Solar neutrino detection sensitivity in DARWIN via electron scattering

We detail the sensitivity of the proposed liquid xenon DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five solar neutrino components: pp, 7Be, 13N, 15O and pep. The precision of the 13N, 15O and pep components is hindered by the double-beta decay of 136Xe and, thus, would benefit from a depleted target. A high-statistics observation of pp neutrinos would allow us to infer the values of the electroweak mixing angle, sin 2θw, and the electron-type neutrino survival probability, Pee, in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, with 10 live years of data and a 30 tonne fiducial volume. An observation of pp and 7Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high- (GS98) and low-metallicity (AGS09) solar models with 2.1–2.5σ significance, independent of external measurements from other experiments or a measurement of 8B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of 131Xe

Solar Neutrino Detection Sensitivity in DARWIN via Electron Scattering

We detail the sensitivity of the proposed liquid xenon DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five solar neutrino components: pp, 7Be, 13N, 15O and pep. The precision of the 13N, 15O and pep components is hindered by the double-beta decay of 136Xe and, thus, would benefit from a depleted target. A high-statistics observation of pp neutrinos would allow us to infer the values of the electroweak mixing angle, sin2θw, and the electron-type neutrino survival probability, Pee, in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, with 10 live years of data and a 30 tonne fiducial volume. An observation of pp and 7Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high- (GS98) and low-metallicity (AGS09) solar models with 2.1–2.5σ significance, independent of external measurements from other experiments or a measurement of 8B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of 131Xe

The plasticity of berry shrivelling in 'Shiraz' : a vineyard survey

Berry water loss during late ripening is a cultivar dependent-trait and is accentuated in wine grape varieties such as 'Shiraz'. 'Shiraz' berry development was monitored in twelve vineyards over two seasons to characterise the extent of weight loss that can occur within a grape growing region. From veraison onwards, berry fresh mass was greatest in vineyards using excessive irrigation and least in vineyards using cautious irrigation strategies. In the first season, berry fresh mass increased, reached a maximum and subsequently declined. Conversely, in the second season, characterised by rain and high humidity, berry fresh mass increased, then stabilised without a consistent decline. In both seasons, berry sugar import rates were highest shortly after veraison but then declined gradually, terminating several weeks after the weight maximum. Notwithstanding that berries with large maximum weights tended to undergo greater rates of weight loss, these berries remained heavier at harvest compared to those berries that were smaller prior to the onset of weight loss. Canopy size, yield and crop load were not key determinants of berry weight loss rates. Berry anthocyanin and sugar accumulation were closely correlated during early ripening but anthocyanin degradation took place during the late weight loss phase

Acta Hortic.

Optimisation of nitrogen (N) supply and other nutrients in vineyards is critical to quality and quantity of fruit and wine production. However, there are major challenges to balance N availability for canopy growth in spring, reproductive development, fruit maturity rates and optimum grape composition at harvest. Therefore, frequent monitoring of nutrient status is essential to better predict and target inputs and consequentially maximise profitability. Rapid and convenient assessment of grapevine N status in the field can help identify N requirements during the season. A replicated experiment was undertaken in a glasshouse using two-year-old ‘Shiraz’ vines from dormancy to veraison that were pruned back to four two-bud spurs. The vines were previously water stressed, re-potted in washed river sand and then placed into a cool room at approximately 5-6°C for 14 days. From the end of dormancy, different nutrient solutions were applied to create a range of leaf nutrient levels for N, supplying approximately 100, 50 and 0% of N required for the bud burst to veraison period. Spectrometer measurements (reflectance) and leaf samplings were conducted at three times (at flowering, four weeks before and after) and three locations along the shoots (opposite the basal bunch, and two and four nodes above the basal bunch). The leaves were washed, separated into blades and petioles, ground and analysed for N concentration. The reflectance, particularly around 550 nm, showed considerable difference between N treatments, and these were more pronounced on the older leaves and later in the season. Leaf and petiole N concentrations were closely related, allowing the calibration of the indirect measurements with a spectrometer to establish petiole standards for flowering. Better understanding of changes in leaf N concentrations during vine development will allow for more accurate predictions of N requirements throughout the growing season

Within-season temporal variation in correlations between vineyard canopy and winegrape composition and yield

Remote optical imaging can rapidly acquire information describing spatial variability in vineyard block performance. Canopy characteristics were derived from very high spatial resolution (0.25 m) optical imagery of a Cabernet Sauvignon vineyard acquired at various canopy growth stages. Within-season changes to correlation coefficients between vineyard canopy and ultimate composition and yield of harvested fruit were then investigated. Canopy area and density were observed to have significant relationships with yield and fruit quality indicators including berry size, anthocyanins and total phenolic content, but less significant relationships with total soluble solids. The strength and type of correlation varied with canopy growth stage. For anthocyanins and total phenolic content, correlations varied from non-significant before flowering to negative after flowering. For berry weight and yield, correlations varied from negative before flowering to positive after flowering. For total soluble solids, there were some significant relationships but no clear temporal pattern. The results confirm that remote sensing is a useful tool to determine spatial variability in fruit composition and yield. However, both the timing of image acquisition and the way in which canopy is quantified are important determinants of the direction and strength of correlations with fruit composition and yield

Sugar accumulation in roots of two grape varieties with contrasting response to water stress

Root sugar accumulation was studied in two grapevine varieties contrasting in tolerance to water stress. During a 10-day water withholding treatment, the drought-tolerant variety, Grenache, sustained less negative predawn and midday leaf water potentials as well as root water potential compared with the sensitive variety, Semillon. Grenache vines also maintained lower stomatal conductance and transpiration than Semillon vines throughout the drying period. In both varieties there was accumulation of sucrose in the roots and concentrations were inversely correlated to leaf and root water status. In both Grenache and Semillon, elevated root osmolality was associated with decreased soil moisture indicating that sugar accumulation may play a role in osmotic protection. Petiole xylem sap abscisic acid (ABA) concentrations increased with water deficit in both varieties and were highest for vines with the most negative root and predawn leaf water potentials. Furthermore, root sucrose concentrations were positively correlated with leaf xylem sap ABA concentrations, indicative of integration between carbohydrate metabolism and the ABA signalling system. Similar root sugar accumulation patterns between the two varieties, however, demonstrate that other factors are likely influencing the ability of the drought-tolerant variety to remain hydrated

Root growth during postharvest irrigation of warm-climate grapevines

In warm climate regions of Australia grapevines may retain leaves for up to four months after harvest. However, a dry postharvest period may reduce root growth, nutrient uptake and the replenishment of carbohydrate reserves. This can impact on canopy function in the current season as well as canopy development and berry ripening in the following season. This research examined the role of the root environment, particularly soil temperature and moisture, on fine root growth after harvest in 2013. Three postharvest irrigation strategies were compared using mature field-grown Shiraz. These included no postharvest irrigation (NPHI), early postharvest irrigation (EPHI) and late postharvest irrigation (LPHI). The EPHI treatment maintained soil moisture in the readily available range for a period of 15 days after harvest. The LPHI treatment was applied at 30 days after harvest, and similarly maintained soil moisture for a period of 15 days. Minirhizotron tubes were used to monitor root growth across all three treatments. Fine root growth in EPHI increased nearly sixteen-fold 20 days after irrigation. Maximum root growth rates were observed at seven days after harvest in the EPHI treatment and these growth rates were maintained for seven days prior to declining. The root growth response to the LPHI treatment was much less pronounced. Soil temperature during EPHI was warmer by 6̊C when compared with LPHI. These results indicate that moisture but not necessarily soil temperature (in the conditions of this experiment) are critical factors influencing fine root growth in the postharvest period

Circadian regulation of grapevine root and shoot growth and their modulation by photoperiod and temperature

Some plant species demonstrate a pronounced 24 h rhythm in fine root growth but the endogenous and exogenous factors that regulate these diel cycles are unclear. Photoperiod and temperature are known to interact with diel patterns in shoot growth but it is uncertain how these environmental factors are interrelated with below-ground growth. In this particular study, the fine root system of two grapevine species was monitored over a period of ten days with a high resolution scanner, under constant soil moisture and three different photoperiod regimes. Pronounced diel rhythms in shoot and root growth rates were apparent under a fixed 14 h photoperiod. Maximal root growth rate occurred 1–2 h prior to- and until 2 h after the onset of darkness. Subsequently, during the latter part of the dark period, root growth rate decreased and reached minimal values at the onset of the light period. Relative to 22 °C, exposure to a 30 °C air and soil temperature halved root growth but stimulated shoot growth. Notably, the shoot extension rate peak shifted from late afternoon to midnight at this higher temperature zone. When plants were exposed to a delayed photoperiod or progressively shortening photoperiod, the diel changes in root growth rate followed the same pattern as in the fixed photoperiod, regardless of whether the plant was in light or dark. This suggests that light was not the predominant trigger for stimulating root elongation. Conversely, shoot growth rates were not fixed to a clock, with minimum growth consistently at the completion of the dark period regardless of the time of day. In summary, fine root growth of grapevines was found to have a pronounced diel pattern and an endogenous circadian clock appears to orchestrate this rhythm. Soil temperature modified the amplitude of this pattern, but we argue here that, as evidenced from exhausted starch reserves within root tips by early morning, carbon supply from photosynthesis is also required to maintain maximum root growth

Diurnal dynamics of fine root growth in grapevines

Fine roots can grow more rapidly at certain points during the day depending on species and environmental conditions. The grapevine is a large perennial that has an extensive below-ground structural system; however its diurnal root growth pattern has received little attention. The aim of this study was to characterize the diurnal fine root growth dynamics of four grapevine genotypes and to assess the impact of soil temperature on this growth. One-year-old vines of Shiraz (Vitis vinifera), and the rootstocks Ramsey (V. champinii), 140 Ruggeri (V. berlandieri x V. rupestris) and Schwarzmann (V. rupestris x V. riparia) were grown in tapered rectangular pots with transparent acrylic windows to assess diurnal root growth dynamics using sequential image acquisition with a high resolution scanner. All four genotypes displayed a pronounced diurnal root growth pattern that positively followed daily soil temperature fluctuations. Maximum growth rates did not differ between the genotypes and were highest in the afternoon, declined through the night and reached a minimum the next morning. While diurnal root growth rates were influenced by soil temperature, this was not the only factor as evidenced by an extensive range of growth rates between the individual roots of a plant even when exposed to optimal temperatures. It is argued here that other environmental and endogenous factors will likely have an influence on the maximum rate of growth