This study describes two phenotypes of Arabidopsis thaliana (ecotype Columbia) developed in vitro under salt stress (75 mM NaCl). The phenotypes 01 and 02 appeared visibly distinguishable by rosette morphology and competence to produce flowers. Phenotype 01, sensible to salt stress, accumulated high quantities of Na+, showed a slight reduction in dry mass, and high protein and chlorophyll contents. Moreover, its anatomy exhibited some xeromorphic traits. Phenotype 02, clearly salt tolerant, showed a morphology similar to control plants, displaying typical phyllotactic rosette and flowering stalk production. Accumulation of Na+, protein and chlorophyll contents were close to control plants. Reversion experiments on NaCl free MS medium, showed a partially recovered phenotype 01. A threshold salt stress concentration that permits the simultaneous development of two phenotypes, was found.