Is weight loss in ripening grape berries cv. Shiraz caused by impeded phloem transport?

Berry shrinkage in ripening grapes cv. Shiraz is systemic within a given grapevine and coincident between grapevines in any given season. In this present study on weight loss in ripening berries, ripening curves of non-solutes per berry (largely water) were similar to curves for berry weight (as a function of time). Both sets of curves were equivalent with respect to timing of maximum weights and subsequent rates of weight loss. However, curves of solutes per berry (largely sugar) increased steeply up to the time of maximum berry weight, then slowed and plateau-ed. We suggest that phloem sap is the sole source for water and solutes that enter grape berries subsequent to veraison, and accumulate until maximum berry weight. We further suggest that phloem flow becomes impeded at maximum berry weight.
As berry ripening proceeds, continuation of berry transpiration leads to berry shrinkage and a concentration of solutes; i.e. any increase in juice Brix depends on shrinkage. One implication is that assimilates enter a berry up to the onset of shrinkage, whereafter accumulation of non-anthocyanin glycosides (including glycosides of flavour compounds) depends upon their synthesis in situ.     

Accumulation of potassium and calcium by ripening berries on field vines of Vitis vinifera (L) cv. Shiraz

Ripening berries of Vitis vinifera (L) cv. Shiraz can show pre-harvest weight loss at sub-optimal sugar content (shrinkage). This later-age decline in berry weight implies that water loss from mature berries has begun to exceed water inflow from the parent grapevine. Such decrease in net inflow has been attributed to a cessation of xylem flow subsequent to veraison, followed by a cessation of phloem flow into berries during later stages of ripening. We address this issue in this present paper, and show a continuing increase in berry content of both potassium and calcium throughout ripening. We measured changes in berry fresh weight and berry content of potassium (phloem mobile) and calcium (phloem immobile) in fruit on field vines sampled from set to harvest. Berry fresh weight reached a plateau between 81 and 95 days after flowering, then declined to 75% of maximum fresh weight by 115 days. Dry weight maximum occurred 14 days after the onset of the fresh weight plateau. Potassium accumulation was slow pre-veraison, increased 3.5-fold post-veraison, and continued during berry shrinkage. Calcium content per berry also showed a linear increase throughout fruit enlargement and ripening phases. Assuming both potassium and calcium were entering berries via vascular conduits, our results imply a continuing connection between parent grapevine and ripening berries. Moreover, an abrupt change (increase) in the ratio of potassium/calcium content per berry subsequent to veraison implies that phloem inflow has increased relative to xylem inflow during post-veraison enlargement.     

Physiological and modelling approaches to understand water and carbon fluxes during grape berry growth and quality development: a review

Recent advances in the understanding of the physiology of berry growth and in modelling allow simulation of fruit growth and sugar accumulation from the perspective of water and carbon balance. This review summarises present knowledge on the modelling and molecular physiology of carbon and water fluxes related to grape berry growth and quality. It focuses principally on the effects of environmental factors and cultural practices on fruit quality through their consequences on water and carbon fluxes during fruit growth. Together with ecophysiological and molecular approaches, process-based models show promising ability to aid in integrating physiological results, generating novel hypotheses and consequently providing a full picture of the control of berry growth and quality development. In the future, nitrogen and sulfur fluxes, necessary for the synthesis of secondary metabolites important for quality, should also be integrated. Modelling at the organ level should extend to metabolic content and metabolite fluxes (metabolomic and fluxomic studies). Genotypes naturally or artificially affected on a key gene or function will also be helpful to validate modelling hypotheses.     

不同类型果袋对葡萄果实有关性状的影响

以晚熟葡萄品种红地球为试材,探讨了几种不同透光率的果袋对葡萄果实有关性状的影响,结果表明:不透光的复合袋极为显著地降低果实单粒重、总糖含量和糖酸此;透光率为16％的红色袋显著降低果实糖酸比,但对总糖含量、单粒重无显著影响;透光率为60％的无纺布袋对果实品质有一定提高作用;套袋处理的果实钙含量显著低于对照,且随着果袋透光率的降低而降低;透光率高的果袋袋内果实单宁含量偏高;各处理果实Vc含量均无显著差异.葡萄果实对光照强度的需求存在临界值,当袋内光照强度低于外界自然光照的1.4％左右时,果实生长发育开始受到影响.     

巨峰浆果生长过程中的酒石酸,苹果酸变化

巨峰葡萄浆果中的主要有机酸为酒石酸、苹果酸。苹果酸含量随浆果生长呈低－高－低的变化趋势，酒石酸前期含量较高，随浆果生长不断降低。苹果酸、酒石酸在浆果生长前期存在明显的由果梗端向果顶端的递降梯度，果实发育后期这两种酸的纵向梯度不明显。     

葡萄果实发育过程中花色素还原酶的免疫组织化学定位

以赤霞珠葡萄果实为试材,采用免疫组织化学方法,对果实发育过程中花色素还原酶(ANR)的分布及其动态变化进行原位分析.结果表明,在果皮、果肉和种子中均可观察到ANR的存在;种子中的ANR主要定位于内珠被(in),果皮和果肉中的ANR则主要分布在维管束(VB)、果皮(BS)细胞壁和果肉(BP)细胞壁中,而且这种特异性分布并不随果实发育进程而发生改变.     

根域限制对巨峰葡萄果实生长发育的影响

通过调查巨峰葡萄根域限制下果实生长发育规律,探讨了根域限制对巨峰葡萄果实生长的影响。结果表明,根域限制下巨峰果实的第二次快速生长量显著高于对照,果实的体积和干物质积累以及种子数目也高于对照,这说明根域限制促进了葡萄果实的发育,增加了光合产物向果实端的运输。     

适合酿酒葡萄果实、果皮及种子的蛋白质提取方法

制备高质量的蛋白质样品是进行蛋白免疫印迹(Western blot)分析的前提.酿酒葡萄果实中含有大量的多酚和多糖等物质,给蛋白质的提取带来了因难.本研究比较了不同聚乙烯聚吡咯烷酮(PVPP)浓度和料液比对赤霞珠葡萄果实、果皮和种子中粗蛋白提取的影响.结果表明,采用10%PVPP及1:2料液比对果实、5%PVPP及1:3料液比对果皮或10%PVPP及1:3料液比对种子的蛋白进行提取,可获得较好的SDS-PAGE图谱;对花色素还原酶(ANR)的蛋白免疫印迹分析显示,ANR在果实、果皮和种子中均有表达,分子量约为43kDa.     

Understanding the microbial ecosystem on the grape berry surface through numeration and identification of yeast and bacteria

Microbial species present on the surface of grape berries at harvest play an important role in winemaking, thus counting and identifying them is of great importance. The use of conventional microbial techniques and molecular methods allowed a quantitative and qualitative inventory of the different microbial species present on the grape berries. These experiments were carried out in several areas of the Bordeaux region on the red grape varieties Merlot, Cabernet Sauvignon and Cabernet Franc. Populations and species clearly varied according to berry development stage. The most widespread yeast species at berry set, Aureobasidium pullulans was never detected at harvest. Fermentative yeasts were detected at harvest and not in the first stage of grape growth. Oenoccocus oeni was detected on immature as well as on mature berries. Gluconobacter oxydans was detected mainly at harvest. Detection of Pediococcus parvulus , was dependent on the vineyard. Veraison appeared to be a key stage for yeast colonisation and the increase in population involved a change in the proportion of each species. The number of A. pullulans fell significantly at veraison as it was superseded by fermentative yeasts. Microbial populations peaked at harvest when the berry surface available for adhesion was largest and no agrochemical treatments had been applied for some weeks. Soil, grape variety and grapegrowing practices may also influence this microbial ecosystem. Based on these and published data, we formulated hypotheses to describe this microbial ecosystem, thus enabling us to develop the concept of a microbial biofilm.     

Inhibition of vacuolar proton pumps by ethanol impairs grape berry compartmentation

Tonoplast vesicles were extracted from mature grape berries in order to study the effect of ethanol on their vacuolar proton pumps, vacuolar ATPase (V-ATPase) and inorganic pyrophosphatase (PPase). Ethanol significantly inhibited their functioning; PPase was more sensitive than V-ATPase. The effectiveness of alcohols with different carbon-chain length indicated that a localised modification of the lipidic environment of the pump may be involved in this phenomenon. However, ethanol did not seem to significantly increase passive proton permeability of tonoplast vesicles. The inhibition of the hydrolytic activity of the inorganic pyrophosphatase PPase led to a decrease in the proton pumping rate into the vacuole and consequently in the generated pH gradient. PPase inhibition by ethanol was not compensated by an activation of the less sensitive V-ATPase when both pumps operated simultaneously. The response of proton pumps to ethanol would be expected to impair cellular compartmentation during anaerobic metabolism. This phenomenon would explain the cell death in grape berries during 'carbonic maceration' or 'vinification beaujolaise'.     

Variation in Shiraz berry size originates before fruitset but harvest is a point of resynchronisation for berry development after flowering

Background and Aims:  Asynchronous berry development results in variation in berry size and berry composition. Variation in berry size affects vineyard yield, wine quantity and berry composition, while variation in berry composition affects fruit flavour and wine quality. The objective of this study is to identify when variation in berry size begins.
Methods and Results:  Shiraz bunches were sampled at seven stages throughout the growing season and the development of individual berries was characterised by measurements of weight, volume, surface area, deformability, seed number and seed weight. Coefficients of variation with respect to berry weight, volume and surface area were elevated throughout the post-flowering period but declined as the berries approached harvest ripeness.
Conclusions:  Variation in berry size originates prior to berry set, most probably during differentiation in the floral primordium at budburst. Harvest represents a point of resynchronisation in berry development when a number of physiological changes become synchronised between berries and within the bunch.
Significance of the Study:  Variation in berry size is presumed by the wine industry to have a negative impact on crop level, fruit composition and wine quality. Much of this presumption is scientifically unsubstantiated. The findings of this paper should encourage grapegrowers and winemakers to modify the timing of the harvest to coincide with a reduction in variation in berry size.     

Effect of pre‐ and post‐veraison water deficit on proanthocyanidin and anthocyanin accumulation during Shiraz berry development

Background and Aims: Water deficit is known to influence berry development as well as flavonoid metabolism. The aim of this study was to investigate the influence of pre‐ and post‐veraison water stress on the proanthocyanidin and anthocyanin accumulation on berry samples selected at comparable physiological maturity, especially after veraison while avoiding sugar influence. Methods and Results: Three irrigation treatments were applied by a drip irrigation system on three rows of 30 vines from an experimental Shiraz vineyard. Pre‐veraison water stress had no effect on total proanthocyanidin accumulation but increased accumulation of all anthocyanins except malvidin and p‐coumaroylated derivatives, whereas post‐veraison water stress enhanced the overall anthocyanin biosynthesis, particularly malvidin and p‐coumaroylated derivatives. Conclusions: Pre‐ and post‐veraison water stress affected the anthocyanin composition differently, suggesting a differential regulation of the genes involved in the last steps of anthocyanin biosynthesis pathway. Significance of the Study: The study identifies the effect of pre‐ and post‐veraison water stress while avoiding sugar influence on anthocyanin accumulation which could be maximised since both stresses differently impacted hydroxylation and methylation of anthocyanins.     

Canopy microclimate and berry composition: The effect of bunch exposure on the phenolic composition of Vitis vinifera L cv. Shiraz grape berries

Studies on the effect of light exposure on specific phenolic compounds of berries from Shiraz vines grown in a hot climate are reported. Berries that had developed on bunches receiving high levels of ambient light generally had the highest relative levels of quercetin-3-glucoside and a lower proportion of their malvidin anthocyanins as the coumarate derivative, compared to berries that had developed on bunches in shaded canopy conditions. The response of total anthocyanin levels to treatment conditions was variable and depended on the degree of bunch shading and the resultant berry temperature. It appears that a high degree of bunch exposure in hot climates is not conducive to optimal anthocyanin accumulation in berries. The interactive effects of light and temperature on berry phenolic content and concentration are discussed.     

Fruit ripening in Vitis vinifera L.: possible relation of veraison to turgor and berry softening

Background and Aims:  Vitis vinifera L. berries exhibit dynamic changes in water relations during development, but the possible connections between water relations, particularly cell turgor pressure ( P ), and ripening have received little attention, and the water relations have been studied by mostly indirect methods.
Methods and Results:  The cell pressure probe was utilized to examine directly the in situ P of cells in the mesocarp. Mesocarp cell P demonstrated a consistent pattern of a high value early in development, followed by a decrease to less than 1.0 bar that was maintained during ripening. Sugar accumulation did not increase significantly until P had declined to less than 1.0 bar. Fruit 'elasticity' was used to evaluate fruit firmness during development. Fruit elasticity changed dynamically and synchronously with P . When growth was prevented with plastic boxes, the decline in cell P was delayed over 14 days, and the onset of skin colour and sugar accumulation was similarly delayed.
Conclusions:  The results show that when the decrease in P was delayed, the onset of ripening was delayed, and, therefore, are consistent with a central role of P in the onset of ripening.
Significance of the Study:  This study showed that boxing preveraison berries similarly delayed P decrease and colour increase in Cabernet Sauvignon berries. Thus, this system may be useful to study the relationship between P and gene expression in developing berries.     

CIELAB coordinates in response to berry skin anthocyanins and their composition in Vitis

Abstract: Berry skin color OIV index, anthocyanin composition, and content of 78 grape cultivars were surveyed using a CIELAB system and high‐performance liquid chromatography (HPLC)‐mass spectrometry (MS) coupled with photodiode array detection. There were high correlations between L*, b*, and color, while a* was not a representative parameter. L* and b* values declined as berry skin color OIV became darker, and a* increased as berry skin color OIV became darker in pink and red grape cultivars only. The composition and content of anthocyanins varied widely among the cultivars. Total anthocyanins and types of anthocyanins were significantly correlated with color OIV parameters. Through multiple linear regression analysis, cyanidin derivatives had a positive effect on values of L* and b*. Delphinidin derivatives had positive effects on the value of a*. The CIELAB system gave good results for differentiation of grape berry skin color OIV.