| Seasonal variations in carbohydrate content of Carica papaya plants | Allan, P. | 2001 |
KeywordsCarbohydrate, Carica papaya, papaw, starch, sugar AbstractMonthly samples were collected of roots, stems, petioles and leaf blades of clonal female ‘Honey Gold’ papaw (Carica papaya L.) plants, in the cool subtropical Pietermaritzburg area, to study any seasonal variations in carbohydrate content of this tropical plant which grows continuously under favourable conditions. Under cool subtropical conditions, active leaf and stem growth ceased during autumn and winter, and there was a build up of sugars and starch at that time, in the petioles and stems in particular, and to a lesser extent in the roots. Most of the sugars were reducing sugars, especially in the leaf blade and petiole. The levels of starch attained were much lower than in deciduous fruit trees. Reducing sugar and starch levels dropped with the resumption of active growth during spring, summer and early autumn. Little accumulation would be expected under favourable tropical conditions. AuthorsAllan, P. Year Published2001 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2001.10634402 This article contributed by:
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| Macadamia cultivar evaluation in Natal | Allan, P. | 1989 |
KeywordsCultivars, macadamia, Natal AbstractVegetatively propagated macadamia cultivars were grown in six ecologically different areas in Natal. Nut quality was tested over a number of years. The warm, moist north coast area is best for most cultivars tested with Keaau, Ka'u, Kakea and Beaumont giving nuts of best quality. The relatively newer Hawaiian cultivars Keaau and Ka'u produce nuts of reasonably acceptable quality in the cooler subtropical areas where the quality of the older cultivars Keauhou, Ikaika and Kakea is more limiting. The most recently released higher quality Hawaiian cultivars have yet to produce nuts. Hybrid cultivars are best for the cooler areas but their kernels and those of some other cultivars are more suitable for the dry kernel trade. Breeding of locally adapted M. integrifolia cultivars is an urgent priority. Sound management practices are essential to produce good quality kernels. AuthorsAllan, P. Year Published1989 PublicationSouth African Journal of Plant and Soil Locations- Lianwarne Farm, Magut, South Africa (-27.6, 31.75)
- Trust Timbers, Kwambonambi, South Africa (-28.55, 32.133)
- Gibraltar, Paddock, South Africa (-30.617, 30.25)
- Litchi Syndicate, Port Shepstone, South Africa (-30.683, 30.417)
- UkulingaPietermaritzburg, KwaZulu-Natal, South Africa (-29.667, 30.417)
- Windy Mill, Wartburg, South Africa (-29.5, 30.55)
- Magut, Natal (-27.6, 31.75)
- Kwambonambi, KwaZulu Natal (-28.55, 32.1333)
- Paddock, KwaZulu Natal (-30.6167, 30.25)
- Port Shepstone, KwaZulu Natal (-30.6833, 30.4167)
- Pietermaritzburg, KwaZulu Natal (-29.6667, 30.4167)
- Wartburg, KwaZulu Natal (-29.5, 30.55)
DOI10.1080/02571862.1989.10634501 This article contributed by:
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| Growth regulator manipulation of apple bud dormancy progressions under conditions of inadequate winter chilling | Allderman, L.A. | 2011 |
Keywordscytokinin, abscisic acid, Malus x domestica Borkh, rest, South Africa AbstractElgin (34°S, 19°E; 305 m.a.s.l.), typical of South African apple growing regions, accumulates 745 Utah Chill Units (CU) p.a. The chilling requirement of ‘Golden Delicious’ apple (Malus xdomesf/ca Borkh.) is c.a. 1100 CU. Consequently, the chilling requirement is not satisfied and delayed foliation is common. The aim of this study was to use plant growth regulators (PGR’s) to manipulate the progression of dormancy in order to reduce the chilling requirement of ‘Golden Delicious’ shoots in mature commercial orchards. A trial was conducted in a commercial orchard in Elgin during the winters of 2004, 2006 and 2007. To advance the onset of dormancy, 250 mg −1 abscisic acid (ABA) was sprayed several times during April and May of 2004 and 2006. To induce a shallower state of dormancy, cytokinins were applied during April and May of 2006 and 2007. Benzyl adenine (BA) was applied at concentrations between 250 and 1000 mg −1 and forchorfenuron (CPPU) at 15 mg −1. Progression of dormancy was assessed by harvesting shoots every 2–3 weeks from initial spray date until commercial rest breaking agents were applied in the orchard. The time interval for 50% of the shoots to exhibit budburst under controlled conditions was used as a parameter for depth of dormancy. Although shoots were sprayed on c.a. the same calendar dates each year and before any significant CU had accumulated, the physiological state of the buds at application varied from shallow to deep dormancy depending on the season. Therefore calendar dates were not a good criteria for spray applications and CU accumulation was not a prerequisite for the onset of dormancy. PGR’s altered the dormancy progression of ‘Golden Delicious’ shoots. However, their efficacy was dependant on the dormancy status of the buds at the time of application. Furthermore, the effect was not sustainable. The trees appeared to “normalize” after a short period of time and consequently the PGRs had no effect on the dormancy release or budburst the following spring. AuthorsAllderman, L.A., Steyn, W.J. and Cook, N.C. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640020 This article contributed by:
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| Screening of some South African maize (Zea mays L.) cultivars for acetochlor tolerance | Allemann, J. | 2010 |
KeywordsAcetochlor, corn, cultivar, phytotoxicity, tolerance AbstractAcetochlor containing a safener is registered for pre-emergence use on maize to control mainly annual grasses. It is applied at rates of between 0.49 and 1.89 kg ai ha-~ on soils with a clay content from <10% to 55%. Some cases of acetochlor injury to maize have occurred in the field despite the correct application rates being used. A randomised complete block design trial was conducted in a glasshouse set at 28/18°C day/night to screen 21 maize cultivars for their tolerance to acetochlor (WENNER 700 S EC®). Maize was planted in pots containing a sandy loam soil (15% clay). Five acetochlor rates (0, 0.74, 1.47, 2.94 and 5.88 kg ai ha ~) were applied the next day and leached into the soil. Characteristic symptoms of acetochlor phytotoxicity occurred, particularly at higher application rates. Most cultivars showed significant decreases in both plant height and dry mass at the recommended application rate. Significant differences were noted between cultivars, with slight variations in results for seedling height and dry mass. cultivars were grouped into tolerant, intermediate and sensitive classes based on their reaction to the herbicide. Most cultivars were rated as intermediate, although both tolerantand sensitive cultivars were found, so proving the existence of cultivar differences with respect to acetochlor tolerance. AuthorsAllemann, J. and Mphundi, P.M. Year Published2010 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2010.10639992 This article contributed by:
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| Screening of South African sunflower (Helianthus annuus L.) cultivars for alachlor sensitivity | Allemann, J. | 2007 |
KeywordsAlachlor, sensitivity, sunflower, tolerance AbstractOccasionally a herbicide that is considered safe to use at prescribed rates causes damage to crop plants at those same rates. Alachlor (Lasso EC®) is registered for use on sunflower at a rate of 1.5 to 1.92 kg ai ha−1. Occasional injury to sunflower plants at these rates is usually caused by incorrect application or unsuitable weather conditions, but sometimes no explanation can be found. In many crops it has been shown that genetic differences can make specific cultivars more susceptible to alachlor injury. The objective of this study was to screen 22 of the available sunflower cultivars for sensitivity to alachlor in a glasshouse trial. Planting took place in pots filled with a sandy loam soil (20% clay). Five rates of alachlor (0, 0.96, 1.92, 3.84 and 7.68 kg ai ha−1) were applied and leached into the soil with 100 ml of water. Pots were laid out in an air-conditioned glasshouse set to 28/18°C day/night in a randomised block design with three replicates. Plants were harvested 38 days after planting, at which stage plant height and mass were determined. The results indicated that cultivar differences with respect to alachlor tolerance were present. Plant height appeared to be the best predictor of alachlor activity in sunflower. Cultivars were divided into three classes (tolerant, intermediate and sensitive) based on their reaction to the herbicide. AuthorsAllemann, J. and Ceronio, G. M. Year Published2007 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2007.10634775 This article contributed by:
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| Allelopathic influence of soils planted to Amaranthus cruentus L. on two tomato (Lycopersicon esculentum Mill.) cultivars | Allemann, J. | 2006 |
KeywordsAllelopathy, Amaranthus cruentus, amaranth, tomato AbstractAmaranthus cruentus L. is being evaluated as a potential high value niche market crop for small-scale farmers in South Africa. This is largely due to the demand for organically produced seed for the European health food market where it is used in a variety of products. Tomatoes were planted six months after a pilot planting of amaranth at Rust de Winter, near Pretoria. Problems with the growth and development of the tomato plants were noticed within a fairly short period. Investigations revealed no nutritional or pest and disease problems. Soil was collected from the problem field, as well as from an adjacent field with similar soil to investigate possible soil problems. Two tomato (Lycopersicon esculentum Mill.) cultivars (Rodade and Floradade) were grown in pots containing these soils in an air-conditioned glasshouse under natural light conditions. Both cultivars exhibited signs of significantly inhibited growth (reduced height, leaf area, leaf number and shoot mass) when grown in soil from the amaranth field. It was concluded that A cruentus residues were probably allelopathic to these two cultivars of tomato. AuthorsAllemann, J. and Denner, F.
D.N. Year Published2006 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2006.10634745 This article contributed by:
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| Suitability of two types of plastic covering on mini-tunnels for paprika seedling production in warm areas | Allemann, J. | 2004 |
KeywordsPaprika, plastic type, seedling production, temperature, tunnels AbstractA trial was conducted at the ARC-Roodeplaat Vegetable and Ornamental Plant Institute to determine the difference between the two types of plastic (clear and opaque) used as covering for mini-tunnels during paprika (Capsicum anuum L.) seedling production. Two cultivars (PapriKing and PapriQueen) were tested in a split-plot experiment, with type of plastic allocated to main plots and cultivar to sub-plots. Tunnels were opened 33 days after planting and seedling survival rates determined. Seed germination tests were conducted in order to eliminate differences in germination between the two cultivars, and temperature sensitivity of the seed during germination was also determined. No differences between cultivars was noted, and both reacted in the same way. Type of plastic used to cover the tunnels significantly affected seedling survival, and position in the tunnel also played a role. Temperatures above 32°C during germination had a detrimental effect, resulting in reduced germination and abnormal seedlings. Temperatures below the opaque plastic were lower than those below the clear plastic, and it was concluded that the opaque plastic should be used when temperatures are high. AuthorsAllemann, J., Viljoen, J. and Niederwieser, J. G. Year Published2004 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2004.10635036 This article contributed by:
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| High availability of alachlor affects the roots and general growth of sunflower seedlings | Allemann, J. | 1995 |
KeywordsAlachlor, phytotoxicity, sunflower, tolerance AbstractThe tolerance to alachlor [α-chloro-2′,6′?diethyl-N-(metoxy- methyl) acetanilide] of three sunflower (Helianthus annuus L.) cultivars was evaluated in an aqueous medium in a glass- house. Alachlor (0.79 - 6.32 mg L−1) caused significant reductions in the root and shoot growth of sunflower seedlings exposed to the herbicide in nutrient solution. The roots of seed- lings exposed to alachlor became progressively shorter, thicker and darker in colour as the herbicide concentration increased. Differential cultivar tolerance was demonstrated. AuthorsAllemann, J. and Reinhardt, C. F. Year Published1995 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1995.10634333 This article contributed by:
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| Evidence that alachlor selectivity in sunflower is based on depth-protection | Allemann, J. | 1994 |
KeywordsAbsorption, alachlor, selectivity, sunflower, tolerance AbstractThe relative importance of the underground shoot parts (hypocotyl) and roots of sunflower (Helianthus annuus L.) seedlings on the absorption of alachlor [a-chloro-2′,6′-diethyl- N-(methoxymethyl) acetanilide] was studied in a glasshouse experiment. A layer of activated charcoal divided the soil in each pot into a shoot and a root zone. Three herbicide treatments entailed the mixing of alachlor with soil from either the shoot or the root zone, as well as with soil from both zones. Exposure of sunflower roots, or roots plus shoots, to alachlor caused significant reductions in growth. Alachlor, present in the shoot zone only, had little or no effect. Results indicate that alachlor absorption occurred primarily in the root zone, thus implying that selectivity of the herbicide in sunflower may, at least partly, be dependent on depth-protection. AuthorsAllemann, J. and Reinhardt, C. F. Year Published1994 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1994.10634324 This article contributed by:
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| Effect of nitrogen supply on the production and distribution of dry matter in sugarcane | Allison, J.
C.S. | 2002 |
KeywordsNitrogen supply, productivity, sugarcane AbstractSugarcane productivity is probably limited by characteristically slow early growth and, later, by progressively decreasing leaf nitrogen (N) concentration. Increasing the N supply might increase productivity by influencing these attributes. In a pot experiment on two cultivars N was supplied at either a level corresponding to normal field supply (‘low’), or a level twice this (‘high’). Plants were sampled at 173 days, and then N level supplied to the remaining plants was either maintained or decreased until a final harvest at 270 days. Stem and total dry mass at 173 days were increased by c. 20% by high N, and at 270 days by c. 60%. Dry masses at 270 days were not affected by decreasing N supply at 173 days. Crop growth rate (C) between 173 and 270 days was increased about two and a half-fold by high N, because of both greater leaf area index (L) and net assimilation rate (E); variation in E was related to leaf N concentration. Sucrose yield was increased by c. 60% by high N supply because of greater stem dry mass rather than of increased sucrose concentration. The results suggest that augmenting the N supply during the early part of the growth period should increase productivity, but results from pots should be confirmed in the field. AuthorsAllison, J.
C.S. and Pammenter, N. W. Year Published2002 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2002.10634430 This article contributed by:
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