Physiological characteristics of the response to water stress of two maize cultivars, the
one drought resistant (PAN473) and the other drought sensitive (SR52), were compared.
Mature plants were grown in one of two treatments, control and water stress. The drought
resistant cultivar had a higher growth rate and a greater amount of roots in the lower soil levels
than the drought sensitive cultivar in the water stress treatment. There was no difference
between the cultivars in physiological characteristics in the control treatment, but in the water-stress
treatment the drought resistant cultivar had a higher transpiration rate during the onset
of water stress, and higher relative water content and levels of abscisic acid and proline
throughout the period of water stress. A comparison between the cultivars in their gene
expression response was done to determine if a correlation could be made with the difference
in physiological response. A differential screening of water stress cDNA libraries identified nine
different cDNA species which gave a signal with the water stress probe but not the control
probe. Three of these cDNAs were represented by more than one cDNA clone. The cDNAs
occurred in both libraries, therefore there was no difference between the cultivars in the
presence or absence of the water stress responsive genes. The three genes represented by these
cDNAs were named rws7, rws16 and rws5. All three genes showed increased transcription in
response to water stress in whole plants, and to desiccation and osmotic stress of detached
leaves. No increase in transcription was found in response to exogenously applied abscisic acid
or proline. No difference between the cultivars was observed in the pattern of transcription
response. Two of the three cDNA species that are represented more than once were
sequenced. Rws7 had an open reading frame. A BLAST search found no homologous amino
acid sequences, but the characteristics of the polypeptide suggest that it is a dehydrin. Rws 16
had a partial coding sequence. A BLAST search found two homologous amino acid sequences,
and both were chloride channel proteins. The remaining seven cDNA species were sequenced
at their 5' ends, and no complete homologous nucleotide sequences were found. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1996.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10329 |
| Date | January 1996 |
| Creators | O'Regan, Brian Patrick. |
| Contributors | Cress, William A., Van Staden, Johannes. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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