CATION COTOLERANCE IN CALLUS-CULTURES OF MEDICAGO-SATIVA L TOLERANT TO SODIUM-CHLORIDE

Callus cultures established from a cotyledon explant of Medicago sativa L. cv. Dupuits were used as the inoculum for the establishment of suspension cell-cultures. The cell suspension cultures were grown on selection media of increasing NaCl concentration and a culture growing rapidly at 350 mol m-3 NaCl was obtained. Callus cultures derived from NaCl-selected suspension cultures grew slowly at 350 mol m-3 NaCl but growth was unaffected at 250 mol m-3 NaCl whereas growth of callus cultures derived from unselected cells was completely inhibited at 350 mol m-3 NaCl and 90% inhibited at 250 mol m-3 NaCl. The NaCl-tolerant callus was considerably more tolerant to the chlorides of all the alkali-metals than the non-selected callus as shown by good growth at concentrations of alkali-metal chlorides that inhibited growth of non-selected cells. This tolerance was towards the alkali-metals, not the Cl- ion, and shows that cotolerance to other alkali-metals is imposed by the selection of tolerance to Na+.