diuron (ISO); 3-(3,4-dichlorophenyl)-1,1-dimethylurea

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Endpoint:

toxicity to terrestrial plants: short-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

yes

Details on preparation and application of test substrate:

The test item was applied via an acetonic stock solution (540 mg/L) in test series with concentrations of 0.013 – 1.08 mg/kg dry soil. The necessary volume of stock solution was applied on 20 g dry test soil as a vehicle. In the case of volumes < 1 mL, the stock solution was dissolved in acetone to increase the application volume. In test series with concentrations of 0.133 – 32.4 mg/kg dry soil the necessary amount of test item was transferred on a weight basis in glass beakers and dissolved in 2 mL acetone. After application on dry test soil as a vehicle, the beakers were rinsed with 2 mL acetone. This volume also was applied on the vehicle. The solvent was evaporated over night. Subsequently, the vehicle was added to the test substrate (adjusted on 40 - 60 % water holding capacity) and mixed thoroughly
The soil used in the test was a natural sandy soil (Certified RefeSol 01-A; batch IME-01, loamy sand [DIN], Org C: 0.93 %, pH 5.7, clay: 5 %)

Species:

Allium cepa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: onion
- Plant family: Alliaceae
- Source of seed: Carl Sperling & Co., Lüneburg, Cultivar Vaugirard
- Seed storage: The seeds were stored in the dark at the test facility at room temperature (20 ± 5 °C) and protected from moisture until use

Species:

Triticum aestivum

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: wheat
- Plant family: Poaceae
- Source of seed: Saatgutveredelung Nückel 57392 Schmallenberg-Winkhausen, Cultivar Merlin
- Seed storage: The seeds were stored in the dark at the test facility at room temperature (20 ± 5 °C) and protected from moisture until use

Species:

Glycine max (G. soja)

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: soybean
- Source of seed: Carl Sperling & Co., Lüneburg, Cultivar Hellfrucht
- Seed storage: The seeds were stored in the dark at the test facility at room temperature (20 ± 5 °C) and protected from moisture until use

Species:

Lycopersicon esculentum

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: tomato
- Synonym: Solanum lycopersicum
- Plant family: Solanaceae
- Source of seed: Carl Sperling & Co., Lüneburg, Cultivar Hellfrucht
- Seed storage: The seeds were stored in the dark at the test facility at room temperature (20 ± 5 °C) and protected from moisture until use

Species:

Beta vulgaris

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: sugar beet
- Plant family: amaranthaceae
- Source of seed: KWS Saat AG, 37555 Einbeck, Cultivar Felicita
- Seed storage: The seeds were stored in the dark at the test facility at room temperature (20 ± 5 °C) and protected from moisture until use

Species:

Brassica napus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: rape
- Plant family: amaranthaceae
- Source of seed: KWS Saat AG, 37555 Einbeck, Cultivar Kadore
- Seed storage: The seeds were stored in the dark at the test facility at room temperature (20 ± 5 °C) and protected from moisture until use

Test type:

seedling emergence toxicity test

Study type:

laboratory study

Substrate type:

natural soil

Total exposure duration:

14 d

Test temperature:

20 ± 2 °C

Details on test conditions:

TEST SYSTEM
- Test container (type, material, size): Round containers of nonporous plastic with a diameter of 85 - 95 mm
- Amount of soil: ca. 280 g of moist soil
- No. of seeds per container: 5
- No. of replicates per treatment group: 4
- No. of replicates per control: 4
- No. of replicates per vehicle control: 4

GROWTH CONDITIONS
- Photoperiod: 16 hours per day
- Light source: light colour 25, universal white
- Light intensity and quality: > 7000 lux
- Day/night temperatures: 20 ± 2 °C
- Relative humidity (%): 70 ± 25 %
- Watering regime and schedules: Continuous bottom watering of the test container via glass fibre wicks.
- Any pest control method/fertilization (if used): The water was amended with fertilizer as necessary, COMPO GmbH & Co. KG, P.O. Box 2107, 48008 Münster, Germany. The concentration applied in the test was 1 mL fertilizer per liter water

EFFECT PARAMETERS MEASURED: The 14-day growth phase started when 50 % of the seedlings in the control group had emerged. This day was determined as "growth day 1". On this day, the number of emerged seedlings from all containers was recorded.
At "growth day 14", all seedlings were counted and the aboveground biomass was measured. For this, the wet mass of the plants was measured immediately after harvesting.

Nominal and measured concentrations:

The nominal concentrations in the test containers were 0.013, 0.04, 0.12, 0.36, and 1.08 mg test item/kg (onion, tomato, sugar beet, and rape), 0.133, 0.40, 1.20, 3.60, and 10.8 mg test item/kg (wheat), and 0.40, 1.20, 3.60, 10.8, and 32.4 mg test item/kg (soy bean), respectively.
The results of HPLC-UV measurements of the highest concentrated application solution showed recovery rates of 105.6 – 110.7 %

Reference substance (positive control):

yes

Remarks:

trichloroacetate

Species:

Allium cepa

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1.08 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Allium cepa

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.35 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Allium cepa

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.12 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Beta vulgaris

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1.08 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Beta vulgaris

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.49 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Beta vulgaris

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.12 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Brassica napus

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1.08 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Brassica napus

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.21 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Brassica napus

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.12 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Glycine max (G. soja)

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 32.4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Glycine max (G. soja)

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

1.51 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Glycine max (G. soja)

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Lycopersicon esculentum

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1.08 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Lycopersicon esculentum

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.27 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Lycopersicon esculentum

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.12 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Triticum aestivum

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 10.8 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Triticum aestivum

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

0.42 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Species:

Triticum aestivum

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.13 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Details on results:

There was no significant effect on seedling emergence of Allium cepa (onion), Triticum aestivum (wheat), Glycine max (soy bean), Solanum lycopersicum (tomato), Beta vulgaris (sugar beet), and Brassica napus (rape) up to the highest concentration of Preventol A 6 tested.
There were statistically significant concentration related effects on growth (on a fresh weight per plant basis) of all species tested. The EC50growth for these tested species was found to be 0.21 mg (rape), 0.27 mg (tomato), 0.35 mg (onion), 0.42 mg (wheat), 0.49 mg (sugar beet), and 1.51 mg (soy bean), test item per kg soil. The NOECgrowth were 0.12 mg test item per kg soil for tomato, onion, rape and sugar beet, 0.13 mg test item per kg soil for wheat, and 0.40 mg test item per kg soil for soy bean. The biomass decrease observed in rape in the three lowest treatments is assumed to be by chance and not substance depending. Even when there are statistical differences in mean biomass, with a decrease of 5 – 9 % deviations from control showed comparable values. Therefore, the deviation up to 0.12 mg test item per kg soil is not assessed as an effect concentration.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels:
The results of the last reference study are in agreement with experience EC50-values obtained in this institute.
Seedling emergence
Allium cepa: EC50 = 63 mg/kg
Triticum aestivum: EC50 = > 100 mg/kg
Glycine max: EC50 = > 500 mg/kg
Solanum lycopersicum: EC50 = > 500 mg/kg
Beta vulgaris: EC50 = 33 mg/kg
Brassica napus: EC50 = > 500 mg/kg

Biomass
Allium cepa: EC50 = 56 mg/kg
Triticum aestivum: EC50 = 0.8 mg/kg
Glycine max: EC50 = 0.1 mg/kg
Solanum lycopersicum: EC50 = 46 mg/kg
Beta vulgaris: EC50 = 27 mg/kg
Brassica napus: EC50 = 448 mg/kg

Reported statistics and error estimates:

The percent inhibition of seedling emergence for each plant species was calculated as an absolute value and in comparison to the control. Survival of emerged seedlings was calculated as an absolute value. The percent inhibition of fresh weight was calculated in comparison to the control. All statistical tests (depending on normal distribution and homogeneity of variances the Fisher`s Exact Binomial Test, Williams test, Dunnett's t-test, or
Welch t-test for comparison of controls and the NOEC calculation; EC calculation) were performed with the computer software ToxRat Professional by ToxRat® Solutions GmbH. For the EC50 calculation a probit-analysis assuming log-normal distribution of the values was applied.

Verification of test item concentration: Analytical verification (HPLC-UV) of the stock solution (coevally the application solution, nominal concentration of 540 mg/L) resulted in a mean recovery of 588.4 ± 13.0 g/L, corresponding with a recovery rate of 109.0 %. Due to the high comparability of the measured concentration with the nominal concentration, effect concentrations were determined based on nominal test concentrations

Table 1.                               Pathological symptoms (% plants)

TI = Test item, - = no visual symptom, a = discolouration, b = deformation, c = necrosis, d = dead plant; *: significant when compared to control (Fisher's t-test, p = 0.05, one-sided smaller)

Test species	Solvent control	0.013 mg TI/kg	0.04 mg TI/kg	0.12 mg TI/kg	0.36 mg TI/kg	1.08 mg TI/kg
Allium cepa	-	5.6 % d	-	-	100 % a	100 % d*
Solanum lycopersicum	-	10.5 % d	-	-	10.5 % d	100 % d*
Brassica napus	-	-	-	-	78.9 % d*	100 % d*
Beta vulgaris	-	-	-	-	-	52.6 % d*
	Solvent control	0.13 mg TI/kg	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg
Triticum aestivum	-	-	-	-	88.2 % a	100 % a 52.9 % c
	Solvent control	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg	32.4 mg TI/kg
Glycine max	6.3 % d	-	-	100 % c	100 5c 1808 5 d	100 % d*

 

 

Table 2.              Emergence rate at test end (%)

TI = Test item; Concentrations given as nominal concentration per kg dry mass.

Test species	Solvent control	0.013 mg TI/kg	0.04 mg TI/kg	0.12 mg TI/kg	0.36 mg TI/kg	1.08 mg TI/kg
Allium cepa	90	90	95	85	95	80
Solanum lycopersicum	90	95	100	90	95	90
Brassica napus	100	100	100	100	95	100
Beta vulgaris	95	100	100	95	95	95
	Solvent control	0.13 mg TI/kg	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg
Triticum aestivum	95	95	100	95	85	85
	Solvent control	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg	32.4 mg TI/kg
Glycine max	80	70	85	80	80	75

 

 

Table 3.              Emergence inhibition related to control at test end (%)

TI = Test item; Concentrations given as nominal concentration per kg dry mass; no significant deviation when compared to control (Fisher's t-test, p = 0.05, one-sided smaller); negative value = emergence stimulation.

 

Test species	0.013 mg TI/kg	0.04 mg TI/kg	0.12 mg TI/kg	0.36 mg TI/kg	1.08 mg TI/kg
Allium cepa	0	-6	6	0	11
Solanum lycopersicum	-6	-11	0	-6	0
Brassica napus	0	0	0	5	0
Beta vulgaris	-5	-5	0	0	0
	0.13 mg TI/kg	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg
Triticum aestivum	0	-5	0	11	11
	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg	32.4 mg TI/kg
Glycine max	13	-6	0	0	6

 

 

 

Table 4.           Fresh weight of the shoots. Mean values ± SD (g)

 

TI = Test item; n.s.s. = No survived seedling; Concentrations given as nominal concentration per kg dry mass

 

Test species	Solvent control	0.013 mg TI/kg	0.04 mg TI/kg	0.12 mg TI/kg	0.36 mg TI/kg	1.08 mg TI/kg
Allium cepa	0.220 ±0.061	0.221 ±0.031	0.228 ±0.004	0.235 ±0.033	0.101 ±0.010	n.s.s.
Solanum lycopersicum	1.264 ±0.096	1.157 ±0.116	1.307 ±0.070	1.615 ±0.111	0.197 ±0.062	n.s.s.
Brassica napus	1.318 ±0.075	1.256 ±0.061	1.203 ±0.028	1.208 ±0.058	0.131 ±0.072	n.s.s.
Beta vulgaris	1.010 ±0.025	1.039 ±0.041	1.005 ±0.042	1.061 ±0.074	0.761 ±0.062	n.s.s.
	Solvent control	0.13 mg TI/kg	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg
Triticum aestivum	0.881 ±0.064	0.883 ±0.071	0.360 ±0.036	0.202 ±0.040	0.051 ±0.013	0.054 ±0.015
	Solvent control	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg	32.4 mg TI/kg
Glycine max	2.141 ±0.665	2.512 ±0.306	1.008 ±0.116	0.491 ±0.142	0.416 ±0.177	n.s.s.

 

 

Table 5.            Growth inhibition related to control at test end (%FM)

TI = Test item; n.s.s. = No survived seedling; Concentrations given as nominal concentration per kg dry mass; *: significant when compared to control (Williams t-test, p = 0.05, one-sided smaller); negative value = growth stimulation

 

Test species	0.013 mg TI/kg	0.04 mg TI/kg	0.12 mg TI/kg	0.36 mg TI/kg	1.08 mg TI/kg
Allium cepa	-1	-4	-7	54*	n.s.s.
Solanum lycopersicum	9	-3	-4	84*	n.s.s.
Brassica napus	5	9*^#	8*^#	90*	n.s.s.
Beta vulgaris	-3	1	-5	25*	n.s.s.
	0.13 mg TI/kg	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg
Triticum aestivum	0	59*	77*	94*	94*
	0.40 mg TI/kg	1.20 mg TI/kg	3.60 mg TI/kg	10.8 mg TI/kg	32.4 mg TI/kg
Glycine max	-17	53	77	81	n.s.s.

^#No concentration - and therefore substance - depending effects up to concentration of 0.12 mg/kg

 

Table 6.         NOECs and EC₅₀values for emergence (mg TI/kg DM)

NOEC = No observed effect concentration; EC = Effect concentration; CL = Confidence level; n.d. = not determined due to mathematical reasons; TI = Test item; Concentrations given as nominal concentration per kg dry mass.

 

Test species	Brassica napus	Triticum aestivum	Solanum lycopersicum	Allium cepa	Beta vulgaris	Glycine max
NOEC	=1.08	=10.8	=1.08	=1.08	=1.08	=32.4
EC50 (95% CL)	> 1.08 (n.d.)	> 10.8 (n.d.)	> 1.08 (n.d.)	> 1.08 (n.d.)	> 1.08 (n.d.)	> 32.4 (n.d.)

 

Table 7.   NOEC and EC values for growth inhibition on the basis of fresh mass (EC_growth) and mortality (LC) [mg TI/kg DM]

NOEC = No observed effect concentration; EC = Effect concentration; CL = Confidence level; n.d. = not determined due to mathematical reasons; TI = test item; Concentrations given as nominal concentration per kg dry mass

Test species	Brassica napus	Triticum aestivum	Solanum lycopersicum	Allium cepa	Beta vulgaris	Glycine max
NOECgrowth	0.12	0.13	0.12	0.12	0.12	0.40
EC10growth (95% CL)	0.11 (0.04-0.15)	0.12 (n.d.)	0.19 (0.17-0.21)	0.22 (0.20-0.23)	0.27 (0.25-0.29)	0.33 (n.d.)
EC50growth (95% CL)	0.21 (0.14-0.30)	0.42 (n.d.)	0.27 (0.26-0.29)	0.35 (0.34-0.35)	0.49 (0.47-0.51)	1.51 (n.d.)
NOECmortality	0.12	=10.8	0.36	0.36	0.36	10.8
LC50 (95% CL)	0.26 (0.21-0.32)	> 10.8 (n.d.)	0.49 (n.d.)	0.62 (n.d.)	0.58 (0.28-2.01)	10.4 (9.7-21.5)

 

Executive summary:

An acute toxicity test is available for this study, in accordance with the prevailing OECD testing guidelines (208), with GLP. Six recommended plant species were used to test for seedling emergence and growth. The EC50 values for seedling emergence ranged from > 1.08 to > 32.4 mg test substance/kg. In all cases this equated to the highest concentration tested for each species and hence no significant effects of seedling emergence could be determined. The (14 d) EC50 values for seedling growth ranged from 0.21 to 1.51 mg test substance/kg. The most sensitive species used in this study was the monocot. Brassica napus (rape) with an EC50 (growth) of

0.21 mg/kg and an LC50 of 0.26 mg/kg.

Description of key information

Of six recommended test species of plant the most sensitive to the test substance was the monocot. Brassica napus (rape) with an (14 d) EC50 (growth) value of 0.21 mg/kg, a NOEC (growth) of 0.12 mg/kg and a LC50 of 0.26 mg/kg. No significant effects on seedling emergence were found for any of the species tested.

Additional information

An acute toxicity test is available for this study, in accordance with the prevailing OECD testing guidelines (208), with GLP. Six recommended plant species were used to test for seedling emergence and growth. The NOEC (14d) values for seedling emergence ranged from > 1.08 to > 32.4 mg test substance/kg. In all cases this equated to the highest concentration tested for each species and hence no significant effects of seedling emergence could be determined. The (14 d) EC50 values for seedling growth ranged from 0.21 to 1.51 mg test substance/kg and the NOEC values ranged from 0.12 mg/kg to 0.40 mg/kg. The most sensitive species used in this study was the monocot. Brassica napus (rape), with an EC50 (growth) of 0.21 mg/kg and an LC50 of 0.26 mg/kg (Simon, 2009).