Table 2.

Characteristic values of P–E curves, oxygen evolution versus irradiance, calculated by the fit according to Jassby and Platt (1976) in four Zygnema sp. strains in BBM and after osmotic stress (800 mM sorbitol, 3 h).

	Sample	Pmax	Respiration	Ec	Ek	α
Zygnema sp. B	Control	324.6 ± 44.4	−133.4 ± 36.9	25.1	83.8	5.5 ± 1.5
	Osm. stress	53.0 ± 16.4	−84.1 ± 14.5	26.1	36.5	3.8 ± 3.8
Zygnema sp. G	Control	145.5 ± 27.0	−116.9 ± 23.2	26.7	55.8	4.7 ± 1.3
	Osm. stress	51.0 ± 7.8	−30.67 ± 6.7	25.1	63.4	1.3 ± 0.3
Zygnema sp. D	Control	239.7 ± 37.1	−262.6 ± 30.7	50.5	87.1	5.8 ± 1.2
	Osm. stress	40.2 ± 24.3	−87.3 ± 20.4	62.7	74.8	1.7 ± 0.9
Zygnema sp. E	Control	752.9 ± 115.1	−181.7 ± 88.2	26.2	133.3	7.0 ± 2.4
	Osm. stress	196.3 ± 44.5	−83.7 ± 38.7	15.0	48.6	5.8 ± 2.5

P_max – maximal rate of photosynthesis at optimal irradiance (μmol O₂ h⁻¹ mg⁻¹ Chl a), respiration – respiration in the dark (μmol O₂ h⁻¹ mg⁻¹ Chl a), E_c – light compensation value (μmol photons m⁻² s⁻¹), E_k – initial light saturation point (μmol O₂ h⁻¹ mg⁻¹ Chl a). E_c and E_k values were calculated with the help of the three parameters P_max, the respiration and α emanated from the fit. Standard error could not calculate for these values. α – initial slope at low light levels (μmol O₂ h⁻¹ mg⁻¹ Chl a (μmol photons m⁻² s⁻¹)⁻¹).