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photosynthetic parameters varied, as shown by the rangę of EC|₀ values. The three cyanobacteria showed no sensitivity of the TRq/RC parameter, while chlorophytes were sensitive to this parameter. with EC_i0 varying from 164 to 598 pg I*¹. For the other parameters, the EC|₀ valuesfor the different species varied between 192-788 pg I'¹ (F_V/F_M), 11-717 pg I’¹ (ABS/RC), <10-356 pg F^l (DIo/RC) and 74-451 pg I*¹ (ETo/RC) (see table 2.4). In generał, and for all growth and photosynthetic parameters, the most sensitive specie was Microcystis aeruginosea (CPCC632) and the least sensitive was Ankistrodesmus falcatus.

Tableau 2.4 EC|® valucs (pg I'¹ of glyphosate) for each parameter (growth and photosynthesis) and each species exposcd to incrcasing glyphosate concentrations for a

48 hours period

Species •				Parameters
	Growth	Fv/Fm	ABS/RC	l)lo/RC	TR()/RC	ETo/RC
Microcystis aeruginosea	<10	192	11	<10	>1000	78
(CPCC632)
Microcystis aeruginosea	<10	704	152	63	>1000	176
(CPCC299)
Microcystis sp.	<10	406	94	76	>1000	74
Scenedesmus oblic/uus	<10	280	37	35	186	328
(CPCC5)
Oocystis solitaria	<10	272	109	81	294	325
Ch/amydomonas reinhardtii	70	788	83	46	256	451
(CPCC125)
Chlamydomonas snowii	91	476	99	84	164	370
Cryptomonas obovata	214	>1000	547	356	>1000	>1000
Ankistrodesmus falcatus	860	745	717	>1000	598	>1000

2.7 Discussion

Strasser et al. (2000) explains the inerease of the amount of photons absorbed by rcaction centers (ABS/RC) by an inereased amount of inactivated reaction centers (RC). Indeed, the