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Ecotoxicological information

Toxicity to terrestrial plants

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Administrative data

Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Published public domain study

Data source

Reference
Reference Type:
publication
Title:
Phytotoxicity of foliar-applied urea
Author:
Krogmeier, M.J., McCarty, G.W. & Bremner, J.M.
Year:
1989
Bibliographic source:
Proceedings of the National Academy of Sciences of the United States of America 86(21): 8189-8191

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Determination of leaf tip necrosis following administration of urea fertiliser
GLP compliance:
no
Remarks:
: published study

Test material

Constituent 1
Reference substance name:
Urea
EC Number:
200-315-5
EC Name:
Urea
Cas Number:
57-13-6
IUPAC Name:
urea
Details on test material:
Urea, obtained from Fisher.
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Sampling and analysis

Analytical monitoring:
not specified
Details on sampling:
No information available

Test substrate

Vehicle:
yes
Details on preparation and application of test substrate:
After 42 days growth, the leaves of the plants were treated with 0.6 ml water; 0.6 ml water containing 3, 9, 15, 21, or 27 mg urea. The water contained 1% Tween as a dispersant.

Test organisms

Species:
other: Glycine max. (L.) Merr.
Plant group:
other: legume
Details on test organisms:
Soybean (legume), grown from seeds obtained from the Plant Pathology Department at Iowa State University. The plants were grown in a soil/sand/peat mixture, 2:1:1 (wt/wt). The seeds were placed 2 cm below the surface in clay pots containing 400 g substrate (one seed per pot). The pots were placed in a greenhouse and watered twice daily, and every 2 weeks the substrate was treated with 25 ml of water containing 20 mg K2SO4 ad 20 mg NaH2PO4

Study design

Test type:
other: leaf tip necrosis
Study type:
laboratory study
Substrate type:
other: leaf
Limit test:
no
Total exposure duration:
7 d
Post exposure observation period:
Not examined.

Test conditions

Test temperature:
No information available
pH:
No information available; plants were kept in a greenhouse
Moisture:
No information available; plants were kept in a greenhouse
Details on test conditions:
The plants were reared in a greenhouse and were watered twice daily. After 42 days growth, the leaves of the plants were treated with 0.6 ml water; 0.6 ml water containing 3, 9, 15, 21, or 27 mg urea. The water contained 1% Tween as a dispersant. After 7 days treatment, 3 treated leaves were removed from each plant and one was rinsed with distilled water, weighed and analysed for urease activity. The other two leaves were rinsed with distilled water, dried for 3 days at 65°C and weighed. Leaf-tip necrosis was assessed by separating the necrotic portions of the dried leaves from the nonnecrotic portions, weighing both portions and calculating the percentage of leaf tip necrosis as total weight. Urea and ammnoium were extracted from the leaves, urea content was determined by a colorimetric procedure and ammonium content determined with an Orion ammonium electrode. All experiments were performed in triplicate.
Nominal and measured concentrations:
Nominal concentrations in 0.6ml water: 0, 3, 9, 15, 21 or 27 mg of urea
Reference substance (positive control):
no

Results and discussion

Effect concentrations
Species:
other: Glycine max. (L.) Merr.
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
9 other: mg/leaf/day
Nominal / measured:
nominal
Conc. based on:
other: dissolved in 0.6 ml water
Basis for effect:
other: leaf tip necrosis
Details on results:
NOEC of urea in soybean plant = 9mg/leaf/day in 0.6 ml water for 7 days
Results with reference substance (positive control):
Not examined
Reported statistics and error estimates:
No information available

Any other information on results incl. tables

The NOEC of urea in soybean plant = 9mg/leaf/day in 0.6 ml water for 7 days.

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
Conclusions:
The NOEC of urea in soybean plant = 9mg/leaf/day in 0.6 ml water for 7 days. It was concluded in this study that necrosis resulted from accumulation of toxic amounts of urea rather than from formation of toxic amounts of ammonia.
Executive summary:

The NOEC of urea in soybean plant = 9mg/leaf/day in 0.6 ml water for 7 days.

It was concluded in this study that necrosis resulted from accumulation of toxic amounts of urea rather than from formation of toxic amounts of ammonia.