Berry Growth Research Articles

Pre-anthesis CPPU Treatment Modifies Quality and Susceptibility to Post-harvest Berry Cracking of Vitis vinifera cv. ‘Thompson Seedless’

Plant growth regulators (PGRs), especially gibberellic acid (GA), are often used in table grape (Vitis vinifera) production to increase berry size. However, overuse of this PGR (for example, more than 200 g·ha−1·season−1 of GA) may result in problems with berry condition at the post-harvest stage. A synthetic cytokinin, florchlorfenuron (CPPU), could be considered an alternative to GA. Thus, our objective was to study the effects of pre-anthesis CPPU treatment on berry quality and susceptibility to post-harvest cracking of table grapes. CPPU applied to ‘Thompson Seedless’ inflorescences 48 or 36 days prior to anthesis increased ovary size, number of cells in the ovary pericarp at bloom and berry size at harvest. It also increased the amount of soluble solids and decreased titratable acidity of the fruit, thus allowing an earlier harvest. Finally, if GA was applied during berry growth, CPPU at pre-anthesis improved berry potential tolerance to post-harvest cracking and spoilage. This work demonstrates that application of CPPU at the pre-anthesis stage modifies grape development, improving berry size and potential post-harvest fruit performance facilitating also an early harvest.

Discharge of surplus phloem water may be required for normal grape ripening.

At the onset of ripening, some fleshy fruits shift the dominant water import pathway from the xylem to the phloem, but the cause for the decline in xylem inflow remains obscure. This study found that xylem-mobile dye movement into grape berries decreased despite transient increases in berry growth and transpiration during early ripening, whereas outward dye movement continued unless the roots were pressurized. Modeling berry vascular flows using measurements of pedicel phloem sap sugar concentration, berry growth, solute accumulation, and transpiration showed that a fraction of phloem-derived water was used for berry growth and transpiration; the surplus was recirculated via the xylem. Changing phloem sap sugar concentration to a much higher published value led to model simulations predicting xylem inflow or backflow depending on the developmental stage and genotype. Mathematically preventing net xylem flow resulted in large variations in phloem sap sugar concentration in pedicels serving neighboring berries on the same fruit cluster. Moreover, restricting water discharge via the xylem and/or across the skin impaired berry solute accumulation and color change. Collectively, these results indicate that discharge of surplus phloem water via berry transpiration and/or xylem backflow may be necessary to facilitate normal grape ripening.

Double sigmoidal models describing the growth of coffee berries

ABSTRACT: This study aimed to verify if the growth pattern of coffee berries, considering fresh mass accumulation over time, is double sigmoid and to select the most suitable nonlinear model to describe such behavior. Data used consisted of fourteen longitudinal observations of average fresh mass of coffee berries obtained in an experiment with the cultivar Obatã IAC 1669-20. The fits provided by the Logistic and Gompertz models were compared in their single and double versions. Parameters were estimated using the least squares method using the Gauss-Newton algorithm implemented in the nls function of the R software. It can be concluded that the growth pattern of the coffee fruit, in fresh mass accumulation, is double sigmoid. The double Gompertz and double Logistic models were adequate to describe such a growth curve, with a superiority of the double Logistic model.

Application of sprinkler cooling within the bunch zone during ripening of Cabernet Sauvignon berries to reduce the impact of high temperature

Background and Aim High temperature stress has been linked to detrimental effects on berry composition during ripening. This study aimed to assess the impact of an evaporative cooling system located inside the grapevine canopy to mitigate extreme temperature effects on grape berry composition during ripening. Methods and Results During three seasons (2012 to 2015), an intra-canopy sprinkler system at the bunch zone was tested on Cabernet Sauvignon vines. The system cyclically sprayed (20 s/10 min) for an air temperature above 38°C, cooling the air inside the canopy by 3 to 5°C. This is in agreement with an air cooling simulation model. The relative humidity in the canopy also increased in the sprinkler-cooled canopy. No differences were detected in TSS, although sugar per berry was significantly higher in treated vines because of increased berry mass. There was a tendency for higher anthocyanins and phenolic substances per berry in cooled berries measured from two seasons and higher concentration of anthocyanins in wine from cooled fruit measured only in one season. We define indices that can be used to assess the efficiency of sprinkler cooling and to demonstrate the high efficiency of intra-canopy sprinklers compared to other systems. Conclusion Despite cooling operating only over a small duration of the ripening period, the increased berry mass indicates that high temperature, even for a short period, has a profound effect on berry growth. Other berry compositional properties and wine, however, were not impacted. Significance of Study This research demonstrates the potential of an efficient intra-canopy sprinkler system to reduce heat stress during ripening.

Crecimiento, acumulación de biomasa seca y nutrientes en los frutos de café (Coffea arabica L.) variedad Pacas, Masatepe, Nicaragua

De abril a diciembre de 2012, en un ensayo ya establecido se realizó un estudio en el cultivo de café variedad pacas, con el objetivo de determinar las curvas de crecimiento, acumulación de biomasa seca y acumulación de nutrientes (N, P, K, Ca y Mg) en los frutos de café uva. El ensayo fue establecido en el año 2000 en el Jardín Botánico hoy conocido como Centro Nacional de Educación y Cooperativismo (CENECCOP), Masatepe, Nicaragua. Se seleccionaron cuatro parcelas grandes con combinación de árboles de sombra maderables y de servicio y una parcela a pleno sol. Los tratamientos en estudio fueron a) Inga laurina y Simaruba glauca, b) Samanea saman y Tabebuia rosea, c) Samanea saman e Inga laurina, d) Tabebuia rosea y Simaruba glauca y e) una parcela a pleno sol. Las parcelas fueron distribuidas en un diseño de bloques completos al Azar (BCA). Las variables evaluadas en los frutos de café fueron diámetro polar, diámetro ecuatorial y peso seco. Los frutos se secaron en el horno a 70 °C y posteriormente se utilizó un molino Foss Tecator Cyclotec para obtener una muestra fina. De la muestra molida de los frutos, en el laboratorio de suelo y agua de la UNA se determinaron las concentraciones de N, P, K, Ca y Mg. Los datos fueron colectados cada 30 días. Para el análisis estadístico se utilizó SAS 9.1. Las curvas de crecimiento del fruto y la acumulación de peso seco se ajustaron a regresiones no lineales simples y dobles exponenciales. Se realizó una correlación entre el diámetro polar y diámetro ecuatorial de los frutos dando un coeficiente de determinación r de 98% (Pr>F= 0.0001). Para el ajuste de la curva de aumento de peso seco se utilizó el modelo Probit normal. El mayor crecimiento de los frutos se dio durante los primeros 90 días y la mayor acumulación de nutrientes se dio entre los 90 y 210 días. La combinación de árboles leguminosos presentó el diámetro polar y ecuatorial más alto. También la acumulación de biomasa seca fue mayor en el tratamiento con sombra de leguminosas.Revista Científica Vol. 15. Nº 24, p. 6-12 mayo 2015

Anthocyanin biosynthesis during berry development in corvina grape

For the production of a highly qualitative wine, such as “Amarone”, variations in the grape (Corvina) pigment composition are not negligible. The aim of this work was the investigation of the Corvina anthocyanin profile changes during ripening. The experiment took place in 2015, in two vineyards located in Valpolicella (Italy) with different training systems (Guyot and pergola). Micro-meteorological survey, carpological characterization, chemical analysis and transcriptional studies were carried out to clarify the anthocyanin biosynthesis regulation. Air and grape temperatures and global solar radiation inside the canopy were measured during the season. Grape samples were collected at seven stages of berry development from bunches hang until harvest. Berry growth was followed by volume increase. At the beginning of the lag phase, anthocyanin quantification and characterization by spectroscopy and HPLC were carried out. The expression level of structural and regulatory genes of anthocyanin pathway was studied via real-time RT-PCR. At color appearance, the di-substituted anthocyanins prevailed. During ripening, it was observed a progressive increase of tri-substituted, methoxylated, and acylated pigments. A clear correlation among expression of anthocyanin biosynthetic gene, UDPglucose:flavonoid 3-O-glucosyltransferase (UFGT), transcription factors, MybA1 and MybA2, and total anthocyanin content during berry development has been identified. Chalcone synthase, flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) genes of the flavonoid pathway showed high correlation as well. The proportion changes between tri- and di-substituted anthocyanins were associated with an increasing ratio of F3′5′H/F3′H gene transcription during ripening. The AOMT genes were expressed with a maximum at the onset of ripening, coherently with the rapid increase of methoxylated anthocyanin proportion in this stage.

Uneven ripening in ‘Bangalore blue’ grape (Vitis vinifera × Vitis labrusca) berries in India is linked to seed viability

ABSTRACTUneven ripening (UR) is a physiological disorder of unknown origin in ‘Bangalore blue’ grape (Vitis vinifera × Vitis labrusca) leading to wine of inferior quality. A preliminary study found wide variations in total dehydrogenase activity (TDH) of seeds from unevenly ripe berries. In our experiments, gibberellin (GA3) applied to young grapes increased seed TDH activity and reduced the incidence of uneven ripening to 2% compared with 35% in the control. In contrast, paclobutrazol (PBZ) decreased TDH activity and increased the incidence of the disorder to 58%. GA3-treated berries had higher concentrations of sucrose and TDH activity in seed representing mature seeds with high viability. In contrast, PBZ-treated and control berries had higher concentrations of glucose and lower TDH activity, indicating immature seeds with low viability. These results suggested that competition among developing berries can lead to differences in seed gibberellin content, seed viability and the rate of berry growth resulting in green, purple, and black berries at harvest. The study established the role of seed viability in uneven ripening and demonstrated that the incidence of the disorder is reduced by the application of GA3 to immature berries.

Fruit growth and proximate composition of deshi (Diospyros peregrina) and bilati gab (D. discolor)

Fruit (berry) growth, maturity and nutritional composition of deshi (Diospyros peregrina Gurke) and bilati Gab (D. discolor Gurke) were investigated at the Botanical Garden of Bangladesh Agricultural University, Mymensingh (24o26' and 24054' N and 90015' and 90030' E) between April and August, 2011. Flowers were tagged at first opening (days after flowering, DAF) and fruit growth was investigated up to maturity. Fruit size (length and diameter), individual fruit weight, AGR and proximate composition of matured fruits were investigated. Morphological and growth parameters were recorded at 7-days interval up to 63 DAF in deshi and 85 DAF in bilati gab. All the morphological characters of fruits were gradually increased with increasing DAF and followed sigmoid pattern. The length and diameter of the berry became 5.80 and 4.61 cm, respectively at 63 DAF in deshi gab, and 9.13 and 7.62 cm, respectively at 85 DAF in bilati gab. The fresh and dry weights of berries were also maximum at 63 DAF in deshi and at 85 DAF in bilati gab. The maximum dry weight of seed i.e. PM in deshi gab attained at 56 DAF and that of bilati gab at 83 DAF. The proximate composition of matured berries of deshi and bilati gab at PM showed little variation between the species and hence, average crude protein, crude fat, ash and total carbohydrate was 5.35, 1.08, 3.74 and 67.47%, respectively. It might be concluded that harvest maturity attained around two months after flowering in deshi gab with yellowish green colour on fruit coat and three months from flowering in bilati gab when fruits turn into deep red colour with average fruit fresh weight of 60 g and 220 g, respectively.J. Bangladesh Agril. Univ. 12(2): 261-266, December 2014

Seedless Berry Growth and Bioactive Compounds of cv. ‘Recel Uzümü’ (V. Vinifera L.) as Affected by Application Doses and Times of Pre-Harvest Thidiazuron

The purpose of this research was to appreciate the impact of the synthetic cytokinin, well known as thidiazuron (TDZ) on seedless berry quality of cv. ‘Recel Uzumu’. Three concentration levels including 0, 5 and 10 mg/L were applied on the grapevines during different phenological stages of grapevine such as Time 1: beginning of berry stetting, Time 2: berries pepper corn size and Time 3: berries pea size. While TDZ application times had no impacts on cultivar characteristics, it was determined that the application doses of TDZ had major impacts on yield and quality components of cv. ‘Recel Uzumu’. Consequently, ascending TDZ doses increased berry and cluster size and led to decreases in total soluble solids content, total phenolic compound content, total anthocyanin content and p-value of grape juice regardless of TDZ application time. The most effective TDZ dose was 10 ppm for improving berry and cluster size in cv. ‘Recel Uzumu’.

Canopy management effects on ‘Syrah’ grapevines under tropical semi-arid conditions

The aim of this study was to evaluate the effects of shoot topping and leaf removal practices on vegetative vigor, yield and physicochemical characteristics of the 'Syrah' grape in the semi-arid tropical climate conditions of the Sao Francisco River Valley in the northeast of Brazil. The experiment was conducted over five growing cycles from 2010 to 2012 in a 'Syrah' commercial vineyard in the municipality of Casa Nova, Bahia, Brazil. Treatments consisted of leaf removal once or twice during fruit set or at the beginning of bunch closure, and one or two shoot toppings of the berry when pea-sized or 10 days after berry growth had commenced. Leaf removal and shoot topping did not affect yield, plant vigor components nor the main attributes of fruit quality. In contrast, there was a seasonal effect with higher yield and better balance between production and vigor in grapes produced in the first half of 2012. The Syrah grape quality was favored in cycles in the first half of the year when its ripening phase coincided with the period of mild temperatures.

Impact of grapevine exposure to smoke on vine physiology and the composition and sensory properties of wine

Smoke was applied to seven different grapevine cultivars (Chardonnay, Sauvignon Blanc, Pinot Gris, Pinot Noir, Shiraz, Cabernet Sauvignon and Merlot) for 1 h at approximately 7 days post-veraison. A range of viticultural measurements were subsequently performed to evaluate any effects on crop yield, vegetative growth and vine physiology. Few significant differences in berry growth or maturation (as sugar accumulation), yield or vine growth were observed between control and smoke-affected grapevines; but the photosynthetic capacity of some varieties, Merlot and Cabernet Sauvignon in particular, decreased significantly following smoke exposure. The extent of smoke taint in the resultant wines was then determined by quantification of volatile phenols and guaiacol glycoconjugates, and by descriptive sensory analysis. Elevated concentrations of volatile phenols and guaiacol glycoconjugates were observed in wines made from smoke-affected grapes; with smoke-affected Pinot Gris and Cabernet Sauvignon wines found to exhibit the most intense smoke-related sensory attributes. The physiological, compositional and sensory consequences of grapevine exposure to smoke were found to vary amongst cultivars, suggesting some grape varieties might be more susceptible to the effects of smoke exposure than others. Further research into the impact of smoke exposure by different cultivars might inform varietal selection in smoke-prone wine regions, in order to mitigate the risk of smoke exposure.

Establishment of the soil water potential threshold to trigger irrigation of Kyoho grapevines based on berry expansion, photosynthetic rate and photosynthetic product allocation

Background and Aims Irrigation is an important management practice in viticulture. Irrigation scheduling established by previous researchers was based mainly on the irrigation level for optimal berry composition and size at harvest. Because eventual berry size and composition depend on the accumulation of daily growth, a more precise study must be implemented to establish the soil water potential (ψsoil) threshold to trigger irrigation at different development stages of the berry. Methods and Results Photogrammetry, 13C isotope labelling and other techniques were applied to study the relationship between ψsoil and real-time change of berry expansion, net photosynthetic rate, and the distribution of photosynthetic products in 3-year-old Kyoho grapevines. The diurnal variation of berry size presented a regular pattern, shrinking in daytime and expanding at night. Analysis of a time series model revealed a close correlation between berry growth and ψsoil. With the decline in ψsoil, berry growth presented four phases of change: high speed growth phase, rapid growth phase, slow growth phase and shrinking phase. Conclusions The optimal ψsoil threshold to trigger irrigation at different berry developmental periods was established: −10 kPa after berry setting (berry diameter 20 mm). Significance of the Study The established ψsoil threshold in this study has significant value for the implementation of precision irrigation, which favours normal berry expansion and composition while saving water.

Manipulation of ripening via antitranspirants in cv. Barbera (Vitis vinifera L.)

Background and Aims Accelerated berry sugar accumulation resulting in wines of excessive alcohol concentration, sub-optimal colour and atypical flavour has become increasingly frequent in warm growing districts, a trend induced by factors that include global warming. The application of a film-forming antitranspirant may be an effective way of reducing early sugar accumulation without affecting colour development. Methods and Results An antitranspirant emulsion was applied in 2013 and in 2014 on field-grown cv. Barbera vines at pre-flowering (PF), pre-veraison (PV) and at both dates (PFPV), and compared with the unsprayed control. Post-treatment assessment included seasonal gas exchange, yield components, growth of berry organs and must composition. Although all treatments were effective in reducing gas exchange by as much as 46% compared with that of the control, berry growth was not affected. Conversely, whereas PF slightly modified the ripening pattern, PV and PFPV markedly delayed accumulation of sugar in the warm 2013 season (−2.4 and −3.7° Brix, respectively, vs control) without detriment to colour development because the onset of anthocyanins occurred at lower TSS. In the cooler, wet 2014 season, PV and PFPV were again able to delay sugar accumulation without affecting colour development. Conclusions Pre-veraison application of the antitranspirant alone or in combination with a PF spray proved effective in slowing sugar accumulation while avoiding concurrent delay of colour development. Significance of the Study The use of antitranspirants is a practical and flexible way of regulating the sugar : anthocyanin ratio under conditions of excessively fast ripening.

GC–MS metabolic profiling of Cabernet Sauvignon and Merlot cultivars during grapevine berry development and network analysis reveals a stage- and cultivar-dependent connectivity of primary metabolites

Information about the total chemical composition of primary metabolites during grape berry development is scarce, as are comparative studies trying to understand to what extent metabolite modifications differ between cultivars during ripening. Thus, correlating the metabolic profiles with the changes occurring in berry development and ripening processes is essential to progress in their comprehension as well in the development of new approaches to improve fruit attributes. Here, the developmental metabolic profiling analysis across six stages from flowering to fully mature berries of two cultivars, Cabernet Sauvignon and Merlot, is reported at metabolite level. Based on a gas chromatography–mass spectrometry untargeted approach, 115 metabolites were identified and relative quantified in both cultivars. Sugars and amino acids levels show an opposite behaviour in both cultivars undergoing a highly coordinated shift of metabolite associated to primary metabolism during the stages involved in growth, development and ripening of berries. The changes are characteristic for each stage, the most pronounced ones occuring at fruit setting and pre-Veraison. They are associated to a reduction of the levels of metabolites present in the earlier corresponding stage, revealing a required catabolic activity of primary metabolites for grape berry developmental process. Network analysis revealed that the network connectivity of primary metabolites is stage- and cultivar-dependent, suggesting differences in metabolism regulation between both cultivars as the maturity process progresses. Furthermore, network analysis may represent an appropriate method to display the association between primary metabolites during berry developmental processes among different grapevine cultivars and for identifying potential biologically relevant metabolites.Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-015-0927-z) contains supplementary material, which is available to authorized users.

Establishing the temperature dependency of vegetative and reproductive growth processes and their threshold temperatures of vineyard-grown Vitis vinifera cv. Semillon vines across the growing season.

A hydrocooling system provided canopy temperature control of Vitis vinifera L. cv. Semillon vines at set points of 30, 35 and 40°C. The impacts on vegetative and reproductive growth over the growing season were assessed. Dynamics and rates of leaf expansion, bunch biomass and sugar accumulation were strongly affected by canopy temperatures - being highest at 30°C and lowest at 40°C. Leaf and stem biomass accumulation at 40°C was detrimentally affected but was otherwise little affected by temperature. Leaf expansion was earliest, leaf sizes greatest and rates of expansion all optimal at 30°C and all were strongly temperature dependent. Bunch biomass accumulation was earliest at 35°C but amount of biomass in bunches and rates were both highly temperature dependent and optimal at 30°C. Rates of sugar accumulation and total amounts accumulated at harvest were both highly temperature-dependent processes: fastest and greatest at 30°C. Many of the temperature-dependent processes decreased in rates and amounts linearly between 30 and 40°C. Despite the effects of temperature on bunch and berry growth, there were no treatment effects on the yield per vine. The study confirms that the threshold temperature for most processes was 35°C, where some depreciation in dry matter and sugar accumulation occurred, whereas 40°C was detrimental to all growth processes.

Differential effects of shading fruit or foliage on the development and composition of grape berries

Grape vines ( Vitis vinifera L. cv. Cabernet Sauvignon) were selectively shaded with polypropylene doth to separate the effects of shading fruit from the effects of shading foliage on berry development and on the accumulation patterns of sugar, anthocyanins, malate, tartrate and potassium in the fruit. Shading the foliage led to both a delay and a decrease in berry growth. Leaf shading also affected the timing and the magnitude of sugar accumulation. Total sugar per berry was reduced more by shading than was sugar concentration because of the simultaneous effect of shading on fruit size. The rate of pre-veraison malate accumulation, the maximum malate content at veraison, and the rate of post-veraison malate loss in the berries were all highest in the fully sun-exposed vines and were progressively lower with increasing foliage shade. Tartaric acid was significantly lower in fruit from heavily shaded vines than in fruit from the more exposed treatments. Leaf shading was also significantly correlated with an increase in potassium concentration in the fruit. At harvest, juice pH was more dosely correlated with the concentrations of tartaric acid and potassium in the berries than with malate content. Grapes from heavily shaded vines had the highest pH. Anthocyanin accumulation in the fruit was affected more by duster shading than by leaf shading. Shaded fruit had significantly less anthocyanin than sun exposed fruit. These results indicate that in addition to a general delay in ripening there were also specific effects of shading on individual components of berry composition, and that the specific effects were different for leaf and duster shading.

Characterization of major ripening events during softening in grape: turgor, sugar accumulation, abscisic acid metabolism, colour development, and their relationship with growth.

Along with sugar accumulation and colour development, softening is an important physiological change during the onset of ripening in fruits. In this work, we investigated the relationships among major events during softening in grape (Vitis vinifera L.) by quantifying elasticity in individual berries. In addition, we delayed softening and inhibited sugar accumulation using a mechanical growth-preventing treatment in order to identify processes that are sugar and/or growth dependent. Ripening processes commenced on various days after anthesis, but always at similarly low elasticity and turgor. Much of the softening occurred in the absence of other changes in berry physiology investigated here. Several genes encoding key cell wall-modifying enzymes were not up-regulated until softening was largely completed, suggesting softening may result primarily from decreases in turgor. Similarly, there was no decrease in solute potential, increase in sugar concentration, or colour development until elasticity and turgor were near minimum values, and these processes were inhibited when berry growth was prevented. Increases in abscisic acid occurred early during softening and in the absence of significant expression of the V. vinifera 9-cis-epoxycarotenoid dioxygenases. However, these increases were coincident with decreases in the abscisic acid catabolite diphasic acid, indicating that initial increases in abscisic acid may result from decreases in catabolism and/or exogenous import. These data suggest that softening, decreases in turgor, and increases in abscisic acid represent some of the earliest events during the onset of ripening. Later, physical growth, further increases in abscisic acid, and the accumulation of sugar are integral for colour development.

ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non-structural carbohydrates in leaves, enhancement of phloem area and expression of sugar transporters.

Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.

Impact of light exposure on fruit composition of white 'Riesling' grape berries (Vitis vinifera L.)

Microclimate and irradiation have long been known to influence winegrape (Vitis vinifera) quality. However, microclimate influence on white grape quality has remained understudied, as most research efforts have focused on red varieties and their anthocyanin content. In this study, we investigated microclimatic effects on the phenolic and amino acid composition of white 'Riesling' grapes using bunch shading and leaf removal to manipulate grape microclimate. Both treatments were applied directly after fruit set (modified E‑L 27; (Coombe 1995)) as well as at the onset of veraison (E-L 34), and compared to a non-manipulated control. The concentration of malic acid, amino acids and total nitrogen were decreased by illumination during the berry growth, while content and concentration of phenolics were significantly increased by illumination. Strong negative correlations were observed between accumulation of amino acids and flavonols. Although accumulation of flavonols occurred throughout berry development, the most important phase of accumulation was post-veraison.

The effects of pre- and post-veraison water stress on growth and physiology of potted Pinot Noir grapevines at varying crop levels

The interactions of water stress timing and crop level on growth, gas exchange, water relations and ripening of potted Pinot Noir grapevines were examined. Pre-veraison water stress induced a greater reduction of shoot and berry growth and a more rapid limitation of net photosynthesis (Pn) and stomatal conductance (g(s)) as compared to post-veraison stress. At the end of stress, when mid-day and pre-dawn leaf water potential were below -1.1 and -0.6 MPa, the reduction in Pn of stressed vines was more marked in the 2- and 4-cluster plants versus 1-cluster plant. Crop level had almost no significant effects on gas-exchange, growth and ripening and but few interactions with timing of water stress. These responses seem to reflect the high leaf area-to-fruit ratios at each crop level which probably buffered the effects of reduced leaf function induced by water stress.