Abstract
Ten species of terrestrial plants, including 6 dicotyledonous and 4 monocotyledonous species, were exposed to a direct overspray of atrazine according to US Environmental Protection Agency seedling emergence and vegetative vigor study guidelines and subsequently evaluated for potential recovery. For each species, no-observed-effect rate (NOER), 10% effect rate, 25% effect rate, and 50% effect rate values were calculated (where possible) for a variety of guideline-required endpoints (but focusing on growth rate) for both the standard experimental phase and a recovery phase; and the rates subsequently were compared. For the seedling emergence study, the standard experimental (designated test 1) and recovery (designated test 2) phases encompassed days 0 to 14 and days 14 to 28, respectively. Similarly, for the vegetative vigor study, test 1 and test 2 encompassed days 0 to 21 and days 21 to 42, respectively. Plants were exposed to atrazine at nominal application rates ranging from 1.1 g active ingredient (a.i.)/ha (0.0010 lb a.i./A) to 28,000 g a.i./ha (25 lb a.i./A), depending on the species; the 28,000 g a.i./ha rate is greater than 12 times the maximum application rate of 2250 g a.i./ha (2 lb a.i./A) registered on corn. For seedling emergence, only 2 of 10 species tested, cabbage and tomato, provided clear rate responses in the initial 14 d of exposure (test 1). Based on a comparison of x% effect rate (ERx) and NOER values for growth rates of shoot length and shoot dry weight for days 0 to 14 relative to days 14 to 28, recovery was apparent for cabbage shoot length growth rate and tomato shoot length and shoot dry weight growth rates. Test application rates selected for the remaining 8 species showed either a weak response that did not allow a clear assessment of recovery or no response at all. For the vegetative vigor study, 9 of the 10 species tested provided clear rate responses in test 1 (days 0-21); corn did not demonstrate any herbicidal response up to the highest rate tested, 28,000 g a.i./ha. Based on comparison of day 0 to 21 (test 1) relative to day 21 to 42 (test 2) ERx and NOER values for shoot length, average growth rates indicated that 8 of 9 species clearly demonstrated an increase in 2 or more metrics (cabbage did not demonstrate a response based on shoot length). Clear recovery was also indicated by an increase in ERx and/or NOER values from test 1 to test 2 for shoot dry weight average growth rates for 7 of the 9 species (corn did not show a response, and oat and soybean showed variable responses). Thus, in most species, where initial herbicidal effects were observed, the effects are largely ameliorated over time.
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Claims 11
Claim · model-written summary
Cabbage showed a clear initial seedling emergence rate response.
- Taxon
- cabbage
Brassica oleracea var. capitatae0 - Outcome
- clear rate responsese0
- Value
- 2 of 10 species testede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“only 2 of 10 species tested, cabbage and tomato, provided clear rate responses in the initial 14 d of exposure (test 1)”
Claim · model-written summary
Tomato showed a clear initial seedling emergence rate response.
- Taxon
- tomato
Solanum lycopersicume0 - Outcome
- clear rate responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“only 2 of 10 species tested, cabbage and tomato, provided clear rate responses in the initial 14 d of exposure (test 1)”
Claim · model-written summary
Cabbage shoot length growth rate showed recovery.
- Taxon
- cabbageBrassica oleracea var. capitatae0
- Outcome
- shoot length growth ratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“recovery was apparent for cabbage shoot length growth rate”
Claim · model-written summary
Tomato shoot length growth rate showed recovery.
- Taxon
- tomatoSolanum lycopersicume0
- Outcome
- shoot lengthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tomato shoot length and shoot dry weight growth rates”
Claim · model-written summary
Tomato shoot dry weight growth rate showed recovery.
- Taxon
- tomatoSolanum lycopersicume0
- Outcome
- shoot dry weight growth ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tomato shoot length and shoot dry weight growth rates”
Claim · model-written summary
The remaining eight species had weak or absent responses, preventing clear recovery assessment.
Verbatim
e0“remaining 8 species showed either a weak response that did not allow a clear assessment of recovery or no response at all”
Claim · model-written summary
Nine of ten species showed clear vegetative vigor rate responses.
Verbatim
e0“9 of the 10 species tested provided clear rate responses in test 1 (days 0-21)”
Claim · model-written summary
Corn showed no herbicidal response at the highest atrazine rate.
- Taxon
- corn
Zea mays subsp. mayse0 - Treatment
- 28,000 g a.i./hae0
- Outcome
- herbicidal responsee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“corn did not demonstrate any herbicidal response up to the highest rate tested, 28,000 g a.i./ha”
Claim · model-written summary
Eight of nine species increased at least two shoot length growth metrics during recovery.
Verbatim
e0“8 of 9 species clearly demonstrated an increase in 2 or more metrics (cabbage did not demonstrate a response based on shoot length)”
Claim · model-written summary
Seven of nine species showed recovery in shoot dry weight growth rate.
Verbatim
e0“Clear recovery was also indicated by an increase in ERx and/or NOER values from test 1 to test 2 for shoot dry weight average growth rates for 7 of the 9 species”
Claim · model-written summary
Oat and soybean had variable shoot dry weight responses.
- Taxon
- oat and soybean
Glycine max
Avena sativae0 - Outcome
- variable responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“oat and soybean showed variable responses”