RESUMEN
Interspecific differences in sensitivity of the Antarctic moss Sanionia uncinata from King George Island (KGI) and James Ross Island (JRI) to photoinhibitory treatment were studied in laboratory conditions using chlorophyll fluorescence techniques. Slow (Kautsky) and fast (OJIP) kinetics were used for the measurements. Samples were exposed to a short-term (60 min) photoinhibitory treatment (PIT, 2000 µmol·m-2 ·s-1 PAR). The photoinhibitory treatment (PIT) led to photoinhibition which was indicated by the decrease in FV /FM and ΦPSII in KGI but not in JRI samples. However, this decrease was small and full recovery was reached 90 min after PIT termination. Non-photochemical quenching (NPQ) was activated during the PIT, and rapidly relaxed during recovery. Early stages of photoinhibition showed a drop in FV /FM and ΦPSII to minimum values within the first 10 s of the PIT, with their subsequent increase apparent within fast (0-5 min PIT) and slow (5-50 min PIT) phases of adjustment. The PIT caused a decrease in the performance index (Pi_Abs), photosynthetic electron transport per reaction centre (RC) (ET0 /RC). The PIT induced an increase in thermal dissipation per RC (DI0 /RC), effectivity of thermal dissipation (Phi_D0 ), absorption per RC (ABS/RC) and trapping rate per RC (TR0 /RC). In conclusion, PIT led to only slight photoinhibition followed by fast recovery in S. uncinata from KGI and JRI, since FV /FM and ΦPSII returned to pre-photoinhibitory conditions. Therefore, S. uncinata might be considered resistant to photoinhibition even in the wet state. The KGI samples showed higher resistance to photoinhibition than the JRI samples.