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cnergy fluxes in the reaction centers of the photosystem (I (PSU), from light absorption to electron transport, based on the model proposed by Strasser et al. (1995). At first, photons are absorbed by chlorophyll molecules in the antennas and become cxcited (Chi*) (ABS). A ccrtain amount is dissipated by hcat or fluorescence (DI), while the other part is trapped (TR) by the reaction centers, reducing plastoquinones A (Q_A) to Q_A" and transported towards the electron transport chain (ET), through the reoxydation of Q_A\ These specific parameters can be expressed as a ratio by reaction centers (RC), which is referred to the «specific cnergy

t

fluxes» by Strasser et al. (2000) (table 2.2).

Tableau 2.2 Photosynthetic parameters as describcd by Force et al. (2003), cnergy fluxcs model, based on Strasser et al. (1995), mcasurcd using the Plant Efficicncy

Analyscr

Parameter	Formula
ABS/RC	[(TRo/RC)/(TRo/ABS)]
TRo/RC	(M0/VJ)
ETo/RC	[(TRo/RC) • (ETo/TRo)]
DIo/RC	[(ABS/RC)-(TRo/RC)]
Vj	[(F*2ms- F50ms)/(Fm- FsOps)]
Mo	[4 x (F30oms- Fsops) / (FM - F5oMS)]

The parameters Vj and M₀ are used to calculatc the TRq/RC parameter and correspond,

i

c

respectively to the number of closed reaction centers at 2ms and to the net ratę of PSII closure (Force et al2003).

2.5.4 Statistical analysis

To compare the growth rates and photosynthetic parameters for each glyphosate concentration (10, 50, 100, 300,500 and 1000 pg I¹) and for each species, mean paired comparisons were conducted using the non parametric Wilcoxon test, sińce the data did not fulfill the test conditions for normality. The lowest observed adverse effect level (LOAEL)