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mostly through the organization of the antenna complex. Indeed, the antenna complex in cyanobacteria is located in the cytoplasm and is composed mainly of phycobilisomes as the light absorbing pigment (Govindjee et al.₉ 2010). As proposed by Perron et Juneau (2011), cyanobacteria could be morę sensitive to pollutants through their prokaryotic naturę, sińce their photosynthetic apparatus is less complex and their antioxydant response, less efficient. Algae from the Cryptophyceae family also have phycobilins as part of their antenna complex (Gantt et cii, 1971), while green algae possess mainly chlorophyll a and b, and carotenoids (Jeffrey et cii., 201 I). It is known that the phycobilisomes are vcry mobile, moving betwecn PSII and PSI, allowing the distribution of the light energy through their reaction centers (Joshua and Mullineaux, 2004). This process, known as state-transition, might modulate the effects of glyphosate-bases herbicides on the PSII reaction centers, espccially on the amount of energy trapped by PSII (TRo/RC), sińce the energy can be distributed to PSI if an excess occurs at the PSU level. State-transition mechanism will help maintaining a highcr photosynthetic yield when cryptophytes or cyanobacteria are subjected to environmental stress. Indeed, the absorption of light energy by PSII (ABS/RC) will decrease sińce there is less antennas associated to this photosystem (Finazzi and Forti, 2004), thus reducing possible damages to the photosynthetic apparatus. This might explain why the maximal PSII quantum yield (F_V/F_M) was the least sensitive photosynthetic parameter, following a glyphosate-based herbicide exposure, in our study. These results indicate that the type of pigments found in the light harvesting compIex seems to impact the glyphosate-based herbicide toxicity in algaes and cyanobacterias.

The growth and photosynthetic capacity of the green alga Ankistrodesmus falcatus did not fit the pattern of any other species, and were the least alTectcd by the glyphosate-based herbicide used in this study. At the highest glyphosate concentration, this spccie evcn showed a smali increase of the PSII photosynthetic efficiency (F_V/F_M and ETo/RC). This is in accordance with Cedergreen and Olsen (2010) who proposed that plants could increase their photosynthetic ability at Iow glyphosate concentrations by increasing their carbon fixation capacities. Wong (2000) also found a growth stimulation for the green alga Scenedesmus ąuadricauda, at glyphosate concentration of 20 pg I*¹. However, in our study there was no growth stimulation, which is in accordance with other studies on the effects of glyphosate-based herbicides on algae and cyanobacteria growth (Christy et al_y 1981; Ycndrell et al,