Table 1.

Parameters of the log-logistic equations^a used to calculate the glyphosate rates required for 50% dry weight (GR₅₀) and reduction survival (LD₅₀), expressed as percentage of the mean untreated control of the A. hybridus population.

Growth reduction (GR50)
Population	D	b	GR50 (g ae ha-1) ± SE	P-value	RIb
MR2	97.0	2.9	2222.0 ± 49.6	< 0.001	125.5
S	100.8	1.5	17.7 ± 0.8	< 0.001	–

Plant survival (LD50)
Population	d	b	LD50 (g ae ha-1) ± SE	P-value	RI
MR2	98.8	4.7	4508.3 ± 57.2	< 0.001	93.6
S	100.9	4.1	48.2 ± 3.7	< 0.001	–

^a Y = c + {(d-c)/[1 + (x/g)^b]}, where d is the coefficient corresponding to the upper asymptote, c is the limit of the coefficient of the lower asymptote (fixed at 0 for GR₅₀ and LD₅₀), b is the slope of the line, x is the herbicide dose, and g is the dose at the inflection point and hence the GR₅₀ or LD₅₀. ± SE is the standard error of the mean (n = 10). The P-value is the level of significance of the non-linear regression model.

^bRI (resistance index) = GR₅₀, or LD₅₀ (MR2)/GR₅₀, or LD₅₀ (S).