In Asia, the recent rapid growth in production of higher value, more pesticide intensive, horticultural crops and inland aquatic foods in linked agri-aquatic systems poses numerous environmental, health and wider livelihood threats in these often multi-use aquatic systems. ‘Green Revolution’ technologies have enhanced food security and pesticides have been promoted, however, the sustainability of prolonged pesticide use from a functional, environmental and socio-economic perspective is increasingly questionable. Further, despite international pesticide trade agreements and country-specific legislation, illegal practices still prevail. In Thailand and Sri Lanka the influence of pesticide marketing and regulation on pesticide use and hazards was investigated. Community livelihood relationships with three very different agri-aquatic systems (in Central and Northeast Thailand and Northwest Sri Lanka), pesticide use and associated aquatic and health hazards were explored with respect to surface water use and well-being status. Quantitative and qualitative data collection methods utilised participatory community appraisals, household surveys, pesticide fate in surface waters and dietary risk assessment and modelling, key informant semi-structured interviews and stakeholder workshops, to assess these relationships. Enhanced environmental and human pesticide hazards were contributed by pesticide sales incentives and weak regulation allowing illegal practices to prevail. Preliminary risk assessments found greater aquatic and human dietary pesticide hazards within communities, with the poorest at greatest vulnerability from applying pesticide and higher dependency on threatened natural aquatic food resources. The poorest in communities were most likely to overuse pesticide in Sri Lanka and were most vulnerable to illegal practices in the pesticide industry that are often linked with unauthorised traders and credit arrangements. Most horticultural production is for fresh wholesale markets with no food safety controls, and despite growing demand for safer horticultural produce, most farmers perceive pesticides as necessary, the associated hazards low and have little knowledge of safe food production and markets. These circumstances help sustain pesticide use. Some unofficial certification and misleading labelling in the ‘safe’ fruit and vegetable sector in Thailand potentially misinforms consumers and undermines trust that may threaten pesticide reduction efforts. Good Agricultural Practice (GAP) and vegetable Integrated Pest Management (IPM) are evolving practices and techniques of producing horticultural crops with less or no pesticide, the latter sometimes through Farmer Field Schools (FFS), however, evidence of success varies. Teaching through lectures and more lengthy and costly participatory methods is evident, with the former more successful on GAP and higher educated farmers and the latter with IPM and worse-off farmers, particularly when addressed within livelihood issues as a whole. However, production scale, farmer enthusiasm, produce marketing and facilitator expertise all influence outcomes, particularly with IPM, whilst proper evaluation could improve progress. Growing rural consumer interest in organic produce offers further incentives for small to medium scale farmers to implement IPM and reduce pesticide use and hazards. As value of aquatic resources was an incentive to reducing pesticide use, particularly the most dangerous products, exploration of this component of agri-aquatic systems is another exciting prospect for empowering farming community livelihoods over established and failing fear based chemical practices. Such new practices may lead the way towards affordable and trustworthy agri-aquatic systems produce with ethical certification. Greater pesticide use savings on a wider scale come from use of efficient flat fan spray nozzles compared with conventional pesticide spray nozzles. Complementary policies and stakeholder co-operation could aid pesticide use and hazard reduction efforts. A number of recommendations arose from the research.

published_or_final_version / Architecture / Master / Master of Architecture

La rivière Essonne est influencée quantitativement et qualitativement par la nappe de Beauce. L'eau de cette nappe possède des concentrations en nitrates élevées et qui continuent d'augmenter, représentant ainsi une menace croissante pour la qualité du cours d'eau. Des cressonnières (zones humides artificielles où le cresson de fontaine [Nasturtium officinale R. Br.] est cultivé) étaient autrefois très nombreuses entre ces deux masses d'eau, mais sont aujourd'hui massivement abandonnées. Or, ces zones humides jouent potentiellement un rôle épurateur vis-à-vis des nitrates, et pourraient contribuer au bon état du cours d'eau en limitant les transferts de ces nutriments (zones tampons) de la nappe vers la rivière. Ce travail a donc pour objectif d'étudier l'élimination des nitrates dans les cressonnières, mais également l'évolution de ces zones humides après l'abandon de la culture du cresson, et ses conséquences sur l'épuration. Pour cela, nous nous sommes basés sur l'étude d'un site expérimental (Maisse, 91, France) comprenant plusieurs stades d'abandon et sur des expérimentations en laboratoire (bioréacteurs). Les successions de macrophytes après l'abandon de la culture ont été étudiées sur le site expérimental et dans 14 autres sites de la vallée de l'Essonne. Après l'abandon de la culture, le cresson ne se maintient pas dans les fosses. On observe alors une évolution progressive vers un milieu terrestre, avec la colonisation successive par des hydrophytes pionnières ou invasives (Lemna minuta Kunth.), puis par des hélophytes pionnières (Epilobium hirsutum L., Typha latifolia L., Phragmites australis (Cav.) Steud.). Enfin, il s'établit une roselière avec l'apparition d'espèces arbustives et ligneuses (Salix sp), qui s'accompagne d'un comblement des fosses et qui semble constituer une transition vers une forêt alluviale. Au cours du passage de l'eau dans les fosses du site expérimental, une partie des nitrates a été éliminée. Les fosses cultivées ont été les plus efficaces avec un taux moyen de 1770 mg NO3-/m²/jour au cours des trois années de suivi. En comparaison, les fosses abandonnées ont montré des taux d'élimination largement inférieurs allant de 550 à 750 mg NO3-/m²/jour. Toutefois, ces taux n'ont permis qu'une faible diminution des concentrations (approximativement 44 mg/L en entrée à 42 mg/L en sortie) à cause de temps de séjour trop courts de l'eau dans les fosses. Les taux d'élimination des nitrates ont varié de façon saisonnière, avec un maximum en été et un minimum en hiver. L'ampleur des variations saisonnières a cependant été beaucoup plus forte dans les fosses cultivées que dans les fosses abandonnées. L'estimation des prélèvements par les macrophytes a montré que la dénitrification est la voie majoritaire de l'élimination des nitrates (70 à 85% de l'élimination totale). Des mesures de dénitrification potentielle en bioréacteurs ont montré que ce processus était limité par la disponibilité du carbone organique. Or, le cresson des fosses cultivées représente une source de carbone très disponible, par rapport aux hélophytes (Phragmites australis) qui dominent les cressonnières abandonnées. L'effet des cressonnières sur les concentrations en nitrates de la rivière Essonne est actuellement limité, mais peut être amélioré par la gestion des sources de carbone et des temps de séjour de l'eau dans ces zones humides.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Rind colour is one of the most important external quality characteristics of citrus fruit and plays an important role in purchasing decisions by consumers. Consumers perceive brightlycoloured fruit to be sweet and mature, whereas citrus with a green rind is perceived to be sour and immature. However, there is a poor correlation between rind colour and internal quality, contradicting what is generally assumed by the fruit-buying public. In general, a bright orange rind colour improves consumer acceptance. Thus, it is important to ensure that the rind of citrus fruit is well-coloured on arrival at the market. Various pre-harvest cultural practices and postharvest techniques can be applied to improve rind colour. Degreening with ethylene gas is the most commonly used postharvest technology to improve rind colour, but has various negative side-effects. Degreened fruit are more prone to decay, have rinds which appear dull and flaccid, have been reported to develop off-flavours and have a shorter shelf-life period. Therefore, it is necessary to find alternatives to ethylene degreening and to extend shelf-life of citrus fruit. Under normal orchard conditions, rind colour development is associated with low night temperatures, usually experienced during autumn or following the passing of a cold front. To simulate cold front conditions, a hydrocooler and cold room were used to rapidly drop fruit temperature to 4 ºC for 6 hours, and then fruit were incubated at 20 to 22 ºC for 72 hours. This “cold shock” treatment of ‘Nules Clementine’ mandarin improved rind colour to a level similar to that of degreened fruit in the 2002 season due to a decrease in chlorophyll content and increase in carotenoid content. However, this result could not be repeated. Storage temperature is one of the most important postharvest factors affecting rind colour. Citrus fruit shipped to export markets requiring low temperatures (-0.6 ºC) for pest disinfestations purposes have been reported to arrive with poor rind colour. Shipping under low temperatures results in poor rind colour of fruit on arrival in the market. To comply with the USA’s phytosanitary requirement for imported citrus, fruit is held at -0.6 ºC for a minimum of 22 days. The effect of shipping at various temperatures (-0.6 ºC or 4.5 ºC), durations and the influence of initial rind colour, “orange” or “yellow”, on fruit colour upon arrival in the market was evaluated. Fruit shipped at a higher temperature (4.5 ºC) had a marginally better rind colour than fruit shipped at -0.6 ºC. The perceived loss of rind colour following shipping at sub-zero temperatures is probably due to carotenoid degradation. Therefore, initial rind colour plays a critical role in final product quality. Depending on market destination and shipping temperature, pale-coloured fruit should not be packed for markets sensitive to rind colour. Holding temperature after shipping can be effectively used to improve the rind colour of fruit arriving in the market with undesirable rind colour. An intermediate holding temperature of between 11 and 15 ºC resulted in the greatest improvement in rind colour after 2 weeks. A high holding temperature (20 ºC) caused colour degradation, whereas a low holding temperature (4.5 ºC) resulted in the maintenance of rind colour. By selecting the correct holding temperature, even after shipping at sub-zero temperatures, final colour can be improved. / AFRIKAANSE OPSOMMING: Tyd-temperatuur interaksie op na-oes skilkleur ontwikkeling by sitrus Skilkleur is een van die belangrikste eksterne kwaliteitseienskappe van die sitrusvrug en spëel ʼn belangrikke rol in wat verbruikers koop. Verbruikers verwag dat heldergekleurde vrugte soet en ryp sal wees, terwyl sitrus met ʼn groen skil geassosieer word met onrypheid en ʼn suur smaak. In teenstelling hiermee is daar egter ʼn swak korrelasie tussen skilkleur en interne kwaliteit. Aangesien ʼn heldergekleurde oranje skil verbruikersaanvaarding verbeter, is dit dus belangrik om te verseker dat die sitrusvrug ʼn goeie skilkleur het teen die tyd wat dit die mark bereik. Verskeie voor-oes bestuurspraktyke en na-oes tegnieke kan toegepas word om die skilkleur te verbeter. Ontgroening met etileen gas is die tegnologie wat mees algemeen gebruik word om skilkleur na oes te verbeter, maar dit het egter verskeie newe effekte tot gevolg. Ontgroende vrugte is meer vatbaar vir bederf en verwelkde skille met ʼn dowwe voorkoms. Afsmaake kan voorkom en ʼn verkorte rakleeftyd is al gerapporteer. Dit is dus noodsaaklik om ʼn alternatief vir etileen ontgroening te ontwikkel en die rakleeftyd van sitrusvrugte te verleng. Onder normale boordomstandighede word skilkleur ontwikkeling geassosieer met lae nag temperature wat gewoonlik in die herfs of na ʼn kouefront ondervind word. Om soortgelyke omstandighede na te boots, was ʼn “hydrocooler” en koelkamers gebruik om die temperatuur vinnig te laat daal tot by 4 °C en dit vir 6 uur daar te hou. Die vrugte was dan by 20 tot 22 °C geinkubeer vir 72 uur. Hierdie “koueskok” behandeling van ‘Nules Clementine’ mandaryn het skilkleur verbeter tot ʼn vlak vergelykbaar met ontgroende vrugte in die 2002 seisoen wat ontstaan het weens ʼn verlaging in chlorofil en ʼn toename in die karotinoïed inhoud van die skil. Opbergingstemperatuur is een van die belangrikste na-oes faktore wat skilkleur beinvloed. Sitrusvrugte wat verskeep word na uitvoermarkte wat lae temperature (-0.6 °C) vir disinfestasie vereis arriveer soms by die mark met ʼn swak skilkleur. Om die fitosanitêre vereistes vir die invoer van sitrus deur die VSA na tekom, was vrugte vir ʼn minimum van 22 dae by -0.6 °C gehou. Die effek van verskeping by verskeie temperature (-0.6 °C of 4.5 °C), tydperke en die invloed van aanvanklike skilkleur, “oranje” of “geel” was geevalueer by aankoms in die mark. Vrugte wat by hoër temperature (4.5 °C) verskeep was het ʼn effens beter skilkleur as vrugte by -0.6 °C getoon. Die verlies in skilkleur wat waargeneem word na verskeping onder vriespunt kan moontlik toegeskryf word aan karotenoiëd afbraak. Daarom speel aanvanklike skilkleur ʼn kritieke rol in finale produk kwaliteit. Die finale mark bestemming en verskepingstemperatuur sal bepaal of swakgekleurde vrugte verpak kan word. Opbergingstemperatuur na verskeping kan effektief gebruik word om die skilkleur van vrugte wat swak gekleur was met aankoms by die mark te verbeter. Matige temperature tussen 11 en 15 °C het na 2 weke die beste verbetering in skilkleur gelewer. Hoër temperature (20 °C) het skilkleur nadelig beinvloed, terwyl lae temperature skilkleur behou het. Deur die korrekte temperatuur te kies, selfs na verskeping by temperature onder vriespunt, kan uiteindelike skilkleur steeds verbeter word.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2008. / ‘Brookfield Gala’ apple trees were planted out in July 2003 in a Dundee soil form, consisting of well-aerated sandy loam soil. During the first 12 months trees received young tree solutions high in nitrogen. The nutrient solution of the 2nd leaf trees was based on a yield estimation of 10 ton. ha-1 plus 30%. Nutrient solutions for the 3rd leaf trees were based on 25 ton. ha-1 yield estimations and adapted upwards. Seasonal uptake and distributions were determined for macro and micro elements, using twoand three-year-old apple trees during the seasons 2004/2005 and 2005/2006. In the bearing apple trees the macro nutrient accumulated rapidly from late winter to late autumn. Prior to leaf drop most of the N, P, S, Mg and a small portion of K were redistributed back into the permanent parts of the tree. On the other hand, all Ca in the leaves was lost through leaf drop. Apple fruit contains comparatively large quantities (±60.2%) of K, which are removed during harvest. Guidelines for minimum and maximum nutritional requirements based on the amount necessary to produce 1 kg fruit were determined. For the 3rd leaf trees the minimum macro nutrient requirements (g. kg-1 yield) of N, P, K, Ca, Mg and S were ±1.7, ±0.3, ±2.3, ±0.5, ±0.2 and ±0.2, respectively. The maximum nutrient requirements (g. kg-1 yield) for N, P, K, Ca, Mg and S were ±2.6, ±0.4, ±3.3, ±1.9, ±0.4 and ±0.2, respectively. For the 3rd leaf trees the minimum micro nutrient requirements (mg. kg-1 yield) of Na, Mn, Fe, Cu, Zn, B and Mo were ±75.1, ±1.3, ±28.7, ±0.9, ±3.0, ±5.7 and ±0.3, respectively. The maximum nutrient requirements (mg. kg-1 yield) of Na, Mn, Fe, Cu, Zn, B and Mo were ±102.9, ±7.8, ±32.6, ±1.1, ±6.5, ±7.6 and ±0.3, respectively. Labelled N uptake and distribution for two- and three-year-old apple trees were also determined during the same seasons. The labelled N uptake and distribution results indicated that there was a low labelled N uptake in the initial growth stages, suggesting the importance of internal N reserves for plant development at the beginning of the season. In the active growing period more than 60% of the labelled N was found in the new growth. Uptake efficiency improved as the trees grew older. The effect of different nutrient levels on tree growth, yield and fruit quality was assessed: lower (80%) than the standard (100%) and three higher (120%, 140% and 160%). Results indicated that different nutrient levels had no effect on yield, blush or TSS during the 18 months of application over two bearing seasons. The application of biological products (humic acid, and compost plus compost extract) over a period of 18 months had a significant influence on the TSS, malic acid and citric acid concentrations. A tendency towards an increase in total fine root number and length occured with the addition of biological ameliorant.

Thesis (MScAgric (Horticulture))--Stellenbosch University, 2008. / Sweet cherries (Prunus avium L.) have a high chilling requirement and grow best in areas receiving >1 100 Utah chill units during winter. The main production areas in South Africa, and particularly the eastern Free State, frequently receive insufficient winter chilling and late spring frosts leading to problems of poor budburst, flowering, floral abnormalities and poor fruit set. Research was conducted on the cultivar ‘Bing’ to determine the main factors causing its low fruit set. Various trials were conducted to optimize the timing of rest breaking agents, identify suitable cross pollinizers that flower synchronously with ‘Bing’, and evaluate the influence of temperature and pollen-pistil interactions on fertilization and fruit set. Pollen biology studies using 2- to 3-year-old ‘Bing’ sweet cherry trees were conducted near Clarens, eastern Free State, during the 2005 and 2006 seasons to determine the most suitable cross pollinizer/s for ‘Bing’ and to assess the influence of temperature and pollen-pistil interactions on pollen tube growth and ovule longevity. Significant differences in pollen germination (‘rates’ deleted) occurred between pollinizers, although differences were noted in pollen performance on the stigma and style (in vivo) compared to the artificial media (in vitro), indicating a lack of correlation between in vitro germination and in vivo pollen-pistil interactions. Pollen tube growth, following cross pollination, was influenced by pollinizer genotype, temperature, and the number of pollen grains deposited on the stigma. The highest pollen tube growth rates in ‘Bing’ styles were recorded for the pollinizers ‘Black Tartarian’ (2006), ‘Lapins’ and ‘Rainier’ sweet cherry cultivars at temperatures of approximately 21°C. Temperature had the most significant influence on ovule longevity with the lower orchard temperatures extending ovule viability compared to the higher laboratory temperatures, although pollen tube growth rates were also reduced, thus shortening the effective pollination period. Cross pollination was also shown to extend ovule viability. The results indicate that ‘Black Tartarian’, ‘Lapins’ and ‘Rainier’ were the most suitable pollinizers for ‘Bing’. Hand-pollination with pollen from these donors resulted in a several-fold increase in seed set over naturally-pollinated control flowers. It appears that the principle factors causing poor fruit set in ‘Bing’ sweet cherry are premature abortion of the ovule before fertilization and inadequate transfer of sufficient viable pollen under orchard conditions. Rest breaking trials were conducted on 4-year-old ‘Bing’ sweet cherry trees on ‘Gisela® 5’ rootstock near Clarens (28°28’S; 28°19’E, 1860m) and Reitz (28°0’S; 28°28’E; 1717m) in the eastern Free State, South Africa, during the 2005 and 2006 seasons respectively. In 2005 five treatments were evaluated; viz. 1% and 2% Dormex® (hydrogen cyanamide, HCN); 1% Dormex® + 3% mineral oil; and 3% Lift® (thidiazuron and mineral oil) sprayed at three dates (29 July 2005, 5 August 2005 and 12 August 2005) preceding expected the “green-tip” stage of flower development, plus an unsprayed control. In 2006 four treatments were evaluated; viz. 1% Dormex®; 1% Dormex® + 3% mineral oil; 3% Lift® applied on three dates (26 July 2006, 7 August 2006 and 12 August 2006) and an unsprayed control. No interaction was observed between time of application and type of rest breaking agent (RBA). RBAs were effective at improving budburst and yield during both seasons with the time of application of RBAs having the most significant influence on budburst and production efficiency in ‘Bing’ sweet cherry trees. RBAs were most effective at improving vegetative budburst when applied 9 to 16 days before the (‘actual’ deleted) “green-tip” stage of flower development. Floral budburst and yield were increased by 1% Dormex® + 3% mineral oil and 3% Lift®, but results varied between seasons indicating that time of RBA application should be based on chilling accumulation and bud development stage and not based on calendar date. This current research suggests that ‘Bing’ sweet cherry is poorly suited climatically to the current production areas of the eastern Free State and short-term research needs to identify methods of improving chilling and fruit set by means of evaporative cooling and fruit set-enhancing plant growth regulators. Longer term work requires the identification of new, lower chill cultivars with improved climatic adaptation to South African conditions.

Thesis (MScAgric)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Stone fruit is susceptible to chilling injury and intermittent warming has been shown to alleviate chilling injury during cold storage. A dual temperature storage regime was developed in South Africa for plums based on the principles of intermittent warming. The regime consists of an initial period at -0.5°C, a variable duration warming period at 7.5°C, followed by -0.5°C. Refrigerated integral containers were designed to maintain product temperature and not to reduce product temperature, per se. Considering that dual temperature shipment requires significant refrigeration and effective distribution of cool air to remove sensible- and respiratory heat, the capacity of integral containers to ship plums successfully at dual temperature is questioned. The objectives of this study were, firstly, to analyse pulp temperature data and possibly identify different temperature zones within containers shipping plums at dual temperature. Secondly, to understand the underlying processes differentiating the temperature zones and thirdly, to determine the effect of container performance on fruit quality. Three processes were identified as important characteristics of pulp temperature data sets recorded during dual temperature shipping, namely cooling down, heating up and over heating in the container. The order of importance differed according to the cultivar shipped and the container’s performance. Three temperature zones were identified in dual temperature containers, where the average pulp temperature, time to heat up and time to cool down for each temperature zone increased along the length, across the width from the left to the right and up the container system. The variable temperature conditions were possibly due to a variation in delivery air temperature, poor airflow and the effect of increased respiration and, therefore, production of vital heat by the fruit. The cooling down process was identified as the most important process discriminating the temperature zones. With the exception of ‘Fortune’, variable temperature conditions found within integral containers shipping plums at dual temperature had a significant influence on the fruit firmness post-shipment, where deterioration levels increased from the front to the door end of the container due to an increase in pulp temperature. However, it was also shown that fruit firmness prior to shipment could have a determining effect on differences found. It could not be proven that variable temperature conditions resulted in significantly higher levels of internal defects within the integral container. Temperature zones could not be identified within refrigerated integral containers shipping plums at single temperature, suggesting that the containers are able to maintain the temperature well throughout the container area. A constant 2°C storage temperature could possibly replace the commercial dual temperature regime in the case of ‘Pioneer’ plums due to improved fruit firmness, similar colour development to the control and less sensible heat produced in the container resulting in a more stable container environment. However, unacceptably high levels of shrivel and internal browning were found. / AFRIKAANSE OPSOMMING: Steenvrugte is vatbaar vir koueskade en dit is bewys dat periodieke verwarming gedurende koelopberging koueskade kan verlig. Die dubbeltemperatuur opbergingsregime is in Suid- Afrika ontwikkel vir pruime en is gebaseer op die beginsels van periodieke verwarming. Die regime bestaan uit ‘n inisiële periode by -0.5°C, ‘n variërende periode by 7.5°C, gevolg deur -0.5°C. Verkoelde integrale houers is ontwerp om produktemperature te handhaaf en nie soseer om produktemperatuur te verlaag nie. Die kapasiteit van integrale houers om pruime suksesvol teen dubbeltemperatuur te verskeep word dus bevraagteken, in ag geneem dat dubbeltemperatuurverskeping betekenisvolle verkoeling en effektiewe verspreiding van koue lug vereis om die waarneembare- en respiratoriese hitte te verwyder. Die doelwitte van die studie was eerstens om die pulptemperatuurdata te analiseer en moontlik verskillende temperatuursones binne houers wat pruime teen dubbeltemperatuur verskeep te identifiseer. Tweedens, om die onderliggende prosesse wat die temperatuursones van mekaar onderskei te verstaan, en derdens om die effek van die houer se werkverrigting op vrugkwaliteit te bepaal. Drie prosesse is geïdentifiseer as belangrike eienskappe van pulptemperatuur datastelle aangeteken gedurende dubbeltemperatuurverskeping, naamlik afkoeling, opwarming en oorverhitting wat binne die houer plaasvind. Die volgorde van belangrikheid het gevarieer afhangende van die kultivar verskeep en die houer se werkverrigting. Drie temperatuursones is geïdentifiseer binne integrale houers wat pruime teen dubbeltemperatuur verskeep, waar die gemiddelde pulptemperatuur, die opwarmingstyd en die afkoelingstyd vir elke temperatuursone in die lengte, oor die wydte van links na regs en van onder na bo in die houersisteem toegeneem het. Die variërende temperatuur toestande kan moontlik toegeskryf word aan ‘n variasie in leweringstemperatuur, swak lugvloei en die effek van toenemende respirasie, en dus die produksie van hitte vrygestel deur die vrugte. Die afkoelingsproses is geïdentifiseer as die belangrikste proses wat die temperatuursones van mekaar onderskei. Behalwe in die geval van ‘Fortune, het variërende temperatuurtoestande in integrale houers wat pruime teen dubbeltemperatuur verskeep ‘n betekenisvolle invloed op die vrugfermheid na verskeping gehad, waar vrugveroudering toegeneem het van voor in die houer na die deur van die houer as gevolg van ‘n toename in pulptemperatuur. Daar is egter bewys dat die vrugfermheid voor verskeping ook ‘n bepalende effek kon hê op die fermheidsverskille. Dit kon nie bewys word dat die variërende temperatuurtoestande betekenisvol hoër vlakke van interne defekte binne die integrale houer veroorsaak het nie. Temperatuursones kon nie geïdentifiseer word binne verkoelde integrale houers wat pruime teen enkeltemperatuur verskeep het nie, wat dus impliseer dat die houers daartoe instaat is om temperatuur goed te onderhou binne die houer. ‘n Konstante 2°C opbergingstemperatuur kan moontlik die kommersiële dubbeltemperatuurregime vervang in die geval van ‘Pioneer’ pruime as gevolg van verbeterde vrugfermheid, soortgelyke kleurontwikkeling as die dubbeltemperatuurregime en minder hitte geproduseer binne die houer deur die pruime, wat ‘n meer stabiele houeromgewing veroorsaak. Onaanvaarbare hoë vlakke van verrimpeling en interne verbruining is egter gevind.

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.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2008. / Commercial production of sweet cherries has recently increased in South Africa, with more than 400 ha planted by 2006. Cherry, a high chilling fruit variety, is however not suited for the mild winter climate of South Africa. This was recognizable through common observed symptoms of delayed foliation and poor fruit set. In addition, cherry is exposed to long and hot summers in the postharvest period. The objective of this study was to evaluate cherry cultural practices that can manipulate (reduce) the trees chilling requirement under South African conditions. Cultural practices where aimed at increasing reserves (nitrogen, cytokinin and carbohydrates) in the tree. In addition, bud dormancy progression of cherry buds was quantified to determine the bud dormancy progression pattern under mild winter conditions. This was achieved through sampling of cherry shoots from different cherry production areas which was then forced in the growth cabinets. A model was developed to identify possible factors and groupings that can explain the cherry bud dormancy pattern. A model, comprising two joined straight lines, was fitted in order to characterize bud dormancy behaviour for sweet cherry cultivars under mild winter conditions. All cherry cultivars followed the expected pattern of entrance and exit from dormancy. Factor analysis showed that factors related to the entrance into dormancy primarily characterize bud dormancy behaviour. Bud dormancy patterns were also a function of environmental conditions within a year as shown by cluster analysis. In addition, buds entered dormancy in mid-summer and remained dormant until chilling accumulation commenced. Bud dormancy release was generally extended over a three to five-month period for all cultivars. Prior to spring budburst exit of both lateral and terminal buds occurred rapidly. Data indicate that there is no ecodormant phase for cherry under the prevalent climatic conditions in South Africa. Further experimentation was aimed at increasing reserves within the trees through cultural practices. In the nitrogen trials, fertilization in the postharvest period had no significant effect on field budburst or bud dormancy progression in one-year-old shoots. Time of flowering was advanced in N treatments during 2007 only. Yield was not significantly increased. Therefore, in this trial, N fertilization in the postharvest period did not significantly reduce the chilling requirement of mature sweet cherry trees under mild winter conditions. Application of particle films (Surround® and Raynox®) or ethylene inhibitors (Retain®) in the summer did not reduce the heat stress the trees experienced. Treatments had no significant effect on carbon assimilation, stomatal conductance, leaf surface temperature, fluorescence, bud dormancy, budburst, flowering and fruit set. Cytokinins sprays (benzyladenine) in autumn did not affect bud dormancy progression, spring budburst or flowering. Hydrogen cyanamide application in spring significantly advanced budburst, time to full bloom and increased yield. Promalin® and Retain®, however, had no significant effect on budburst, flowering or yield. It is therefore evident that cherry, due to its unexpected bud dormancy behaviour and its inability to be significantly influenced by several cultural practices, adapts poorly to South African climatic conditions through not reducing its chilling requirement significantly.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Commercial fig production with popular European cultivars, Bourjasotte Noire, Col de Damme Noire and Noire de Caromb, is new to the Western Cape. Little research on fig production has been conducted in South Africa and producers are struggling to implement effective commercial practices. In order to establish practices that will maximise yield of quality fruit, the most productive one-year-old shoot lengths were identified in a phenological study. All shoot length categories evaluated in ‘Bourjasotte Noire’ (10 – 15 cm, 25 – 40 cm, 50 – 65 cm, 75+ cm) yielded fruit and will probably yield well the following season. In ‘Col de Damme Noire’, shoots longer than 60 cm seem to be suited to reproduction, yet they might produce a poor yield the following season. Shoots 10 – 20 cm long in ‘Noire de Caromb’ are productive relative to their length, while shoots 30 – 50 cm and 60 – 80 cm long are also fairly productive. Shoots longer than 100 cm produced suitable shoot lengths for yield the following season. Two experiments were conducted on ‘Bourjasotte Noire’ and ‘Col de Damme Noire’ to establish the type (Experiment 1, different intensity heading cuts) and timing (Experiment 2) of pruning cuts required to stimulate the growth of shoots of the same length as the shoots selected to be optimal for yield in the phenology study, and to reduce the expression of distal branching. In ‘Bourjasotte Noire’, removing one third of the total length of one-year-old shoots on 21 July by heading stimulated the development of more growth and longer current season shoots compared to other treatments, while reducing yield slightly. Heading back to three nodes in ‘Col de Damme Noire’ stimulated the growth of current season shoots of the optimal length established in the phenology study, while heading cuts on 30 June produced the longest average current season shoot length in ‘Col de Damme Noire’. To further address the effects of distal branching (acrotony), an experiment was conducted to establish whether rest breaking agents (RBA’s) in combination with tip-pruning can increase tree complexity by improving bud break, and whether increased complexity would increase yield in all three cultivars. A second experiment was conducted to evaluate the effects of timing RBA applications on bud break and harvest scheduling. Lift® increased the number of buds breaking in ‘Bourjasotte Noire’, while in ‘Noire de Caromb’ Dormex® and oil increased bud break. Tip-pruning increased the average shoot length in ‘Bourjasotte Noire’ and ‘Col de Damme Noire’, while causing a reduction in the amount of new growth in ‘Noire de Caromb’. Lift® applied 3 August and Dormex® applied 30 June shortened the number of days to 50% bud break in ‘Bourjasotte Noire’ and ‘Col de Damme Noire’. Both Lift® and Dormex® applied on 30 June decreased the number of days to 50% bud break and 50% harvest of the breba crop in ‘Noire de Caromb’. These treatments increased the number of fruit in both the breba and main crop of ‘Noire de Caromb’, but reduced fruit size. In conclusion, different approaches with regards to pruning needs to be followed for each cultivar to establish or maintain the optimal shoots for reproduction, while RBA’s can be used to force earlier, increased- bud break and harvest of breba fruit. / AFRIKAANSE OPSOMMING: Kommersiele verbouing van drie Europese vykultivars, Bourjasotte Noire, Col de Damme Noire en Noire de Caromb is nuut tot die Wes-Kaap. Baie min navorsing oor die verbouing van vye is al in Suid-Afrika gedoen, met die gevolg dat produsente sukkel om effektiewe kommersiële verbouingspraktyke te implementeer. ‘n Fenologiese studie van die drie kultivars is uitgevoer om vas te stel wat die mees produktiewe een-jaar-oue lootlengte is, met die doel om die opbrengs van kwaliteit vrugte te maksimeer. Al vier kategorieë wat ge-evalueer is in ‘Bourjasotte Noire’ (10 – 15 cm, 25 – 40 cm, 50 – 65 cm, 75+ cm) is gevind om geskik te wees vir huidige en volgende seisoen opbrengs. Lote langer as 60 cm is geskik vir opbrengs in ‘Col de Damme Noire’ in die huidige seisoen, maar mag in die volgende seisoen swak presteer a.g.v. die gebrekkige lengte van nuwe lote wat daarop ontwikkel. In ‘Noire de Caromb’ is gevind dat lote 10 – 20 cm lank baie produktief is relatief tot hul lengte en dat lote 20 – 50 cm en 60 – 80 cm lank ook relatief produktief is. Lote langer as 100 cm was minder produktief, maar het nuwe lote gelewer wat geskik is vir opbrengs die volgende seisoen. Twee snoei eskperimente is uitgevoer op ‘Bourjasotte Noire’ en ‘Col de Damme Noire’ om vas te stel wat die mees geskikte tipe snoeisnit (Eksperiment 1, verskillende dieptes van topsnitte) en tydstip om te snoei (Eksperiment 2) is met die doel om lote te produseer soortgelyk in lengte aan die wat in die fenologie studie uitgewys is as die produktiefste, en om moontlik die voorkoms van “kaalnekke” te verminder. In ‘Bourjasotte Noire’ is gevind dat die wegsnoei van ‘n derde van die loot op 21 Julie aanleiding gee tot meer groei, langer een-jaar-oue lote en ‘n effense afname in opbrengs. Geskikte lote langer as 60 cm kan in ‘Col de Damme Noire’ verkry word deur lote te top sodat net drie nodes oorbly. Die uitvoer van topsnitte op 30 Junie het langer gemiddelde lootlengtes tot gevolg gehad. Om die probleem van “kaalnekke” (apikale dominansie) verder aan te spreek, is ‘n eksperiment uitgevoer om vas te stel of rusbreekmiddels gekombineerd met tip-snoei gebruik kan word om kompleksiteit te vermeerder deur knopbreek te verhoog, en indien wel, of dit sal aanleiding gee tot verhoogde opbrengs in al drie kultivars. ‘n Tweede eksperiment met verskillende toedieningstye van rusbreekmiddels is uitgevoer om vas te stel of oeste geskeduleer kan word. Lift® het knopbreek verhoog in ‘Bourjasotte Noire’, terwyl Dormex® en olie knopbreek verhoog het in ‘Noire de Caromb’. Tip-snoei het die gemiddelde lootlengtes verhoog in ‘Bourjasotte Noire’ en ‘Col de Damme Noire’, terwyl dit groei verminder het in ‘Noire de Caromb’. Lift® toediening op 3 Augustus en Dormex® toediening op 30 Junie het die aanvang van 50% knopbreek vervroeg in ‘Boujasotte Noire’ en ‘Col de Damme Noire’. Beide Lift® en Dormex® toediening op 30 Junie het die bereiking van 50% knopbreek- en 50% oes vervroeg in ‘Noire de Caromb’. Hierdie behandeling het ook die aantal vrugte van die breba- en hoofoes vermeerder, maar vruggrootte verminder. Verskillende snoeibenaderings behoort dus gevolg te word om vir elke kultivar die regte lootlengtes te genereer of te onderhou, terwyl rusbreekmiddels gebruik kan word om knopbreek te vervroeg en verhoog, en om die breba oes te vervroeg.