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Title: Salt tolerance and toxicity in NaCl-selected and nonselected cells and regenerated plants of Medicago media
Author: Chaudhary, M. T.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1996
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Batch suspension cultures of Lucerne (Medicago media cv Rambler), initiated directly from surface-sterilized leaflet explants, were used to produce cell lines tolerant to 200, 250 and 300 mol m-3 NaCl by successive subculture into media of progressively higher salinity. The degree of salt tolerance of the cell lines was highly dependent on the concentration of Ca++ in the growth medium. The plants of M media regenerated from salt-adapted cell suspension culture were significantly more tolerant to NaCl than the unselected Rambler plants, another cultivar of M. media and 5 cultivars of M. sativa. Cells re-cultured from leaflets of the regenerated plants retained increased salt tolerance. The salt-tolerant plants showed enhanced Na+ and Cl- exclusion and were able to maintain lower Na+/K+ ratios in the shoots when compared with the unselected cultivars. Ca++ gave some amelioration of salt toxicity but the salt-tolerant plants did not differ from the susceptible plants in this respect. Comparing 250 mol m-3 NaCl selected and unselected Rambler plants, a multiple regression equation has bee computed accounting for 90% of the observed variation, that relates the growth of the plants to Na+/K+ ratios and Cl- concentrations of roots and shoots and their interactions. The NaCl-selected cell line showed even greater tolerance to Na2SO4 or K2SO4 but rather poor tolerance to KCl. Na+ concentrations were significantly lower in the selected cell line than the unselected cell line under salt stress. The salt-tolerant cell lines showed higher K+ , lower Na+/K+ ratios and higher proline concentration than the unselected cell line. Experiments carried out with Na2SO4 and K2SO4 suggest that the toxic effect is due to the accumulation of Cl-. The addition of osmoprotectants in the external growth medium supported the growth of the NaCl-selected cell lines under 400 mol m-3 NaCl stress.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available