Thesis (PhD(Agric))--Stellenbosch University, 2012 / ENGLISH ABSTRACT: Field spectroscopy was used to study leaf composition and selected factors (including canopy
growth manipulation and water status changes) that may impact on it in a Vitis vinifera cv. Shiraz
vineyard, showing considerable variability in vigour. Temporal and spatial variability in leaf
composition were incorporated into measurements by analysing leaves in different shoot positions
and at different developmental stages during three different growing seasons. Irrigation and
canopy manipulation treatments were also imposed in order to provide new insights into assessing
the grapevine leaf and possibly also the canopy growth and ageing dynamics as well as pigment
content, as a basis of executing a generally non-destructive measurement approach.
Despite large climatic differences between the seasons, canopy size seemed of crucial importance
in determining grapevine water relations in the grapevines from the different canopy manipulation
treatments. Drastic compensation effects in terms of secondary shoot growth also followed the
canopy reduction treatment. Despite this, canopy microclimate was apparently improved,
considering the results from light measurements as well as the ripening dynamics in the reduced
canopies. Reduced canopies also seemed to display a different canopy composition, in favour of
secondary growth. This could have impacted positively on water use efficiency as well as ripening,
due to higher photosynthetic efficiency of these leaves during the ripening stages. The reduced
canopy treatments offered the possibility of attaining technological ripeness at an earlier stage and
at comparatively lower potential alcohol levels.
This study illustrated the relevance of considering the vegetative development of the grapevine,
along with leaf ageing in the canopy, when conducting calibrated non-destructive measurements of
leaf pigments, structure and water content. The relevance of using multivariate techniques in leaf
spectroscopy was shown. This can be applied and simplified to aid in non-destructive leaf pigment,
structure and water content estimation in future studies. Even with the general variation
encountered in this vineyard, predictions of the major pigments in grapevine leaves were within
acceptable error margins. Further work is required to improve the modelling of xanthophylls, which
may require non-linear multivariate techniques.
Logistical shoot growth modelling was used in leaf age estimation and classification, which made it
possible to simplify statistical analysis of the leaf parameters mentioned. Practical application of
the modelled and predicted parameters was shown for a specific period in season two by
comparing the reaction of different treatments to developing water deficits. The results indicated
that several parameters, with special mention of the carotenoid:chlorophyll ratio and chlorophyll a:b
ratio, can be monitored on young and old leaves in the canopy in order to monitor developing water
deficit stress. The modelled parameters, however, did not seem to be sensitive enough to allow
specific prediction of predawn leaf water potential values. Specific leaf mass, equivalent water
thickness, total specific leaf mass as well as leaf chronological age were successfully predicted
from leaf spectral absorbance data, and this may be useful in future work on quantifying leaf
adaptation to the micro-environment within the canopy. / AFRIKAANSE OPSOMMING: Veldspektroskopie is gebruik om blaarsamestelling en spesifieke faktore (insluitend lowergroei
manipulasie en waterstatus veranderinge) wat ‘n impak kan hê in ‘n Vitis vinifera cv. Shiraz
wingerd, met beduidende variasie in groeikrag, te ondersoek. Ruimtelike, asook tydsgebonde,
variasie in blaarsamestelling is geïnkorporeer in die metings deur blare van verskillende
lootposisies en vir verskillende ontwikkelingstadia gedurende drie verskillende groeiseisoene te
meet. Besproeiings- en lowermanipulasie behandelings is ook uitgevoer om die dinamiek van
blaar- en lowergroei, veroudering, asook pigmentinhoud te bestudeer binne die konteks van die
uitvoering van ‘n nie-destruktiewe meetstrategie.
Ondanks groot klimaatsverskille tussen die seisoene, blyk lowergrootteverskille belangrik te wees
in die bepaling van wingerdstok-waterverhoudings in die verskillende lowermanipulasie
behandelings. Drastiese kompensasiereaksies ten opsigte van sylootgroei is waargeneem in
reaksie op die gereduseerde lowerbehandeling. Indien die resultate van ligmetings en
druifrypwording in die gereduseerde lowerbehandeling in ag geneem word, is lowermikroklimaat
egter steeds verbeter. Hierdie behandeling het oënskynlik ook veranderde lowersamestelling
gehad, tot voordeel van sylootgroei. Dit kon moontlik ‘n positiewe invloed gehad het op
waterverbruikseffektiwiteit asook druifrypwording, as gevolg van moontlike hoër fotosintetiese
effektiwiteit van die blare gedurende die rypwordingstadia. Die gereduseerde lowerbehandeling het
die moontlikheid gebied om tegnologiese rypheid by ‘n vroeër datum te bereik, met moontlike laer
alkoholvlakke in die wyn.
Hierdie studie het die belangrikheid beklemtoon om die vegetatiewe ontwikkeling van die
wingerdstok in ag te neem wanneer gekalibreerde nie-destruktiewe metings van blaarpigmente,
blaarstruktuur asook waterinhoud onderneem word. Die belang van multi-variant meettegnieke in
blaarspektroskopie is aangetoon. Dit kan verder vereenvoudig word ter ondersteuning van niedestruktiewe
meting van blaarpigment, -struktuur en -waterinhoudsbepaling in toekomstige studies.
Selfs met die variasie wat in die wingerd voorgekom het, was die voorspellings van die vlakke van
die belangrikste pigmente wat in wingerdblare aangetref word binne aanvaanbare foutgrense.
Opvolgwerk is nodig om die modellering van xanthofil te verbeter, aangesien dit moontlik nielineêre
multi-variant analise mag benodig.
Logistiese groeimodellering is gebruik om blaarouderdom te bepaal en te klassifiseer, wat dit
moontlik gemaak het om statistiese analise te vereenvoudig vir die genoemde blaarparameters.
Die praktiese toepassing van die gemodelleerde en voorspelde parameters is aangetoon vir ‘n
spesifieke gedeelte in seisoen twee, deur die reaksie van verskillende behandelings op
toenemende watertekorte te bestudeer. Resultate het aangetoon dat verskeie parameters, met
spesifieke klem op die karotenoïed:chlorofil verhouding, asook die chlorofil a:b verhouding,
gemoniteer kan word op jong en ouer blare in die lower ten einde ontwikkelende
waterstrestoestande te identifiseer. Die gemodelleerde parameters was egter klaarblyklik nie
sensitief genoeg vir akkurate voorspelling van voorsonsopkoms-waterpotensiaalvlakke nie.
Spesifieke blaarmassa, ekwivalente waterdikte, totale spesifieke blaarmassa, sowel as
blaarouderdom kon suksesvol voorspel word deur gebruik te maak van absorpsieblaarspektroskopie,
wat nuttig kan wees in toekomstige studies wat handel oor die kwantifisering
van blaaraanpassing by die mikro-omgewing binne ‘n wingerdlower.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/19963 |
| Date | 03 1900 |
| Creators | Strever, Albert (Albert Erasmus) |
| Contributors | Hunter, J. J., Young, P. R., Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 236 p. : ill. |
| Rights | Stellenbosch University |
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