Browsing by Author "De la Harpe, A. C."
Now showing 1 - 5 of 5
Results Per Page
- ItemA comparative anatomical study of the grapevine shoot : I Epidermis(South African Society for Enology and Viticulture, 1984) Swanepoel, J. J.; De la Harpe, A. C.; Orffer, C. J.Material gathered from three positions on the shoot and cane during veraison and two weeks after harvest were investigated for taxonomic features concerning the epidermis. Stomata and lenticels were present in all the cultivars studied, but trichomes were frequently present only on 99 Richter. Based on epidermal characteristics a dendogram giving the percentage similarity between cultivars, was constructed, and from this was concluded that concerning taxonomic features on Vitis vinifera L. cultivars tend to have a more than 90% similarity irrespective of the position on the shoot.
- ItemA comparative anatomical study of the grapevine, shoot and cane : II: periderm and secondary phloem(South African Society for Enology and Viticulture, 1984) Swanepoel, J. J.; De la Harpe, A. C.; Orffer, C. J.The taxonomic value of ten periderm and secondary phloem features of canes of different grapevine species was investigated. A scatter diagram showed that with few exceptions the American cultivars have a larger periderm with smaller secondary phloem, while the reverse was true for European cultivars. Crosses tend to cluster with one of their parents. It has been found that the largest intercultivar variation occurs at either the middle of the shoot length or the ventral sides of the basal part of the shoots.
- ItemThe determination of the homogeneity of a vitis vinifera L. cv. Cape riesling vineyard(South African Society for Enology and Viticulture, 1983) De la Harpe, A. C.; Visser, J. H.The value of Principal Component and Stepwise Discriminant analyses in selecting uniform plants for experimental purposes is discussed. Twenty seven variables were taken into account to establish the homogeniety (uniform plants) of 297 Vitis vinifera L. cv. Cape Riesling vines. A detailed study of the relationship and interrelationship of these variables resulted in 208 vines being selected as a uniform population. This selection provides the researcher with the possibility of using single vines as experimental units. However, it must be pointed out that Principal Component and Stepwise Discriminant analyses can only be used as an aid to normal statistical evaluation of experimental results and not as substitute for statistical experimental design.
- ItemEffect 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.
- ItemGrowth characteristics of vitis vinifera L. cv. Cape Riesling(South African Society for Enology and Viticulture, 1985) De la Harpe, A. C.; Visser, J. H.The effect of topping on the growth behaviour of Vitis vinifera L. cv. Cape Riesling vineyard was investigated. Shoot and leaf growth of both topped and untopped vines, can be described as sigmoidal. Shoot (cm) and leaf growth (cm') of the topped vines were significantly more than that of the untopped vines and are attributed to lateral shoot growth. Topping had no effect on bunch development. The development of skin, pulp and seed of both topped and untopped vines expressed as a percentage dry mass per berry can be described by a hyperbolic function for the skin, linear for the pulp and parabolic for the seed.