| dc.description.abstract | In recent years, with the influence of climate change and sea level rise, the
problems of drought, flood and salinity have become more and more severe.
Such problems are anticipated to get worse in the forthcoming years. Therefore,
agriculture in many areas of the world has been challenged with shortage of
fresh water and saline soil as the major constraints. Both of these abiotic factors
cause osmotic stress, thus conferring similar negative effects on plant growth
and development, as well as triggering similar plant responses. In a previous
research, MTD720 and DT51 were two local soybeans that had been identified
as drought-sensitive and drought-tolerant cultivars, respectively. Therefore, it
was of interest to find out if these soybean varieties with contrasting droughttolerant phenotypes also displayed differential salt tolerance. Within the cover
of this thesis, as a part of a large project, several analyses were conducted,
including the effects of salt stress on shoot/root length and biomass, and tissue
water content reservation. Following hydroponically grown under normal
conditions and under salt stress at NaCl concentrations of 50 mM, 100 mM, or
150 mM, the results showed a negative impact of the stress on the biomass, root
length, and shoot development of both cultivars, particularly under 150 mM
NaCl condition. According to the analyses, tap root elongation was probably not
an advantage for DT51 over MTD720. However, the former showed a better
maintainence in their biomass under the stress conditions due to better axillary
root formation, whereby the reduction rates in biomass under 150 mM NaCl
application compared to the controlled couterparts were approximately 8% in
DT51 and 27% in MTD720. It has been also noted that the relative water content
(RWC) of DT51 was consistently greater than that of MTD720 under the same
condition of all applied NaCl concentrations. With these preliminary data, DT51
might also have a better salt resistance capacity than MTD720, thus suggesting
the necessity to continue the investigation in order to have solid lines of
supporting evidence for this conclusion. | en_US |
