Elsa S. du Toit

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

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Publications (28)21.74 Total impact

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    ABSTRACT: Moringa oleifera is becoming increasingly popular as an industrial crop due to its multitude of useful attributes as water purifier, nutritional supplement and biofuel feedstock. Given its tolerance to sub-optimal growing conditions, most of the current and anticipated cultivation areas are in medium to low rainfall areas. This study aimed to assess the effect of various irrigation levels had on floral initiation, flowering and fruit set. Three treatments namely, a 900mm (900IT), 600mm (600IT), and 300mm (300IT) per annum irrigation treatment were administered through drip irrigation, simulating three total annual rainfall amounts. Individual inflorescences from each treatment were tagged during floral initiation and monitored throughout until fruit set. Flower bud initiation was 65.3% higher at the 300IT and 4.6% higher at 600IT compared to the 900IT. Fruit set however, was 22.0% lower for the 300IT and 4.4% lower for 600IT, compared to the 900IT. Floral abortion, reduced pollen viability, as well as moisture stress in the style were contributing factors to the reduction in fruiting/yield observed at the 300IT. Moderate water stress prior to floral initiation could stimulate flower initiation, this should however be followed by sufficient irrigation to ensure good pollination, fruit set, and yield.
    2012 ASHS Annual Conference; 08/2012
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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
    Embryogenesis, 04/2012; , ISBN: 978-953-51-0466-7
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    Fungicides for Plant and Animal Diseases, 01/2012; , ISBN: 978-953-307-804-5
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    ABSTRACT: Moringa oleifera Lam. is a fast growing, drought tolerant tree with numerous beneficial uses, such as for nutritious food, animal forage, green manure, water purification, traditional medicine and bio-fuel (Anwar et al., 2007). The developmental seed morphology and anatomy of Moringa has not been researched, especially with regards to the accumulation of protein, carbohydrates and oil bodies. Five-year old Moringa oleifera trees were divided into three different irrigation treatments namely 300mm, 600mm and 900mm of irrigation over a one year period. Individual flowers were tagged on each tree and monitored to determine the number of days from swelling of flower buds to flowering and fruit set. Pollen viability tests between the various irrigation treatments were also performed. Moringa fruit were then harvested at various developmental stages. Both light- and electron microscopy were used to determine the time of synthesis as well as the locality of the various compounds. After monitoring of the flowers development at the various irrigation treatments, it was evident that irrigation did have an effect on fruit/seed production. Both the light and electron microscopy work revealed the locality of the protein, carbohydrates and oil bodies within various stages of developing seed with the use of various staining techniques. Electron microscopy revealed the intracellular synthesis of these compounds. REFERENCES ANWAR, F., LATIF, S., ASHRAF, M. & GILANI, A.H., 2007. Moringa oleifera: A food plant with multiple medicinal uses. Phytother. Res., 21: 17–25.
    2011 ASHS Annual Conference; 09/2011
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    ABSTRACT: Allium sativum (garlic) is considered as a vegetable and as an herbal crop throughout the world, including South Africa. Yield and quality can be improved through nitrogen (N) and sulphur (S) nutrition. The objective of the study was to determine the influence of ammonium sulphate and calcium nitrate fertilization on the bioactivity of A. sativum plants against Alternaria solani and Sclerotium rolfsii. The experimental layout was a randomized complete block design (RCBD) with four replications. A. sativum plants were treated with ammonium sulphate or calcium nitrate fertilizers applied as topdressing to give a total of 0, 50, 100, 150 and 200 kg/ha, divided into three applications at three week intervals. Crude extracts were prepared separately from the leaves and bulbs of A. sativum. The results obtained indicated that leaf extracts of the plant which were treated with calcium nitrate fertilizer demonstrated low bioactivity when compared to plants that were treated with ammonium sulphate. A. sativum bulb extracts were found to have very low bioactivity at 54 days after planting (DAP) and high at 175 DAP, however leaf extract bioactivity increased from young (54 DAP) to full vegetative maturity of the shoots (82 to 112 DAP) and declined with maturity of the bulb (140 to 175 DAP), regardless of N source supplied to the plants. Calcium nitrate failed to improvethe medical properties of A. sativum while ammonium sulphate enhanced the bioactivity.
    2011 ASHS Annual Conference; 09/2011
  • Elsa S. Du Toit, MO Cloete, PJ Robbertse
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    ABSTRACT: Pappea capensis Eckl. & Zeyh. is a member of the Sapindaceae family and widely distributed throughout Southern Africa. This tree is considered drought and frost tolerant, with its edible fruit being of economical importance. The seed contains a high concentration of oil that shows great potential to be used as a bio-diesel. No information is available on the phenology of the tree, seed yields or the quality of the oil. In this study it was found that the trees are andromonoecious, starting with male flowers and switching to the production of female flowers. Flowers and fruit are borne on shoot terminals mostly on the canopy surface. The seed, embedded in an aril, is contained in a capsule. A frame counting technique was applied to determine fruit and seed yield per tree. An average of 21.85 kg of seed was obtained from trees with an average canopy surface area of 20 m2. The seed contains about 73.5% oil which conformed to the 14.81 litres of oil we obtained from 21.85 kg seed. From these results extrapolations were made, showing that yields of 3018 kg of seed (1996.41 litre oil) from 200 trees per hectare should be possible. The oil was extracted with a press and samples were analysed by the company ‘BioServices’ in Randburg, South Africa, according to the American Oil Chemist Society standards and it was found suitable for the use in bio-fuel production as a B5-blend. This is a first study attempting to estimate the fruit/seed/oil yield of Pappea capensis trees. There is a strong correlation between yield obtained from frame counting and manual harvesting. Figures where obtained from wild population trees, therefore higher yields can be expected from grafted and cultivated trees. Keywords: biodiesel, seed yield, oil
    2011 ASHS Annual Conference; 09/2011
  • Quintin Ernst Muhl, Elsa S. Du Toit, PJ Robbertse
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    ABSTRACT: Moringa oleifera Lam. is a fast growing, drought tolerant tree with numerous beneficial uses, such as for nutritious food, animal forage, green manure, water purification, traditional medicine and bio-fuel (Anwar et al., 2007). The effect of hardening-off tree seedlings and consequent cultivation at lower temperatures on growth and flowering of this tropical/subtropical tree was the main aim of the study. After germinating seed under favourable greenhouse conditions between 20/25°C, half the seedlings were left in the greenhouse, while the other half was hardened-off by placing them outside where the average minimum/maximum temperatures fluctuated between 15/30°C. Equal numbers of hardened-off (132) and non hardened-off (132) trees were randomly placed into three temperature controlled glasshouses at the Experimental Farm of the University of Pretoria, each with a different night/day temperature regime (TR) (10/20°C±2°C; 15/25°C±2°C; 20/30°C±2°C). During the 224-day trial period, bi-weekly measurements of individual tree heights were taken, while flower development was monitored throughout. After trial termination the fresh and dry mass of the roots, stems and leaves from each treatment were measured. Overall, tree height increased with temperature. At the 10/20°C, 15/25°C and 20/30°C TRS, the respective growth rates of the non hardened-off seedlings were 67.6%, 30.5% and 18.7% lower compared to their hardened-off counterparts. The increase in total tree biomass with the increase in TR was largely due to the above ground parts. Fresh and dry root mass did not differ significantly (P≤0.05) amongst the three temperature regimes (TRS), however the dry root mass in relation to the above growth decreased with an increase in TR. The root:shoot ratios were 0.2, 0.5 and 1.4 for the 10/20°C, 15/25°C and 20/30°C TRS, respectively. The highest instances of flowering trees (87.5%) were observed at the 15/25°C TR with noted instances of inflorescence reversion at the 20/30°C TR. The 10/20°C TR probably did favour floral induction, however the generally low temperatures hindered flower production. The 20/30°C TR was found to be the most favourable for vegetative tree growth, however the hardening-off of the seedlings prior to transplanting has proven to increase the tree growth rate across all three TRS and is therefore highly recommended for M. oleifera trees, especially if intended cultivation is at low temperature environments. REFERENCES: ANWAR, F., LATIF, S., ASHRAF, M. & GILANI, A.H., 2007. Moringa oleifera: A food plant with multiple medicinal uses. Phytother. Res., 21: 17–25.
    2011 ASHS Annual Conference; 09/2011
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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 04/2011; 77(2):425-429. · 1.34 Impact Factor
  • 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 04/2011; 39(1). · 0.71 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: 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 07/2008; · 1.50 Impact Factor
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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 06/2008; 3608:137-144. · 0.27 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. · 1.24 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. · 1.63 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 04/2007; 73(2):230-235. · 1.34 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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    ABSTRACT: Bush tea (Athrixia phylicoides DC.) is a plant indigenous to South Africa and is commonly known as bushman's tea (English); Boesmanstee (Afrikaans); Icholocholo, itshelo, umthsanelo (Zulu). It is a herbaceous plant that belongs to the Asteraceae family. People of South Africa have predominantly used it throughout history as a medicinal tea, for cleansing or purifying the blood, treating boils, headaches, infested wounds, cuts and the solution may also be used as a foam bath. The foam bath brew can also be used as lotion dabbed on to the boil, skin eruption or cut. The tea is also excellent for coughs and colds and as a gargle for throat infections and loss of voice. It is also believed to have aphrodisiac properties in some parts of southern Africa. The leaves contain 5-hydroxy-6,7,8,3',4',5'- hexamethoxy lavon-3-ol as a new flavonol which is a recently discovered flavonoid. Today, herbal tea cultivation is a big business in many parts of the world. South Africa is well known for its indigenous herbal tea production such as honey bush, rooibos and bush tea. There are increasing demands for such products, especially in the light of growing health consciousness worldwide. This necessitated the establishment and revival of bush tea as a healthy herbal beverage alternative to caffeine-containing beverages. Current research suggests that there is a great need to standardize processing methods and production protocols for consistent quality.
    01/2007;
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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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    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 08/2006; 72(3):398-402. · 1.34 Impact Factor