Biochemical and Physiological Response of Salsola arbuscula Callus to Salt Stress

Salsola arbuscula is a halophytic plant which is tolerant to high salinity stress. The present study is an attempt to determine the extent to which the callus of this plant is tolerant to salt stress, indicated by the amounts of proline, total protein, carbohydrates, and inorganic ions including Na+, K+, Cl-, and Ca2+. The plant seeds were cultured in MS medium for 2 months and the resulted seedling explants were transferred to media with different hormonal concentrations. Then, the produced calli were transferred to the previous medium with 0, 100, 200, 300, and 400 mM of NaCl. Being kept in the culture room at 25 +/- 2 degrees C with a 12-h photoperiod (irradiance of 800 mu mol m(-2) S-1) for 1 month, calli were measured in terms of their salt stress parameters. The obtained results indicated that the best medium for callus induction was MS + 2,4-D (1 mg/L) + Kin (1 mg/L). The proline, protein, carbohydrate, sodium, and chloride levels of concentration increased up to 300 mM of NaCl, but decreased significantly in the 400 mM of NaCl. However, potassium and calcium ion concentrations and K+/Na+ ratio reduced noticeably in the salt-stressed calli compared to control medium. It should be noted, however, that in terms of K+/Na+ ratio, the various salt treatments did not differ significantly from each other, thereby indicating callus tolerance to salt stress. Thus, salt stress tolerant callus is not because of vacuolar compartmentation, but rather is due to increasing osmolarity and synthesis of different transcription factors and stress proteins.