THE EFFECT OF SALINITY ON LIGHT AND DARK CO2-FIXATION OF SALT-ADAPTED AND UNADAPTED CELL-CULTURES OF ATRIPLEX AND TOMATO

The effect of salinity on light and dark CO2-fixation was determined in cells of Atriplex portulacoides and tomato (Lycopersicon esculentum Mill.) grown in culture. CO2-fixation of tomato cells was also determined in cultures adapted to mannitol and polyethylene glycol (PEG). Salinity up to 400 mM NaCl in the case of Atriplex and up to 50 mM in the case of tomato enhanced the rate of light-induced CO2-fixation in unadapted cells. Higher salt concentrations led to a marked decline in CO2-fixation in both species. In salt-adapted Atriplex cells no decline in the rate of light CO2-fixation was seen even at 500 mM NaCl. Dark CO2-fixation was approximately 40% and 80% of the light fixation in control cell cultures of Atriplex and tomato, respectively. No enhancement in dark CO2-fixation was seen as salinity was increased, but a decline was found at similar salt concentrations that decreased fixation in the light. Mannitol- and PEG-adapted tomato cells fixed CO2 at somewhat lower rates than the control cells in the light but not in the dark.