Department of Viticulture and Oenology

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Browsing Department of Viticulture and Oenology by Author "Archer, E."

Now showing 1 - 9 of 9
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    Effect of growth arrestment disease on the anatomy and ultrastructure of vitis vinifera L. var. sultana
    (South African Society for Enology and Viticulture, 1981) De la Harpe, A. C.; Archer, E.
    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.
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    The effect of plant spacing on the water status of soil and grapevines
    (South African Society for Enology and Viticulture, 1989) Archer, E.; Strauss, H. C.
    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.
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    Effect of shading on the performance of vitis vinifera L. cv. cabernet sauvignon
    (South African Society for Enology and Viticulture, 1989) Archer, E.; Strauss, H. C.
    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.
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    The effect of trellis systems on the performance of vitis vinifera L. cvs. sultanina and chenel in the Lower Orange River Region
    (South African Society for Enology and Viticulture, 1990) Swanepoel, J. J.; Hunter, J. J.; Archer, E.
    The effect of six trellis systems on the reproductive and vegetative performance of Sultanina and Chene), grown in the lower Orange River region of South Africa, was investigated. Larger trellis systems significantly increased the yield of both cultivars, and the photosynthetic activities of the leaves at veraison as well as the canopy light environment tended to be higher for these systems. The higher yields recorded for Sultanina were attributed to improved budding percentages, which were caused by improved light environments at the basal 'buds. The improved yield obtained for Chene! however, was due to higher bunch masses, which were most likely caused by the higher photosynthetic activities of the leaves.
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    The effect of vine spacing on some physiological aspects of vitis vinifera L. (cv. pinot noir)
    (South African Society for Enology and Viticulture, 1990) Archer, E.; Strauss, H. C.
    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.
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    The effect of vine spacing on the vegetative and reproductive performance of vitis vinifera L. ( cv. Pinot noir)
    (South African Society for Enology and Viticulture, 1991) Archer, E.; Strauss, H. C.
    Data concerning growth, yield, grape composition and wine quality are presented for five years. Closer spacing reduced cane mass and yield per vine but increased them per hectare. Less dense canopies as well as a larger leaf area: fruit mass ratio with more closely spaced vines au~mented grafe and wine quality. Given the specific circumstances of this trial, a vine spacing resulting in between 1,0 m and 2,0 m soil surface per vine proved to be optimum for Pinot noir.
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    Shoot heterogeneity effects on Shiraz/Richter 99 grapevines. II, Physiological activity
    (SASEV, 2008) Cloete, H.; Archer, E.; Novello, V.; Hunter, J. J.
    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 véraison, 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 véraison, 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 véraison, 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 véraison.
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    Shoot heterogeneity effects on Shiraz/Richter 99 grapevines. III, Leaf chlorophyll content
    (SASEV, 2008-03) Cloete, H.; Archer, E.; Novello, V.; Hunter, J. J.
    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 véraison. 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.
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    Young grapevine response and root colonisation following inoculation with arbuscular mycorrhizal fungi
    (South African Society for Enology and Viticulture, 2004) Meyer, A. H.; Valentine, A. J.; Botha, A.; Archer, E.; Louw, P. J. E.
    The host plant response following inoculation with commercially available arbuscular mycorrhizal (AM) fungi was determined in young grapevines under field conditions which would prevail on a typical farm. Measurements regarding growth improvement, nutrition and water relations were made in a field trial carried out on a commercial farm in the Stellenbosch region. Merlot noir grafted onto 101-14 Mgt and 110 Richter (110 R) in a Westleigh soil form and 99 Richter (99 R) in a Fernwood soil form was planted in December 1998. Vine roots were inoculated during planting with Biocult, Vaminoc and Glomus sp. 1054. Inoculation generally had little effect on xylem sap and leaf nutrient concentrations, water relations or growth responses. This was mainly ascribed to indigenous AM fungi, which seemed to have masked the effects of inoculation. A high soil P concentration was also implicated as a possible contributing factor to the general lack of grapevine response to AM inoculation.