GROWTH, PROLINE ACCUMULATION AND WATER RELATIONS OF NACL-SELECTED ANDNONSELECTED CALLUS LINES OF DACTYLIS-GLOMERATA L

Sodium chloride-tolerant calli were selected from leaf-derived embryog enic calli of Dactylis glomerata L. on agar solidified medium suppleme nted with 200 mM NaCl, a concentration lethal to non-selected calli. G rowth characteristics, water relations and proline accumulation patter n were compared in selected and non-selected lines. The objective was to gain an understanding of the mechanism(s) of tolerance in the NaCl- tolerant line. Growth in the selected line, as expressed in terms of t olerance index (ratio of fresh wt. on NaCl medium:fresh wt. on NaCl fr ee medium x 100), was greater than that of the non-selected line at al l levels of NaCl between 50 and 300 mM. There was no significant diffe rence in proline accumulation in the selected and non-selected Lines. Maintenance of turgor by osmotic adjustment was observed in the nonsel ected line despite decreased growth. In contrast, the selected Line lo st either the need or the ability to adjust osmotically. There was lit tle or no increase in symplastic osmolality in the selected line when exposed to NaCl. Presumably, selection was made for a salt-excluding t issue that has lost the ability to accumulate solutes and adjust turgo r with NaCl stress.