Comparative responses of Helianthus annuus plants and calli exposed to NaCl: I. Growth rate and osmotic regulation in intact plants and calli

Sunflower (Helianthus annuus L. cv. SH222) plants and calli were directly e xposed to 0, 50, 100, 200 and 300 mmol/L NaCl and to 50 g/L of polyethylene glycol (PEG 6000). Salinity decreased plant and callus growth rates, with plane presenting an inhibition dose (ID50) of 66 mmol/L NaCl whereas calli, more tolerant, had an ID50 of 183 mmol/L NaCl. Plants and calli died when directly exposed to 200 and 300 mmol/L NaCl. Salt stress increased Na and C l- and decreased NO3-, SO42- and K contents in the whole plant. Ca and Mg l evels decreased only in shoots. NaCl stress increased Na and Cl- and decrea sed Ca, K, SO42- and NO3- levels in calli. NaCl stress decreased the levels of Fe and Zn in whole plants, Cu and B in roots and Mo in shoots, not affe cting Mn, Fe, B and Mo levels also decreased in NaCl stressed calli. PEG st ress was less severe to plants and calli than the equiosmolal concentration of 100 mmol/L NaCl. There was an increase in soluble sugars and total amin o acid (mainly Pro) contents in plants and calli exposed to 50 and 100 mmol /L NaCl and to PEG. Asp and Ser levels increased in plants exposed to NaCl and to PEG, while Ser, Ala and Arg increased in calli exposed to NaCl and t o PEG.