Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Plants, Soils, and Climate

Committee Chair(s)

William F. Campbell


William F. Campbell


J. R. Simmons


E. E. Hood


M. D. Rumbaugh


J. O. Evans


To study the effect of NaCl stress on gene expression in alfalfa (Medicago sativa L.), greenhouse and laboratory experiments were conducted with 22 cultivars during germination and post-germination growth. The ability of alfalfa cultivars to germinate at the different NaCl concentrations was not related to their postgermination performance (salt tolerance) under those conditions.

Genetic effects were evident for Na and Cl ion uptake and accumulation in alfalfa shoots and roots. The strategies of alfalfa cultivars to cope with NaCl stress includes exclusion of Na from shoots and Cl from roots or from the whole plant depending on cultivar and NaCl level. The reduction in shoot dry weight was not related to water stress or reduction in Ca, Mg, or chlorophyll concentrations. Results of this study indicated that the reduction in K ion uptake and more directly

the toxic effects of high Na and Cl in plant tissues contributed to the reduction in shoot dry weight . The possible subpartitioning of Na and Cl ions between different tissues, cell types, cell components, and/or the different changes in protein structure and enzyme activity at the high Na and Cl concentrations, independent of total concentration of ions, might also contribute to differences in salt tolerance (shoot dry weight) among cultivars. The factors determining shoot dry weight in alfalfa grown under the different NaCl treatments of this study were not the same for all cultivars.

Sodium chloride stress induced qualitative and quantitative changes in shoot and root proteins of alfalfa. These changes were dependent on cultivar and salt concentration, as well as length of exposure to salt stress.