Thesis (M.Sc. (Botany))-- University of Limpopo, 2013 / The aim of the study was to identify drought tolerant South African soybean cultivars
for cultivation where water is a limited resource. Soybean [Glycine max. (L.) Merr] is
one of the most important legumes in the world. A lot of attention has been focused
on soybean cultivation in South Africa recently. Soybean production is mainly
affected by several biotic and abiotic factors which reduce the yield and quality of the
crop.
Six South African soybean cultivars (LS 677, LS 678, Mopanie, Sonop, Knap and
Pan 1564) and two American cultivars (R01 416 and R01 581) were carefully studied
for morphological and physiological markers which contribute to drought tolerance.
The study was conducted at the University of Limpopo (Turfloop campus). Soybean
plants were grown in a glasshouse in a randomised block design given same
amounts of nutrients and differing amounts of water (limited and overwatering).
Data was collected at R3 growth stage by measuring several morphological (stem
length, leaf surface area, flowers and seeds counts) and physiological (percentage
chlorophyll, moisture content, total phenolics, total flavonoids, ureide content and
antioxidant activity) parameters. An anatomical study was also carried out on the
transverse sections of leaves, roots, leaf stalk and nodules.
The different cultivars reacted differently to the three water treatments. LS 678
produced the tallest plants whereas those of Pan 1564 were the shortest. Water
stress affected plants by reducing the number of flowers produced, the leaf surface
area as well as the relative leaf water content. The moisture content of the growth
medium was reduced faster as the plants matured and it was also lowered by the
limited water availability. Percentage chlorophyll is another trait which was affected
by water limitation. Cultivars with high phenolic and flavonoids content were
associated with high antioxidant activity and slightly yielded higher than the others.
The anatomical transverse sections of the roots and petioles have shown some
secondary growth. The anatomy of the nodules of Mopani has shown some
interesting differences in response to the three treatments. Limited water decreased
xii
the size of the vascular tissue and sclerenchyma as a result altering the functionality
of the nodule. The anatomy of Sonop’s petiole had a thickened sclerenchymatous
bundle sheath covering the phloem tissue. The sclerenchyma tissue is thought to
guard against loss of water. The cross section of the leaf had a double layer of
palisade mesophyll (upper surface) and only a single layer of spongy mesophyll
(lower surface). In addition, the mesophyll and the epidermal cells of Mopani
appeared much thicker.
In terms of yield, there was no cultivar which yielded the highest but Mopani yielded
the lowest. Since Mopani was low yielding, the main focus of the discussion was on
the features (morphological, physiological and anatomical) of Mopani which can be
associated with drought susceptibility. Some of these features include reduced stem
length, large leaf surface area, low relative leaf water content, low growth medium
moisture content and low antioxidant activity.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/1041 |
| Date | January 2013 |
| Creators | Mabulwana, Paseka Tritieth |
| Contributors | Mokwala, P. W. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xii, 83 leaves :ill. |
| Relation | Adobe acrobat reader, version 7 |
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