Elsa S. du Toit

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

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Publications (45)32.16 Total impact


  • No preview · Article · May 2015 · South African Journal of Botany
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    Helene Fotouo-M · Elsa S du Toit · Petrus J Robbertse
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    ABSTRACT: Seed ageing during storage is one of the main causes of reduction in seed quality and this results in loss of vigour and failure to thrive. Finding appropriate storage conditions to ameliorate deterioration due to ageing is, therefore essential. Ultrastructural changes in cellular organelles during storage, and seed germination rates are valuable indices of damage that occurs during seed ageing. There is increasing interest in Moringa oleifera because of its multiple uses as an agroforestry crop. Seeds of this species lose their viability within 6 to 12 months of harvest but no scientific information is available on the longevity of seed stored in the fruit (capsules). In most undeveloped countries, seeds are still stored inside the fruit by traditional methods in special handmade structures. In this experiment we tried to simulate these traditional storage conditions. Capsules of Moringa were stored at ambient room temperature for 12, 24 and 36 months. The ultrastructure, solute leakage and viability of seed were investigated. The ultrastructure of one year old seed showed no sign of deterioration. It was evident; however, that some cells of the three year old seed had deteriorated. The remnants of the outer and inner two integuments that remain tightly attached to the cotyledons probably play a role in seed dormancy. No significant difference was found between germination percentage of fresh and one year old seed. The germination percentage decreased significantly from two years of storage onward. The decrease in seed viability during storage was associated with a loss in membrane integrity which was evidenced by an increase in electrolyte leakage. Our findings indicate that the longevity of Moringa oleifera seeds can be maintained if they are stored within their capsules. Published by Oxford University Press on behalf of the Annals of Botany Company.
    Full-text · Article · Feb 2015 · AoB PLANTS
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    ABSTRACT: Background: The aim of this study was to evaluate the variation in antimicrobial and antioxidant activities of the leaf acetone extracts of 12 Moringa oleifera trees harvested in order to select the best material for clonal propagation. Methods: A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against a panel of fungal (Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans) and bacterial (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa) species. The radical scavenging capacity was determined using 2,2 diphenyl-1-picryhydrazyl (DPPH). Results: There was a large variation in antimicrobial activities with MICs between 0.04 and 2.50 mg/ml against bacteria and from 0.16 to N2.50 mg/ml against fungi. For samples harvested in winter: trees L3 and LP2 had significant activity against E. faecalis (MIC 0.08 mg/ml) and E. coli (MIC 0.04 mg/ml). Trees L5, LP1 and LP6 had weak activity against E. coli (MICs 1.25 and 2.50 mg/ml), S. aureus (MIC 1.25 mg/ml), and E. faecalis (MIC 2.50 mg/ml), while other samples had moderate activity against the four bacteria (MICs 0.16–0.63 mg/ml). From samples collected in summer: L5 (MIC 0.08 mg/ml), L6 (MIC 0.08 mg/ml after 1 h incubation), LP1 (MICs 0.08 mg/ml), LP2 (MICs 0.08 mg/ml after 1 h incubation), LP4 (0.08 mg/ml) and LP5 (MICs 0.04 and 0.08 mg/ml) had significant activity against E. faecalis (L5, L6, LP1, LP2, LP4, and LP5), S. aureus (LP1, and LP5), and E. coli (LP2, and LP5), respectively. Other extracts had weak antibacterial activity with MICs ranging from 0.16 to 0.63 mg/ml. Most of the samples harvested in winter had moderate antifungal activity: L1, L2, L3, L4, L5, L6, LP1, LP2, and LP3 had moderate activity against C. albicans (ATCC strains) with MIC of 0.63 mg/ml in all cases while L2, L3 and L4 as well as L6, LP1, LP2, LP3, LP5 and LP6 against A. fumigatus (MICs 0.63 mg/ml) and C. neoformans (MICs 0.63 mg/ml), respectively. Apart from L1 (MIC 0.31 mg/ml), L2, L3 and LP6 (MICs 0.63 mg/ml in all cases) with moderate activity, all the samples collected during summer had weak activity against A. fumigatus (MICs 1.25–2.50 mg/ml). All the extracts had a low radical scavenging activity with the IC50 values ranging from 34.72 to 109.62 μg/ml, compared to the reference standard L-ascorbic acid (IC50 2.41 μg/ml). This may be related to the extractant used. Conclusion: The large variation in antimicrobial activity and antioxidant activities of 24 acetone leaf extracts of 12 M. oleifera trees may lead to the selection of clonal material to serve as a source of propagation materials. Successful propagation and growth of tree LP with very good activity against E. coli and a high total activity could provide an additional use of this valuable plant species to rural people. Keywords: Moringa oleifera; Leaves; Antimicrobial; Minimum inhibitory concentration; Antioxidant; DPPH
    No preview · Article · May 2014 · South African Journal of Botany
  • N. Ratshilivha · M.D. Awouafack · E.S. du Toit · J.N. Eloff
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    ABSTRACT: Background The aim of this study was to evaluate the variation in antimicrobial and antioxidant activities of the leaf acetone extracts of 12 Moringa oleifera trees harvested in order to select the best material for clonal propagation. Methods A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against a panel of fungal (Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans) and bacterial (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa) species. The radical scavenging capacity was determined using 2,2 diphenyl-1-picryhydrazyl (DPPH). Results There was a large variation in antimicrobial activities with MICs between 0.04 and 2.50 mg/ml against bacteria and from 0.16 to > 2.50 mg/ml against fungi. For samples harvested in winter: trees L3 and LP2 had significant activity against E. faecalis (MIC 0.08 mg/ml) and E. coli (MIC 0.04 mg/ml). Trees L5, LP1 and LP6 had weak activity against E. coli (MICs 1.25 and 2.50 mg/ml), S. aureus (MIC 1.25 mg/ml), and E. faecalis (MIC 2.50 mg/ml), while other samples had moderate activity against the four bacteria (MICs 0.16–0.63 mg/ml). From samples collected in summer: L5 (MIC 0.08 mg/ml), L6 (MIC 0.08 mg/ml after 1 h incubation), LP1 (MICs 0.08 mg/ml), LP2 (MICs 0.08 mg/ml after 1 h incubation), LP4 (0.08 mg/ml) and LP5 (MICs 0.04 and 0.08 mg/ml) had significant activity against E. faecalis (L5, L6, LP1, LP2, LP4, and LP5), S. aureus (LP1, and LP5), and E. coli (LP2, and LP5), respectively. Other extracts had weak antibacterial activity with MICs ranging from 0.16 to 0.63 mg/ml. Most of the samples harvested in winter had moderate antifungal activity: L1, L2, L3, L4, L5, L6, LP1, LP2, and LP3 had moderate activity against C. albicans (ATCC strains) with MIC of 0.63 mg/ml in all cases while L2, L3 and L4 as well as L6, LP1, LP2, LP3, LP5 and LP6 against A. fumigatus (MICs 0.63 mg/ml) and C. neoformans (MICs 0.63 mg/ml), respectively. Apart from L1 (MIC 0.31 mg/ml), L2, L3 and LP6 (MICs 0.63 mg/ml in all cases) with moderate activity, all the samples collected during summer had weak activity against A. fumigatus (MICs 1.25–2.50 mg/ml). All the extracts had a low radical scavenging activity with the IC50 values ranging from 34.72 to 109.62 μg/ml, compared to the reference standard l-ascorbic acid (IC50 2.41 μg/ml). This may be related to the extractant used. Conclusion The large variation in antimicrobial activity and antioxidant activities of 24 acetone leaf extracts of 12 M. oleifera trees may lead to the selection of clonal material to serve as a source of propagation materials. Successful propagation and growth of tree LP with very good activity against E. coli and a high total activity could provide an additional use of this valuable plant species to rural people.
    No preview · Article · May 2014 · South African Journal of Botany
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    Quintin E Muhl · Elsa S Du Toit · Joachim M Steyn
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    ABSTRACT: To cite this paper: Muhl, Q.E., E.S. du Toit and J.M. Steyn, 2014. Irrigation amounts affect the compositional changes of Moringa oleifera seeds throughout different developmental stages. Int. Abstract The compositional development of Moringa oleifera seed across a range of growth stages was monitored at three irrigation treatments, simulating total annual rainfall of 900 mm, 600 mm and 300 mm/annum over two consecutive growing seasons (24 months). Fruit developmental stages were categorized according to fruit diameter (0 mm – 28 mm) at 2 mm increments. Starch was the first to accumulate during the initial histo-differentiation phase (fruit diameters of 0 mm-12 mm), while oil levels remained comparatively low. During the subsequent expansion phase (fruit diameters of 12 mm – 24 mm) however, stored starch was mobilized and used in oil biosynthesis, reducing the starch content. The bulk of oil and protein were synthesised throughout this phase with their content increasing sigmoidally. As the seed moisture content decreased during the final maturation phase (fruit diameters of 24 mm – 28 mm), the average oil content reached 24.8%, while the protein contents were 24.8% and the starch contents were 8.7%. The different irrigation treatments had less of an effect on the final starch, oil and protein content than on the time and rate of their synthesis throughout seed development. Higher irrigation levels principally favoured oil biosynthesis. The highest final oil contents were measured at the intermediate irrigation treatment (600 mm/annum), suggesting that both lower and higher irrigation levels could possibly reduce final oil contents. The reduction in irrigation amount delayed the onset of oil biosynthesis and as a result the starch content reached higher levels prior to its remobilization during oil biosynthesis.
    Full-text · Article · Jan 2014 · International Journal of Agriculture and Biology
  • M.S. Pholo · P. Soundy · E.S. Du Toit
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    ABSTRACT: Pelargonium sidoides (family Geraniaceae) is one of several geophytic species of the genus that are important traditional medicines (anti-microbial, anti-viral and immune boosting actions) in South Africa. Although domesticated, vegetative propagation of the species is not documented. Therefore, the study was conducted to investigate the influence of rooting medium (sand and sand + coir), rooting hormone (with and without Dynaroot No. 2, 0.3% IBA), planting depth (1.5 and 3 cm) and season (summer and autumn) on leaf-bud cuttings of P. sidoides. The experiment was conducted using a mist bed in a greenhouse at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa. A 23 factorial experiment laid out in a randomized complete block design (RCBD) with 3 replicates was conducted. Cuttings were analyzed by destructive sampling at 5-day intervals up to 25 days after establishment. Results of the study demonstrated that sand medium, compared to a mixture of sand + coir medium, resulted in a higher rooting percentage. However, sand + coir medium showed improved root length of the cuttings. Planting depth of 3 cm resulted in a higher rooting percentage and good establishment of cuttings as compared to a depth of 1.5 cm. Untreated cuttings when compared to those treated with Dynaroot™ No. 2 (0.3% IBA), resulted in increased root number, stem circumference and number of leaves. There was an increased rooting percentage in autumn as compared to summer. Therefore, the results of the study demonstrated that sand is an ideal propagation medium and a planting depth of 3 cm is suitable for improved establishment of the cuttings.
    No preview · Article · Sep 2013 · Acta horticulturae
  • R. Smit · E.S. Du Toit · B.J. Vorster

    No preview · Article · May 2013 · South African Journal of Botany
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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 on floral initiation, flowering and fruit set. Three treatments namely, a 900 mm (900IT), 600 mm (600IT) and 300 mm (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 highest at the 300IT and lowest at the 900IT for two consecutive growing seasons. Fruit set on the other hand, decreased with the decrease in irrigation treatment. 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, however, this should be followed by sufficient irrigation to ensure good pollination, fruit set and yield.
    Full-text · Article · Jan 2013 · Journal of Agriculture and Rural Development in the Tropics and Subtropics
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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.
    Full-text · Conference Paper · Aug 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.
    Full-text · Dataset · May 2012
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    How-Chiun Wu · Elsa S. du Toit

    Full-text · Chapter · Apr 2012
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    Full-text · Chapter · Jan 2012
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    Quintin Ernst Muhl · Elsa S. Du Toit · J.M. Steyn · Z. Apostolides
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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.
    Full-text · Conference Paper · Sep 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
    No preview · Conference Paper · Sep 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.
    No preview · Conference Paper · Sep 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.
    No preview · Conference Paper · Sep 2011
  • 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.
    No preview · Article · Apr 2011 · Seed Science and Technology
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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.
    Full-text · Article · Apr 2011 · South African Journal of Botany
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    Quintin E Muhl · Elsa S Du Toit · Petrus J Robbertse
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    ABSTRACT: Moringa oleifera trees are naturally found in tropical climates around the world, while the extent of their adaptability to cooler climates was the main objective of this study. A total of 264 trees, made up of an equal number hardened and non-hardened seedlings were randomly assigned to three temperature-controlled greenhouses each with a different fluctuating night/day temperature regime (TR) namely; 10/20˚C ± 2˚C, 15/25˚C ± 2˚C and 20/30˚C ± 2˚C. During the 32-week trial period, biweekly measurements of tree height, stem diameter and leaf area estimates of each individual tree within all three temperature regimes (TRS) were taken. The 20/30˚C TR was the most favorable towards overall tree growth, as the highest values were obtained across most measured parameters. The increase in temperature re-sulted in growth rate increases of over 650% between the 10/20˚C and 20/30˚C and over 250% between the 10/20˚C and 15/25˚C night/day TRS. The hardening-off pre-treatment increased both final tree height and stem diameter, re-sulting in increases of 3.09 × (10/20˚C), 1.44 × (15/25˚C) and 1.23 × (20/30˚C) compared to their non-hardened off counterparts. Although the average leaf area increased with the increase in TR and remained higher for the duration of the trial, cycles of regular leaf drop and renewed flushes were prevalent at both the 15/25˚C and 20/30˚C temperature treatments.
    Full-text · Article · Jan 2011 · American Journal of Plant Sciences
  • Quintin E. Muhl · Elsa S. Du Toit · Petrus J. Robbertse
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    ABSTRACT: Geographical distribution and growth of plants are to a great extent governed by temperature. As Moringa oleifera trees are mainly found throughout the tropics around the world, the extent of their physiological adaptability to lower temperature was the main objective of this study. The successful cultivation of M. oleifera trees in cooler climates would greatly increase their production areas. A total of 264 trees were randomly assigned to three temperature-controlled greenhouses, each with a different fluctuating night/day temperature regime namely; 10/20°C, 15/25°C and 20/30°C. Throughout the trial period, stomatal index, leaf conductance as well as leaf sampling for microscopical analysis were conducted to identify morphological adaptations to lowers temperatures in the leaves across all three temperature regimes. Leaves from the 10/20°C treatment had an average thickness of 0.239 mm, compared to 0.136 mm at 20/30°C. This is a 43.1% increase in leaf thickness, as a result of a mere 10°C decrease in temperature. Leaves were thicker mostly due to a broader spongy mesophyll layer. Despite larger stomata observed at the 20/30°C TR, the lower stomatal index resulted in a significant 18.9% reduction in leaf conductance compared to the 10/20°C TR. Although higher temperatures generally favoured tree growth, plants acclimatized to lower temperatures through physiological adaptations.
    No preview · Article · Jan 2011 · International Journal of Agriculture and Biology

Publication Stats

242 Citations
32.16 Total Impact Points

Institutions

  • 2001-2015
    • University of Pretoria
      • • Department of Plant Production and Soil Science
      • • Faculty of Natural and Agricultural Sciences
      Πρετόρια/Πόλη του Ακρωτηρίου, Gauteng, South Africa