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Ecotoxicological information

Toxicity to terrestrial plants

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Administrative data

Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)

Data source

Reference
Reference Type:
publication
Title:
Identification and phytotoxic activity of compounds produced during decomposition of corn and rye residues in soil.
Author:
Chou C.H.and Patrick ZA
Year:
1976
Bibliographic source:
Journal of Chemical Ecology 2(3):369-387. With kind permission from Springer Science and Business Media

Materials and methods

Test guideline
Guideline:
other:
Principles of method if other than guideline:
The main purpose of the study was to identify compounds formed during the decomposition of corn and rye in soil. Because of the important role of phytotoxins, the isolation and identification was confined mainly to substances with phytotoxic properties.
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
Resorcinol
EC Number:
203-585-2
EC Name:
Resorcinol
Cas Number:
108-46-3
Molecular formula:
C6H6O2
IUPAC Name:
benzene-1,3-diol

Test organisms

Species:
Lactuca sativa
Details on test organisms:
Lettuce seeds, Lactuca sativa (var Great Lakes)

Study design

Test type:
other: Determination of phytotoxicity
Study type:
laboratory study
Substrate type:
filter paper
Total exposure duration:
30 d

Test conditions

Test temperature:
21 – 22C
Reference substance (positive control):
not specified

Results and discussion

Effect concentrations
Remarks on result:
other: See section Any other information on results
Remarks:
See section Any other information on results
Details on results:
In the lettuce seed assay, most of the compounds from the corn deposition  products exhibited phytotoxicity (including resorcinol).  In resorcinol a significant reduction in growth was observed at 100 ppm. 
Results with reference substance (positive control):
Control: growth of lettuce was normal.
Control: Series consisted of soil without added crop residue.
Reported statistics and error estimates:
Statistical Analysis:  Student’s t-test. 

Any other information on results incl. tables

The phytotoxicity of aqueous extracts obtained from the decomposing corn residues was determined using the volatile bioassay method.  The test seeds received the volatiles from the surrounding extracts held by sponges without direct contact with the extract. 

Toxicities tended to decrease with the second extraction and were almost lost after the fifth extraction.  It appears that the phytotoxicity of the extracts is mainly on the amount of organic substrate decomposing in the soil.  The toxicity decreased as the amounts of soil incorporated into the corn residue was increased or as the decomposition period was increased.

Chromatographic bioassay of Phytotoxic extracts:

By using the chromatographic bioassay, the phytotoxicity was determined on 30µl (about 1.5% concentration of extracts) of the ether fraction or each extract.  Most of the toxic spots were located in the zone between 0.37 and 0.97.  Two distinguishable toxic spots were located on the chromatogram at Rf 0.63 – 0.73 and at Rf 0.73 – 0.84.  At these two spots not only was lettuce seed germination inhibited but radical growth was also suppressed.  Toxicity was maximum after 25 – 30 days’ decomposition, which is consistent with the results obtained in the volatile assay.  As more soil was incorporated with the corn residue, the toxicity was decreased.  The chromatograph bioassay of three subsequent extracts was also performed. At 25 days decomposition, the toxic spots remained in the Rf 0.63 –  0.84 zone.  In the third extracts, however, the toxicity was almost lost in both the 1:1 and 1:2 corn to soil ratios.

The toxic spots were further analyzed.  Eighteen compounds were identified in which it was determined that resorcinol was not considered to be volatile under the test conditions.  In the chromatographic assay, resorcinol was identified as one of the four toxic zones.  An attempt was made to determine the concentration levels of the various phytotoxins in the decomposing corn residues.  The results were inconclusive, but it appeared that the concentration ranged between 5 and 100 µg/g soil. 

Results of the bioassay conducted in the synthetic chemical, resorcinol were compared to those when testing the corn residue (of which resorcinol was detected and labeled as phytoxin 9). 

The following results are available:

Gas chromatography

Paper chromatography

Retention

Rf values (x100)

Colour Reaction

distance

(mm)

2% AA

BuAW

BzAW

sUV

DPNA

DQC

Resorcinol

188

70

86

38

ab

yel

gr pu

Phytotoxin 9

188

67

85

40

ab

yel

gr pu

*absorption; yel = yellow; gr = gray; pu = purple


Relative Concentration of Phytotoxin in 3 treated Corn-Soil mixtures

Decomposition Period

5 days

15 days

30 days

1:0

1:1

1:2

1:0

1:1

1:2

1:0

1:1

1:2

Resorcinol

+

+

+

+ the concentration was determined using gas chromatograph and determined to be 5 µg/g soil

Effects of known compounds in aqueous solution on radical growth of Lactuca sativa after 72 hours at 21 – 22C

Radicle growth (% of control)

Concentration (ppm)

100

200

300

400

resorcinol

63

49

41

25

Results were significantly different from the control below the 5% level of confidence.

Applicant's summary and conclusion

Conclusions:
In the case of resorcinol 100% growth inhibition was observed.  The seeds exposed to the toxic atmosphere from the extracts were damaged, and some turned black or dark brown.  Some of the seeds were also swollen.  In addition, the radical was abnormal and lacked root hairs, and there was necrosis of the root tips.