Sustainable rehabilitation can be compromised by the inability of vegetation to survive in hostile
mine wastes on a long-term basis. The adverse chemical and physical properties of mine wastes,
together with extreme pH conditions and lack of nutrients, provide poor growth conditions for
vegetation during seed development and germination. This raises concern for the long-term
survival of vegetation through means of seed production when under stress from the punitive
properties of mine wastes.
Seed vigour is a function of a variety of factors to which the parent plant is subjected during seed
formation and maturation. Environmental conditions experienced by the maternal plant during
the growth season plays a significant role in determining subsequent germination rates in seeds.
Traits of offspring seed depend on the abiotic environment attributed by the growth medium
during seed development and maturation
The general aim of this study was to determine the viability of seed produced by a previous
generation of grass species established in eight different mine wastes and two soils (namely:
gypsum wastes; gold tailings with low pyrite content; gold tailings with high pyrite content;
platinum tailings; kimberlite mine waste; fluorspar mine waste; andalusite mine waste; coal
discard; red soil; and vertic soil) in order to identify suitable species for specific mine wastes to
ensure long-term survival through means of seed production. The species selected included:
Eragrostis curvula; Eragrostis tef; Cenchrus ciliaris; Eragrostis curvula; Digitaria eriantha;
Cynodon dactylon; Chloris gayana; Hyparrhenia hirta; and Sorghum bicolor.
The progeny seed‟s viability and ability to germinate were determined through a pot trial study
and additional germination testing at the laboratory of Advance Seed (Pty) Ltd. (AS). The
germination results were correlated with the growth media analyses by statistical non-parametric
correlations which indicated several significant correlations among the growth media properties
themselves, and with the germination of the progeny seed. C. gayana (Rhodes grass) seed had
poor germination percentages, especially seed harvested from Rhodes grass grown in acidic
wastes. Seed harvested from each of the E. curvula grasses grown in various mine wastes, had
excellent germination percentages.
According to the Repeated Measures ANOVA statistical analysis, there was a significant
influence of the growth media in which the parent grass were grown as a variable on the
germination of the progeny seed batches from S. bicolor, C. ciliaris, C. gayana, and D. eriantha,
indicating that the environmental factors as attributed by the growth media, i.e. the eight
different mine waste materials and two soils, and experienced by the maternal plant, did indeed
influence the germination of progeny seed. However, it was found that significant correlations
between the properties of the growth media and the germination of the progeny seed, was species
dependent.
The second general aim for this study was to evaluate above-ground re-growth of parent plants
after cutting in the mine waste materials and soil types mentioned above. The ability of
established grasses to re-grow after a cutting event was determined by cutting the above-ground
biomass of the parent grasses, after which it was scored according observable above-ground
growth in the following growth season. The measurement of re-growth was subjectively done by
scoring the grasses according to observable above-ground biomass.
Re-growth was observed for all the perennial grass species. This can be ascribed to the grasses
showing resilience to stress factors attributed by the growth media; or new grasses which
emerged from seed that collected in the pots, being mistaken for re-growth; or new emerging
grasses from the nodes of stolons and/or rhizomes being mistaken for re-growth. However, the
emergence of new grasses was an indicator of good health, as biomass allocation to rhizomes
and stolons is reduced under low nutrient availability and stress conditions. Therefore the
emergence of new grasses is indicative that the plant is either tolerant to stress conditions or that
the plant adapted to the restriction of growth due to the roots being bound to the size of the pot. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/15455 |
| Date | January 2014 |
| Creators | Muller, Irma |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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