Table 2 Toxicity threshold summary.

Herbicide	Endpoint	Specific growth rate (SGR)	Photosynthetic efficiency (ΔF/F_m′)	SGR (EC₅₀) : ΔF/F_m′ (EC₅₀)
Diuron	EC₅₀	12.4 (11.8–13.0)	4.25 (3.96–4.55)	2.92
	EC₁₀	1.79 (1.60–1.98)	0.97 (0.81–1.15)
	NEC	1.47 (1.15–1.83)
	ReP	1	1
Propazine	EC₅₀	98.2 (91.7–105)	48.6 (45.6–51.7)	2.02
	EC₁₀	21.5 (18.4–25.0)	8.12 (7.04–9.33)
	NEC	12.9 (9.29–32.0)
	ReP	0.126	0.087
Tebuthiuron	EC₅₀	187 (179–195)	47.7 (44.1–51.5)	3.92
	EC₁₀	26.8 (23.9–29.9)	6.95 (5.79–8.27)
	NEC	16.0 (13.0–19.1)
	ReP	0.066	0.089
Haloxyfop	EC₅₀	> 4570	> 4570	NA
	EC₁₀	> 4570	> 4570
	NEC	> 4570	> 4570
	ReP	NA	NA

Effect concentrations that inhibit the specific growth rate (SGR) and photosynthetic efficiency (ΔF/F_m′) by 10% or 50% (EC₁₀ and EC₅₀ from Fig. 1) and no effect concentrations (NECs from Fig. 2), with 95% confidence intervals derived for Diuron, Propazine, Tebuthiuron and Haloxyfop. The potencies for each of the herbicides were contrasted using the relative equivalent potencies (ReP) in comparison to the reference herbicide diuron. NA indicates values could not be calculated. Concentrations are reported in µg L⁻¹.

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