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Effect of cultivation practices on Lachenalia cultivars for a potential cut flowerKoch, Carmen Marlene 05 September 2005 (has links)
Trials were done on four Lachenalia cultivars (Romaud, Robyn, Rolina and Romelia) to improve flower quality and inflorescence stem length and to evaluate vase life, as these criteria are important for the cut flower grower. Flowering size bulbs were grown under five different shade nets (white 18%, green 40%, black 40%, black 55%, black 7O%) and in the open as a control. Under each shade net, bulbs were planted at a low planting density of two bulb diameters apart (56 bulbs/m2), as well as a high planting density of one bulb diameter apart (111 bulbs/m2). The effect (If the growth hormone gibberellic acid (GA3) on plant growth was investigated to determine if longer stems could be obtained. The plants were treated with gibberellic acid at 10 ppm and 0 ppm, which was applied as a foliar spray and as El bulb dip treatment. It is necessary to identify and describe specific flowering stages to be able to establish a standard rating system for Lachenalia vase life. The morphology of Lachenalia cultivar Romaud was described to determine the real succession of opening flowers on the inflorescence. The stages of 'first flower', 'full flower' and '50% wilt' were described. A high photosynthetically active radiation (PAR) measurement of 1250 µ.mol.m-2.s-1 in the control, resulted in the shortest inflorescence stem length of 13 cm for all four cultivars compared to the rest of the shade nets. The longest inflorescence stem length of 24 cm was produced for cultivars Rolina and Romelia by a low PAR of 400 µ.mol.m-2.s-1 under the black 70% shade net. The inflorescence stem length of all four Lachenalia cultivars tend to decrease to a minimum of 13 cm when average temperatures are 30oC and higher and to a maximum of 24 cm when temperatures are in the range from 24 to 27oC. A long vase life of 12 to 14 days for cultivar Rolina was observed under the green 40% and black 40% shade nets, compared to 10 to 11 days in the control. The green 40% shade produced a long vase life of 14 to 16 days for cultivar Romelia, compared to the 12 to 14 days in the control. Planting density significantly increased inflorescence stem length by about 2.5 cm and vase life by 2 days at the high planting density compared to the low planting density for all four cultivars. Inflorescence stem length for cultivars Romaud and Romelia increased significantly by 3 cm for both the GA3 foliar spray and bulb dip treatments. The number of flowers per inflorescence decreased significantly by about 3 to 5 flowers for cultivar Romaud and Romelia when GA3 was applied as a foliar spray or bulb dip treatment. A significant increase in vase life (2 days) of GA3 treated plants was observed. All four Lachenalia c:ultivars are suitable for cut flower production, as inflorescence stem lengths were either just below or above the 20 cm mark and vase life was longer than the five to six days required by the cut flower industry. / Dissertation (MSc (Agric): Horticulture)--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted
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Cape elements on high-altitude corridors and edaphic islands.Carbutt, Clinton. 28 November 2013 (has links)
Common to the temperate floras throughout sub-Saharan Africa is a group of taxa with strong ties to the Cape Floristic Region (CFR) (≈ Cape elements). Their distribution is limited to the eastern escarpment of Africa (e.g. the Drakensberg Alpine Centre - DAC), on nutrient-rich humic soils, as well as on isolated sandstone outcrops of low elevation, on nutrient-poor soils (e.g. the Pondoland Centre - PC), suggesting that intrinsic soil fertility is not the primary determinant of their distribution. The principal aim of this study was to determine which aspect of the edaphic environment of the DAC is most
influenced by temperature, that may indirectly render it nutrient-poor and
therefore provide suitable niches for Cape elements, as in the PC. A
multidisciplinary approach involving aspects of plant biogeography, plant
ecology, plant ecophysiology and soil chemistry was therefore adopted. The
study regions were the DAC, PC and the KwaZulu-Natal Midlands. The flora of the DAC was resurveyed for this study, and is richer than previously thought: 2818 native taxa, most of which (2520) are angiosperms. The phytogeography of the DAC and PC is discussed, and comparisons are made with the floras of KwaZulu-Natal and the CFR. Their climatic environments, as well as those for the CFR and Sneeuberge, were compared using rainfall and temperature data from a range of sources. These climatic regimes were correlated with the floristic patterns of Cape elements for the high-altitude regions of South Africa and Lesotho. Altitude and rainfall increased, and temperature decreased, as the
number of Cape elements increased towards the DAC. This study provided a contemporary inventory of the Cape elements of the DAC and PC. A total of 89 genera are recognised as Cape elements, of which 60 (c. 67%) are shared between the two regions. The highest number of Cape elements recorded for the eastern escarpment was the DAC (72 genera), with the highest number from all sites analysed being the PC (77 genera). The most Cape elements are contributed by the Asteraceae, Scrophulariaceae, Iridaceae, Fabaceae, Orchidaceae and Restionaceae, partly due to the success of annual aerial parts and their geophytic growth forms, which are convergent in these families. Further compartmentalisation into life and growth forms shows that most Cape elements of the DAC and PC are either ericoid (and sclerophyllous) or mesic herbs and shrubs. The ecological and ecophysiological aspects of this study involved the use of reciprocal pot experiments established along a gradient of altitude from coastal hinterland to mountain, that investigated the interactions between altitude, temperature and substrate on plant productivity in sites known either to support or to exclude Cape elements. Three soils were used at
each site, representative of the DAC, PC and KwaZulu-Natal Midlands. The
interactions between 'soil' and 'site' (≈ the climatic environment) were
quantified using a temperate test taxon (Diascia) that has a strong Cape-centred distribution. Plant characters relating to morphology and nutrient content, and soil characters relating to fertility, were used as the basis for comparing treatment effects (soil-site interactions). Soil nitrogen availability was assayed using pot experiments with Eragrostis curvula (Schrad.) Nees. Wheat pot experiments revealed no Al³⁺ toxicity in 'Drakensberg' soil. Non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) indicated that all soil-site interactions were significant contributors to biomass differences, and that the Cape taxon performed poorly in the nutrient-rich Drakensberg soil at low altitude. Soil samples indicated that Drakensberg soil was the most nutrient-rich, and Pondoland soil the most nutrient-poor. Although total nitrogen
in Drakensberg soil was six times higher than Pondoland soil, both soils
mineralised similar low levels of nitrogen at their respective spring
temperatures. The result for Drakensberg soil (simulated so as to include the effect of altitude) meant that only 1.7% of its total nitrogen was mineralisable at 12°C (its mean spring temperature). These findings suggest that nitrogen mineralisation rate is a key growth-limiting factor in the DAC, exacerbated by a number of complex interactions with soil pH and organic matter. It is hypothesized that Cape elements are preadapted to high-altitude habitats. These habitats are nutrient-deprived due to low temperatures, which reduce metabolic rates and the movement of ions in cold soils. This constraint imposes nutrient-related stresses similar to those of the CFR and PC. Taxa that are adapted to the nutrient-poor soils of the CFR are preadapted to the temperature-induced 'nutrient-poor' soils of the DAC and vice versa. This 'compatibility' has allowed the reciprocal exchange of taxa between regions, as suggested by cladistic biogeographical analyses using Cliffortia, Disa, Moraea and Pterygodium. The strong overlap of Cape elements between the CFR and PC is a product of similar nutritional niches and ancient floristic continuity. The result therefore is a high number of Cape elements common to the DAC and PC. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.
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Investigating the most favourable seed establishment methods for restoring sand plain fynbos on old fieldsCowell, Carly Ruth January 2013 (has links)
Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Horticulture
in the Faculty of Applied Sciences
at the Cape Peninsula University of Technology, 2013 / Cape Flats Sand Fynbos (CFSF) is one of the most poorly conserved vegetation types in
the Cape Floral Kingdom, and a large proportion of unconserved land is degraded,
primarily as a result of transformation by agricultural, urban developments and invasion by
alien plants. Fynbos restoration is one of the most important management interventions,
both within the current conservation areas and in any future land remnants acquired for
conservation. Many extant remnants are fragmented and isolated, and if successful
restoration protocols are found, it may be possible to improve the conservation targets for
this critically endangered vegetation type. On old fields, where indigenous soil seed banks
have been lost due to alien plant invasion and anthropogenic action, it is essential to reintroduce
the longer-lived fynbos components that contribute to vegetation structure, in
order to facilitate the progress of the ecosystem on a more natural trajectory.
This research is built on an earlier study of optimal ground-preparation treatments for
restoring Sand Fynbos to old fields. This former study indicated that fossorial mammals
(molerats and gerbils) may occur in dense colonies on old fields and present an obstacle
to successful seedling establishment. The project aims to provide protocols for the
establishment of indigenous seedlings from harvested seed onto old fields, in order to
restore Sand Fynbos vegetation. Different pre-sowing treatments and sowing techniques
were tested on large field plots to determine the most efficient protocol. The objectives of
the research were: a) to investigate optimal pre-sowing treatments of indigenous seed for
restoring degraded Sand Fynbos vegetation in old field sites; b) to investigate optimal
sowing techniques on large field plots for restoring degraded Sand Fynbos vegetation in
old field sites with depleted indigenous seed banks; c) to provide guidelines and
disseminate information on optimal sowing protocols, and their costs, for restoring Sand
Fynbos vegetation in degraded areas and old fields. A further component of the research
was to calculate the costs of all treatments on a per hectare basis in order to assess the
cost-effectiveness of the different options.
Several different seed treatments may potentially increase the germination rate and
promote fynbos restoration. These are scarifying, smoke, smoke water, chemical, light and
temperature pre-sowing treatments. In order to keep the number of treatments (including
their interactions) to a manageable level, only soaking in smoke water extract and seed
coat scarification with course sand and grit were tested. A seed sample of each species
was x-rayed at the Millennium Seed Bank in the United Kingdom, to test for viability in the
seed samples, 52 % of the seed collected were empty, a typical indication of wild
harvested seed. All species were germinated at 10/25 °C and 16/8 hours light/dark
respectively. Scarification had a larger overall germination success, smoke water had very
little effect on CFSF species, it is rather that germination is related to temperatures during
a fire that result in seed coat splitting. It was recommended that further investigation using
more species across the Sand Fynbos vegetation be conducted on pre-germination
effects of heat and scarification.
The study site had been cleared of woody invasive alien vegetation and additional site
preparation included the application of a systemic herbicide to kill undesirable herbaceous
weeds, prescribed fire to clear the site of woody debris and destroy weed seeds, and the
local control of fossorial mammals (gerbils and molerats) by placing raptor perches and
owl nesting boxes around the site. This research found that the use of herbicide shortly
after the prescribed fire and once again prior to sowing was successful in controlling
herbaceous weeds and the indigenous grass Cynodon dactylon. The challenge to using
prescribed burning on old fields was low fuel loads, which resulted in a cool patchy. It is
suggested that cutting and spreading of alien plant biomass is tested as a solution,
however, the material must be evenly spread across the site and not stacked into piles
which can cause excessively hot fires and scorching of the soil. In order to better
understand soil conditions across the site, soil samples were collected prior to sowing, to
analyse for soil macronutrients, organic matter and pH. It was established that all the
excess nutrients added to the site from agriculture and pasturage over the years had
leached from the soil. However, the organic matter content of the soil was extremely low
and research needs to be done on the organic carbon content of the soils, how these
relate to soil micro biota (which species are present and their relationship with CFSF
species) and how best to enrich the site with humic matter for restoration and
establishment of Cape Flats Sand Fynbos. The field trial was set up in the Blaauwberg
Nature Reserve, a random split-plot block design, was replicated five times and used to
investigate the selected seedbed preparation and sowing techniques, namely: broadcast
sowing onto unprepared seedbed, broadcast with plank embedding of seed onto disked
seedbed, broadcast onto disked seedbed and hydro-seed with disked seedbed. Results
from the research found that the most successful methods for sowing seeds were the
hydro-seeding and broadcast with plank embed. These methods may have provided
better contact between the soil and seeds and better protection from predation and wind.
Economically the broadcast and embed was better as machinery was more efficient and
effective than manual labour. This study recommended that these two methods be
combined with the additional planting of rare and threatened species in clumps to
determine the benefits and interactions of each technique over the long term.
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Determination of the optimal preservatives for preventing stem bending of Gebera jamesonii "Black Diamond"Maluleke, Mdungazi Knox 10 1900 (has links)
Postharvest stem bending is one of the most detrimental factors that affect postharvest quality life of Gerbera jamesonii cutflower varieties. Stem bending is of economic importance in the cutflower industry in South Africa because it negatively affects the overall total sales. Growers and retailers want to improve the postharvest vaselife of this crop using suitable preservatives. The aim of this study was to determine suitable preservatives and optimal vaselife conditions that could prevent or minimise postharvest stem bending of Gerbera jamesonii “Black diamond”.
The variety “Black diamond was selected and treated with four different floral preservative solutions. The relationship between stem bending and absorption rate of the preservative solutions was established. The data gathered indicated that there was a significant difference to the solution absorption rate and stem bending. Stem bending differed from 0 to 38 degrees. Stems treated on control, preservative 3 and 4 recorded the highest degrees of bending, while preservative 1 and 2 recorded the lowest degrees of stem bending within 12 day period. The performance results of the preservatives and control repeated three times under the same experimental conditions showed that preservative 1 and 2 can be used to minimise postharvest stem bending of Gerbera jamesonii ‘Black diamond’ / College of Agriculture and Environmental Sciences / M. Sc. (Ornamental Horticulture)
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