Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The potential importance of soilless production, particularly in tomatoes, in an increasingly water scarce South Africa prompts a need for research under local conditions. In soilless production systems the application and availability of nutrients is closely linked to that of water, necessitating the research of methods to increase water and fertiliser use efficiency in soilless production systems, while diminishing environmental pollution and maintaining, or ultimately improving, tomato yield and quality. Poor management of hydroponic fertigation water results in pollution, and wastes precious water and expensive fertiliser. Pruning is an important cultural practise for ensuring high productivity of hydroponic tomatoes. Adapting pruning practises to climatic conditions could be a cheap and effective manner to improve productivity without increasing inputs. Improving water and fertiliser use efficiency is crucial to ensuring sustainable production of intensive crops, such as the tomato. Three experiments were carried out to investigate the effects of pruning and fertilisation on growth and yield and water and fertiliser use efficiency of hydroponic tomatoes. In the first experiment the effect of EC (electrical conductivity), irrigation frequency and growing media on water use, nutrient uptake, yield and quality of greenhouse tomato was examined. A factorial design with split plots was used. Two EC treatments (1 and 2 mS.cm-1) in factorial arrangement with 3 irrigation treatments (5x, 10x, 20x) were applied to the main plots. Plants grown in different growing media (coir, sand, sawdust) represented the split plots. Plants grown at EC 1 mS.cm-1 were still able to uptake sufficient nutrients to achieve leaf nutrient contents associated with optimal production. Also, increasing the absolute nutrient concentration had a small effect on nutrient uptake. The organic media, coir and sawdust, reduced available N early in the tomato crop life, and tomatoes grown in coir had reduced Ca uptake compared to plants grown in sand and sawdust. Coir grown plants used more water compared to sand and sawdust grown plants. Plants grown at EC 1 mS.cm-1 used less water compared to plants grown at EC 2 mS.cm-1. Tomatoes grown at an EC 1 mS.cm-1 did not differ significantly from higher EC plants in terms of marketable and green fruit yield. Plants cultivated at the lower EC had significantly lower percentage soluble solids content (Brix) compared to the higher EC treatment. The second experiment examined the effect of leaf and fruit pruning on fruit size, total yield and marketable yield of tomatoes. Plants were grown using the high wire system and pruned to two stems. Three different leaf pruning treatments were applied: no leaf pruning, pruning every 2nd young leaf after 1m plant height, and pruning every 2nd young leaf after 2m plant height. Two fruit pruning treatments were also applied: no fruit pruning and trusses pruned to 4 fruits. The experiment used a factorial design. Leaf pruning treatments had no effect and this was probably due to too late a removal of young leaves. Fruit pruning resulted in no significant difference between treatments in terms of marketable yield. Plants with unpruned trusses did have a significantly higher total yield, higher early yield, lower average marketable fruit weight, and higher yield of unmarketable fruit (particularly small fruit compared to the pruned treatment). From these results it can be concluded that fruit pruning isn’t necessary on short tomato crops but this may be different over a longer cropping cycle. The third experiment determined the combined effects of different EC and stem pruning practices on nutrition, growth and early yield of hydroponically grown tomatoes in coir. A factorial design was used, with two EC treatments (1 and 2 mS.cm-1) in factorial arrangement with 2 stem pruning treatments (single and double). Stem pruning had little effect on plant growth but did alter plant development. Plants pruned to two stems produced significantly more trusses, but did not produce a significantly higher DM or leaf area compared to single stem plants. Stem pruning’s major effect appears to be influencing fruit load; this may in the long term result in differences in plant growth and nutrition. EC 1 mS.cm-1 plants produced significantly lower leaf area and organ dry masses but had a significantly higher marketable yield compared to EC 2 mS.cm-1 plants. Over fertilisation in young tomatoes can negatively impact on early yield, whereas lower fertiliser application in early tomato growth improves early yield but limits canopy development which may limit plant productivity in the long term. These differences in growth are believed to be primarily related to differences in N and P nutrition. / AFRIKAANSE OPSOMMING: Die potensiële belang van grondlose produksietegnieke, veral by tamaties, in Suid-Afrika wat toenemend meer water skaars raak, motiveer dat navorsing onder plaaslike toestande gedoen moet word. By grondlose produksie stelsels word die toediening en die beskikbaarheid van voedingstowwe nou gekoppel aan dié van water. Navorsing rakende metodes wat water en kunsmis gebruiks doeltreffendheid sal verhoog en terselfdertyd besoedeling van die omgewing voorkom asook die opbrengste en kwaliteit van tamaties behou of verbeter is dus van uiterste belang. Swak bestuur van bemesting in hidroponiese stelsels gee aanleiding tot water besoedeling en vermorsing van kosbare water en duur kunsmis. Snoei is 'n belangrike kulturele praktyk om hoë produktiwiteit by hidroponiese tamaties te verseker. Die aanpassing van snoei praktyke by klimaatstoestande is 'n goedkoop en doeltreffende manier om produktiwiteit te verbeter sonder om insette te verhoog. Die verbetering van water en kunsmis gebruiks doeltreffendheid is dus noodsaaklik om te verseker dat intensiewe gewasse, soos tamaties, volhoubaar geproduseer word. Drie eksperimente is uitgevoer om die effek van snoei en bemesting op die groei, opbrengs en water en kunsmis gebruiks doeltreffendheid van hidroponiese tamaties te ondersoek. In die eerste eksperiment is die effek van die EG, besproeiings frekwensie en groeimedium op die water gebruik, voedingstofopname, opbrengs en kwaliteit van tamaties ondersoek. 'n Faktoriaal ontwerp met gesplete plotte is gebruik. Twee EG behandelings (1 en 2 mS.cm-1), 3 besproeiings behandelings (5x, 10x, 20x per dag) en 3 groei media (kokos, sand, saagsels) is ondersoek. Selfs by ‘n EG van 1 mS.cm-1 was die voedingstof opname van plante vergelykbaar met waardes wat geassosieer word met blaar ‘n voedingstof inhoud wat voorgeskryf vir optimale produksie. die verhoging van die absolute voedingstof konsentrasie het ook 'n klein uitwerking op voedingstofopname gehad. In die organiese media - kokos en saagsels – het die beskikbare N vroeg in die seisoen verminder, en die tamaties wat in kokos gegroei het, het ook ‘n verminderde Ca opname getoon in vergelyking met die plante wat in sand en saagsels gegroei het. Die plate wat in kokos gegroei het, het meer water gebruik in vergelyking met plante wat in sand en saagsels gegroei het. Plante besproei met ‘n voedingsoplossing van 1 mS.cm-1 EG het minder water gebruik as die plante wat besproei met ‘n voedingsolossing by ‘n EG van 2 mS.cm-1. Tamaties wat gekweek word by 'n EG van 1 mS.cm-1 het nie beduidend verskil van hoër EG plante in terme van bemarkbare en groen vrugte nie. Plante wat gekweek is by die laer EG het ‘n aansienlike laer persentasie oplosbare vastestof inhoud (Brix) in vergelyking met die hoër EG-behandeling gehad. Die tweede eksperiment het die effek van blaar- en vrug snoei op die vruggrootte, totale opbrengs en bemarkbare opbrengs van tamaties ondersoek. Plante is vertikaal opgelei tot by die horisontale draad en na twee stamme gesnoei. Drie verskillende blaar snoei behandelings is toegepas: geen blaar snoei, snoei elke 2de jong blaar na 1m plant hoogte en snoei van elke 2de jong blaar na 2m plant hoogte. Twee vrug snoei behandelings is ook toegepas: geen vrugte gesnoei en trosse gesnoei tot 4 vrugte. ‘n Faktoriale ontwerp is vir hierdie eksperiment gebruik. Blaar snoei behandelings het geen effek gehad nie, waarskynlik omdat die jong blare te laat verwyder was. Met die vrug snoei behandelings was daar geen beduidende verskil tussen die behandelings in terme van bemarkbare opbrengs nie. Plante waarvan die trosse nie gesnoei was nie het 'n aansienlik hoër totale opbrengs gelewer, asook ‘n hoër vroeë opbrengs maar ‘n laer gemiddelde bemarkbare vrug massa en ‘n hoër persentasie onbemarkbare vrugte (baie klein vrugte in vergelyking met die gesnoeide behandeling). Vanuit hierdie resultate kan daar afgelei word dat vrug snoei nie nodig is tydens ‘n kort groeiperiode vir tamaties nie, alhoewel dit wel ‘n rol mag speel gedurende ‘n langer groeiperiode. Met die derde eksperiment is die gekombineerde effek van verskillende EG en stam snoei praktyke op voeding, groei en vroeë opbrengs van hidroponies verboude tamaties bepaal. 'n faktoriale ontwerp is gebruik, met twee EG behandelings (1 en 2 mS.cm-1) en 2 stam snoei behandelings (enkel en dubbel). Stam snoei het ‘n geringe uitwerking op die groei van die plant gehad, maar het wel die ontwikkeling van plante verander. Plante gesnoei na twee stamme het aansienlik meer trosse gehad, maar nie 'n hoër DM of blaar oppervlak as die enkele stam plante nie. Stam snoei se grootste effek blyk te wees op die aantal vrugte per plant en dit kan op die lang termyn lei tot verskille in die groei van plante en hul voeding. EG 1 mS.cm-1 plante het ‘n aansienlik laer blaaroppervlakte en droë massas geproduseer, maar het 'n aansienlik hoër bemarkbare opbrengs in vergelyking met EG 2 mS.cm-1 plante gelewer. Oorbemesting kan 'n negatiewe impak op die vroeë opbrengste van tamaties hê, terwyl laer bemesting in die vroeë stadiums van groei vroeë opbrengs bevoordeel maar blaaroppervlak ontwikkeling beperk wat dan ook produktiwiteit beperk in die lang termyn. Hierdie verskille in groei word hoofsaaklik toegeskryf aan verskille in die N-en P-voeding.

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2017 / Tomato is popularly consumed as fresh vegetable or processed product due to its nutritional and health benefits. However, due to its high perishability, tomato cannot be stored for longer duration. Therefore, the aim of this study was the determination of appropriate dipping times into different calcium chloride concentrations to preserve the postharvest quality, storage and the shelf-life of tomato fruit. 'Classic round' tomato fruit were harvested at their pink maturity stage. The experiment was carried out as a completely randomized design (CRD), factorial arranged as 4 × 3 × 8. Treatment factors were: 4 × CaCl2 (0, 0.0045, 0.01 and 0.03%), 3 × dipping times (0, 30 and 60 minutes) and 8 × shelf-life (0 - 7 days). Fruit were stored at 15⁰ C for 30 days, thereafter, held under room temperature for 0 - 7 days of shelf-life while collecting data. During shelf-life period, fruit were evaluated for weight loss, firmness, colour, TSS, TA, pH, physiological and pathological disorders. The interaction between the treatments and dipping times showed a significant effect on weight loss, firmness, colour parameters [L*, b*, chroma and hue angle (⁰)], total soluble solids (TSS), titratable acidity (TA), pH, decay and black mould occurrence. However, significant interactive effects were not shown on a* colour component and chilling injury. In conclusion, calcium chloride (CaCl2) improved the quality and shelf-life of 'Classic round' tomato fruit. Calcium chloride concentration 0.01% was effective at 30 minutes dipping time, meanwhile, 0.03% CaCl2 was effective at 60 minutes dipping time. Therefore, 0.01 and 0.03% can be recommended for commercial preservation use for tomato fruit quality and shelf-life. / Agricultural Research Council-Tropical and Subtropical Crops (ARC-TSC) and National Research Foundation (NRF)

Call number: LD2668 .T4 1953 S75 / Master of Science

Call number: LD2668 .T4 1964 D32 / Master of Science

Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse in Arizona in order to determine the effect of aeration, flooding, and exogenously applied benzyladenine (BA) on growth and cytokinin production at different growth stages. The structural changes in roots at different soil environments were also studied. Fresh and dry weight of roots and shoots and root exudate were collected at various stages of growth. Results showed that aerated plants significantly outperformed flooded and BA treated plants due to increased root and shoot output. The level of cytokinin in root exudate was higher during the early phase of vegetative growth. At the time of bud formation and anthesis, the level of cytokinin declined. In the vegetative stage, the competition between removed sinks and the rest of the shoot was reduced and, as a result, more cytokinin was believed to come from the roots to the shoots. Besides, additional carbohydrates were available to the roots. Determination of cytokinins in aerated plants showed a significant increase. However, in flooded plants, a smaller amount of cytokinin was detected. This is believed to be due to death of root apices, a major site for cytokinin production. Under experimental conditions, the application of BA to foliage of flooded plants had an adverse effect on growth of roots and shoot of tomato plants. However, a slight increase in cytokinin level was detected. Histological studies showed an increase in air-spaces (aerenchyma) in roots of flooded plants. This acclimation improved survival in inadequately aerated plants that were waterlogged.

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.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

A greenhouse experiment was conducted to study the effectiveness of Dwell, a nitrification inhibitor, on the efficiency of two fertilizers applied to three Arizona soils, Anthony sandy loam, Laveen loam, and Vinton loamy sand. Tomato plants Lycopersicum esculentum cultivar Row Pak were used as an index plant. These plants were grown in soil columns of 10 cm internal diameter and 50 cm in length, containing 4,500 g of soil. Two fertilizers, urea and ammonium sulfate (AS), were applied at two rates: 112 and 224 kg N/ha. The nitrification inhibitor Dwell was applied also at two rates: 0 and 1.27 kg/ha⁻¹ of active ingredient. The active ingredient in the chemical is 5- ethoxy -3- (trichloromethyl)-1, 2,4- thiadizole. Both fertilizers and Dwell were added to the soils using two methods: (1) uniform mixtures, in which the fertilizer and Dwell were mixed with the top 500 cm³ soil volume in the columns, and (2) banded fertilizers and Dwell, in which a soil paste, made by mixing 10 ml of 0.02% Dwell solution with the volume of 50 cm³ soil, was added to the required amount of the fertilizer to soil column about 7cm below the soil surface. This factorial designed experiment was arranged in a randomized complete block with three replications of each treatment. Plants were allowed to grow for 67 days after transplanting to the soil columns. At the end of the experiment, samples from two depths (0 to 18 cm and 18 5o 40 cm) were analyzed for NH₄, NO₃, and organic N. Dry matter yield and N content of plants were also determined. Results showed that Dwell was effective in improving N efficiency, as determined by yield and N content of plants, with all three soils and with both fertilizers. Higher yields were obtained when AS was used in all soils. Higher response to Dwell, but lower yields, were observed in urea treatments as compared to AS treatments. Dwell resulted in yield increase of 139 and 60% with urea in Vinton and Laveen soils, respectively, while with AS, the increases were 74 and 11%. The lowest response to Dwell occurred with the Anthony soil. Generally, higher yield was obtained when AS was thoroughly mixed and when urea was banded. Yield and N content in plants grown in these soils were in the following order: Laveen > Anthony > Vinton. Dwell was effective with both N rates, particularly with the high N rate of urea. Incubation studies showed that Dwell was effective in retarding nitrification for about 10 days. Accordingly, Dwell seems to have had no residual effect on soil nitrogen.

Seedlings were grown at five salinity levels in Hoagland's solution for 4 weeks. Transpiration, leaf diffusive resistance, leaf temperature and plant growth of the tomato (Lycopersicon esculentum Mill.) cultivars 'VF 145B' and 'VF 10' were examined at different levels of NaCl ranging from 0 to -12 bars. Salinity-reduced transpiration increased leaf diffusive resistance and increased leaf temperature for both cultivars. Shoot length, root length, shoot and root weight and leaf area were all lower for the two cultivars at increasing salinity levels. However, the two cultivars responded differently to salinity, with VF 10 showing better growth at the control and the -4 bar treatment than VF 145 B. At -9 and -12 bar treatment, the reverse was true. Selection of tomato for salt resistance should not be based on vigorous growth at non-saline conditions because different genes may control the salt tolerance ability of the plants at high salinity levels.