ROLE OF PHOTORESPIRATION IN ACCUMULATION OF FREE PROLINE IN CELLS OF CHLORELLA-STIGMATOPHORA UNDER CONDITIONS OF SALINITY

In cells of Chlorella stigmatophora Butcher (marine Chlorella), we inv estigated the possibility of involvement of the glycolate pathway in a ccumulation of free proline through metabolism of photorespiratory amm onia under conditions of salinity. It was found that photorespiratory ammonia constitutes from 20 to 70% of the total pool of ammonia under conditions stimulating photorespiration (0.03% CO2 and 425 mM NaCl). G lutamate dehydrogenase (GDH) is the main channel of utilization of bot h the total pool of ammonia and photorespiratory ammonia under conditi ons of salinity. The bulk of the total pool of ammonia and up to 66% o f photorespiratory ammonia is realized through this channel in cells o f marine Chlorella. Active functioning of GDH under conditions of sali nity is also an important link in proline synthesis. Inhibition of GDH activity lowered accumulation of free proline twofold, whereas inhibi tion of glutamine synthetase activity reduced the proline pool by 11-1 4%. The obtained results enable us to assert that the glycolate pathwa y under conditions of salinity can be involved in proline synthesis th rough metabolism of ammonia formed in photorespiration (the ''nitrogen mechanism'').