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Optimum temperatures for colour development in applesGouws, Anton 23 November 2010 (has links)
Thesis (MScAgric (Horticulture))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Peel colour is an important quality factor in the production of bi-coloured apple fruit. Most markets set minimum requirements for red colour coverage. Fruit that do not meet these requirements are downgraded and has a major impact on the profitability of apple production
in South Africa. South African apple production areas are amongst the warmest in the world.
Since anthocyanin accumulation requires induction at low temperature and synthesis require
mild temperatures, experiments were conducted to investigate optimum day and night temperatures for red colour development throughout fruit development for red and bi-coloured apple cultivars grown in South Africa. We found that redder strains of bi-coloured apple cultivars did not appear to owe their enhanced pigmentation to higher temperature optima for anthocyanin synthesis. The optimum day temperatures for red colour development in the
different cultivars seemed to differ between seasons, but not between production areas. In
general, red colour in the cultivars evaluated developed maximally between 17 ºC and 25 ºC.
The optimum day temperature for red colour development remained constant throughout fruit
development for most cultivars, but increased roughly from 14 ºC to 22 ºC in ‘Cripps’ Pink’
between January and April. The extent of red colour development increased during fruit development in all the cultivars assessed. We were unable to determine optimum induction temperatures for red colour development. ‘Royal Gala’ from Ceres seemed to benefit from
induction at 4 ºC while red colour in ‘Fuji’ decreased with decreasing temperature.
To explain the presence of anthocyanins in immature apple fruit, we tested the hypothesis
that anthocyanins protect the peel from photoinhibition and photooxidative damage during
conditions of increased light stress. First we established that the rate of colour change in
response to a passing cold front appears to be sufficient to provide photoprotection during a
cold snap. Also in agreement with the hypothesis, ‘Cripps Pink’ peel incurred significantly
more photoinhibition at low temperature (16 ºC) compared to mild (24 and 32 ºC) and high (40
ºC) temperature under high irradiance with visible light. Recovery rate was temperaturedependent,
being the slowest at low temperature and increasing with temperature. The photoapparatus in ‘Cripps Pink’ peel appears to be particularly sensitive to light stress at low temperature throughout the season, with significant photoinhibition occurring even at
moderate temperature (24 ºC). The sensitivity of the apple peel to photoinhibition increased throughout the season at lower irradiance levels, but remained the same at higher irradiance.
In our final experiment, fruit were exposed to high irradiance at low and mild temperature before exposure to high temperature in combination with high irradiance. This was done to test the hypothesis that photoinhibition incurred during cold snaps predisposes peel to photothermal damage when temperature increases again after the cold snap. Unfortunately, due to the severity of the stress incurred in response to high temperature treatment, the
results were inconclusive. / AFRIKAANSE OPSOMMING: Vrugkleur is ‘n belangrike kwaliteitsfaktor in die produksie van tweekleurappels. Die meeste markte stel minimum vereistes vir rooi kleurbedekking. Vrugte wat nie aan hierdie vereistes voldoen nie, word afgegradeer. Suid-Afrika se appel produksie areas word beskou as van die warmste ter wêreld. Antosianien akkumulasie benodig induksie by lae temperature gevolg
deur sintese in lig by matige temperature. Gevolglik het swak rooi kleurontwikkeling onder
plaaslike toestande ‘n groot impak op die winsgewendheid van appelproduksie in Suid-Afrika.
Eksperimente is uitgevoer om die optimum dag- en nagtemperature vir rooi kleurontwikkeling tydens vrugontwikkeling vir die rooi en tweekleur appel kultivars wat in Suid-Afrika geproduseer word te bepaal. Ons het gevind dat die verhoogde pigmentasie van rooier
seleksies van tweekleurappel kultivars nie aan ‘n hoër temperatuur optimum vir antosianiensintese toegeskryf kan word nie. Die optimum dag temperature vir rooi kleurontwikkeling vir die onderskeie kultivars verskil klaarblyklik tussen seisoene, maar nie tussen produksie areas nie. Oor die algemeen het kleurontwikkeling maksimaal plaasgevind tussen 17 ºC en 25 ºC. Die optimum dagtemperatuur vir rooi kleurontwikkeling het konstant
gebly tydens vrugontwikkeling, buiten vir ‘Cripps’ Pink’ waar dit toegeneem het van ongeveer
14 ºC tot 22 ºC vanaf Januarie tot April. Die mate van rooi kleurontwikkeling het in al die
kultivars toegeneem deur die loop van vrugontwikkeling . Ons kon nie daarin slaag om optimum induksie temperature vir rooi kleurontwikkeling vas te stel nie. Rooi kleurontwikkeling
van ‘Royal Gala’ uit Ceres is moontlik bevorder deur induksie by 4 ºC, terwyl ‘Fuji’ se rooi
kleur afgeneem het met ‘n verlaging in induksie temperatuur.
Ten einde die teenwoordigheid van antosianien in onvolwasse appelvruggies te verduidelik,
het ons die hipotese getoets dat antosianien die vrugskil beskerm teen fotoinhibisie en fotooksidatiewe beskadiging gedurende tydperke van verhoogde ligstres. Eerstens het ons
bevestig dat die tempo van kleurontwikkeling in reaksie op ‘n koue front waarskynlik vinnig
genoeg is om fotobeskerming te verleen. Vervolgens is gevind dat ‘Cripps’ Pink’ vrugskil
aansienlik meer fotoinhibisie ervaar het by lae temperatuur (16 ºC) in vergelyking met matige
(24 ºC en 32 ºC) en hoë (40 ºC) temperatuur onder hoë irradiasie met sigbare lig. Die hersteltempo was temperatuur-afhanklik; dit was die stadigste by lae temperatuur en het toegeneem met ‘n toename in temperatuur. Die foto-apparaat in ‘Cripps’ Pink’ vrugskil blyk
besonder sensitief te wees vir ligstres by lae temperatuur regdeur die groeiseisoen met
aansienlike fotoinhibisie by selfs matige temperatuur (24 ºC). Die sensitiwiteit van die vrugskil
vir fotoinhibisie het toegeneem deur die groeiseisoen by laer ligvlakke, maar het dieselfde
gebly by hoër vlakke van irradiasie. Laastens is vrugte blootgestel aan hoë irradiasie by lae en matige temperatuur voordat dit vervolgens blootgestel is aan hoë temperatuur in kombinasie met hoë irradiasie. Dit was om die hipotese te toets dat fotoinhibisie wat
opgedoen word gedurende ‘n onverwagte koue periode, die skil meer vatbaar maak vir fototermiese
skade sodra die temperatuur weer styg na die koue periode verby is. Ongelukkig het
die hoë temperatuur stres al die behandelings tot so ‘n mate geaffekteer dat dit onmoontlik
was om enige gevolgtrekkings vanuit ons resultate te maak.
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Effect of climate and soil water status on Cabernet Sauvignon (Vitis vinifera L.) grapevines in the Swartland region with special reference to sugar loading and anthocyanin biosynthesisMehmel, Tara Olivia, Van Heerden, Tara Olivia 23 November 2010 (has links)
Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosach, 2010. / ENGLISH ABSTRACT: Cabernet Sauvignon, the most planted red wine cultivar in South Africa, is prone to vigorous
growth with low yields. The aim of the study was to describe how Cabernet Sauvignon
grapevines react to climate and irrigation within the Swartland region. Such knowledge would
assist growers in decisions regarding long term as well as short term cultivation practices. This
study was part of a larger project carried out by the Infruitec-Nietvoorbij institute of the
Agricultural Research Council at Stellenbosch to determine effects of soil type and climate on
yield and wine quality of Cabernet Sauvignon. The larger project was carried out in selected
grape growing regions, i.e. Stellenbosch, Swartland, Lower Olifants River and Lower Orange
River.
Due to the proximity to the Atlantic Ocean, the study area in the Swartland region could
be divided into two climatic regions for viticulture. Grapevines near Philadelphia closer to the
ocean experienced less water constraints compared to those further inland near Wellington.
Variation in stem water potential could also be related to soil water matric potential. Climate
tended to have a more pronounced effect on the grapevine response to water constraints
further inland than closer to the ocean. Vegetative growth, berry size and yield depended on
water constraints experienced by the grapevines. In the warmer climate, severe constraints
reduced yield.
In the warmer climate, grapes started to ripen earlier than those in the cooler climate.
Sugar concentration (mg/mL) was highest where grapevines experienced moderate water
constraints. These seemingly balanced grapevines had the highest sugar accumulation,
probably due to optimum photosynthesis and carbohydrate utilization. Low water constraints
increased vegetative growth which could have been a sink for sugar loading. In addition to
sugar loading, degree Balling (°B) increases could also have been due to a concentration effect
where water constraints reduced berry volume. Therefore, °B is probably not a representative
indicator of grapevine functioning.
Anthocyanin biosynthesis, as quantified on a per berry basis, showed that sugar and
anthocyanin could be co-regulated, with anthocyanin biosynthesis reaching a plateau when the
sugar content per berry reached 200 mg/mL to 220 mg/mL. At véraison, the most intense grape
colour occurred where grapevines experienced moderate water constraints, i.e. single drip line
at Wellington and no irrigation at Philadelphia. However, at harvest grapes from the cooler
climate tended to have more intense colour and higher phenolics, indicating that lower
temperatures favoured anthocyanin biosynthesis. These results supported earlier findings that
grapevine water status influences berry volume and dynamics of berry ripening.
Water constraints tended to increase sensorial wine colour intensity, as well as wine
fullness. Moderate water constraints at both localities resulted in the best sensorial wine quality.
Yet there were indications that too severe water constraints could be detrimental to wine quality. Irrigation can be used to manipulate grapevine growth in warmer climates, but might be less
effective in cooler climates. In warmer climates, moderate water constraints required to achieve
balanced grapevine functioning can be obtained with single drip irrigation, but this might not be
the case in cooler climates. / AFRIKAANSE OPSOMMING: Cabernet Sauvignon, die mees aangeplante rooiwynkultivar in Suid-Afrika, is geneig tot kragtige
groei met lae opbrengste. Die doelwit van hierdie studie was om te beskryf hoe Cabernet
Sauvignon-wingerdstokke reageer op klimaat en besproeiing in die Swartland-streek. Hierdie
kennis sal kwekers help wanneer hulle besluite moet neem oor langtermyn sowel as korttermyn
verbouingspraktyke. Hierdie studie was deel van ‘n groter projek deur die Infruitec-Nietvoorbij
Instituut van die Landbounavorsingsraad op Stellenbosch om die effekte van grondtipe en
klimaat op die opbrengs en wynkwaliteit van Cabernet Sauvignon te bepaal. Die groter projek is
in geselekteerde wingerdverbouingstreke uitgevoer, nl. Stellenbosch, Swartland, Benede
Olifantsrivier en Benede Oranjerivier.
As gevolg van die nabyheid daarvan aan die Atlantiese Oseaan kon die studiegebied in
die Swartland-streek in twee klimaatstreke vir wingerdbou verdeel word. Wingerdstokke by
Philadelphia, wat nader aan die oseaan is, het minder waterstremming ervaar as dié verder
binnelands naby Wellington. Veranderinge in stamwaterpotensiaal hou moontlik ook verband
met die grondwater- matrikspotensiaal. Klimaat het ‘n groter effek op die reaksie van die
wingerdstok op waterstremming verder binnelands as nader aan die oseaan. Vegetatiewe groei,
korrelgrootte en opbrengs was afhanklik van die waterstremminge wat deur die wingerdstokke
ervaar is. In die warmer klimaat het die ernstige stremminge opbrengs verminder.
In die warmer klimaat begin druiwe vroeër ryp word as in die koeler klimaat.
Suikerkonsentrasie (mg/ml) was die hoogste waar wingerde matige waterstremming ervaar het.
Hierdie skynbaar gebalanseerde wingerdstokke het die hoogste suikerakkumulasie vertoon,
moontlik as gevolg van optimum fotosintese en koolhidraatverbruik. Lae waterstremming het
vegetatiewe groei verhoog, wat ook ‘n vraagpunt vir suikerlading kon wees. Benewens
suikerlading kon verhogings in grade Balling (°B) ook moontlik aan ‘n konsentrasie-effek
toegeskryf word in terme waarvan waterstremming die korrelvolume verminder het. °B is dus
moontlik nie ‘n verteenwoordigende indikator van wingerdstokfunksionering nie.
Antosianienbiosintese, soos gekwantifiseer op ‘n per-korrel basis, het getoon dat suiker
en antosianien saam gereguleer kon word, en dat antosianienbiosintese ‘n plato bereik het
wanneer die suikerinhoud per korrel 200 mg/mL tot 220 mg/mL was. By deurslaan het die mees
intense druifkleur voorgekom waar die wingerdstokke matige waterstremming ervaar het, d.w.s.
enkel druplyn op Wellington en geen besproeiing op Philadelphia. Teen oes was die druiwe in
die koeler klimate egter geneig om meer intense kleur en meer fenole te bevat, wat aandui dat
laer temperature antosianienbiosintese bevoordeel. Hierdie resultate ondersteun vroeër
bevindings dat die waterstatus van die wingerdstok ‘n invloed op korrelvolume en die dinamika
van korrelrypwording het.
Waterstremming neig om die sensoriese wynkleurintensiteit te verhoog, asook die
volheid van die wyn. Matige waterstremming op beide liggings het aanleiding gegee tot die beste sensoriese wynkwaliteit. Tog was daar aanduidings dat waterstremming wat te straf was,
nadelig kon wees vir wynkwaliteit. Besproeiing kan gebruik word om wingerdgroei in warmer
klimate te manipuleer, maar is moontlik minder effektief in koeler klimate. In warmer klimate kan
die matige waterstremming wat benodig is vir gebalanseerde wingerdstokfunksionering, verkry
word deur enkel drupbesproeiing, maar dit is moontlik nie die geval in koeler klimate nie.
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