
A COMPARISON OF THE CHARACTERISTICS OF GLUTAMINE SYNTHETASE AND GLUTAMATE DEHYDROGENASE FROM LEMNA MINOR L.
Authors: STEWART G. R. , RHODES DAVID 
Published: May 2006

SUMMARYThe high affinity of Lemna minor glutamine synthetase for ammonium (Kappm 1.2 – 1.5 × 10−5 M) and its strong inhibition by ADP and 5‐AMP contrasts with the low affinity (Kappm 3 × 10−2 M) for ammonium and lack of inhibition by ATP shown by glutamate dehydrogenase. Glutamine synthetase was inhibited by alanine, aspartate, glycine and serine while glutamate dehydrogenase was not affected by any amino acid, other than the product of the reductive amination reaction, glutamate. The properties of glutamine synthetase and glutamate dehydrogenase are consistent with the view that the glutamine pathway is the major route for ammonia assimilation when there is a restricted availability of ammonia. The characteristics of glutamate dehydrogenase, when contrasted with those of glutamine synthetase, and considered in relation to the concurrent regulation of the two enzymes, support the view that the glutamate pathway may contribute towards ammonia assimilation under conditions of high ammonia availability or low energy charge. Comparison of the properties of glutamate dehydrogenase purified from ammonium‐ and nitrate‐grown plants suggests that only a single form of the enzyme is present.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: MACFARLANE J. D. , KERSHAW K. A. 
Published: May 2006

SUMMARYThe seasonal levels of nitrogenase activity in Peltigera praetextata and P. canina var. rufescens have been examined at 5, 10, 15, 20, 25, 30, 35°C, under 75, 150, 300 and 450 μEinsteins m−2 s−1 illumination and for all levels of thallus moisture content. The results show only a small increase in activity at high light intensities but a marked temperature optimum at 25–30 C in both species. Of outstanding interest however are the very large rate changes occurring throughout the year. The changes are clearly evident at all temperatures and light levels.These results are discussed in relation to concurrent seasonal changes of net photosynthetic rate and the need for experimental design of physiological work in a multivariate framework is strongly emphasized.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: KERSHAW K. A. , DZIKOWSKI P. A. 
Published: May 2006

SUMMARYThe recovery rate of nitrogenase activity in Peltigera polydactyla, is shown to be rapid after short drought periods but takes progressively longer as the drought period is extended. After more extreme levels of dehydration achieved using calcium chloride, recovery of nitrogenase activity is considerably slower. The importance of adequate pretreatment of material collected from the field after exposure to unknown periods and levels of drought stress is emphasized.
LIGHT AS A FACTOR IN GROWTH AND MORPHOGENESIS I. EFFECT OF ARTIFICIAL SHADING ON CROTALARIA JUNCEA L. AND C. SERICEA RETZ.
Authors: PANDEY B. N. , SINHA R. P. 
Published: May 2006

SUMMARYTwo species of Crotalaria, C. juncea L., a fibre‐yielding plant, and C. sericea Retz., have been grown in a glasshouse at three different light‐intensities. Comparisons have been made of their rates of increase in dry weight, relative growth rate, leaf area ratio, specific leaf area, leaf weight ratio, net assimilation rate, the ratio a of Whitehead & Myerscough and shoot/root ratio. C. sericea appears to be the more shade‐tolerant because its increased leaf area ratio compensates for a reduced net assimilation rate and so maintains the level of its relative growth rate.
ANATOMICAL, PHYSIOLOGICAL, AND BIOCHEMICAL EVIDENCE FOR THE C3 PATHWAY IN VERBASCUM THAPSUS L.
Authors: WILLIAMS G. J. , KEMP P. R. , OULTON K. 
Published: May 2006

SUMMARYAnatomical, physiological and biochemical characteristics of Verbascum thapsus demonstrate that this species is a C3 carbon fixation type rather than C4 as suggested by Parkhurst (1976). Leaf anatomy, net photosynthesis rate, carbon dioxide compensation point, photorespiration rate, temperature optimum for photosynthesis and ratio of ribulose‐1,5‐diphosphate carboxylase to phosphoenolpyruvate carboxylase activity for V. thapsus are all typical of C3 rather than C4 species. The data presented illustrate the danger of assuming a species is either C3or C4 based on a single characteristic. Parkhurst (1976) predicted that optimum photosynthesis for V. thapsus would occur at high temperature and would increase faster than transpiration with increased temperature. Our data are contrary to these predictions.
PRELIMINARY STUDIES ON SAPFLOW IN COCOS NUCIFERA L.
Authors: MILBURN JOHN A. , ZIMMERMANN MARTIN H. 
Published: May 2006

SUMMARYA technique has been devised to study changes in the xylem‐sap tensions in Cocos using a pressure bomb. Preliminary studies indicate that xylem tensions range from 2 to 13 bar depending on solar radiation and other environmental changes. One surprising observation is that xylem sap tensions are somewhat lower in the dry season, apparently due to earlier stomatal closure during the mid‐late morning. Despite the close proximity of lagoons of saline water, there was no indication that the uptake of water was reduced through osmosis, and a hidden supply of fresh water is implied. Finally, some precautions are listed which avoid certain anomalous results using the pressure bomb.
FINE STRUCTURAL AND CYTOCHEMICAL CHANGES OCCURRING IN BEET DISCS IN RESPONSE TO WASHING
Authors: HALL J. L. 
Published: May 2006

SUMMARYDuring washing of excised beetroot tissue discs the most prominent changes in fine structure were the development of amyloplasts and enhancement of the membrane systems of the Golgi bodies and endoplasmic reticulum. When D(‐)threo‐chloramphenicol was present during washing, the appearance of crystalloid bodies in the cytoplasm was accelerated. Staining with phosphotungstic acid‐chromic acid (PTAC) was largely restricted to the plasma membrane in freshly excised cells. After washing, additional PTAC staining was associated with the starch grains and with whorled arrangements of the plasma membrane close to the developing amyloplasts. Silver nitrate staining showed an intense particulate reaction in the vacuole and in the region of the tonoplast; the vacuolar staining was reduced in washed tissues. Biochemical analysis showed increased activities for both glucose‐6‐phosphatase and peroxidase. Cytochemical staining for glucose‐6‐phosphatase was localized largely in the plasma membrane and tonoplast in both fresh and washed tissues. Peroxidase staining was most prominent in the cell wall in freshly excised tissues. After washing, the reaction of the cell wall was increased and additional staining appeared associated with the Golgi bodies and endoplasmic reticulum. These findings are discussed in relation to the development of the wound response in plant tissues.
EARLY EFFECTS OF FLOODING ON NITROGEN DEFICIENCY AND LEAF CHLOROSIS IN BARLEY
Authors: DREW M. C. , SISWORO E. J. 
Published: May 2006

SUMMARYEffects of flooding the root system on nitrogen status, leaf chlorosis and shoot growth have been studied in barley seedlings. Within 2 days, oxygen in the soil water decreased to a low concentration (< 2%), and net uptake of nitrogen to shoots was inhibited. Simultaneously, there was a decrease in the average concentration of nitrogen in shoots, due to translocation from older leaves to younger expanding ones. These changes pieceded the onset of chlorosis of the older leaves. It is suggested that inhibition of nitrogen uptake, and the consequent redistribution of nitrogen within the shoot, are important contributory factors in the early senescence of leaves and the retarded growth of shoots in flooded plants.
WOUND REPAIR IN YAM TUBERS: THE EFFECTS OF INHIBITORS OF RESPIRATION AND PROTEIN SYNTHESIS ON REPAIR PHYSIOLOGY
Authors: PASSAM H. C. , HUGHES P. A. , READ S. J. 
Published: May 2006

SUMMARYThe effects of inhibitors of respiration (KCN and salicylhydroxamic acid, SHAM) and of protein synthesis (cycloheximide and chloramphenicol) on the induction of wound respiration and acid invertase in bisected yam tubers and tissue discs are described. The respiration of tissue discs aged in tris‐HCl buffer increases markedly during 3 days following cutting. Respiration is largely insensitive to KCN. Inclusion of KCN or SHAM in the ageing medium inhibits the increase in respiration. Residual respiration is either sensitive to KCN when added to the Warburg vessel (SHAM‐aged) or insensitive (KCN‐aged). Ageing of discs in KCN + SHAM together, or in the presence of chloramphenicol, totally suppresses the induction of respiration. Ageing in the presence of cycloheximide increases the sensitivity of respiration to KCN. The same inhibitors were also applied to the cut surfaces of bisected, but otherwise intact, tubers for one hour after cutting. The respiration of the tubers increases after bisection, but the total respiration of the tuber halves is unaffected by inhibitor treatment. However, the increase in respiration measured in unaged discs taken from the surface starch/suberin layer is either inhibited (KCN, SHAM and chloramphenicol) or unaffected (cycloheximide) by treatment. The increase in respiration of the periderm is essentially unaffected by the inhibitors except for chloramphenicol which promotes. The induction of acid invertase activity in tissue discs following cutting, is inhibited to a varying degree by all treatments. In contrast, in the starch/suberin layer of bisected yams treated with KCN and/or SHAM the invertase activity is enhanced; chloramphenicol causes some inhibition, but cycloheximide has no effect. The development of invertase in the periderm is reduced by chloramphenicol but is unaffected by other treatments. In all treatments, activity in the corticular tissue (3 cm beneath the cut surface) remains low throughout the healing period. The results may largely be explained by the known metabolic effects caused by these inhibitors.
A LIGHT AND ELECTRON‐MICROSCOPICAL STUDY ON THE STRUCTURE AND FUNCTION OF THE SALT GLAND OF GLAUX MARITIMA L.
Authors: ROZEMA JELTE , RIPHAGEN INGRID , SMINIA TAEDE 
Published: May 2006

SUMMARYThe salt glands of Glaux maritima are regularly distributed on the adaxial and abaxial leaf surface. The gland consists of three cell types: a collecting cell, a stalk cell and secretory cells. The collecting cell is characterized by a large central vacuole, containing electron‐dense material. The stalk cell contains many small vesicles and is connected with both the collecting cell and the secretory cells by numerous plasmodesmata. The secretory cells possess a strongly infolded plasmamembrane (cell wall protuberances) which could facilitate rapid ion transport to the subcuticular space. The large number of mitochondria in the secretory cells suggests energy‐requiring steps in ion transport. The chloroplast‐free stalk cell and the secretory cells may be supplied with energy by transport across the numerous plasmodesmata. It is speculated that small (pinocytotic) vesicles are involved in ion transport in the salt gland.
A HISTOCHEMICAL STUDY OF POLYSACCHARIDE DISTRIBUTION IN EUCALYPT MYCORRHIZAS
Authors: LING‐LEE M. , ASHFORD A. E. , CHILVERS G. A. 
Published: May 2006

SUMMARYThis paper describes a histochemical study of the distribution of polysaccharides in un‐infected and mycorrhizal Eucalyptus fastigata roots. The most striking influence of mycorrhizal infection is the suppression of starch accumulation in the root cap cells and meristematic region of the root. In addition, there is a very substantial reduction in the amount of acidic polysaccharide (root cap slime) accumulated around the outer root cap cells in mycorrhizal roots, compared with uninfected roots. These observations generally hold for roots collected from a wide variety of conditions and at different times of the year. The reduction in amounts of these two important polysaccharides is presumed to result from lack of availability of precursors for polysaccharide synthesis, due to diversion of carbohydrate into the fungus partner. The histochemical observations in E. fastigata mycorrhizas are thus in accord with experimental data from other mycorrhizas which indicate transfer of large quantities of carbohydrate from root to fungus, and suggest that carbohydrate transfer is likely also to occur in mycorrhizas of E. fastigata.
ACETYLENE REDUCTION BY MATS OF BLUE‐GREEN ALGAE IN SUB‐TROPICAL GRASSLAND: POSSIBLE CONTRIBUTION BY OTHER MICRO‐ORGANISMS
Authors: JONES K. 
Published: May 2006

SUMMARYCounts using the most probable number method show that there are aerobic and anaerobic nitrogen‐fixing bacteria associated with mats of blue‐green algae in kikuyu lawns. Both types of bacteria are more numerous in the surface layers of soil adjacent to the mats of algae. Acetylene reduction by bacteria was only detected when glucose was added to either the soils or the algal mats.Mats of algae composed entirely of non‐heterocystous blue‐green algae were unable to reduce acetylene in situ or in any of the experimental conditions employed in the laboratory.
AN EARLY FLANDRIAN VEGETATIONAL RECORD FROM THE FLOOR OF THE BRISTOL CHANNEL
Authors: BROWN A. P. 
Published: May 2006

SUMMARYA palynological and plant macrofossil study of a short core of organic sediment from the floor of the Bristol Channel at –36 m (–120 feet) O.D. is presented and discussed. The fossil assemblages were deposited in a freshwater pond and reedswamp. This sediment, the deepest yet examined for Flandrian pollen in the Bristol Channel, is overlain by what are interpreted as intertidal sediments and indicates the approximate sea level and position of the coastline of South Wales about 9500 years B.P. The open nature of the vegetation in the area around the site of deposition is indicated by the presence of Juniperus pollen. Of the only two tree pollen types present Betula is far more frequent than Pinus, a feature common to the early Flandrian of southwest England and northwest France. The age ascribed to this deep sediment is consistent with other observations on submerged deposits both in the Bristol and English Channels.
LEAF RESPIRATION AND ATP LEVELS AT CHILLING TEMPERATURES
Authors: WILSON J. M. 
Published: May 2006

SUMMARYIn the extremely chill‐sensitive species Episcia reptans the dark respiration rate of leaves after 80 min chilling at 5°C was three times greater than in leaves maintained at 25°C. The rate and size of the respiratory increase depended on the chilling temperature and the growth conditions prior to chilling and was at a maximum at the same time as the onset of visible injury. The addition of 2,4‐dinitrophenol and potassium cyanide to the leaves of E. reptans accelerated the rate of oxygen uptake at 5°C. In contrast, there was no increase in the respiration rate of the leaves of the less chill‐sensitive species Phaseolus vulgaris after prolonged chilling at 5°C.A reduction in ATP supply below that necessary to maintain the metabolic integrity of the cytoplasm is not considered to be important in the development of chilling‐injury to Episcia reptans or Phaseolus vulgaris as the ATP level decreased only after the onset of visible leaf injury. Furthermore, the increase in ATP level on chilling P. vulgaris leaves which had been either chill‐hardened or maintained in a saturated atmosphere on transfer from 25 to 5°C (Wilson, 1976) demonstrated that leaf injury and water stress are the primary cause of the decline in ATP level during chilling and not low temperature per se.