Bibliography: leaves 280-300. / xix, 338 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2000

A replacement for silver thiosulphate as a commercial post-harvest treatment needs to be found. The longevity of cut carnation flowers is extended by all concentrations of ethanol tested. Compared to a water control, the vase-life of ethanol-treated flowers is between 150 and 250% longer. The greatest longevity increases are recorded with 3% ethanol. The use of ethanol as a post-harvest treatment was tested. The longevity increase as a result of ethanol application only occurs if the ethanol is applied as a holding solution. Pulse treatments are not effective at delaying the senescence of the flowers. The sooner the ethanol is applied, the greater the increase in vase life. If ethanol treatment is halted at any point during the experiment, the longevity of the flowers is reduced. It was observed that the longer the stems of ethanol-treated flowers, the greater the longevity increases. The ethanol holding solution does not prevent the action of external ethylene, thereby restricting the potential of ethanol as a commercial post-harvest treatment. Physiologically, flowers treated with ethanol exhibit a different senescence process to control flowers. The typical in-rolling of the petals of carnation flowers is not seen, instead the petals appear burnt. The ovaries are also notably effected by ethanol, being smaller and more yellow in colour. Ethanol treatment results in longevity increases by inhibiting the formation of ethylene, the plant hormone responsible for senescence. The concentration of the direct precursor to ethylene, ACC, as well as the activity of the enzyme that converts ACC to ethylene, ACC oxidase, is reduced to almost zero in the tissues of treated flowers. Another physiological factor affected by ethanol treatment is the carbohydrate status of the flowers. The normal sink activity of the ovary is inhibited by ethanol treatment. Although the carbohydrate content of the petals is found to decrease sharply in ethanol-treated flowers, these carbohydrates are not relocated to the ovary. The ovary does not increase in dry matter or chlorophyll content. The carbohydrate content decreases as a result of ethanol treatment, and when ¹⁴C sucrose was applied to petals, no radioactivity was recovered in the ovary. The petals and ovary are the organs most effect by ethanol activity, as when ¹⁴C ethanol was applied to cut carnation flowers as a pulse, the majority of the radioactivity was discovered here. The protein content of cells of both organs decreases significantly compared to control flowers. This is a total protein loss, rather than the destruction of specific systems. If the activity of alcohol dehydrogenase is prevented in ethanol-treated flowers, inhibiting the conversion of ethanol to acetaldehyde, no longevity increases are seen. The airspace surrounding treated flowers was found to contain ethanol and small amounts of acetaldehyde. The tissues of flowers treated with ethanol show an increase in the acetaldehyde content, as well as the ethanol content, especially in the ovary. The application of acetaldehyde directly to cut carnation flowers as a holding solution resulted in the vase life of the flowers increased by 150%. To determine the effectiveness of acetaldehyde as a post-harvest treatment, various concentrations of acetaldehyde were applied to cut carnation ftowers as a pulse treatment and a holding solution. Pulse treatments did not increase the vase life of flowers, and resulted in a number of negative effects in the flower. A holding solution of acetaldehyde does increase the longevity of cut carnation flowers, provided it is above a certain concentration. Treatments at concentrations below 1% acetaldehyde appear to promote flower senescence. The use of acetaldehyde as a post-harvest treatment has many of the same disadvantages as ethanol treatment. Acetaldehyde must also be applied as a holding solution for as long as possible. If removed from this solution, death of the organ occurred quickly. Acetaldehyde is also ineffective against external ethylene. A negative effect of acetaldehyde not found in ethanol-treated flowers, is that the longer the stem of cut carnation flowers, the shorter the resultant vase life. Physiologically the responses in cut carnation flowers were very similar to those seen in ethanol-treated flowers. Acetaldehyde inhibited the formation of ethylene completely. Almost no ACC can be found in treated tissues, and the action of ACC oxidase is completely reduced. The petals of acetaldehyde-treated flowers suffer from severe petal browning, rather than in rolling. The ovaries are particularly badly effected by treatment. There are large scale losses in fresh weight and chlorophyll content. The latter results in the ovaries appearing yellow in colour. They also show a loss in structure. The sink activity of these ovaries is destroyed. Like ethanol-treated flowers, the carbohydrate content of both the petals and ovaries are dramatically reduced. When ¹⁴C sucrose was applied to one of the. petals, almost no radioactivity was recorded in the ovary. There. is also a major loss in general protein content, slightly more severe than in ethanol-treated flowers. The conversion of ethanol to acetaldehyde is necessary in order to achieve longevity increases in ethanol-treated flowers. If the conversion of this acetaldehyde to ethanol is prevented in acetaldehyde-treated flower there is once again no longevity increase. Both ethanol and acetaldehyde are required within the system to result in increased longevity. Although ethanol and acetaldehyde treatments result in decreases in the total protein content of the flowers, certain enzymes remain active. Alcohol dehydrogenase is a bi-directional enzyme, capable of converting ethanol to acetaldehyde and then back to ethanol again. The activity of this enzyme, in both orientations, is increased in ethanol and acetaldehyde-treated flowers. The activity of pyruvate decarboxylase, which converts pyruvate to acetaldehyde, is also increased as a result of both treatments. The similarities of the physiological response of cut carnation flowers to ethanol and acetaldehyde post-harvest treatments, and the increased activity of these enzymes, indicate that the effect of both compounds on longevity is closely linked. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2000.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Quality of certain Leucospermum and Leucadendron cultivars after approximately 21 days shipping has been reported to be substandard due to ‘drying out’ of leaves and, in the case of Leucadendrons, involucral leaves. The nature of the symptoms of this ‘drying out’ and the conditions under which they form, viz. long exposures to low temperatures, has led us to hypothesize that these are symptoms of chilling injury (CI). Chilling injury, as far as we are aware, has not been documented on Leucospermums or Leucadendrons. Typical CI symptomology is discussed and shown for Leucospermum ‘Gold Dust’, ‘High Gold’ and ‘Succession’ and for Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’. The nature of CI symptoms for Leucospermums and Leucadendrons was generally membranous breakdown that manifested in some cases as a ‘water soaked’ appearance which, at a more advanced stage, was generally visible as ‘dried out’ patches on the leaves. In the case of the Leucadendrons CI was also visible on the immature involucral leaves which are more sensitive to chilling conditions than mature leaves. Dark discoloration of especially immature involucral leaves is also a symptom of CI. As water uptake of shoots with chilling injury is hindered the styles of the Leucospermums wilt. As can be expected, the lower the temperature below the threshold temperature and the longer the exposure the more severe the symptoms. CI was recorded on cut flower shoots of Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ and ‘Vlam’ after 21 and 24 days storage at 1ºC. After 24 days storage the chilling injury was more severe than after 21 days storage in most cases. Each cultivar was pulsed with 5 ml per stem of a 2% (w/v) sugar solution of either lactulose, sucrose, glucose, fructose or mannose before storage. After storage, CI was recorded on day 0, 3, 7 and 10 of the vase phase. Of the cultivars tested ‘Vlam’ and especially ‘Rigoletto’ were more prone to chilling injury development. ‘High Gold’ and ‘Vlam’ shoots were pulsed with 0 (control), 1.5, 3 or 4% (w/v) solutions of either mannose or fructose. The best control of CI for both cultivars was achieved with 1.5% (w/v) solution. Lower concentrations of mannose and fructose were tested on ‘High Gold’ shoots, with a 1% (w/v) solution giving the best control for both. At high concentrations signs of toxicity became evident directly after pulsing. ‘High Gold’ shoots were pulsed with 1% (w/v) solutions of mannose and fructose and sugar analyses were performed on shoots at different stages of storage and after 10 days in the vase. A slight increase in mannose and fructose was detectable in the stems of the shoots directly after pulsing but not in the leaves or the inflorescences. This is due to the low concentrations being used. The levels of all the carbohydrates decreased during the 21 days storage and more so during the vase phase of the flowering shoots. The fact that such low concentrations were effective in controlling chilling injury suggests that the sugars may have an effect other than on the osmotic potential. Cut ‘flower’ shoots of Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ were stored for 14, 21 and 28 days, at 1º, 3º and 5ºC and CI development recorded during the subsequent 10 day vase phase. ‘Laurel Yellow’ and ‘Safari Sunset’ showed signs of chilling injury on the leaves after 28 days storage at 3ºC or lower and ‘Safari Sunset’ stored for 21 days developed chilling injury during the vase phase. Immature involucral leaves were more sensitive to chilling injury than leaves. CI increased with longer exposure times and lower storage temperatures for all three cultivars evaluated. ‘Chameleon’ was the most chilling tolerant of the cultivars up to 21 days. At 5ºC chilling injury was low irrespective of cold storage duration but longer exposures to 1º and 3ºC resulted in increased chilling injury development during the vase phase. All three cultivars were pulsed with 5 ml per stem of a 1% (w/v) solution of lactulose, sucrose, glucose, fructose or mannose and stored for 14, 21 and 28 days at 1ºC. The sugars reduced chilling injury on the leaves for ‘Safari Sunset’ when stored for 28 days and, to a lesser extent, in ‘Chameleon’. The sugars failed to reduce chilling injury of the involucral leaves of ‘Chameleon’ and ‘Laurel Yellow’ whereas there was some control especially after 28 days for ‘Safari Sunset’. In some cases the sugar pulse exacerbated chilling injury. Chilling injury generally increased rapidly after storage during the first three days in the vase and then at a lower rate for the next seven days. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ ‘cut flower’ shoots were pulsed with a 1% (w/v) glucose solution. Expressed on a dry weight basis, an increase in glucose concentration was not detected. The reduction in chilling injury of leaves by a sugar pulse is speculated, as for the Leucospermums, to be as a result of their presence in the apoplast and not the symplast and that their presence there protects the membranes against chilling conditions in some way. / AFRIKAANSE OPSOMMING: Die kwaliteit van sekere Leucospermum en Leucadendron kultivars na ongeveer 21 dae verskeping is waargeneem as substandaard as gevolg van die uitdroog van blare en, in die geval van Leucadendrons, die ‘involucral’ blare. Die aard van die simptome van hierdie uitdroging en die toestande waaronder dit plaasvind nl. lang periodes van blootstelling aan lae temperature, het ons tot die hipotese gebring dat hierdie simptome van koueskade is. Sover as wat ons bewus is, is koueskade nog nie gedokumenteer op Leucospermums of Leucadendrons nie. Tipiese koueskade simptomologie word bespreek en gewys vir Leucospermum ‘Gold Dust’, ‘High Gold’ en ‘Succession’ en vir Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’. Die koueskade simptome vir Leucospermums en Leucadendrons was oor die algemeen membraan afbraak wat ‘n water deurdrenkte voorkoms tot gevolg gehad het wat in ‘n meer gevorderde stadium sigbaar was as uitgedroogde kolle op die blare. In die geval van Leucadendrons was koueskade ook sigbaar op die onvolwasse ‘involucral’ blare wat meer sensitief is vir koue toestande as volwasse blare. Donker verkleuring van veral onvolwasse ‘involucral’ blare is ook ‘n simptoom van koueskade. Aangesien wateropname van stele met koueskade verhinder word, verwelk die ‘styles’ van die Leucospermums. Soos verwag kan word hoe laer die temperature onder die drempel temperatuur en hoe langer die blootstelling, hoe meer ernstig die simptome. Koueskade is aangeteken op gesnyde blomstele van Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ en ‘Vlam’ na 21 en 24 dae opberging by 1°C. Na 24 dae opberging was die koueskade meer ernstig as na 21 dae opberging in meeste gevalle. Elke kultivar het 5ml per steel van ‘n 2% (g/v) suiker oplossing van laktolose, sucrose, glucose, fruktose of mannose voor opberging opgeneem. Na opberging is koueskade aangeteken op dag 0, 3, 7 en 10. Van die kultivars wat getoets is, was ‘Vlam’ en veral ‘Rigoletto’ meer geneig tot koueskade ontwikkeling. ‘High Gold’ en ‘Vlam’ stele is geplaas in oplossings van 0 (kontrole), 1.5, 3 of 4 % (g/v) oplossings van mannose of fruktose. Die beste beheer van koueskade vir beide kultivars is deur die 1.5 (g/v) oplossing behaal. Laer konsentrasies van mannose en fruktose is getoets op ‘High Gold’ stele met ‘n 1% (g/v) mannose oplossing wat die beste beheer gegee het. Met hoë konsentrasies het tekens van toksisiteit sigbaar geword direk na opneem van die oplossing. ‘High Gold’ stele is geplaas in 1% (g/v) oplossings van mannose of fruktose en suiker analises is uitgevoer op stele by verskillende stadiums van opberging en na 10 dae in die vaas. ‘n Effense toename in mannose en fruktose is waargeneem in die stele van die blomme direk na opname van die oplossing, maar nie in die blare of die blomme nie. Dit is as gevolg van die lae konsentrasies wat gebruik is. Die vlakke van al die koolhidrate het afgeneem gedurende die 21 dae opberging en nog meer so gedurende die vaas periode van die blommende stele. Die feit dat sulke lae konsentrasies effektief is in die beheer van koueskade dui daarop dat die suikers ‘n effek het anders as op die osmotiese potensiaal. Snyblomme van Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ is opgeberg vir 14, 21 en 28 dae, by 1º, 3º en 5°C en koueskade ontwikkeling is aangeteken gedurende die opvolgende 10 dae vaas periode. ‘Laurel Yellow’ en ‘Safari Sunset’ het tekens gewys van koueskade op die blare na 28 dae opberging by 3°C of laer en ‘Safari Sunset’ opgeberg vir 21 dae het koueskade ontwikkel gedurende die vaas periode. Onvolwasse ‘involucral’ blare was meer sensitief vir koueskade as die blare. Koueskade het toegeneem met langer blootstellingstye en laer opbergins temperature vir al drie kultivars geëvalueer. ‘Chameleon’ was die mees koueverdraagsaam van die drie kultivars tot op 21 dae. By 5°C was laag ongeag van die koue opberging tydperk, maar langer blootstellings aan 1º en 3°C het gelei tot toename in koueskade ontwikkeling gedurende die vaas periode. Al drie kultivars is voorsien met 5ml per steel van ‘n 1% (g/v) oplossing van lactulose, sucrose, glucose, fruktose of mannose en opgeberg vir 14, 21 en 28 dae by 1°C. Die suikers het koueskade verminder op die blare van ‘Safari Sunset’ wanneer opgeberg vir 28 dae en, tot ‘n mindere mate, in ‘Chameleon’. Die suikers het egter nie koueskade verminder van die ‘involucral’ blare van ‘Chameleon’ en ‘Laurel Yellow’ nie, waar daar egter wel in ‘n mate beheer was veral na 28 dae vir ‘Safari Sunset’. In sommige gevalle het die voorsiening van suiker die koueskade vererger. Koueskade het oor die algemeen vinnig toegeneem na opberging gedurende die eerste drie dae in die vaas en dan teen ‘n laer tempo vir die volgende sewe dae. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ snyblom stele is voorsien van ‘n 1% (g/v) glukose oplossing. Uitgedruk op ‘n droëmassa basis is ‘n toename in glukose konsentrasie nie waargeneem nie. Die afname in koueskade van blare deur die voorsiening van ‘n suiker oplossing is gespekuleer vir die Leucospermums, om ‘n resultaat te wees van hulle teenwoordigheid in die apoplas en nie die simplas nie, en dat die teenwoordigheid daar die membrane op ‘n manier beskerm teen koue toestande.