The application of seaweed concentrates to plants has been shown to enhance
growth and improve yield parameters. How these natural products elicit their
beneficial responses is still unclear. While many of the growth responses have been
attributed to cytokinins, it is obvious that this group of plant hormones cannot
account for all the beneficial effects incurred from seaweed use. This study was
therefore initiated to investigate the effects of a commercial seaweed concentrate
(Kelpak) on several aspects of plant growth and development.
Tentative determination of plant growth regulators in the seaweed concentrate
(SWC) using bioassay systems, indicated the presence of compounds with
gibberellin- , abscisic acid- and auxin-like properties. Tentative identification of the
auxins present in the SWC and Ecklonia maxima using High Performance Liquid
Chromatography revealed the presence of tryptophan, indole-3-acetamide, indole-3-
acetic acid, indole-3-carboxylic acid and indole-3-acetaldehyde.
The effect of SWC on the growth of nodal potato explants cultured in vitro was
examined. 0.2% SWC significantly accelerated shoot growth and development.
When applied at a concentration of 0.4% the number of axillary shoots per node
increased. This treatment also stimulated the development of potato tubers on the
shoots.
The SWC was also shown to enhance the growth of tomato (Lycopersicon
esculentum Mill.) roots cultured in vitro. Filtration of the SWC indicated a promotory
filtrate phase and an inhibitory cell wall phase. ' The application of the SWC to
nematode-infested roots, cultured in vitro, reduced the degree of infestation In
susceptible roots but induced host/parasite compatibility in a resistant variety. One of the most pronounced effects noted with seaweed application was the
promotion of adventitious roots on several species of garden plants. The application
of similar dilutions to Eucalyptus cuttings increased the average root mass but had
little effect on the number of roots initiated per cutting. The rooting factors, purified
by HPLC, were tentatively identified as indole-3-acetamide, indole-3-acetic acid,
indole-3-carbo. xylic acid or indole-3-acetaldehyde by co-chromatography with
authentic standards.
Finally, the effect of seaweed concentrate on the growth of tomato plants grown in
nematode-infested soil was investigated. SWC applied as a soil drench, improved
plant vigour, significantly increased shoot and root fresh weights and resulted in a
marked reduction in the number of nematode galls per unit length and per unit
weight of root. Plants treated with a foliar spray of SWC were invariably the first to
produce ripe fruit. Total yield was improved by over 10%. Ashing the SWC indicated
that the active constituents are possibly of an organic nature. Filtering the SWC
confirmed earlier reports that promotory and inhibitory compounds are present in the
concentrate. Chromatographic separation of the SWC into 10 Rf zones indicated the
presence of several components with growth regulatory properties. It was found that
the same fractions that improved plant growth also reduced nematode infestation.
The significance of these findings and the possible relationship between the
endogenous plant growth regulators in Ecklonia maxima and the effect of the SWC
on plant growth is discussed. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1990.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10513 |
| Date | January 1990 |
| Creators | Crouch, I. J. |
| Contributors | Van Staden, Johannes. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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