Changes in antioxidant enzymes and organic solutes associated with adaptation of citrus cells to salt stress

Embryogenic callus cultures of lemon (Citrus limon L. Burm f. cv Verna), were selected for resistance to salt stress (170 mM NaCl). Inorganic analysis showed that selected callus accumulated more Na+ and Cl- ions than the non-selected one. Moreover, the salt-tolerant C. limon callus exhibited an increase in the activity of antioxidant enzymes involved in oxygen metabolism, with the induction of a new superoxide dismutase isozyme and an increase of the peroxidase activity while the catalase activity was unchanged. Proline and total sugar, mainly sucrose, concentrations increases significantly in salt-tolerant cells as compared to control cells. On the other hand, the selected cell line also showed an increase in choline and glycine betaine, but to lesser extent.