E. Archer

Effect of shading on the performance of vitis vinifera L. cv. cabernet sauvignon

The effect of shading on the performance of Cabernet Sauvignon was studied. Significant different levels of canopy density were created using the growth of neighbouring vines, thus ensuring no artificial change in natural light composition. Light penetration in these canopies differed significantly between treatments. Berry mass, bunch mass and yield as well as skin colour were decreased with increasing levels of shading, while pH, K-concentration and TT A were increased. Tartaric acid decreased while malic acid increased with an increase in shading. Wine quality was negatively affected.

Effect of Plant Density on Root Distribution of Three-Year-Old Grafted 99 Richter Grapevines

The effect of plant density on root distribution of a three-year-old vineyard (Pinot noir /99 Richter) planted on a Glenrosa soil under dryland conditions, was investigated. Although narrower plantings induced smaller root systems per vine, root density was increased. Three years after planting the roots of more closely spaced vines utilised soil more intensively than those of more widely spaced vines. More closely spaced vines have an earlier vegetative period than more widely spaced vines. The ratio of primary, secondary and tertiary roots is not affected by plant density.

The effect of plant spacing on the water status of soil and grapevines

The effect of plant spacing on soil water content and plant water status is described. The higher root densities of narrower plantings resulted in a more rapid depletion of soil water content. This resulted in a more negative leaf water potential which, in turn, resulted in earlier stomatal closure, affecting transpiration rate negatively. Consequently grapes from narrower spaced vines ripened under higher water stress conditions than those from wider spaced vines.

The effect of alternative pruning methods on the viticultural and oenological performance of some wine grape varieties.

Three different trials, at three different localities, each with different growing conditions, were conducted with nine different wine grape varieties. Four different pruning methods, hand, mechanical, minimal and no pruning were tested. Growth responses, grape composition and morphology, wine quality as well as labour inputs were evaluated. Huge labour savings were obtained with the alternative pruning methods compared to hand pruning. A reduction in vigour and increase in yield were evident in each variety. Wine quality was not decreased and in some cases even a quality increase was evident. Varieties differ in their adaptability to alternative pruning methods with Cabernet Sauvignon, Pinotage and Chardonnay performing well and Sauvignon blanc and Merlot poorly. Chenin blanc, Shiraz, Colombar and Ruby Cabernet showed acceptable performance. Alternative pruning methods proved to be viable, especially for the production of medium and low priced wines.

The effect of vine spacing on some physiological aspects of vitis vinifera L. (cv. pinot noir)

The effect of vine spacing on leaf temperature, radiant energy, some canopy characteristics, leaf-water potential, stomata! conductance, the rate of transpiration and the rate of photosynthesis was measured and discussed. With more closely spaced vines, canopies were less dense than with more widely spaced vines mainly because of less vigorous shoot growth. The consequent better sunlight penetration favoured the physiology of more closely spaced vines early in the season. During the latter part of the season the situation was reversed and the physiology of more widely spaced vines was favoured mainly because of better water supply.

Effect of Bud Load and Rootstock Cultivar on the Performance of V. vinifera L. cv. Red Muscadel (Muscat noir)

The effect of four different bud loads and six rootstock cultivars on the performance of V. vinifera L. cv. Red Muscadel (Muscat noir) was investigated. Parameters such as yield, cane, cluster and berry mass, budding percentage, bud fertility, leaf surface area, grape composition and wine quality were measured in an effort to establish the best root-stock and bud load for this cultivar. Both bud load and rootstock cultivar had significant effects on all parameters measured. The effect of bud loads depended on the rootstock cultivar used. Considering all parameters, the rootstock cultivars 110 Richter and Ramsey showed the best performance.

The effect of vine spacing on the vegetative and reproductive performance of vitis vinif era L. ( cv. Pinot noir)

CITATION: Archer, E. & Strauss, H. C. 1991. The effect of vine spacing on the vegetative and reproductive performance of vitis vinif era L. ( cv. Pinot noir). South African Journal of Enology & Viticulture, 12(2):70-76, doi:10.21548/12-2-2211.

Effect of Growth Arrestment Disease on the Anatomy and Ultrastructure of Vitis vinifera L. var. sultana

The anatomical and ultrastructural changes caused by the so called Growth Arrestment Disease (G.A.D.) in Vitis vinifera L. var. sultana were investigated by means of scanning and transmitted electron microscopy as well as light microscopy. Important morphological symptoms are described. Anatomical abnormalities were found, especially in the leaves and Hower clusters of the affected vines. Heat and moisture stress may induce abnormal physiological changes, and this may give rise to G.A.D.-symptoms.

Shoot Heterogeneity Effects on Shiraz/Richter 99 Grapevines. II. Physiological Activity

In this study, the physiology of normally developed and underdeveloped shoots is compared in an attempt to quantify the effect of shoot heterogeneity in a Shiraz/Richter 99 vineyard, located in the Stellenbosch area of the Western Cape, South Africa. Comparisons are made between normally developed and underdeveloped shoots from shaded and well-exposed canopies. In the first five weeks after veraison, photosynthetic and transpiration rates, stomatal conductance and water-use efficiency (WUE) decreased as berry ripening progressed, while the internal CO2 levels of the leaves increased. Since differences in activity between individual leaves from normally developed and underdeveloped shoots only became apparent in the third week after veraison, it seemed as if the leaf area per shoot played a more important role than the photosynthetic output per unit leaf area in determining photosynthetate supply to the rest of the vine up to this stage. From the third week after veraison, higher levels of photosynthetates were produced by normally developed shoots than by underdeveloped shoots, due to the larger effective leaf area per shoot as well as the higher photosynthetic activity per unit leaf area. This points to premature senescence of the leaves on underdeveloped shoots. The quantity and quality of the yield from normally developed shoots are expected to benefit from the higher physiological output of the leaves. The enhancing effect on leaf functioning induced by canopy exposure became apparent from the third week after veraison.

Shoot Heterogeneity Effects on Shiraz/Richter 99 Grapevines. III.Leaf Chlorophyll Content

In this study, the leaf chlorophyll content of normally developed and underdeveloped shoots was compared in an attempt to quantify the effect of shoot heterogeneity in a Shiraz/Richter 99 vineyard, located in the Stellenbosch area of the Western Cape, South Africa. Comparisons are also made between normally developed and underdeveloped shoots from shaded and well-exposed canopies. No positive correlation was found between the photosynthetic activity and the chlorophyll concentration of the leaves at five weeks after veraison. Equal amounts of chlorophyll per cm2 and a non-significant difference in the assimilation rate were calculated for the leaves of normally developed and underdeveloped shoots. No significant differences were found between the shaded and well-exposed canopies. It therefore appears that it is the effective surface area per leaf or per shoot rather than the chlorophyll concentration or activity that may be responsible for any apparent difference in the photosynthetic output of the leaves from normally developed and underdeveloped shoots in shaded or well-exposed canopies.