Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: In South Africa tomato production in greenhouses normally occurs out of season when conditions are unfavourable for production and for the pollination process. Pollination is of special importance and the backbone of production. High temperatures contribute to the formation of abnormalities in flower morphology such as splitting of the anther cone and style exsertion. Low temperatures inhibit growth of the anther cone and therefore the style is uncovered. The movement of pollen from the anther to the style is inhibited by the higher style position in relation to the anther cone. Under humid conditions the pollen tends to stick to the anther surface. Another factor contributing to the problem is the banning of European bumble bees in South Africa. Alternative methods of pollen transport have to be found. Truss vibration, honey bees and plant growth regulators (PGR) are the most popular alternatives. Truss vibration and the use of PGR's are labour intensive and honey bees tend to get disorientated inside a plastic greenhouse. During the first part of this study pollen from plants, grown at four different B-levels (0.02; 0.16; 0.32 and 0.64 mg rl) was germinated in vitro. It was kept at different temperatures and periods before incubating on different growth media. No proof was found that pollen from B-deficient plants germinated poorly. Germination of pollen decreased significantly after one week storage. Deterioration of pollen viability could be lowered by storage at 5°C. At least 10% sucrose is needed in the growth medium for in vitro germination but addition ofB had no positive effect. In a second phase of the study, the influence of the mentioned B application rates were tested. The experiment was done in a glasshouse where temperatures were mechanically regulated (22°C and 10°C day/night). Seedlings of the greenhouse tomato cultivar, Abigail, were planted in acid washed river sand. Plants were grown with the main stem trellised vertically and the side shoots removed weekly. Only the first, third and fourth cluster were used for this part of the study. The uptake of all the essential nutrient elements, fruit set, the relation of larger to smaller fruits, physical and chemical quality and fruit shelf life were evaluated. The application of B at higher rates increased the uptake of Ca and decreased K-uptake. Fruit set, fruit development, fruit color and shelf life were the best at a B-Ievel of 0.16 mg r'. At this rate the abortion of flowers was the least. The same plants were used for the second part of the study, using the third cluster. The influence of the same four B-Ievels, the relative humidity (RH) of the truss atmosphere and truss vibrations were tested. The second cluster was covered with a plastic bag. Dry {<I 0% relative humidity (RH)}, normal {60-7S% RH} and moist {8S-97% RH} air were constantly applied to the bags at ± 50 ml min-I. As a third factor, truss vibration was applied daily by means of an electric vibrator (polli-bee), The amount of flowers per cluster, fruits per cluster, fruit set, weight of the cluster (yield), fruit weight, seed production, fruit weight per amount of seeds formed and fruits with blossom-end-rot (BER) were evaluated. The application of higher B-Ievels, air with the normal RH and the vibration of the clusters positively affected fruit weight, weight of the cluster and fruit set. High RH increased the occurrence of BER, probably due to a lack of transpiration from the fruit surface and therefor a lack in Ca translocation. / AFRIKAANSE OPSOMMING: Die verbouing van kweekhuistamaties in Suid-Afrika geskied meestalonder toestande wat ongunstig is vir produksieprosesse en veral die bestuiwingsproses wat die basis van produksie is. Onder toestande van hoë temperature is die voorkoms van afwykings in die blommorfologie (gesplete meeldraadbuis en verlengde styl) algemeen. Net so, onder toestande van lae temperature, sal gebrekkige groei van die meeldraadkrans ook tot die blootstelling van die stempel lei. Die oordraging van die stuifmeel vanaf die helmknop na die stempel word hierdeur benadeel. Tydens humiede toestande mag vasklewing van stuifmeel aan die helmknoppe ook die beweging van stuifmeel belemmer. 'n Verdere faktor wat tot die probleem bydra is die verbod op die invoer van hommelbye uit Europa. Alternatiewe metodes vir oordraging van stuifmeel moet dus gevind word. Trosvibrasie, heuningbye en die gebruik van plantgroeireguleerders (PGR's) is die mees populêre alternatiewe. Trosvibrasie met 'n 'polli-bee' en die aanwending van PGR's is arbeidsintensief. Heuningbye ondervind navigasieprobleme in plastiek kweekhuise en is nie so effektief as hommelbye nie. Tydens die eerste fase van die ondersoek is stuifmeel vanaf plante, wat by vier verskillende Bvoedingspeile (0.02; 0.16; 0.32 en 0.64 mg rl) verbou is, versamel en in vitro ontkiem. Dit is by verskillende temperature en periodes opgeberg en op verskillende media vir ontkieming geïnkubeer. Geen bewyse kon gevind word dat stuifmeel vanaf B-gebrekkige plante swak ontkiem nie. Kiemkrag van stuifmeel het na sewe dae opberging betekenisvol verswak. Verswakking in kiemkrag kon beperk word deur die stuifmeel by SoC op te berg. 'n Ontkiemingsmedium met ten minste 10% sukrose is vir goeie in vitro ontkieming van stuifmeelkorrels nodig terwyl die byvoeging van B geen voordelige effek getoon het nie. Tydens die tweede gedeelte van hierdie ondersoek is die invloed van die genoemde vier B-voedingspeile ondersoek. Die ondersoek is in 'n glashuis, waarvan die temperature meganies beheer is (22°C en 10°C dag/nag), uitgevoer. Plantmateriaal van die kweekhuistamatiekultivar, Abigail, is in suurgewasde riviersand geplant. Hoofstamme is vertikaalopgelei en die sylote is een maal per week uitgebreek. Die eerste, derde en vierde bloeiwyses is vir die ondersoek gebruik. Die opname van al die essensiële voedingselemente (blaarontledings), vrugset, die verhouding van groot vrugte tot kleiner vrugte, fisiese en chemiese kwaliteite van die vrugte en die raklewe daarvan is ge-evalueer. Die toediening van B teen hoër peile het die opname van Ca ten koste van K bevoordeel. Die beste resultate ten opsigte van vrugset, vrugontwikkeling, vrugkleur en die houvermoë (raklewe) van die vrugte is verkry teen 'n B-toedieningspeil van 0.16 mg.l'. Vir die derde gedeelte van die ondersoek is die tweede tros van dieselfde aanplanting gebruik. Die invloed van die vier B-voedingspeile, relatiewe humiditeit (RH) van die omgewing rondom die tros en trosvibrasie is ondersoek. Die tweede bloeiwyse is met 'n deursigtige plastieksakkie bedek. Droë {dO% relatiewe humiditeit (RH)}, normale {60-75% RH} en vogtige {85-97% RH} lug is teen 50 ml min-1 oor die tros gestuur. Trosvibrasie is as derde faktor teen twee peile gebruik deur trosse daagliks met 'n elekriese vibreerder ("polli-bee') te vibreer. Die aantal blomme per tros, vrugte per tros, vrugset, trosmassa (opbrengs), vrugmassa, aantal sade, vrugmassa per saad en blom-end-verrotting (BER) is ge-evalueer. Die toediening van hoër B-voedingspeile, 60-75% RH lug en trosvibrasies het vrugmassa, trosmassa en vrugset bevoordeel. Hoë lugvog het die omvang van BER verhoog, waarskynlik weens 'n gebrek aan transpirasie vanaf die vrugoppervlakke wat aanleiding tot 'n beperking in translokasie van Ca kon gee.

No description available.

Thesis(M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 63-64). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 63-64). Also available on the Internet.

Thesis (MScAgric)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2012. / The effects of various water quantities were assessed on Cucumber (Cucumis sativa L.) grown hydroponically in the greenhouse. The objectives of the study were to evaluate influence of water quantities on: i) photosynthesis and chlorophyll content of Cucumis sativa L.; ii) the nutrient uptake in Cucumis sativa L. iii) flavonoid and anthocyanin metabolism in Cucumis sativa L. and iv) growth and yield in Cucumis sativa L. The treatments included 8 various water regimes (21/h, 41/h, 61/h, 81/h, 101/h, 121/h, 141/h and 161/h. The plants received water five times a day, making it 10, 20, 30, 40, 50, 60, 70, and 80 litres per day. Results showed that generally the Photosynthetic rate (A), intercellular CO2 concentration (Cj) and stomata conductance (gs) and the transpiration rate of the cucumber plants were significantly increased by increasing water quantities compared with lower water quantities. Additionally, there were significant improvements in leaf colour in weeks 2, 3, 4, 5, 6, 7 and 8. Overall, the foliage colour was improved as water supply was increased. The greener leaves were documented in treatments supplied with higher water doses. Additionally, the chlorophyll content of cucumber plants was increased significantly with varying water quantities. The highest chlorophyll contents were found in plants treated with 161/h.

Agricultural educators encounter unique teaching challenges as they teach applications of plant production in the greenhouse classroom. The teacher self-efficacy construct has been used broadly to link student learning outcomes to teachers' beliefs in their ability to attain certain instructional goals in the classroom. Few studies have used this construct to examine teacher-efficacy in the greenhouse classroom. This study uses the teacher self-efficacy construct within the agricultural educator domain. It seeks to measure change in agricultural educator self-efficacy beliefs using established self-efficacy scales to determine if a professional development experience in greenhouse operation and management effects educator beliefs in their ability to teach in the greenhouse classroom.

Thesis (MScAgric (Agronomy)--University of Stellenbosch, 2005. / The seven evergreen Disa species are indigenous to South Africa. These orchids grow on mountain ranges subject to winter rainfall and are found on stream banks, around waterfalls and in other damp areas. Although the Disa genus accommodates more than 130 species, by far the most commonly grown is Disa uniflora and hybrids stemming from this species. Disas have great potential as cut flowers and pot plants, but production techniques need to be further investigated since cultivation methods vary greatly between hobbyists. This study evaluated the effect of N-source, shading, root medium temperature, electrical conductivity (EC), irrigation method, foliar feeding at different plant growth stages and substrate on the growth of evergreen Disa hybrids in a controlled environment. Results showed that Disa plants can be classified as being ammonium tolerant. Disa unidiorosa performed best with 40% of the applied N in the NH4 form, while D.kewensis was more tolerant towards a higher level of NH4 and grew best at 60% NH4. Shading levels (56% and 69%) were compared and did not differ regarding the growth of plants. A cooled root medium was found to have a negative effect on root growth and a positive effect on leaf length. High EC levels produced heavier mother plants with a bigger root:shoot ratio and a bigger stem diameter. Biomass accumulation was the best in plants receiving ‘Drip’ irrigation, compared to ‘Ebb-and-Flood’ irrigation treatments. Plants in the vegetative reproducing stage were more susceptible to leaf abscission and new leaves formed at a low rate compared to small- and potential flowering plants. Where foliar feeding is concerned plants seemed to benefit more by the presence of NH4NO3 than urea. There were no significant differences in root development between substrates in the ‘hardening-off’ phase. ‘Hydroton’ (clay pebbles) was not suitable as substrate for the cultivation of Disa plants. The growth and flowering properties of plants were optimal with sphagnum moss and peat but were negatively affected when the pH of acid peat:sand mixtures were increased. More research is needed before Disas can be cultivated on a commercial scale, while the effect of the treatments on flowering properties has to be investigated.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Horticulture in the Faculty of Applied Sciences at the Cape Peninsula University of Technology, 2012 / The effects of various water quantities were assessed on Cucumber (Cucumis sativa L.) grown hydroponically in the greenhouse. The objectives of the study were to evaluate influence of water quantities on: i) photosynthesis and chlorophyll content of Cucumis sativa L.; ii) the nutrient uptake in Cucumis sativa L. iii) flavonoid and anthocyanin metabolism in Cucumis sativa L. and iv) growth and yield in Cucumis sativa L. The treatments included 8 various water regimes (2l/h, 4l/h, 6l/h, 8l/h, 10l/h, 12l/h, 14l/h and 16l/h. The plants received water five times a day, making it 10, 20, 30, 40, 50, 60, 70, and 80 litres per day. Results showed that generally the Photosynthetic rate (A), intercellular CO2 concentration (Ci) and stomata conductance (gs) and the transpiration rate of the cucumber plants were significantly increased by increasing water quantities compared with lower water quantities. Additionally, there were significant improvements in leaf colour in weeks 2, 3, 4, 5, 6, 7 and 8. Overall, the foliage colour was improved as water supply was increased. The greener leaves were documented in treatments supplied with higher water doses. Additionally, the chlorophyll content of cucumber plants was increased significantly with varying water quantities. The highest chlorophyll contents were found in plants treated with 16l/h. The fresh and dry weights of roots, leaves and stems were significantly (P≤0.001) influenced by different water quantities supplied to Cucumis sativa L. The largest quantity of fresh roots was recorded in the control treatment (2l/h) in comparison with all other treatments. However, the best growth with regard to fresh and dry weights of leaves and stems were recorded by supplying the water quantities ranging from 10-16l/h. Altering water supply significantly (P≤0.001) affected the uptake of nitrogen, phosphorous, potassium, calcium, sodium, copper, zinc, aluminium and iron in roots of Cucumis sativa L. Irregular results were recorded in the uptake of these nutrients in the roots. However, leaf uptake of N, P, K, Ca, magnesium, sulphur, Cu, Zn, manganese, boron, and Al responded significantly (P≤0.001) to the different water quantities. The best result for each was observed at quantities involving 16l/h. In stems of cucumber water quantities significantly (P≤0.001) affected the uptake of N, P, K, Ca, Mg, Na, S, Cu, Zn, Mn and B. The highest uptake of N, P, Ca, Mg and S were found at the maximum supply of water (16l/h) compared with the control (2l/h). Sodium uptake showed irregular patterns, whereas K and Zinc uptake peaked at 14l/h. The data from this study showed that flavonoid metabolism was not significantly affected by the different water quantities supplied to cucumber plants. However, the anthocyanin content in roots, leaves, and stem was significantly influenced by water levels. The lowest water quantity (2-6l/h) significantly increased the levels of anthocyanins in all tissues tested. Increasing water quantities significantly decreased the anthocynanin metabolism in all tissues. Plant height displayed significant differences with water quantities from weeks 1-8. In week 1, the plant height was superior at supplying 4l/h in comparison with other treatments. In week 2 and 5 irregular trends were detected. At weeks 3 and 4, plants supplied with 8-12l/h displayed superior plant height performance. At weeks 7-8, significant and optimal results were observed at water quantities ranging from 4-16l/h compared with the control treatment. Water quantities significantly (P≤0.001) affected the number of leaves per plant from weeks 2-8. Irregular results were displayed in weeks 2 and 3. At weeks 4 and 5, the highest numbers of leaves were in water quantities of 12l/h and 10l/h, respectively. Generally, leaf numbers increased with increasing water levels from weeks 6-8. Plant vigour was significantly affected by the alteration of water quantities at weeks 1, 2, 4, 5, 6, 7 and 8. At weeks 1 and 4, more vigorous plants were found in the treatments that received from 10-16 l/h. At weeks 2 and 5, optimal results were found at treatments that received from 6-14l/h. At weeks 6, 7 and 8, the most vigorous plants were found at the highest water quantity of 16l/h. With fruit length, fruit width, rind colour, fruit quality (marketable fruit) and weight, results from the harvest done in the first, second and third week showed that water quantities significantly influenced these parameters. Optimal results were reported when the plants were supplied with water ranging between 14-16l/h. During harvesting at week 4, the fruit length, width, rind colour, were of marketable quality at 16l/h. Generally, the plants that received highest amount of water (16l/h) had the highest cucumber yields compared with all other treatments. Higher water quantities in this study resulted in increased physiological responses such as photosynthesis and nutrient uptake which resulted in the higher fruit yields. In water-limited environments, results from this study could assist growers with reasonable cucumber yields while saving water for other farm uses.