Elsa S. du Toit

University of Pretoria, Πρετόρια/Πόλη του Ακρωτηρίου, Gauteng, South Africa

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Publications (20)12.82 Total impact

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    H C Wu, E S Du Toit
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    ABSTRACT: Protea cynaroides L. is a slow-growing, difficult-to-propagate plant. Due to problems such as phenolic browning and their sensitivity to the phosphorous nutrient, in vitro multiplication of P. cynaroides explants have not been successful. The present study was conducted to induce shoot proliferation of established P. cynaroides microshoots, and investigate the effects of high phosphorous concentration during explant multiplication. Microshoots with either one or two nodes were cultured on Murashige and Skoog (MS) medium containing modified macronutrients and full strength micronutrients. Two concentrations of NH 4 H 2 PO 4 were tested: 0 mg L -1 NH 4 H 2 PO 4 , and a high P concentration of 1400 mg L -1 NH 4 H 2 PO 4 . Both growth media were also supplemented with gibberellic acid (GA 3) (30 mg L -1), 6-benzylaminopurine (BAP) (2 mg L -1), ethylenediaminetetraacetic acid (EDTA) (50 mg L -1) and indole-butyric acid (IBA) (0.5 mg L -1). Results show that, contrary to what is often reported, the presence of a high phosphorous concentration in the growth media did not adversely affect P. cynaroides explants. The survival rate and mean axillary shoot length of explants cultured on growth media containing 1400 mg L -1 NH 4 H 2 PO 4 were not significantly different from those grown on 0 mg L -1 NH 4 H 2 PO 4 . No phosphorous toxicity symptoms were observed in explants cultured on media with high phosphorous levels. Results also show that explants with two nodes had a higher survival rate and produced significantly longer axillary shoots than those with one node, irrespective of phosphorous concentration. Multiplication of P. cynaroides microshoots was successfully achieved for the first time.
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    How-Chiun Wu, Elsa S. du Toit
    04/2012; , ISBN: 978-953-51-0466-7
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    01/2012; , ISBN: 978-953-307-804-5
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    P. J. Robbertse, E. S. Du Toit, M. O. Cloete
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    ABSTRACT: Gender and the structure of the inflorescence and flowers of Pappea capensis (Sapindaceae) are investigated in a locality around Pretoria (22–27°S and 25–32°E). The trees flower over a long period (December to April) and are basically monoecious, starting with male flowers followed by female flowers towards the end of the flowering period, although some trees may be predominantly male and some predominantly female. The inflorescence is a reduced thyrse with small flowers. Male flowers have five ephemeral petals, eight stamens and a rudimental pistil. Female flowers comprise a 3-lobed ovary, a single style and stigma and eight staminodes.
    South African Journal of Botany - S AFR J BOT. 01/2011; 77(2):425-429.
  • Q.E. Muhl, E.S. du Toit, P.J. Robbertse
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    ABSTRACT: High germination percentages and rates, with relatively good uniformity, are important factors for successful commercial seedling production. Moringa oleifera seeds were planted into seedling trays and placed into three temperature-controlled greenhouses with fluctuating night/day temperature regimes namely; 10/20°C, 15/25°C and 20/30°C. Seedling trays were monitored daily over a period of 40 days, to record differences in germination percentage, rate and uniformity, and seedling growth. Seed at the high 20/30°C temperature regime (TR) exhibited a significantly (P ≤ 0.05) higher germination, rate and uniformity of germination, compared to the two lower temperature regimes (TRs). The germination of 74% for the 20/30°C TR was the lowest, and differed significantly from the 88% germination for the 10/20°C TR. Viability testing of un-germinated seed revealed that although germination percentages increased with the decrease in TR, this was not as a result of uneven seed viability. The higher 20/30°C TR also favoured seedling growth, as growth increased exponentially with an increase in temperature. Among the three TRs studied during this trial, the 20/30°C TR was found to be most favourable for both germination and seedling growth.
    Seed Science and Technology 01/2011; 39(1). · 0.70 Impact Factor
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    H C Wu, E S Du Toit
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    ABSTRACT: Poor and inconsistent germination of Protea cynaroides seeds are often observed in soil. A protocol based on embryo culture was developed for efficient in vitro propagation of P. cynaroides. The effects of temperature, light conditions and gibberellic acid (GA 3) on the in vitro germination of P. cynaroides embryos were studied. The results showed that the use of alternating temperatures of 21/12°C (light/dark) significantly improved the germination percentage of the embryos, where 90% of embryos germinated, compared to a maximum of 55% when grown under a constant temperature of 25°C. Mean cotyledon fresh mass of embryos that germinated on media containing gibberellic acid (2.89, 28.89 M GA 3) were significantly higher than those cultured on media without growth regulators. Conversely, root growth was severely inhibited in embryos germinated on media containing gibberellic acid. The in vitro-germinated seedlings were successfully transplanted to a peat/coir/sand mixture in the mist bed.
    AFRICAN JOURNAL OF BIOTECHNOLOGY 12/2010; 9:8032-8037. · 0.57 Impact Factor
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    ABSTRACT: Examination of callus micro-grafts in Uapaca kirkiana Müell Arg. was carried out with the objective of determining early signs of graft compatibility. Leaves from U. kirkiana, U. nitida and Jatropha curcas trees were used for callus induction. Two pieces of callus were co-cultured on Murashige and Skoog (MS) medium with different supplements. Co-cultured calli were embedded in paraffin wax and dissected. The specimens were stained in safranin and fast green before viewing under a light microscope. Results showed that MS medium with 0.1mgl−1 thidiazuron (TDZ) and 0.5mgl−1 naphthaleneacetic acid (NAA) or 1.0mgl−1 dichlorophenoxyacetic acid (2,4-D) and 0.5mgl−1 NAA was effective for callus induction. There were no necrotic layers at the unions within U. kirkiana clones and provenances, but a differential growth (irregularity) between U. kirkiana and U. nitida co-cultured calli. Phenol deposits were observed at the union interfaces of U. kirkiana combinations and were high on calli derived from mature trees. Phenol deposits were absent at the union of J. curcas heterografts. Necrotic layers developed at the unions of U. kirkiana and J. curcas micro-grafts and indicating an outright graft incompatibility. Accumulation of phenol deposits at the union interfaces inhibited graft compatibility in many U. kirkiana combinations. Callus fusion technique can be used to identify partners with an outright graft incompatibility, especially for distant related plant species.
    Agroforestry Systems 01/2008; 74(2):173-183. · 1.37 Impact Factor
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    ABSTRACT: The objective of the study was to determine the relationship between phenols and graft incompatibility in Uapaca kirkiana. Phenol quantification and identification were carried out using Folin-Ciocalteau reagent procedure, fluorescence microscopy and reverse phase high performance liquid chromatograph (RP-HPLC) above, below and at the graft union. Results showed no vascular cambium continuity above the scion/stock unions. Significant differences in total soluble phenols and cell wall bound phenols were obtained. Fluorescence microscope indicated the presence of flavonoids and other polymers above the union. The RP-HPLC identified ferulic acid as a major phenol component found in U. kirkiana plant cells and responsible for wood discolouration. High phenol concentrations were obtained in less compatible combinations than in compatible combinations. High peaks of ρ-coumaric acid were obtained above the union. It is concluded that phenols, especially ρ-coumaric acids and flavonoids caused poor callus formation at the union, and hence implicated in graft incompatibility.
    Scientia Horticulturae. 01/2008;
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    ABSTRACT: The study was undertaken to identify an effective culture growing system for mass multiplication of jacket plum (Pappea capensis) through somatic embryogenesis. Calli derived from leaf sections were transferred onto Murashige and Skoog (MS) medium with different supplements. The most effective medium for callus induction was MS supplemented with 0.1 mg litre –1 thidiazuron (TdZ) alone or with 0.1 mg litre –1 indole-3-butyric acid (ibA) or a combination of 1.0 mg litre –1 2,4-dichlorophenoxyacetic acid (2,4-d) and 0.2 mg litre –1 benzylaminopurine (bAP). light exposure promoted embryo induction. Three-quarter strength MS medium supplemented with 0.05 mg litre –1 TdZ and 0.3 mg litre –1 casein hydrolysate (CH) was effective for embryo germination and the most effective culture medium for plantlet conversion was three-quarter strength MS supplemented with 0.2 mg litre –1 bAP and 0.3 mg litre –1 CH. There was 60% survival of plants under a mist propagation chamber. The study shows that it is possible to improve P. capensis somatic embryogenesis through manipulation of some culture medium constituents and incubation conditions.
    New Zealand Journal of Crop and Horticultural Science 01/2008; 3608:137-144. · 0.48 Impact Factor
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    ABSTRACT: Analysis of stem extracts identified large quantities of 3,4-dihydroxybenzoic acid and other similar phenolics. The exogenous application of 3,4-dihydroxybenzoic acid on Protea cynaroides explants in vitro significantly increased the root mass at 100mgl−1, but not at lower concentrations, while root inhibition was observed at 500mgl−1. HPLC analysis of cuttings during vegetative propagation showed a considerable increase in 3,4-dihydroxybenzoic acid levels from initial planting to when root formation took place, indicating for the first time that 3,4-dihydroxybenzoic acid may be an important phenolic compound in regulating root formation in P. cynaroides cuttings. HPLC analysis also identified caffeic, ferulic, gallic and salicylic acids in the cuttings.
    Plant Growth Regulation 06/2007; 52(3):207-215. · 1.67 Impact Factor
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    H. C. Wu, E. S. du Toit, C. F. Reinhardt
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    ABSTRACT: We describe a protocol for somatic embryogenesis of Protea cynaroides, with potential for high frequency production of this important horticultural species. Somatic embryos formed directly on both P. cynaroides mature zygotic embryos and excised cotyledons cultured on MS medium without growth regulators. The addition of growth regulators such as naphthalene acetic acid (NAA) (5; 13 and 27μM) and 2,4-dichlorophenoxyacetic acid (2,4-D) (5; 11 and 23μM), in combination with thidiazuron (TDZ) (1μM), benzylaminopurine (BAP) (1μM) or kinetin (1μM) suppressed the formation of somatic embryos. After eight weeks in culture, formation of somatic embryos was observed. Zygotic explants formed the most embryos when cultured in a 12-h photoperiod in comparison to explants cultured in the dark. Up to 83% of these embryos germinated after transferal to the germination medium containing 0.3μM GA3. Significantly fewer embryos germinated in MS medium with no growth regulators, or supplemented with higher concentrations of GA3, while low germination percentages were also observed in MS media containing casein hydrolysate and coconut water. The germination of normal somatic embryos (two separate cotyledons and a single radicle) was observed only in media containing either no growth regulators, 0.3μM GA3 or 1μM GA3. All embryos that germinated in high concentrations of GA3 were malformed.
    Plant Cell Tissue and Organ Culture 01/2007; 89(2):217-224. · 2.61 Impact Factor
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    H. C. Wu, E. S. du Toit, C. F. Reinhardt
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    ABSTRACT: The inability to induce rooting of in vitro-established Protea cynaroides microshoots has prevented the production of complete plantlets. A successful shoot-tip micrografting technique was developed using in vitro-germinated P. cynaroides seedlings as rootstocks and axenic microshoots established from pot plants as microscions. Thirty-day old seedlings, germinated on growth-regulator-free, half-strength Murashige and Skoog medium, were decapitated and a vertical incision made from the top end. The bottom ends of microshoots established on modified Murashige and Skoog medium were cut into a wedge (‘V’) shape, and placed into the incision. The micrografted explants were cultured in a growth chamber with the temperature adjusted to 25 2C, with a 12-h photoperiod. Best results were obtained by placing the microscions directly onto the rootstock without any pre-treatments. Dipping the explants in anti-oxidant solution or placing a layer of medium around the graft area led to the blackening of the microscion.
    Plant Cell Tissue and Organ Culture 01/2007; 89(1):23-28. · 2.61 Impact Factor
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    ABSTRACT: The objective of the trial was to determine an effective propagation protocol for jacket plum (Pappea capensis) tree species. Experiments on in vitro propagation and rooting of stem cuttings were carried out. Dipping stem cuttings in half strength Murashige and Skoog (MS) media for 12 h prior to application of rooting hormones improved bud break and prolonged survival of stem cuttings on a mist bed. Early leaf loss was observed for stem cuttings planted without MS treatment. However, rooting was poor (11% for cuttings pre-treated in MS and 0% for those not pre-treated). For micro-propagation, significant differences (P
    South African Journal of Botany - S AFR J BOT. 01/2007; 73(2):230-235.
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    H C Wu, E S Du Toit, C F Reinhardt
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    ABSTRACT: The role that starch content and blanching play in the root-ing of Protea cynaroides cuttings was studied. P. cynar-oides stems were blanched on the motherplant in the field, which resulted in a higher starch concentration in the cut-tings. The relationship between starch content and rooting was also established, whereby the ability of the blanched cuttings to maintain a consistent starch level throughout the rooting period, resulted in the acceleration of the root-ing process. The blanched cuttings had a higher dry root mass than the control at day 90 when the cuttings were ready to be transplanted. The untreated cuttings were only suitable for transplanting after 120 days. Blanching the cut-tings also resulted in a higher rooting percentage (100%) than the control (60%). Vegetative propagation is known to be slow and inconsistent in P. cynaroides cuttings. Localized light exclusion, such as blanching, is a method used to improve rooting of difficult-to-root woody plants (Gardner, 1937). Blanching is a procedure which involves banding the future cutting base of light-grown shoots with adhesive tape for several weeks before planting into rooting medium (Bassuk & Maynard, 1987). Anatomical studies have shown that blanched shoots have more undiffer-entiated tissues, which result in easier root initiation (Gard-ner, 1937). In addition, Reid (1922) reported that less lignification was found in etiolated stem tissues than light-grown tissues, resulting in a decrease in cell wall thickness and increase in protoplasmic cell contents. The relationship between carbohydrate content and root-ing is controversial. Both negative and positive correlations have been found between carbohydrate content and rooting. A negative correlation was observed in Pinus cuttings by Hansen, Stromquist & Ericsson (1978), where an increase in carbohydrate content reduced the number of roots formed. Similar results were found in Populus cuttings by Nanda & Anand (1970) and Okoro & Grace (1976). Conversely, Veier-skov, Stummann & Henningsen (1982) reported a positive correlation between carbohydrate content and rooting in pea plants. The positive correlation may have been due to the sup-ply of photosynthate being insufficient to support rooting (Veierskov, 1988). The aim of the study reported in this paper was to investi-gate whether blanching could improve the rooting of the cut-tings, and the role starch may play in rooting of blanched cuttings. Semi-hardwood stems of approximately 15 cm from P. cynaroides motherplants, which were grown in an open field, were used as cuttings. Blanching was applied to the stems on the motherplants by taping approximately 20 mm of the stem with insulation tape. After 30 days, the blanched stems were collected from the field by cutting just below the insulation tape. The tape was then removed and the leaves of the bottom three-quarters of each cutting were stripped. The cuttings were then planted into the rooting medium, which consisted of peat moss and polystyrene balls (1:1). For the control treat-ment, cuttings were collected from the motherplants and planted directly into the rooting medium. Each treatment was replicated ten times. The cuttings were collected after 60, 90 and 120 days during which the roots were removed from the cuttings, dried and weighed. The cuttings were then separated into four parts, i.e., the bottom part of the cutting (20 mm), the middle and top parts (equally divided from the remainder of the cutting) of the cutting, and the leaves. For the starch analysis, each of the four parts was freeze-dried, ground into fine powder and 0.05 g was weighed into separate, labeled 10 cm 3 test tubes. The extraction technique used was adapted from Rasmussen & Henry (1990) and Kai-ser & Wolstenholme (1994). A 5 ml aliquot of ethanol (80%) was added into each test tube, and after sealing, placed in a water bath at 80°C for 30 minutes for extraction to take place. The test tubes were then centrifuged in a Kubota  2010 Cen-trifuge for 10 minutes at 3000 rpm, after which the superna-tant containing the sugars were decanted. The procedure as described above was repeated to ensure the removal of all free sugars. Afterwards, 2.5 ml acetate buffer and 50 µl Ter-mamyl  were added to the test tubes, which were sealed and placed in a water bath at 90°C for 30 minutes. Thereafter, the test tubes were allowed to cool to room temperature. Subse-quently, 50µl amyloglucosidase (Novo  300L) was added to each test tube and sealed. The test tubes were then incubated in a water bath at 60°C for 20 hours. Afterwards, the test tubes were removed from the water bath and centrifuged for 10 minutes at 3000 rpm and 100 µl aliquots of the resultant supernatant were transferred to separate test tubes and made up to 5 ml using glucose oxidase colour solution. Thereafter, the test tubes were sealed and placed in the water bath for 15 minutes at 40°C, and then placed at room temperature (21C) for 60 minutes. Using a spectrophotometer (Pharmacia Biotech Ultraspec III ), the absorbance values were read at 505 ηm and compared against a glucose standard curve. Finally, the % starch in the stem samples was deter-mined by taking into account the dilution factor, constant for water of hydrolysis and dry mass. The data were analyzed using the PROC. GLM (General Linear Models) procedure in the SAS (Statistical Analysis System) program. The means were separated according to Duncan's Multiple Range test. Log transformation was used to rectify the normality of the data. The time it took for the blanched cuttings to root was con-siderably faster than under commercial conditions, which can take up to six months (180 days). At day 60, although the starch levels between the control and blanched cuttings were not significantly different, higher concentrations of starch was observed in all the plant parts of the blanched cuttings (Table 1). This indicates that etiolation may have caused an S. Afr. J. Plant Soil 2006, 23(4) 316 increase in the accumulation of starch in the stem. At day 90, the increased starch content in the blanched treatment lead to considerable rooting of the cuttings, which is shown in the significantly higher dry root mass obtained in the blanched cuttings (Figure 1). Similar results were reported by Biricolti, Fabbri, Ferrini and Pisani (1994) where etiolation of chestnut caused an accumulation of starch grains in the stem, which resulted in better rooting. In addition, the improvement in rooting of etiolated Syringa vulgaris cuttings was reportedly due to the accumulation of starch in the stem (Howard & Rid-out, 1992). Importantly, at day 90, the blanched cuttings were rooted well enough to be transplanted, whereas the control was only ready for transplanting at day 120. At day 120, for the first time, the starch content in the control cuttings was higher than in the blanched cuttings (Table 1), even though rooting was similar in both treatments. This could probably be due to the cuttings in the control not rooting as well as the blanched cuttings at day 90, and therefore an increase in the accumulation of carbohydrate in the form of starch is seen at day 120. In addition, it is known that the accumulation of starch alone is not responsible for the rooting of cuttings. It has been reported that endogenous compounds such as phe-nolics, which are found in proteas, play a role in the rooting of cuttings (Wilson, 1994). Investigations into the role of phe-nolics in rooting and the effect of etiolation on changes in phenolic content are currently taking place. The results from this investigation indicate that blanching of P. cynaroides stems prior to planting accelerated the rooting process by several weeks. This may be due to the accumula-tion of starch in the blanched cuttings during the blanching treatment, and the ability of the cuttings to maintain the starch content at a constant level throughout the rooting period. Fur-thermore, it was noted that the blanched treatment had a higher rooting percentage (100%) than the control (60%). Further research is needed to investigate other factors such as phenolic, which may affect rooting in P. cynaroides cuttings.
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    F.N. Mudau, P. Soundy, E.S. du Toit, J. Olivier
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    ABSTRACT: The high concentrations of polyphenols present in leaves of bush tea (Athrixia phylicoides L.), a popular herbal beverage with medicinal properties, were examined in wild and cultivated populations to determine their magnitude of variation with season and application of nitrogenous fertilizers. Concentrations of total polyphenols in leaves of wild plants were lowest in March, April and September and highest in June and July, with nitrogenous fertilizer applications below 300 kg ha− 1 N further elevating polyphenol concentrations in leaves of cultivated plants grown under restricted lighting. These findings, which contradict the Carbon/Nutrient balance hypothesis, conclude that the most suitable conditions for cultivating bush tea to obtain plants with an optimal leaf polyphenol content are those of reduced light intensity during winter and in soils supplemented with a nitrogenous fertilizer.
    South African Journal of Botany 01/2006; 72(3):398-402. · 1.41 Impact Factor
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    ABSTRACT: Flowering-sized bulbs of Lachenalia that developed under three different temperature regimes [S. Afr. J. Plant Soil 18 (1) (2001a) 28] were used to assess the quality of subsequent pot plants. Plants were grown in a growth cabinet at a 15/10 °C day/night temperature regime. When the oldest flower of the inflorescences opened, the pot plants were transferred to a growth cabinet that provided a constant temperature of 22 °C with lower lighting conditions to simulate office conditions. The flowering date, keeping ability as well as the morphology of the inflorescences were evaluated. After the senescence of the inflorescences, the plants were harvested and dissected into different plant parts for evaluation. The temperature pre-treatments had a major effect on the performance of the subsequent pot plants. Flowering occurred 8 weeks earlier compared to plants normally grown in outdoor conditions in the Pretoria region (summer rainfall area). Furthermore, the low temperature regime (LTR) treated bulbs produced inflorescences with the longest keeping ability and simultaneous flowering was noticed. The lower the temperature regime during the bulb production phase, the greater is the peduncle length, rachis length, floret number as well as the peduncle diameter of the primary, secondary and tertiary inflorescences.
    Scientia Horticulturae. 01/2004;
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    ABSTRACT: Carbohydrate partitioning was investigated in different plant organs of Lachenalia cv. Ronina during bulb production under a low temperature regime. At 4-week intervals, data were collected on bulb, roots, leaves, inflorescence and carbohydrate composition. The roots and especially the bulb were found to be the main starch sinks of the plant, whilst the leaves and the inflorescence were the main source for soluble sugars. Changes in the starch concentration closely followed dry weight changes in the bulb during the growing season. When bulbs were initially exposed to a low temperature, starch was converted to soluble sugars, but thereafter sugars were low, indicating continued export and conversion to starch. Low sugar levels in the leaves and high levels in the inflorescence, with continuous starch increase in the bulb and roots, probably indicate that the inflorescence, but especially the leaves, produced ample photosynthates during the growing season.
    Scientia Horticulturae - SCI HORT-AMSTERDAM. 01/2004; 102(4):433-440.
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    H. C Wu, E. S du Toit
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    ABSTRACT: Oxidative browning is one of the reasons why Protea cynaroides is not being extensively propagated via tissue culture techniques. The reduction of oxidative browning was best achieved by stirring the explants for 1h in an antioxidant solution mixture containing 100mgl−1 ascorbic acid and 1500mgl−1 citric acid before inserting them into the medium. In combination with this antioxidant solution, in vitro establishment was highly successful where 100% bud growth was achieved by explants growing under 16h photoperiod.
    Scientia Horticulturae - SCI HORT-AMSTERDAM. 01/2004; 100(1):355-358.
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    ABSTRACT: Temperature plays an important role in the production of high quality Lachenalia bulbs, which is required for successful international bulb trade. The effects of three growth temperature regimes (high, moderate and low) on the development of bulbs prior to harvest and during the storage period were studied. Bulbs planted on 1 March were harvested at 15 November and subsequently stored at 25°C until 15 December. From mid-September until 15 December, 10 plants were sampled randomly from each treatment at 2-week intervals and morphological studies were conducted on these bulbs by means of serial hand sections.The high temperature regime treated bulbs developed more modules, but inflorescence abortion occurred. Bulbs subjected to a low temperature regime treatment developed slightly slower than those of the moderate and high temperature regime treatments. In all the treatments, daughter bulbs were observed in the axils of both swollen leaf bases from mid-November. In spite of the slower development of bulbs subjected to the lower temperature regime, the overall quality was better than bulbs grown in the moderate and high temperature regimes.
    Scientia Horticulturae 01/2002; 94(1):117-123. · 1.40 Impact Factor
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    ABSTRACT: The objective of the study was to determine efficient preconditioning methods for in vitro multiplication of Uapaca kirkiana plant materials from mature stock plants. The efficacy of sodium hypochlorite (NaOCl), calcium hypochlorite {Ca(OCl2)2} or mercuric chloride (HgCl2) as surface sterilant was evaluated in decontaminating explants excised from grafted and field-collected U. kirkiana trees. Different Murashige and Skoog (MS) medium supplements were evaluated for shoot multiplication and root regeneration. Results indicated that preconditioning grafted U. kirkiana trees before excising explants and decontaminating explants in 0.1% w/v HgCl2 were effective methods in establishing aseptic cultures (80%). Lateral shoots (new shoots) responded positively to shoot multiplication on 3/4 strength MS medium supplemented with a combination of 0.1 mg/L benzylaminopurine, 0.04 mg/L naphthaleneacetic acid and 0.3 mg/L casein hydrolysate. High concentrations of thidiazuron (>0.1 mg/L) suppressed bud break. Rooting (36%) was achieved with ½ MS medium supplemented with 2.5 mg/L indole-3-butyric acid. Plantlets were successfully hardened off. in vitro multiplication of mature U. kirkiana plant materials was achieved using lateral shoots excised from grafted U. kirkiana trees after preconditioning with fungicides.
    African Journal of Biotechnology (ISSN: 1684-5315) Vol 6 Num 14.