1,721,007 research outputs found
Phloem and xylem flow contributions to nectarine fruit development
Get PDFThis study aimed at determining how source-sink balance and phloem/xylem flows affect nectarine fruit growth during development. Different levels of water and assimilate availability to growing fruits were induced in vivo by varying leaf:fruit ratio (L:F) of fruiting shoots and by interrupting the phloem stream (girdling) at the base of entire fruiting shoots. Two fruiting shoots in each of six ‘Big Top’ adult nectarine trees were selected, labeled and their L:F was adjusted by thinning fruits or removing leaves to two levels: high L:F and low L:F. Stem water potential, stomatal conductance, continuous fruit diameter and leaf turgor pressure were measured before and after girdling at stage I and stage III of fruit development. At stage I, fruits from high L:F shoots grew more than those from low L:F shoots both before and after stem girdling. At this stage, xylem flow from the whole tree and phloem flow from leaves of the same stem seem to be the major factors contributing to fruit growth. At stage III, fruits from high and low L:F shoots exhibited similar growth before girdling, whereas girdling induced a generally sharp decline of fruit growth and a marked shrinking of low L:F fruits. At this stage, regular fruit growth mostly relied on both water and carbon phloem imports from neighboring branches. Regardless of girdling or stage, the diel leaf turgor pressure (pc) range (maximum pc – minimum pc over 24 h) was always smaller in leaves from low L:F shoots compared to those from high L:F shoots, indicating that the source-sink balance is a major factor driving water status changes in leaves. Overall, at stage I, nectarine fruit growth was mainly driven by water movements through the xylem, whereas at stage III, it mostly relied on phloem contribution (water + assimilates). Leaf pc variations were mostly influenced by L:F possibly via xylem backflow from fruits in both stages I and III
Field non-destructive determination of nectarine quality under deficit irrigation
No full textThis study investigated the effects of deficit irrigation (DI) at different fruit growth stages and tree orientation on fruit quality of ‘September Bright’ nectarines (Prunus persica L. Batsch). Control trees were fully irrigated throughout the entire fruit development period, whereas deficit irrigation was supplied at fruit growth stage I (cell division, DI-I), II (pit hardening, DI-II), IIIa (cell expansion, DI-IIIa) and IIIb (fruit maturation, DI-IIIb). Non-destructive measurements of fruit maturity and quality were carried out using portable devices based on near-infrared spectrometry and pigment fluorescence on west- and east-oriented trees of an Open Tatura system. Chlorophyll degradation (index of absorbance difference, IAD), soluble solid concentration (SSC), dry matter percentage (DM), anthocyanin (fluorescence excitation ratio anthocyanin relative index, FERARI) and flavonol concentrations (FLAV) were measured in the four weeks prior to harvest. Yield, crop load, fruit weight and diameter, flesh firmness, and skin dark red and light red coverage were measured at harvest. DI-I, DI-IIIa and DI-IIIb caused a significant reduction of fruit size and yield. IAD and FERARI declined progressively towards fruit maturity but were not significantly influenced by irrigation. FLAV remained stable until harvest despite a short-term response to water deficit at the beginning of stage IIIb before returning to its previous value. Fruit SSC and DM were highest in DI IIIb and DI I, respectively, and similar to control in DI II and DI IIIa. Tree orientation did not affect fruit quality, except for higher IAD and FLAV in west- compared to east-oriented trees. Overall, all the DI-treatments induced a crop performance loss, even though different crop parameters were affected, with DI-IIIa causing the most detrimental effect on fruit quality. The non-destructive devices proved useful in determining fruit quality in situ
Continuous detection of new plant water status indicators in stage I of nectarine fruit growth
No full textConventional irrigation management is often inefficient in responding to seasonal changes of tree water needs. The use of leaf- and fruit-based sensors might provide helpful insights on tree water status, although they have been poorly investigated so far. Fruit gauges and leaf patch clamp pressure (LPCP) probes were tested during stage I of nectarine fruit growth to evaluate if leaf turgor pressure and fruit size may serve as indicators of water deficit. This experiment was carried out in the 2017/18 season. Four irrigation levels were applied to ‘September Bright’ nectarine trees (100, 40, 20 and 0% of crop evapotranspiration, ETc) and data were collected during stage I of fruit growth. Tree size, fruit doubling, leaf chlorophyll concentration, stomatal conductance (gs), stem water potential (Ψstem), fruit diameter and canopy light interception were measured. Fruit gauges and LPCP probes were mounted on trees for a week interval in the second half of fruit growth stage I. Sensor outputs were expressed as fruit diameter and attenuated pressure of leaf patches (pp). Fruit diameter was reduced in deficit irrigated trees. As expected, gs and Ψstem responded to irrigation inputs. Continuous fruit diameter and pp were found to be both sensitive to water deficit, although they require different analytical approaches for data interpretation. Results of this study suggest that nectarine fruit growth and leaf turgor pressure can be used independently as continuous indicators of plant water status
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Diurnal irrigation timing affects fruit growth in late-ripening nectarines
No full textLittle is known about the best diurnal irrigation timing for maximum fruit growth in stone fruit, despite fruit size being the most important focus for growers to achieve maximum marketable yield. This study investigated the effects of morning and afternoon irrigation on nectarine fruit growth in stage I (cell division) and stage III (cell expansion). In the 2017/18 season, ‘September Bright’ trees were subjected to morning (Iam) and afternoon (Ipm) irrigations. Fruit diameter was monitored continuously (15-min intervals) using fruit gauges and converted into fruit weight, relative growth rate (RGR) and fruit growth efficiency (FGE), with the latter representing RGR per unit of crop water supply (irrigation + rainfall). Irrigation timing affected FGE in opposite fashions during stage I and III. In stage I, maximum FGE occurred in days of Iam, whereas in stage III in days of Ipm. The different observations in the two stages were strongly influenced by the effect of crop evapotranspiration on FGE but were likely dependent on other factors such as stage-specific vascular activity, sugar and starch content and fruit advancement in phenology phases. Overall, this study suggests that optimal irrigation management needs to consider irrigation timing at sub-daily scales in conjunction with stage-specific irrigation strategies
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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