Thesis (PhD) -- Stellenbosch University, 1991. / ENGLISH ABSTRACT: The effect of partial defoliation as canopy management practice on metabolism and grape
composition of the grapevine, Vitis vinifera L cv. Cabernet Sauvignon, was investigated. The
establishment of physiologically sound principles on how to overcome deleterious effects
associated with vigorous and dense-canopy vines is emphasized. Experimental vines were
defoliated 33 % and 66 % evenly over the whole canopy from different developmental stages in
a field study. Effects on canopy microclimate, photosynthesis, photosynthate translocation,
vegetative growth, reproductive growth, root development and distribution, as well as grape and
wine quality, were determined. A method for the simultaneous extraction of sugars and organic
acids from freeze-dried berries at different developmental stages is described.
Partial defoliation of vines improved canopy microclimate and photosynthetic efficiency of
remaining leaves. Normal translocation and distribution patterns of photosynthates were
apparently unaffected by partial defoliation. Translocation to and accumulation of photosynthetic
products in the leaves and bunches of partially defoliated vines were, however, improved.
Remaining leaves of partially defoliated vines were in comparison photosynthetically more active.
Apart from a less favourable canopy microclimate, it seemed that the sink capacity of
non-defoliated vines did not comply to the source capacity, inducing a reduced rate of
photosynthesis.
Normal sigmoidal growth patterns of vines were not affected by partial defoliation as applied in
this study. This is important for the longevity, healthiness and productivity of vines. Vegetative
growth was differentially affected by partial defoliation. No compensatory leaf growth occurred in
reaction to partial defoliation from different developmental stages. Main shoot length, however,
decreased slightly. Lateral shoot length and number of laterals increased, whereas cane mass
decreased when vines were partially defoliated, particularly the earlier and more severe the
defoliation. Reproductive growth in terms of yield was deleteriously affected by 33 % defoliation
prior to pea size and 66 % defoliation prior to veraison. Budding percentage was, however,
improved by 33 % and 66 % defoliation, whereas bud fertility was only improved by 33 %
defoliation. Partial defoliation changed the canopy microclimate to conditions favourable for pest
and disease control and higher grape quality.
Subterranean growth was favourably affected by partial defoliation, particularly when applied from
pea size stage. These changes included higher root densities, development of higher numbers
of fine and medium diameter roots and occurrence of higher total root numbers in all soil layers.
Generally, defoliations from pea size and veraison were more efficient regarding root
development than defoliations from just after bud break and from berry set. Partially defoliated vines reacted by forming new roots, creating a more efficient nutrient absorption capacity and
utilization of soil and available water and that, together with higher photosynthetic activities of
leaves, provided an efficient mechanism for continued high performance.
Grape quality was not affected markedly by partial defoliation. Total soluble solids in berries of
defoliated vines were comparable to and even significantly higher than those of non-defoliated
vines in some cases, in spite of much lower leaf areas. Generally, total titratable acidity of musts
was also slightly higher for partially defoliated vines. Glucose and fructose concentrations in
berries were unaffected by partial defoliation, while tartaric acid concentrations were slightly
increased and malic acid concentrations slightly decreased. Partial defoliation generally
increased the anthocyanin concentration of berry skins. These changes in grape composition
suggest higher grape quality and seemed to result from improved light conditions in the canopy
interior. Berry volume decreased with partial defoliation, which lowered the pulp:skin ratio.
These berries are more desirable for quality wines. Regardless of severity or the developmental
stage defoliation was commenced, wine cultivar character and overall wine quality were
significantly improved.
Partial defoliation changed the general metabolism of vines, mainly in terms of more favourable
source:sink ratios, resulting in more efficient photosynthesis, subterranean performance and
canopy microclimate. In general, the results suggest that an even removal of 33 % of leaves
opposite and below bunches during the period from flowering or berry set to pea size stage may
be applied. lt is further suggested that existing vigorous and dense-canopy vines be 33 %
defoliated evenly on the lower half of the shoot (canopy) from pea size or veraison. This
hypothesis proved effective in improving canopy microclimate, photosynthetic activity and yield,
while vegetative growth was inhibited. Grape and wine quality were higher.
On the whole, partial defoliation as applied in this study, is recommended as canopy
management practice in order to facilitate the abolishment of deleterious effects of excessive
vegetative growth and canopy density on balanced metabolic activity, fruit and wine quantity and
quality, as well as longevity and healthiness of grapevines. / AFRIKAANSE OPSOMMING: Die invloed van blaarverwydering as loofbestuurspraktyk op die metabolisme en
druifsamestelling van die wingerdstok, Vitis vinifera L cv. Cabernet Sauvignon, is ondersoek. Die
vestiging van fisiologies-betroubare beginsels oor hoe nadelige effekte geassosieerd met geil en
lower-verdigte wingerde uitgeskakel kan word, word beklemtoon. Proefstokke is in 'n
veldondersoek 33 % en 66 % eweredig oor die hele lower vanaf verskillende
ontwikkelingstadiums ontblaar. Effekte op lowermikroklimaat, fotosintese, translokasie van
fotosintetiese produkte, vegetatiewe groei, reproduktiewe groei, wortelontwikkeling en
verspreiding asook druif- en wynkwaliteit is bepaal. 'n Metode vir die gelyktydige ekstraksie van
suikers en organiese sure uit gevriesdroogde korrels op verskillende groeistadiums is ontwikkel.
Blaarverwydering het lowermikroklimaat verbeter en fotosintetiese doeltreffendheid van
oorblywende blare op die stok verhoog. Normale translokasie en verspreidingspatrone van
produkte van fotosintese is skynbaar nie deur blaarverwydering befiwloed nie. Translokasie na,
en akkumulering van fotosintetiese produkte in die blare en druiwe van gedeeltelik ontblaarde
stokke, is egter verbeter. Oorblywende blare van gedeeltelik ontblaarde stokke was fotosinteties
meer aktief. Afgesien van 'n ongunstiger lowermikroklimaat, het die sinkkapasiteit van
nie-ontblaarde stokke skynbaar ook nie teen die bronkapasiteit opgeweeg nie en is 'n verlaagde
tempo van fotosintese verkry.
Normale sigmofdale groeipatrone van die stokke is nie deur blaarverwydering befrivloed nie. Dit
is belangrik vir langlewendheid, gesondheid en produktiwiteit van stokke. Vegetatiewe groei is
differensieel deur blaarverwydering befrivloed. Geen kompenserende blaargroei het in reaksie
op blaarverwydering vanaf verskillende ontwikkelingstadiums voorgekom nie. Hooflootlengte
was egter effens korter. Sylootlengte en aantal sylote het toegeneem, terwyl lootmassa
afgeneem het met blaarverwydering, veral hoe vroeer en strawwer dit toegepas is.
Reproduktiewe groei in terme van opbrengs is nadelig befrivloed deur 33 % ontblaring voor
ertjiekorrelstadium en 66 % ontblaring voor die deurslaanstadium. Botpersentasie is egter deur
blaarverwydering verbeter, terwyl oogvrugbaarheid slegs deur 33 % ontblaring verbeter is.
Blaarverwydering het 'n gunstige lowermikroklimaat vir die beheer van plae en siektes en hoer
druifkwaliteit geskep.
Ondergrondse groei is gunstig deur blaarverwydering befrivloed, veral wanneer toegepas vanaf
ertjiekorrelstadium. Hierdie veranderinge het ingesluit hoer worteldigtheid, ontwikkeling van
groter hoeveelhede wortels met 'n fyn en medium deursnit en die voorkoms van 'n groter aantal
totale wortels in alle grondlae. Blaarverwydering vanaf ertjiekorrel- en deurslaanstadia was in die algemeen meer doeltreffend ten opsigte van wortelontwikkeling as blaarverwydering vanaf net
na bot en vanaf korrelset. Gedeeltelik ontblaarde stokke het gereageer deur nuwe wortels te
vorm, waardeur 'n meer doeltreffende vermoe tot voedingstofopname en benutting van grand an
beskikbare water verkry is. Tesame met hoer fotosintetiese aktiwiteite van die blare is 'n
doeltreffende meganisme vir aanhoudende hoe prestasie verkry.
Druifkwaliteit is nie aanmerklik deur blaarverwydering beirwloed nie. Totale oplosbare stowwe in
druiwe van gedeeltelik ontblaarde stokke was vergelykbaar en selfs betekenisvol hoer as die van
nie-ontblaarde stokke in sekere gevalle, ten spyte van die baie laer blaaroppervlakte. In die
algemeen was die totale titreerbare suur in die mos van gedeeltelik ontblaarde stokke oak effens
hoer. Glukose- en fruktosekonsentrasies in die druiwe is nie deur blaarverwydering beinvloed
nie. Die konsentrasie wynsteensuur is egter effens verhoog en die appelsuurkonsentrasie effens
verlaag. Antosianienkonsentrasie van korreldoppe is in die algemeen deur blaarverwydering
verhoog. Hierdie veranderinge in druifsamestelling dui op hoer druifkwaliteit en is skynbaar die
resultaat van verbeterde ligtoestande in die binnekant van die lower. Korrelvolume het
afgeneem met blaarverwydering. Dit het die pulp:dop verhouding verlaag. Sulke korrels is meer
gewens vir bereiding van kwaliteitswyne. Wyn cultivarkarakter en totale wynkwaliteit is
betekenisvol deur blaarverwydering verhoog, onafhanklik van die strafheid of
ontwikkelingstadium waarvandaan blare verwyder is.
Blaarverwydering het die algemene metabolisme van die wingerdstok verander, hoofsaaklik ten
opsigte van meer gunstige bron:sink-verhoudings en derhalwe meer doeltreffende fotosintese,
ondergrondse groei en lowermikroklimaat. Die resultate dui in die algemeen daarop dat 'n
eweredige blaarverwydering van 33 % regoor en onderkant die trosse tydens blomvorming of
korrelset tot ertjiekorrelstadium toegepas kan word. Die resultate dui verder daarop dat 33 %van
bestaande geil en lower-verdigte stokke se blare eweredig verwyder kan word op die onderste
helfte van die loot (lower) vanaf ertjiekorrel- of deurslaanstadium. Hierdie hipotese was
suksesvol in die verbetering van lowermikroklimaat, fotosintetiese aktiwiteit en oesmassa.
Vegetatiewe groei is gestrem. Druif- en wynkwaliteit was hoer.
In die geheel kan blaarverwydering soos toegepas in hierdie ondersoek aanbeveel word as
loofbestuurspraktyk ten einde die uitskakeling van nadelige effekte van oormatige vegetatiewe
groei en lowerdigtheid op gebalanseerde metaboliese aktiwiteit, druif- en wynkwantiteit en
kwaliteit, asook langlewendheid en gesondheid van wingerdstokke te bevorder.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/69374 |
| Date | 03 1900 |
| Creators | Hunter, Jacobus Johannes |
| Contributors | De Villiers, O. T., Stellenbosch University. Faculty of AgricSciences. Dept. of Viticulture & Oenology & Institute for Wine Biotechnology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 1 v. (various pagings) : ill. |
| Rights | Stellenbosch University |
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