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

The effect of light intensity and temperature on berry growth and sugar accumulation in Vitis vinifera 'Shiraz' under vineyard conditions

Temperature and light are key climatic factors which affect grapevine physiology in the growing season. Our aim was to investigate the interactive effects of temperature and light intensity on reproductive growth responses of 'Shiraz' vines in vineyard conditions. Well-watered vines were covered with no shade, light, medium and heavy shade covers in a vineyard over three consecutive seasons. Several heat events, i.e., air temperatures exceeding 40 °C for several days, occurred in two of the seasons. Heavy shade reduced canopy temperatures by 3.2-6 °C in the cooler season and by 4-6 °C in the warmer seasons, relative to air temperature and compared with the open canopy. The onset of berry growth was delayed by the heavy shade but the rate of sugar accumulation was not affected. During the season with the most severe heat events, berry dry matter accumulation was significantly higher in the shaded treatments compared to the unshaded vines. The hypothesis was confirmed that medium and heavy shade conferred high levels of protection on the berry ripening process from high summer temperatures and the concurrent exposure to light intensities

Nitrogen and ultraviolet radiation modify grapevines’ susceptibility to powdery mildew

Potted Cabernet Sauvignon and Chardonnay grapevines were grown in southeastern Australia under either ambient or reduced ultraviolet (UV) radiation to test the effect of UV on powdery mildew (Uncinula necator) susceptibility. Diacetate films were used to screen out UV-B (280-315 nm) and UV-A (315-400 nm). Two nitrogen treatments (0 or 3 g N per plant) were applied at bloom to test interactions of nitrogen status with UV radiation. Cabernet Sauvignon was much less susceptible to U. necator and also responded less to UV and nitrogen. U. necator incidence and severity on leaves were increased dramatically when high nitrogen supply was combined with low UV, particularly in Chardonnay. The differences in infection were not due to variation in canopy microclimate (temperature and humidity) caused by experimental treatments. However, high disease susceptibility in response to high nitrogen status and low UV radiation was related to low concentrations of constitutive phenolic compounds (flavonol glycosides and, to a lesser extent, hydroxy-cinnamic acid derivatives), high leafnitrogen status and photosynthetic rates, high succulence, and reduced cuticular wax deposition. No stilbene phytoalexins could be detected following infection, suggesting that stilbenes are not involved in U. necator resistance in grapevines. These results show that UV radiation affects disease susceptibility of grapevine cultivars and that this susceptibility is modulated by nitrogen supply

Irrigation, nitrogen, and rootstock effects on volume loss of berries from potted Shiraz vines

Shiraz (synonym Syrah) berry volume increases in two phases and this may be followed by shrinkage during the later stages of ripening. Irrigation regime, nitrogen application rate and rootstock were tested for their effects on the onset of volume loss and extent of volume loss. Maximum berry volume correlated well with volume of berries at 35 d after flowering, the end of the cell division phase. Post-maximum berry shrinkage was not as severe of vines grown with split-root irrigation as compared with standard irrigation. However, these berries were smaller at harvest due to less pre-veraison expansion. Berries grown on vines with standard irrigation had greater post-maximum volume loss than those berries grown in a deficit irrigation treatment. Despite this, maximum berry volume correlated well with final volume in all treatments. N application rate had an effect on the onset of post-veraison expansion but not on the amplitude of maximum berry volume or final berry volume. Deficit irrigation delayed the onset of volume loss by 11 d. Rootstock also had an effect on the onset of volume loss with berries from vines grafted on the rootstock 101-14 Mgt losing volume 7 d earlier than berries from vines grafted on Ramsey. These results suggest that onset and degree of volume loss in Shiraz is sensitive to external influences.

Susceptibility of Chardonnay grapes to sunburn

Research Not

Timing of N application and water constraints on N accumulation and juice amino N concentration in Chardonnay grapevines

The amount and timing of nitrogen (N) application to a vineyard is critical for must yeast assimilable nitrogen (YAN) concentrations. YAN concentrations and amino acid profiles are important for the fermentation process and wine composition. Commonly, N is applied at flowering to optimize leaf functioning or after harvest to enhance vine productivity the following season. In this study N was applied at various stages of berry development to determine allocation patterns between vine perennial and annual components and to assess when berry YAN concentrations can best be optimized. Five year old potted 'Chardonnay' vines received ammonium sulfate fertilizer at six different times from full bloom to two weeks before harvest and were also exposed to either full or half irrigation during that period. Reduced water supply resulted in a higher allocation of N to the perennial structures and less to the annual components of the vine. N allocation to the annual components of the vine was greatest when it was applied at full bloom, however allocation to the perennial components was greatest when it was applied after fruit-set to veraison. The timing of N supply had a substantial influence on YAN concentrations, and was highest when N was applied about two weeks after veraison. Low water supply also resulted in higher juice YAN concentrations. The perennial N reserves in the roots were highest under low water supply and when N was applied at veraison, while the allocation to the annual parts was lower under this irrigation regime. The study indicates that timing of N application and the application of water constraints during berry development can impact on N partitioning, while the total amount accumulated by the vine is not altered

Spatiotemporal changes in the accumulation of sugar and potassium within individual 'Sauvignon Blanc' (Vitis vinifera L.) berries

It has been speculated that there may be a link between the transport of sugar and potassium into grape berries during ripening as they exhibit similar accumulation patterns. It is unclear if this proposed link is apparent in individual grape berries and in the grape berry compartments. Single grape berries were therefore analysed for sugar and potassium content and concentration within the skin, seeds and the pulp from pre-véraison until harvest. Sugar and potassium had similar accumulation patterns and positive relationships were confirmed between the sugar and potassium content within individual berries and compartments. The sugar content in the grape berry, however, increased 5-fold during ripening whereas the potassium content only doubled. Both sugar and potassium increased with berry size, suggesting a ternary relationship with berry water. The high variability in sugar and potassium contents between berries however affirms plasticity in their accumulation within individual berries

Mineral sinks within ripening grape berries (Vitis vinifera L.)

Trends in the accumulation of mineral elements into the grape berry components give information about vascular flow into the berry. Shiraz berries were dissected into receptacle, skin, pulp, brush and seeds and the accumulation of 10 mineral elements into these components was followed through development. The elements were separated into two categories according to their accumulation pattern into the berry. The first group of elements continued to accumulate throughout berry growth and ripening, and was comprised of  phloem-mobile potassium, phosphorus, sulphur, magnesium, boron, iron and copper. The second group of elements accumulated mostly prior to veraison, and included the xylem-mobile minerals calcium, manganese and zinc. These results indicate that the xylem contribution to berry growth diminished after veraison. Berry fresh weight, dry weight, as well as berry sugar content, were all highly correlated with berry potassium content. While the pulp and skin were the strongest sinks for potassium and boron, seeds were the strongest sinks for calcium, phosphorus, sulphur, manganese and zinc. With the exception of calcium and manganese, seeds ceased to accumulate most elements during late ripening. The berry receptacle and brush did not accumulate any of the elements to levels above those of the other berry components at any stage of development. Therefore, they did not act as sinks for xylem- or phloem-mobile elements as vascular flow to the pulp and skin slowed.

Solvable Kinetic Gaussian Model in External Field

In this paper, the single-spin transition dynamics is used to investigate the kinetic Gaussian model in a periodic external field. We first derive the fundamental dynamic equations, and then treat an isotropic d-dimensional hypercubic lattice Gaussian spin system with Fourier's transformation method. We obtain exactly the local magnetization and the equal-time pair correlation function. The critical characteristics of the dynamical, the complex susceptibility, and the dynamical response are discussed. The results show that the time evolution of the dynamical quantities and the dynamical responses of the system strongly depend on the frequency and the wave vector of the external field.Comment: 11 page