Thesis (MScAgric)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The effect of shoot heterogeneity on vegetative and reproductive growth parameters, vine
physiology and grape composition was investigated in a ShirazlRichter 99 vineyard.
Comparisons between underdeveloped (typically shorter and less ripened at véraison) and
normally developed shoots in both shaded (non-manipulated) and well-exposed (manipulated)
canopies were made. Compared to underdeveloped shoots, normal shoots had a larger total leaf
area, due to the higher occurrence of secondary shoots as well as larger leaves on primary and
secondary shoots. Since the photosynthetic activity of the leaves from normal shoots was higher
than those from underdeveloped shoots, higher levels of carbohydrates were produced and
stored in the former. Starch was more evenly distributed over the length of the whole shoot in
normally developed shoots compared to underdeveloped shoots. Normally developed shoots
were longer and thicker in diameter than underdeveloped shoots. The larger clusters of the
normally developed shoots are evidence of their more favourable total leaf area per gram berry
mass. Berries from the normally developed shoots were smaller at five weeks after véraison than
those from underdeveloped shoots, displaying a higher skin to pulp ratio and therefore higher
anthocyanin and total phenolic extraction potential for winemaking. The smaller clusters and
fewer berries per cluster found for the underdeveloped shoots indicate an imbalance between
vegetative and reproductive growth initiated during the vegetative growth phase and continued
during the ripening period.
The peculiar absence of statistically significant differences in grape composition between
normally and underdeveloped shoots indicates that assimilates needed for berry ripening of the
latter originated in organs other than the leaves [e.g. from adjacent normal shoots and the rest of
the permanent structure of the vine (cordon, trunk, roots)]. The larger differences in berry size
that occurred between shoot types in the shaded compared to the well-exposed canopies may be
evidence for this. The photosynthetic activity of shoots was lower in shaded than in exposed
canopies. The total carbohydrate production of the normal shoots in shaded canopies seemed
insufficient to supply in the ripening needs of the shoot itself, their own clusters as well as the
ripening of stem tissue and clusters of the underdeveloped shoots in the canopy. This is
illustrated by the lower levels of starch that accumulated in the normal shoots from shaded
compared to that of exposed canopies. Vine shoot heterogeneity clearly leads to visible and
physiological imbalances that would impact negatively on grape and wine quality as well as
production costs and should therefore be avoided on any terroir. / AFRIKAANSE OPSOMMING: In hierdie studie is die effek van heterogene lootontwikkeling in die lower van 'n ShirazlRichter 99
wingerd ondersoek. Vergelykings is getref tussen normale en onderontwikkelde lote in
beskadude en blootgestelde lowers ten opsigte van hul vegetatiewe en reproduktiewe groeieienskappe,
fisiologiese aktiwiteit en druifsamestelling en -gehalte. 'n Groter totale
blaaroppervlak het by die normaalontwikkelde lote voorgekom as gevolg van die groter aantal
sekondêre lote en groter primêre en sekondêre blare. Aangesien die blare van die normaal
ontwikkelde lote fotosinteties meer aktief was as dié van onderontwikkelde lote, het die
eersgenoemde lote groter hoeveelhede koolhidrate geproduseer en gestoor. Styselopberging het
meer eweredig oor die lengte van die normale lote plaasgevind. Laasgenoemde lote was ook
heelwat langer en dikker in deursnee as die onderontwikkelde lote. Die gunstiger totale
blaaroppervlak per korrelmassa verhouding van die normale lote is duidelik weerspieêl in die
groter trosse, terwyl die kleiner korrels (en dus die groter dop:pulp verhouding) op 'n groter
potensiaal vir kleur- en fenolekstraksie tydens die wynbereidingsproses dui. Die kleiner trosse en
kleiner aantal korrels per tros wat by die onderontwikkelde lote gevind is, dui op 'n wanbalans
tussen die vegetatiewe en reproduktiewe groei van die loot wat tydens die vegetatiewe groeifase
van die wingerdstok geïnisieer is en tydens die rypwordingsperiode voortgesit is.
Die vreemde afwesigheid van enige statisties betekenisvolle verskille in druifsamestelling tussen
die normale en onderontwikkelde lote dui daarop dat die verbindings wat vir die rypmaking van
trosse op onderontwikkelde lote aangewend is, waarskynlik van ander wingerdorgane (bv.
naasliggende lote, kordonarms, stam, wortels) as die spesifieke loot se blare afkomstig was. Die
waarneming dat die korrelgroottes van normale en onderontwikkelde lote meer van mekaar
verskil het in die beskadude as blootgestelde lowers, kan moontlik as bewys hiervoor dien. Die
fotosintetiese aktiwiteit van beide loottipes was laer in die skaduryke lowers. Die koolhidrate wat
deur normaalontwikkelde lote in skadu-Iowers geproduseer is, was oênskynlik onvoldoende vir
die rypmaking van die loot self, die spesifieke loot se trosse, asook die trosse en lootweefsel van
naasliggende onderontwikkelde lote. Hierdie bewerings word gerugsteun deur die laer vlakke
van styselakkumulasie wat by die normale lote in beskadude lowers gevind is. Aangesien
heterogene lootontwikkeling en -groei duidelike sigbare en fisiologiese wanbalanse in die
wingerdstok tot gevolg het wat negatief op druifsamestelling, wyngehalte en produksiekoste
inwerk, behoort dit in kommersiêle wingerde vermy te word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50145 |
| Date | 12 1900 |
| Creators | Cloete, Hanle |
| Contributors | Archer, E., Hunter, J. J., Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 232 ill. : col. ill. |
| Rights | Stellenbosch University |
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