High-resolution atmospheric simulations (500 m) were used to assess viticultural areas under climatic stress in South Africa and New Zealand. The potential areas in which high daytime temperature stress was likely to affect grapevine photosynthesis and grape composition were identified. Results indicated different diurnal temperature variations within the two areas due to synoptic and local environmental factors, often associated with the influence of terrain.
Vitis vinifera L. cv. Pinot noir vines grafted onto rootstock 99 Richter and grown under six plant spacings (3 x 3 m; 3 x 1,5 m; 2 x 2 m; 2 x 1 m; 1 x 1 m; 1 x 0,5 m) were investigated in terms of canopy dimension and microclimate, soil conditions, canopy physiology, vegetative and reproductive growth characteristics, grape composition, wine quality and labour input. Vines were pruned to six buds/m2 soil surface and supplementary irrigated just after pea berry size and veraison stages. The number of leaf layers, light intensity and air flow generally decreased with closer spacing, whereas relative humidity increased. In contrast to the virtually stable, albeit lower, soil water content of closer-spaced vines, that of wider spacings noticeably decreased from veraison to ripeness. This may be ascribed to the almost continuous seasonal shading of the soil in the case of the narrower spacings, and the generally higher soil temperatures found for the wider spacings. Leaf and bunch water potentials of both wider- and closer-spaced vines decreased during the ripening period. Bunches were more sensitive to water stress. Leaf and bunch water potential coincided with soil water content. The lower photosynthetic activity of closely spaced vines was accompanied by increased transpirational water loss and is mainly ascribed to less favourable canopy microclimate. Despite the supplementary irrigation and slight differences in leaf water potential between spacings, wider-spaced vines apparently grew under less water stress during the ripening period. This was also evident from leaf xylem sap abscisic acid levels at ripeness. Shoot, leaf and berry growth rates apparently increased with narrower spacing, whereas total leaf area per vine decreased. Fresh berry mass of narrow-spaced vines was, however, slightly lower at ripeness. Budding of narrow spacings increased, whereas fertility and bunch mass were reduced, resulting in decreased yield per vine. Optimum berry set and yield per hectare occurred for medium-spaced vines (2 x 2 m, 2 x 1 m); this was also evident on a m2 soil surface basis. Leaf area per fresh mass of widely spaced vines ( 3 x 3 m, 3 x 1,5 m) was much lower than the generally required 10 - 12 cm2 and points to overcropping. Musts of widely spaced vines had less soluble solids and titratable acidity, whereas must pH increased progressively from widely to closely spaced vines. It would seem that widely spaced vines were overcropped due to low cultivar vigour and/or low yielding capacity of the soil, eventually affecting ripening. Grapes from medium-spaced vines had higher anthocyanin levels in the skin. Sensorially, wines made from closer spacings (2 x 2 m, 2 x 1 m, 1 x 1 m, 1 x 0,5 m) scored distincly higher than those from widely spaced vines. Although yield per hectare was higher, closely spaced vines (1 x 1 m, 1 x 0,5 m) needed significantly higher inputs for canopy management, harvesting and pruning. Considering land utilisation, vine performance, wine quality as well as labour input, medium-spaced vines (2 x 2 m; 2 x 1 m) performed optimally.
Seasonal variation in the water, sugar, organic acid and cation contents of developing grape berries (Vitis viniferaL. 'Grenache noir') under different levels of water supply (with and without deficit irrigation) and leaf:fruit ratios(18, 10 and five leaves per primary shoot, with one bunch per shoot), were investigated over two successive years inMediterranean conditions (South of France). Fourteen shoots per vine were left for each leaf:fruit ratio level, andeach vine was considered as having homogeneous primary shoots. The growth rate of the berries was increased withirrigation. Total dry matter content of the berry was not affected by leaf:fruit ratios, but the sugar loading decreasedduring berry development with a lower leaf:fruit ratio (five leaves per bunch). Treatments had little effect on organicacid contents and pH. Berry cation accumulation depended on vine water status and not on the total leaf area ofthe vine. Under irrigated conditions, calcium continued to accumulate in the berries after véraison. This confirms apartial functioning of the berry xylem during the post-véraison period. The seasonal variation in berry compositionwas less dependent on the leaf:fruit ratio than on the water status of the vine (mainly cations and sugar). This studyprovides evidence for the importance of plant water status effects on berry composition, irrespective of the leaf:fruitratio. Vine water status is a major regulating factor for source-sink relationships.
The distribution of photosynthetates, originating in leaves of different parts of the shoot of Vi tis vinifera L. cv Cabernet Sauvignon at berry set, pea size, veraison and ripeness stages, was investigated.Specific photosynthetic activity of the "CO,-treated leaves gradually decreased during the season.Photosynthetates were hoarded in the leaves at berry set, but were increasingly diverted to the bunches after that.The apical leaves displayed the Itlghes.t.photosynthesis.The leaves opposite and below the bunches accumulated very little photosynthetafes, especially from veraison to ripeness.Redistribution of photosynthetates among the basal, middle and apical leaves was generally very restricted at all stages.Multidirectional distribution from the site of application of 14 CO, occurred at berry set stage, while from pea size to ripeness photosynthetates were mainly translocated basipetally.Highest accumulation in the bunches occurred at veraison, while the basal leaves were primarily used to nourish the bunch.
To optimise the functioning of the grapevine in a specific environment and to improve grape and wine quality,suitability of climatic parameters for key grapevine physiological processes needs to be assessed at fine scales. Thispaper presents methodology using hourly weather data in three wine producing regions of South Africa (CoastalRegion – Stellenbosch district; Breede River Valley – Robertson district; Central Orange River Region – Upingtondistrict) during the pre- (November to December) and post-véraison (January to February) periods. Durationsinside and outside an optimum climatic range and of extreme climatic conditions were calculated over a 5-yearperiod (1999/2000 to 2003/2004) to quantify a climatic profile related to grapevine physiological requirements.Climatic requirements for optimum photosynthetic activity were defined as follows: temperature 25°C to 30°C,windspeed <4 m/s, relative humidity 60% to 70%. Unsuitable climatic periods for vine performance werecalculated as <20°C and >35°C, >4m/s, <50% and >80%. A coefficient was assigned to each climatic parameteraccording to an assumed importance level for physiological processes. Optimum temperature requirements forother physiological parameters were also investigated. A diurnal minimum/maximum temperature range of25°C to 30°C was used for sugar content and organic acid levels and a maximum night/day temperature rangeof 15°C/25°C for colour and flavour. Light intensity was accepted as being sufficient. Stations were classifiedaccording to their potential for meeting the climatic requirements of each physiological parameter. Markedvariation in climatic profiles and available time for optimal physiological functioning occurred between regions.All factors considered, the climatic profile of the Coastal Region (Stellenbosch district) seemed to best satisfy theclimatic requirements of the physiological parameters studied.
Selection of a suitable rootstock lays the foundation for meeting vineyard, grape and wine objectives. Tolerance to biotic and abiotic conditions is a determining factor. Despite the significance of the grapevine root system in vegetative and reproductive growth as well as grape and wine composition and quality, root behaviour under an array of very complex and integrated environmental impacting factors is largely unknown and research in this regard is surprisingly limited. In this paper, a compilation of some of the research done over many years on root system behaviour is presented. Various aspects of the interaction between the root system and the complex natural environment in which it grows as well as commonly known viticulture practices are discussed. Results obtained under controlled and field conditions are shown. Physical and chemical properties and pre-establishment preparation of the soil have defining effects on metabolic behaviour and spatial distribution (horizontally and vertically) of roots. Alleviation of soil impediments to root penetration provides the best possible basis for above-ground growth. The health status of plant material, genetic characteristics and grafting and nursery processes have a steering impact on the ability of the root system to perform within biotic and abiotic constraints of the soil environment to such an extent that expectations in terms of growth, yield and grape quality of the scion are met. Agronomic practices exert a further tailoring impact on root system performance and support to above-ground growth. The study of only above-ground factors is clearly not sufficient to explain vineyard behaviour. Intensified inter-disciplinary research efforts are required in our quest to understand scion-root system inter-relationships and to control scion behaviour in order to facilitate greater sustainability in grape and wine production.
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