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 / The high demand for medicinal plants has favoured over-exploitation of wild plants. The
search for alternative and sustainable methods of medicinal plant cultivation is imperative and
desirable. Biotechnological approaches particularly hydroponic technology has the potential
for large scale plant cultivation and production of secondary metabolites. The current study
aims at optimizing the production of antimicrobial secondary metabolites by an indigenous
South African medicinal plant species (Helichrysum cymosum) through hydroponics N and K
fertilization. In Chapter 1, the conceptual framework and justifications of the study are
presented. In Chapter 2 the research objective was to discern the optimal potassium (K)
supplement level for H. cymosum by evaluating the effects of different hydroponic K levels
on growth, K-leaf content, and anti-Fusarium oxysporum f.sp.glycines (Ascomycota:
Hypocreales) and total activities. Six weeks old seedlings of H. cymosum were treated with
varied concentrations of K in the form of potassium chloride, potassium nitrate and
monopotassium phosphate (58.75, 117.5, 235 and 470 ppm). These concentrations were based
on a modification of Hoagland’s hydroponic nutrient formula. Plants were maintained under
greenhouse conditions and growth parameters (plant height and number of leaves) were
recorded weekly. At 8 weeks post treatment, plants were harvested and fresh weights were
recorded and tissue nutrient content analysed. Sub-samples of the aerial parts of plants grown
in the different treatments were air dried, extracted with acetone and tested against F.
oxysporum. Plants exposed to 235 ppm K showed a marked increase in leaf number, plant
height and fresh weight. Overall there was no significant difference (P > 0.05) among the
treatments with respect to tissue nutrient content; K ranged from 3.56 ± 0.198 to 4.67 ± 0.29
%. The acetone extraction yield increased with increasing K fertilization: 58.75 ppm (16.67 ±
2.35 mg), 117.5 ppm (22.5 ± 4.79 mg), 235 ppm (210 ± 38.5 mg) but dropped to 40 ± 4.08
mg at 470 ppm K. Results from the anti-F. oxysporum bioassay showed that 58.75 and 235 ppm K treatments produced the most bioactive acetone extracts; MIC values of 0.49 and
0.645 mg/l, respectively. Acetone extracts obtained from plants exposed to 235 ppm K
yielded the highest total activity, comparatively (P < 0.05). In conclusion, the optimum
nutrient K level for growing H. cymosum hydroponically was 235 ppm.
Chapter 3 focused on another important macro nutrient N and the objective was to determine
the optimum nutrient requirements for growing the medicinal plant, Helichrysum cymosum
(L.) (Asteraceae), hydroponically. Experiments were conducted to assess the effects of varied
nitrogen (N) concentrations supplied as nitrate and ammonium on growth, tissue nutrient
content, antimicrobial and total activities of acetone extracts of aerial parts. Treatments were
based on a modified Hoagland’s nutrient formula. Six week old rooted cuttings were treated
with 52.5 ppm, 105 ppm, 210 ppm and 420 ppm of N. Leaf number and stem height (cm)
were recorded at weekly intervals and leaf analysis conducted. The effects of N treatments on
plant growth parameters varied significantly among treatments; 52.5 ppm of N yielded the
tallest plants (height) [19.4 ± 0.7 cm], while 105 ppm N yielded the maximum leaf number
(68.1 ± 6.2) as well as maximum fresh weight of aerial parts was obtained with 105 ppm
(15.12 ± 1.68 g). Nitrogen content of plant tissue ranged between 0.53 ± 0.03 and 4.74 ±
0.29% (d, f, 3, 12; f=14; P ≤ 0.002) depending on treatments. Powdered aerial parts (5 g) of
H. cymosum obtained from the different N treatments were extracted with 100 ml of acetone.
N treatment significantly affected the yield of crude extracts, which ranged from 87.5 ± 15.5
(52.5 ppm) to 230 ± 23.5 mg (105 ppm). Acetone extracts of plants that were exposed to
varied N treatments were screened for anti-Fusarium oxysporum activity using minimum
inhibitory concentration (MIC) method. The MIC value (0.073 ± 0.014 mg/ml) obtained with
acetone extracts of plants exposed to 52.5 ppm N was significantly lower compared to the
MICs of the other N treatments (105 [0.47 ± 0 and 0.705 ± 0.135 mg/ml], 210 [0.234 and 0.47
mg/ml] and 420 ppm [0.29 ± 0.101 mg/ml]) at 24 and 48 hours respectively. However, the
total activities of extracts obtained among the four N treatments, which ranged from 0.062 ±
0.02 to 0.26 ± 0.06 ml/g was not statistically different at 24 or 48 hours (P > 0.05). LC-MS
analysis of acetone extracts of H. cymosum plants obtained from the four treatments hinted
that known anti-microbial agents such as apigenin, quercetin, kaempferol, helihumulone and
quinic acids were present in the extracts and the quantity of helihumulone increased with
increased nutrient N level.
These results suggest that H. cymosum may be cultivated hydroponically and that the
antimicrobial activity and/or the phytochemical profile of the crude acetone extracts is
affected by nutrient nitrogen levels. Hydroponic cultivation of plants may be able to alleviate
to an extent the pressure on wild medicinal plants.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/849 |
| Date | January 2014 |
| Creators | Matanzima, Yonela |
| Contributors | Nchu, F., Dr, Laubscher, C.P., Prof |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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