bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strategies for the Study of Individual Development within Naturally‐Existing Peer Groups*
Authors: Kindermann Thomas A. 
Published: April 2006

AbstractThe investigation of peer influences on children's development in natural settings rests squarely on appropriate methods to identify those individuals who are influential for a given child. Traditional methods of sociometric ratings or assessments of friendship choices are not intended to identify reciprocal influences in children's peer groups of social interrelationships. In the study of networks within sociology, researchers have focused on the structural properties of children's networks, instead of the psychologically meaningful characteristics of the children who comprise a target child's network. To complement these strategies, a method is presented that can reliably identify those individuals who constitute children's natural peer groups in a setting. This information is used to form composite maps that represent the psychological peer context of a given child. Strategies are outlined for analyzing processes of group selection and socialization among developing individuals and their changing peer contexts.
Development of the Distinction Among the “Desirable”, Morality, and Personal Preference
Authors: Nisan Mordecai 
Published: April 2006

AbstractIsraeli children of grades 1, 4, and 7 were asked, with respect to nine types of behavior, whether such behavior is bad, whether a child should be brought up to behave otherwise (and why), whether a child should be required to behave otherwise, and whether such behavior should be punished. Analysis of their responses and the reasons they provided supports the hypothesized distinction between three categories of behaviors or reasons for action—morality, “the desirable” and personal preferences—in terms of two dimensions: desirability and obligatoriness. Specifically, moral norms were perceived as both desirable and strictly obligatory, and were justified in terms of inherent goodness/badness and the welfare of others. Behaviors in the category of “the desirable” were perceived as desirable but not obligatory, and were justified in terms of self‐development and long‐term utility. Behaviors in the category of personal preferences were perceived as non‐obligatory and neither desirable nor undesirable, and were justified in terms of personal choice. This distinction was less sharp among first graders, who exhibited some tendency to view desirables and preferences, as well as moral behavior, as obligatory. In light of these findings, it is suggested that the young child's “intuitive morality” relates only to the dimension of desirability and not to that of obligatoriness, which seems to develop somewhat later.
The Semantically Reciprocating Robot: Adult Influences on Children's Early Conversational Skills
Authors: Dunham Philip , Dunham Frances 
Published: April 2006

AbstractTwo‐year‐old children's conversational replies were observed in two social contexts: (a) with a partner who consistently responded to each of their utterances by semantically reciprocating and commenting briefly on their topic; or (b) with a partner who also consistently replied to each of their utterances but did not semantically reciprocate their topic. Children were significantly more likely to reply to a partner who maintained their topic. Given that a child replied, the verbal responses in the semantic reciprocation group were also more likely to have a topic‐comment structure characteristic of more advanced conversational skills. These experimental data confirm previous correlational evidence suggesting that children are sensitive to semantic reciprocation during the early stages of verbal communicative development, and they support recent arguments suggesting that the adult's use of expansions scaffolds the child's tendency to use predicative, topic‐comment replies…and perhaps advances the child's understanding of the adult partner as an attentional/intentional mental agent.
Teaching Three Year‐Olds to Pass False Belief Tests: A Conversational Approach
Authors: Appleton Michele , Reddy Vasudevi 
Published: April 2006

AbstractA training procedure was developed for teaching three year‐old children to pass a standard false belief task. A series of 4 video sequences was developed, in each of which a child showed surprise following the unexpected transfer of an object. A group of 23 three year‐olds who failed a standard false belief task took part in 8 discussions of the 4 video clips, over a period of two weeks, and were compared with a control group of 23 task‐failers who had 8 story reading sessions over the same time period. The training involved (a) interactive recall of the initial events in each sequence, (b) factual questioning about the events and (c) an explanation of the thoughts and actions of the video protagonists. The emphasis was on positive elaboration of children's answers rather than on negative feedback as counter evidence. The training group performed significantly better at an immediate post‐test, and at a follow‐up test two weeks later, on a similar as well as a generalisation task. Task success was unrelated to vocabulary (BPVS) score, but was significantly related to success of responses during the training. The results indicate learning in the Training group of a discursive format for talking about events useful for describing false beliefs.
THE SAP OF PLANT CELLS
Authors: MATILE PHILIPE 
Published: April 2006

SummaryRecent advances in the understanding of the functional relevance of sap of mature plant cells are reviewed. The emphasis is placed on roles of vacuoles played in the temporary storage of saccharides and organic acids, in the accumulation of water soluble products of secondary metabolism and in the intracellular digestion of protein.

Contents

Summary
1

I.
Introduction
1

II.
Functions of vacuoles
2

III.
Vacuoles as pools of saccharides
3

IV.
Organic acids
7

V.
(Potentially) toxic cell saps
9

VI.
Pools of protein
14

VII.
Digestive cell saps
15

VIII.
Tonoplast, cell sap and cytoplasm
18

IX.
Cellular homeostasis
19

Acknowledgement
20

References
20
DIURNAL CHANGES IN THE PHOTOSYNTHESIS OF FIELD‐GROWN GRAPE VINES
Authors: DOWNTON W. J. S. , GRANT W. J. R. , LOVEYS B. R. 
Published: April 2006

SummaryField studies of the gas exchange of Riesling grape vines (Vitis vinifera L.) showed large diurnal changes in net photosynthesis during the period of rapid sugar accumulation by fruit. The onset of the decline in photosynthesis occurred earlier in the day for vines without fruit. Decreases in photosynthesis were approximately proportional to changes in stomatal conductance. Despite the accompanying large changes in stomatal conductance, changes in intercellular CO2 concentration were small and mathematical analysis showed that stomatal changes accounted for only 20 to 40% of the change in assimilation rate. The CO2 compensation point, oxygen enhancement of photosynthesis, light and temperature responses of the leaf did not vary throughout the day. Stimulation of photorespiration was therefore not responsible for the non‐stomatal inhibition of photosynthesis. No obvious correlation existed between the decline in leaf photosynthesis and daily changes in leaf water potential. A field study of Colombard grape vines revealed that frequently watered vines which had received irrigation 2 d prior to measurement showed little change in photosynthetic rate over the day compared with vines subjected to a more usual watering cycle, which had last been irrigated 18 d prior to measurement. Possible non‐stomatal factors responsible for the reduction in photosynthesis during the day are discussed.
PHOTOSYNTHETIC AND RESPIRATORY CHARACTERISTICS OF MALAYAN SUN AND SHADE FERNS
Authors: NASRULHAQ‐BOYCE A. , MOHAMED M. A. HAJI 
Published: April 2006

SummaryA comparative study of four Malayan ferns, Christensenia aesculifolia (Bl.) Maxon, Tectaria singaporeana (Wall.) Ching, Abacopteris multilineata (Wall.) Ching and Hymenophyllum polyanthos Sw. from shady habitats and another four, Dicranopteris linearis (Burm.) Und., Lygodium scandens (L.) Sw., Blechnum orientate Linn, and Stenochlaena palustris (Burm.) Bedd. from sunlit habitats showed that the total chlorophyll content expressed on a gram fresh weight basis was greater in the shade ferns. There was little difference in the chlorophyll content between the sun and shade ferns when it was expressed on a per unit leaf area basis. The protein and protohaem content was greater in the sun ferns. Measurements of the in vitro photochemical activities of the photosystems I and II in isolated chloroplasts by means of an oxygen electrode showed higher rates in the sun ferns. As determined by spectrophotometric analysis, the photosynthetic cytochrome content from isolated chloroplasts was greater in the sun ferns. The results indicate that the sun ferns have physiological characteristics favouring greater capacity for photosynthesis. Mitochondria isolated from the sun ferns showed faster rates of electron transport using exogenous NADH as substrate.
THE ACCUMULATION OF PHOSPHORYLATED GUANOSINE NUCLEOTIDES IN ANABAENA CYLINDRICA
Authors: AKINYANJU J. , SMITH R. J. 
Published: April 2006

SummaryTwo highly phosphorylated guanosine derivatives accumulate in alkaline cultures of Anabaena cylindrica during the early stationary phase and in anaerobic, nitrogen‐deprived cultures. The accumulation of these nucleotides is accompanied by the suppression of the normal accumulation of ppGpp and ppGppp, nucleotides which are effectors of the stringent response in bacteria. The accumulation of the two sets of nucleotides appears to be mutually exclusive. The accumulation of the guanosine derivatives during growth inhibition and their replacement of ppGpp and pppGpp suggests that the newly discovered guanine compounds may also fulfil a regulatory role.
FACTORS AFFECTING THE KINETICS OF INTRA‐AND EXTRACELLULAR CADMIUM UPTAKE BY THE MOSS RHYTIDIADELPHUS SQUARROSUS
Authors: WELLS J. M. , BROWN D. H. 
Published: April 2006

SummaryThe responses of field‐grown and cultured shoots of a moss, Rhytidiadelphus squarrosus (Hedw.) Warnst, to Cd were investigated. Respiration was not affected, but photosynthesis was progressively reduced with increasing Cd uptake. Field‐grown shoots of two morphologically distinct populations differed in their photosynthetic responses to Cd. This could be related to different rates of Cd uptake by the two populations. During storage of Cd‐treated shoots, movement of extracellular Cd to an intracellular location occurred, and this was reflected in altered photosynthetic rates.The maximum extracellular uptake capacity and affinity for Cd were identical for the two populations of field‐grown shoots. Field‐grown material from the two populations differed significantly in their intracellular Cd uptake characteristics, cation contents, gas exchange rates and dry weights per unit length. These differences were eliminated by laboratory culture. Cultured shoots had increased affinity for both intra‐ and extracellular cadmium uptake compared to field‐grown shoots. The results indicate that the activity of Cd and other divalent cations at the plasmalemma may control the affinity for and accumulation of Cd by this moss. The results are discussed in terms of the design of experiments in studies of ion uptake and tolerance in bryophytes.
THE INFLUENCE OF SIMULATED ACIDIC RAIN ON VEGETATIVE AND REPRODUCTIVE TISSUES OF CUCUMBER (CUCUMIS SATIVUS L.)
Authors: JACOBSON JAY S. , OSMELOSKI JOE , YAMADA KAREN , HELLER LAURENCE 
Published: April 2006

Summary Cucumis sativus L. plants were grown in the greenhouse and exposed 21 times to simulated acidic rain over a period of 6 weeks to compare the responses of vegetative and reproductive tissues. Chemical composition and temporal characteristics of rain were patterned according to rainfall in the growing season in the eastern US. Flowers were hand‐pollinated to promote fruit set. Foliar symptoms were the most sensitive response of all the variables measured. Necrosis was visible after exposures to simulated acidic rain at pH 2.6, 3.0, and 34 but not at 3.8, 4.2, 4.6, 5.0, or 5.4. Despite these injury symptoms, there were no significant reductions in most measures of vegetative or reproductive tissues, even at pH 2.6. When durations of exposure were increased from 80 to 160 min, there was an increase in the severity of foliar injury, a significant reduction in dry mass of stems, numbers of female flowers produced and dry mass of flowers and immature fruit. However, there still were no significant reductions in numbers or weight of fruit, even though the plants were exposed to as much as a 20‐fold greater deposition of acidity than ambient rainfall (average pH 4.0 to 4.3) in the north‐eastern US. Evidently, cucumber plants have the capacity to recover and compensate for initial decreases in foliage and flower production, and the reproductive stage is not particularly susceptible to simulated acidic rain. These findings support previous results indicating that considerable increases in acidity of ambient rain would have to occur before the yield of crops would be measurably reduced.
INTERACTION BETWEEN OZONE AND COLD SENSITIVITY IN NORWAY SPRUCE: A FACTOR CONTRIBUTING TO THE FOREST DECLINE IN CENTRAL EUROPE?
Authors: BROWN K. A. , ROBERTS T. M. , BLANK L. W. 
Published: April 2006

SummaryThree‐year‐old clonal saplings of Picea abies L. Karst. were fumigated for 60 d during the summer of 1985 with four different levels of O3. Visible injury (in the form of severe, uniform brown necrosis and shedding of affected needles) occurred after a frost in November on the older needles of three of the clones which had received over 200 μg m−3 of O3 during the summer, 47 d previously. No visible injury occurred during the fumigation period or on the current (1985) year needles. It is suggested that the results provide preliminary evidence for an enhancement of frost sensitivity by O3 which may be significant in the current wave of forest decline affecting high‐altitude forests in central Europe.
THE DISTRIBUTION OF LIGNIN DERIVATIVES IN FOSSIL PLANTS
Authors: LOGAN KAREN J. , THOMAS BARRY A. 
Published: April 2006

SummaryLignin derivatives have been obtained from a range of sub‐fossil woods and fossil plant compressions by cupric oxide oxidation. Fossil woods yield essentially the same products as wood from living spermatophytes. Although some demethoxylation of the phenolic aldehydes occurs during fossilization, the overall difference between conifer and angiosperm wood is maintained. Compressions of varied plant organs yield recognizable phenolic aldehydes, though often in small amounts.
UPWASH AND DOWNWASH OF POLLEN AND SPORES IN THE UNSATURATED SURFACE LAYER OF SPHANGNUM‐DOMINATED PEAT
Authors: CLYMO R. S. , MACKAY D. 
Published: April 2006

SummaryThe vertical movement of Corylus and Cedrus pollen and of Lycopodium spores in Sphagnum and peat was studied in a factorial experiment with four flow regimes (no flow, downward, upward, alternate down and up), three injection depths (1, 5 and 9 cm below the surface) and three forms of packing (natural, hand‐packed at natural density, haphazard). The experiment lasted for 36 d.The results were corrected for compaction and differential recovery of pollen and spores, but the main results were unaffected by these corrections.Downward, upward and alternating flows moved the median pollen position by about 1.5 cm during the experiment. The flows also increased the interquartile span by 2 cm: about 25 % of grains moved at least 3 cm.The velocity of upward flow is probably more than sufficient to overcome the rate of sinking of pollen and spores in the unsaturated zone. Reversals of flow may be of importance in dislodging grains into the main channels again.
THE INFLUENCE OF TEMPERATURE, WATER AND NUTRIENT CONDITIONS DURING GROWTH ON THE RESPONSE OF BRASSICA OLERACEA L. TO A SINGLE, SHORT TREATMENT WITH SIMULATED ACID RAIN
Authors: CAPORN SIMON J. M. , HUTCHINSON THOMAS C. 
Published: April 2006

SUMMARYA single treatment with simulated acid rain [pH 3.0 delivered as a 30 min spray to glasshouse‐grown seedlings of cabbage (Brassica oleracea L.)] caused extensive damage to the adaxial surface of the cotyledons. The extent of this injury was compared between plants which had been grown under different environmental conditions. Seedlings which were germinated and grown out of doors during springtime at a time of low minimum temperatures (full range: 7 to 32 °C) were less injured by the acid spray than were those grown in the glasshouse under warmer conditions (18 to 36 °C). The influence of temperature alone was studied further in controlled environments. Plants grown at 10 °C showed less damage from acid sprays, in terms of visible injury and in the effect on the subsequent rate of growth, than did those grown at 20 °C. In addition to the influence of low temperature, an insufficient supply of either water or nutrients during growth also reduced the extent of visible damage to the cotyledons from simulated acid rain. Estimates of the contact angles between water droplets and cotyledon surfaces, and SEM studies of the epicuticular wax, indicated that temperature–induced changes in the sensitivity of the cotyledon to acidity were not related simply to the wettability and morphology of the surface wax. The results indicate that laboratory or indoor experiments with stimulated acid rain should be interpreted cautiously; in the natural environment the direct effect of acidity on higher plants may change seasonally and spatially according to the plants’growing conditions.
THE PROCESSES OF ANTHER DEHISCENCE AND POLLEN DISPERSAL III. THE DEHYDRATION OF THE FILAMENT TIP AND THE ANTHER IN THREE MONOCOTYLEDONOUS SPECIES
Authors: KEIJZER C. J. , HOEK I. H. S. , WILLEEMSE M. T. M. 
Published: April 2006

The relationship between anther dehiscence and dehydration of the filament tip and the connective tissue were followed in Gasteria verrucosa (Mill.) H. Duval, Allium cepa L. and Lilium hybrida cv.‘Enchantment’using various microscopical techniques, including direct observations of living tissues in the SEM.In G. verrucosa anther dehiscence immediately follows anthesis, with concomitant dehydration and shrivelling of the filament tip. In L. hybrida the filament tip dehydrates and shrivels before anthesis. The anthers start to dehisce immediately after anthesis. In A. cepa the filament tip dehydrates and shrivels slowly after anthesis and dehiscence, which may take up to several days, correlates with the rate of extension of the filament.The attenuated period of dehiscence in A. cepa may be related to the absence of stomata on the anther. Experiments on xylem conductivity and transpiration reveal that the presence of continuously open stomata on the anthers sets the time of dehiscence after anthesis in G. verrucosa and L. hybrida.The shrinking filament tip in all three species functions as a hinge which suspends the dangling anther after dehiscence. The uniformly thickened epidermal cell walls on the anthers opposite the filament prevent the outwardly bending locule walls from embracing the filament.
GENETIC VARIATION IN CANADIAN AND EUROPEAN POPULATIONS OF THE COLONIZING WEED SPECIES APERA SPICA‐VENTI*
Authors: WARWICK S. I. , THOMPSON B. K. , BLACK L. D. 
Published: April 2006

SUMMARY Apera spica‐venti L., a widely distributed weed in Europe, has recently become established as a weed of winter cereals in Canada. Levels of genetic variation were compared between and within nine Canadian and six native European populations grown under uniform conditions. Both the Canadian and European populations showed high levels of variation among populations with respect to 31 life history and morphological traits. As one would have predicted, greater differences were recorded among the European populations, although only one population in each group was clearly distinct from the other populations. High levels of genetic variability in allozyme characters were also evident in both the Canadian and European populations (percentage of polymorphic loci = 57 to 62%, number of alleles per locus = 2.53 and levels of heterozygosity = 0.23). There was, however, little or no divergence in allozyme characters among populations, with all populations having very high genetic identity values (0.948 to 0.998) and only 1.0 to 2.4% of the total gene diversity allocated to the among‐population component. The extent of within‐population variation in the 31 life‐history and morphological characters were similar in both introduced and native populations. Studies of population structure in three Canadian populations indicated that most of the variation in nine morphological characters occurred among progeny within families rather than among families. Estimates of outcrossing rate (t) using allozyme markers at two loci equalled 1.0, indicating random mating. Selfing experiments indicated that the plants were predominantly self‐incompatible. The amounts and patterns of genetic variation are consistent with what one would expect in an outcrossing species and do not support the hypothesis of genetically depauperate introductions.
GAS EXCHANGE CHARACTERISTICS OF HETEROMELES ARBUTIFOLIA DURING FUMIGATION WITH SULPHUR DIOXIDE
Authors: ATKINSON CHRISTOPHER J. , WINNER WILLIAM E. 
Published: April 2006

SUMMARYThe objectives of this study were to determine the gas exchange responses of Heteromeles arbutifolia (Ait.) Roem. to a range of sulphur dioxide (SO2) concentrations applied in various sequences including possible ambient levels. Carbon dioxide and light‐response curves were used to determine the mechanisms of SO2 responses. These experiments were performed with greenhouse‐grown plants.Net photosynthesis (A) of H. arbutifolia was shown to be depressed by SO2 concentrations ranging from 1.5 to 43.8 μmol m−3 (0.04 to 1 μl l−1). In most cases on first exposure to SO2 a larger decrease in stomatal conductance to water vapour (gH) occurred than on subsequent exposures to either the same or greater SO2 concentrations. Acclimation of gH to SO2 appeared to occur with repeated exposure.Light‐response curves determined during exposure to 25 μmol SO2 m−3 (0.6 μl l−1) for a leaf repeatedly exposed to SO2 indicated that inefficiency of photon utilization in the primary reaction of energy transduction or reduction in photosynthetic capacity was unlikely. The maximum rates of A (Amax) determined from these curves were similar in both SO2 and SO2− free air. The limitations of gH to carbon acquisition were removed using CO2−response curves [photosynthesis expressed relative to the internal CO2 concentration (Ci)]. This analysis shows that A may have been limited during repeated exposures by reduced carboxylation efficiency. It appeared that at similar values of gH, plants exposed to SO2 would fix less carbon and water use efficiency (WUE) would decrease in polluted plants.