60 research outputs found
Confocal measurement of the three-dimensional size and shape of plant parenchyma cells in developing fruit tissue
No full textGray, John D. ; Kolesik, Peter ; Høj, Peter B. ; And Coombe, Bryan G
The basis of variation in the size and composition of grape berries
No full textThe objective of this study was to explore the basis of variation in the size and composition of grape berries. The investigation focussed on selected aspects of berry development and ripening that were subject to variation. Shiraz and Chardonnay were chosen as experimental varieties because these cultivars presented a large range of variability in the field – Shiraz is susceptible to variation in colour development at veraison, whereas Chardonnay often displays variation in berry size at harvest. The extent of variation within each of the recorded berry parameters was assessed using the coefficient of variation (CV), a unitless measure of sample variability relative to the sample mean, ideally suited to comparative studies.
Chapter 1 is a literature review that documents research on selected aspects of grape berry development and ripening which are subject to variation. Berry development is explained in terms of berry set, berry growth and ovule/seed development. Berry composition is described by the relative concentration of sugars, acids, phenolics and flavour compounds in the berry tissues. Variation is discussed with respect to the Australian wine industry and the problem of supply and demand. Techniques for identifying and measuring components of variation are recommended. Experimental hypotheses are developed.
Chapter 2 describes an experiment designed to identify when variation in berry size and composition was initiated. The hypothesis was that relative levels of variation in size and
composition would remain constant throughout the postflowering period of berry development. The physical properties of individual Shiraz berries were described in terms of their deformability, mass, volume, surface area and seed mass. The phenolic composition of these same individual berries was assessed. A comparison of CVs between sequential developmental stages indicated when variation in a particular physicochemical parameter was initiated. The CV in berry deformability reached a maximum at softening. The CV for berry mass was above 50% at berry set, but declined as the berries approached harvest maturity. The CVs for berry volume and berry surface area followed a similar trend. Interactions among these parameters were described by linear regressions, multiple regressions and correlation matrices. Seed mass and berry phenolics were analysed for individual berries during the growing, softening and preharvest stages. Both of these parameters were significantly correlated with berry mass, but the relationships were peculiar to each developmental stage. The CV for seed mass increased with maturity. The CV for berry phenolics was lowest during the softening stage. For most parameters, CVs had already attained high levels during the earliest growth stage (setting). The implication is that variation must have arisen at an even earlier time. This places considerable importance on the impact that preflowering events may have on cell division in the floral primordia at budburst.
Chapter 3 describes an experiment that sought to identify the extent of variation present during the early developmental stages of berry growth. The hypothesis was that variation in
berry size was already significant in the early postflowering period of berry development. Individual Chardonnay berries on two bunches from both ungirdled and girdled vines were
assessed on four occasions throughout the flowering period. Individual flowers that had opened during the intervening time period were tagged. One bunch from each vine was sampled at 15 days and another at 43 days after the first flower had opened, giving a range of berry ages: bunch at 15 days comprised berry ages of 1-4, 5-7, 8-11 and 12-15 days; bunch at 43 days comprised berry ages of 29-32, 33-35, 36-39 and 40-43 days. Frequency distributions of berry mass were plotted for each age class for ungirdled and girdled vines. Distributions were negatively skewed for ungirdled vines and positively skewed for girdled vines. No “shot” berries were observed among bunches sampled from girdled vines at 43 days after flowering. Absolute and relative growth rates were typically higher for berries from girdled vines. The relationship between berry mass and seed mass was unaffected by trunk girdling. CVs for berry mass at all ages in the early bunch sample (15 days) were below 44%, and were generally lower for the girdled vines. In the later bunch sample (43 days), CVs in berry mass were all higher than those associated with the early bunch sample, and two- to three-fold
lower for the girdled vines. This reduction is most likely the result of increased organic nutrition to the bunch counteracting the variation that arises from differences in hormonal stimulus to growth by the developing seed.
Chapter 4 describes a novel technique that was developed for the in situ measurement of cell shape and cell size using confocal laser scanning microscopy (CLSM). The technique encompassed the preparation, clearing, staining and whole mounting of large sections of berry tissue. Optical slices were collected at 1 μm intervals to a depth of 150 μm. The digital images were empirically corrected for attenuation of fluorescence intensity and axial distortion due to refractive index mismatch. Cell size and shape were determined from digital 3D reconstructions of the collected image stack. Cell volumes exhibited a 15-fold range with polysigmoidal distribution and groupings around specific size classes. The volume of individual, whole parenchyma cells within a block of grape berry mesocarp tissue could be measured in situ to a precision of 2 μm³.
Chapter 5 describes an experiment that sought to resolve the relationship between fruit size and cell size in a developing grape berry. The hypothesis was that variation in cell size
occurs early in the postflowering period of berry development and that this variation was responsible for the subsequent macroscopic size differences observed between berries. Chardonnay berries belonging to the eight age classes derived in Chapter 3 were sampled from ungirdled and girdled vines. Three berries from each age class were analysed under the CLSM-one “shot”, one “chick” and one “hen”. Volumes were calculated for ten cells from the inner mesocarp tissue of each berry. Differences in cell volume were observed between berry types. Larger berries often had a larger range of cell sizes, indicating they had undergone more cell expansion during the course of their development, but the distribution of cell sizes in “shot” and “chick” berries was similar. Girdling did not affect the berry cell size distribution, but the CVs of girdled vines were ~50% higher. Cell volume for “chicks and “hens” increased between day 15 and day 43, although the increase was proportionally greater for “hens”. Variation in cell size remains relatively constant during the early postflowering development, but variation in berry mass increase regardless. This indicates the operation of different metabolic controls over these two facets of berry growth.
Chapter 6 is a general discussion and an attempt to synthesise the salient points from the preceding experimental chapters. In light of the experimental results, it addresses the validity of each of the original hypotheses on variation in berry size and composition. Concepts of developmental synchronisation among berries are viewed from the perspective of changing levels of variation between developmental stages. Increases in CVs signify a loss of synchronisation (asynchronisation) among berries. Reductions in CVs signify a gain in synchronisation (resynchronisation) among berries. The general conclusion is that averages of measurements of the population reveal nothing about the variation within that population. Calculation of variance permits this, but requires that all individuals be measured. Cell size is only one component of the berry size equation. Cell number is the other. While cell size is determined by cell expansion, cell number is linked to cell division. Future applications of techniques developed in this thesis could resolve the interplay between cell division versus
cell expansion. A better understanding of these processes might ultimately minimise the impact of variability on the quantity and quality of the Australian winegrape crop.Thesis (Ph.D) -- University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 200
Measurement of the changes in the composition of developing undetached grape berries by using 13C NMR techniques
No full textSolute accumulation by grape pericarp cells II. Studies with protoplasts and isolated vacuoles
No full text
Observations of Bºs→ψ(2S)η and Bº(s)→ψ(2S)π+π- decays
No full textFirst observations of the B0s
→ψ(2S)η, B0 →ψ(2S)π
+
π
− and B0s
→ψ(2S)π
+
π
− decays are made
using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in
proton–proton collisions at a centre-of-mass energy of
√
s = 7 TeV. The ratios of the branching fractions
of each of the ψ(2S) modes with respect to the corresponding J/ψ decays are
B(B0s
→ψ(2S)η)
÷
B(B0s
→J/ψη)
= 0.83± 0.14 (stat)±0.12 (syst) ±0.02 (B),
;
B(B0→ψ(2S)π
+
π
−
)
÷
B(B0→J/ψπ
+
π
−
)
= 0.56± 0.07 (stat)±0.05 (syst)± 0.01 (B),
;
B(B0s
→ψ(2S)π
+
π
−
)
÷
B(B0s
→J/ψπ
+
π
−
)
= 0.34± 0.04 (stat)±0.03 (syst)± 0.01 (B),
where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψ
and ψ(2S) meson decays
Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England
No full textMany lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial-interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in the context of the river Kennet, a tributary of the Thames, since c. 13,000 cal. BP). Some similarities with other rivers are present, suggesting that regional climatic shifts are important controls. The Kennet differs from the regional pattern in a number of ways. The rate of response to sudden climatic change, particularly at the start of the Holocene and also mid-Holocene forest clearance, appears very high. This may reflect abrupt shifts between two catchment scale hydrological states arising from contemporary climates, land use change and geology. Stadial hydrology is dominated by nival regimes, with limited winter infiltration and high spring and summer runoff. Under an interglacial climate, infiltration is more significant. The probable absence of permafrost in the catchment means that a lag between the two states due to its gradual decay is unlikely. Palaeoecology, supported by radiocarbon dates, suggests that, at the very start of the Holocene, a dramatic episode of fine sediment deposition across most of the valley floor occurred, lasting 500-1000 years. A phase of peat accumulation followed as mineral sediment supply declined. A further shift led to tufa deposition, initially in small pools, then across the whole floodplain area, with the river flowing through channels cut in tufa and experiencing repeated avulsion. Major floods, leaving large gravel bars that still form positive relief features on the floodplain, followed mid-Holocene floodplain stability. Prehistoric deforestation is likely to be the cause of this flooding, inducing a major environmental shift with significantly increased surface runoff. Since the Bronze Age, predominantly fine sediments were deposited along the valley with apparently stable channels and vertical floodplain accretion associated with soil erosion and less catastrophic flooding. The Kennet demonstrates that, while a general pattern of river behaviour over time, within a region, may be identifiable, individual rivers are likely to diverge from this. Consequently, it is essential to understand catchment controls, particularly the relative significance of surface and subsurface hydrology
Measurement of the branching fraction
No full textThe B
0
s
→ J/ψK
0
S
branching fraction is measured in a data sample corresponding to 0.41 fb−1
of integrated luminosity collected with the LHCb detector at the LHC. This channel is sensitive to
the penguin contributions affecting the sin 2β measurement from B
0
→ J/ψK
0
S
. The time-integrated
branching fraction is measured to be B(B
0
s
→ J/ψK
0
S
) = (1.83±0.28)×10−5
. This is the most precise
measurement to date
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
No full textThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
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