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Hutton R.J.,National Wine and Grape Industry Center | Loveys B.R.,CSIRO
Agricultural Water Management | Year: 2011

In Australian irrigated citriculture, fruit yield and quality outcomes are not tightly related to levels of plant available water, which raises the possibility of using mild water stress applied to part of the root zone, i.e. partial root zone drying, to stimulate physiological mechanisms that reduce tree water use by changing the relationship between stomatal conductance and ambient evaporative conditions.The PRD technique alternates irrigation such that one side of the tree root zone is allowed to dry whilst the other side is irrigated. This significantly reduces the wetted soil volume at any point in time, whilst always maintaining a readily available water supply to part of the root zone. By adopting this irrigation strategy water use of mature Navel orange trees C. sinensis (L.) Osbeck was reduced and water use efficiency was increased. The technique did not induce excessive fruitlet drop and crop yield was unaffected. Both fruit size and juice percentage slightly decreased whereas total soluble solids percentage (TSS) and juice acid percentage increased. As water use was reduced and juice quality attributes were increased, this technique has obvious benefits for juice fruit production.PRD offers an advantage over conventional deficit irrigation strategies because it helps reduce water use by separating the biochemical signaling responses to water deficit in the dry part of the root zone from the physical effects of reduced stomatal conductance due to lower water availability, allowing developmental processes associated with plant growth to remain unperturbed. Irrigating a reduced root zone volume in this way reduces crop water requirement. However, it is also important to understand that this technique pushes the crop to its limits and should only be applied to well established healthy trees.When applying PRD irrigation, it is important that water is supplied with sufficient frequency and depth of wetting to meet the water needs of the whole plant. © 2011 Elsevier B.V. Source

Rogiers S.Y.,National Wine and Grape Industry Center | Rogiers S.Y.,Australian Department of Primary Industries and Fisheries | Holzapfel B.P.,National Wine and Grape Industry Center | Holzapfel B.P.,Australian Department of Primary Industries and Fisheries
Vitis - Journal of Grapevine Research | Year: 2015

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. Source

Rogiers S.Y.,National Wine and Grape Industry Center | Rogiers S.Y.,Australian Department of Primary Industries and Fisheries | Clarke S.J.,National Wine and Grape Industry Center | Clarke S.J.,Charles Sturt University
Annals of Botany | Year: 2013

Background and AimsDaytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown.MethodsHere nocturnal and daytime leaf gas exchange was quantified in 'Shiraz' grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring.Key ResultsDespite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO2 response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature.ConclusionsIn this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable. © 2013 © The Author 2013. Published by Oxford University Press on behalf of the Annals of Botany Company. Source

Holzapfel B.P.,National Wine and Grape Industry Center | Smith J.P.,National Wine and Grape Industry Center
American Journal of Enology and Viticulture | Year: 2012

The overwintering carbohydrate reserve status of grapevines has been linked to fruiting responses in the following season, providing a possible avenue for yield management through manipulation of reserve accumulation. Conducted across four consecutive seasons, this study examined the extent to which carbohydrate reserve accumulation could be altered in Shiraz grapevines using existing, or variations of existing, cultural practices. Removal of one-third or two-thirds of clusters at veraison increased average total nonstructural carbohydrate (TNC) concentrations in the wood by 7% relative to control vines after two seasons of treatment and 20% after three. Hedging all shoots to five nodes after harvest reduced wood TNC concentrations by 14% after two seasons and by 27% at flowering in season 3 due to increased carbohydrate mobilization after budbreak. Deficit irrigation treatments applied between fruit set and veraison, or following harvest, had no significant effect on TNC concentrations in the wood, and none of the five treatments evaluated had a consistent influence on carbohydrate reserve storage in the roots. Shoot hedging after harvest had the most pronounced influence on reproductive development, with an increase in bud necrosis after two seasons of treatment and reduction in inflorescence flower numbers after three. While the results indicate there is some scope to alter carbohydrate reserve storage through cultural practice, no treatment substantially altered the seasonal pattern of reserve dynamics relative to control vines. It is suggested that developmental stage or seasonal climatic factors had a stronger influence on carbohydrate mobilization and storage, and that the manipulation of reserve accumulation through cultural practice change may be more suited to effecting longer-term adjustments in vine productivity than short-term responses to seasonal yield fluctuations. © 2012 by the American Society for Enology and Viticulture. All rights reserved. Source

Yoo Y.J.,National Wine and Grape Industry Center | Saliba A.J.,National Wine and Grape Industry Center | Saliba A.J.,Charles Sturt University | Prenzler P.D.,National Wine and Grape Industry Center | Ryan D.,National Wine and Grape Industry Center
Journal of Agricultural and Food Chemistry | Year: 2012

White and red wines spiked with catechin-rich green tea extract and grape seed extract were assessed for phenolic content, antioxidant activity, and cross-cultural consumer rejection thresholds in relation to wine as a functional food. Health functionality is an important factor in functional foods, and spiking pure compounds or plant extracts is an effective method to increase or control functionality. The total phenolic content and antioxidant activity were measured in wines spiked to different extract concentrations, namely, control and 50, 100, 200, 400, and 800 mg/L, to confirm the dose-response curves in both white and red wines. Consumer rejection thresholds (CRTs) were established for spiked wines in a Korean and in an Australian population. Our results showed that the green tea extract and grape seed extract increased the antioxidant activity dose dependently, and the CRTs varied considerably between the Korean and the Australian groups, with Koreans preferring wines spiked with green tea extract and Australians showing a preference for wines spiked with grape seed extract. These results have implications for producing wine products that are enhanced in phenolic compounds and targeted to different cultural groups. © 2011 American Chemical Society. Source

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