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 exposed 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 Cl- and decreased NO3-, SO42- and K contents in the whole plant. Ca and Mg levels decreased only in shoots. NaCl stress increased Na and Cl- and decreased 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 affecting Mn, Fe, B and Mo levels also decreased in NaCl stressed calli. PEG stress 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 amino 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 to PEG.