Brain Richard A, Hoberg James
Syngenta Crop Protection LLC., Greensboro, North Carolina, USA.
Smithers Viscient, Wareham, Massachusetts, USA.
Environ Toxicol Chem. 2016 May;35(5):1284-96. doi: 10.1002/etc.3298. Epub 2016 Feb 16.
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.
根据美国环境保护局的幼苗出土和营养活力研究指南，将10种陆生植物（包括6种双子叶植物和4种单子叶植物）暴露于莠去津的直接过度喷雾中，随后评估其潜在恢复能力。对于每个物种，针对标准实验阶段和恢复阶段的各种指南要求的终点（但重点是生长速率）计算（如果可能）无观察到影响率（NOER）、10%影响率、25%影响率和50%影响率值；随后比较这些比率。对于幼苗出土研究，标准实验（指定为试验1）和恢复（指定为试验2）阶段分别涵盖第0至14天和第14至28天。同样，对于营养活力研究，试验1和试验2分别涵盖第0至21天和第21至42天。根据物种不同，植物暴露于标称施用量从1.1克活性成分（a.i.）/公顷（0.0010磅a.i./英亩）到28,000克a.i./公顷（25磅a.i./英亩）的莠去津中；28,000克a.i./公顷的施用量大于玉米登记的最大施用量2250克a.i./公顷（2磅a.i./英亩）的12倍。对于幼苗出土，在测试的10个物种中，只有卷心菜和番茄在暴露的最初14天（试验1）中表现出明显的比率响应。基于第0至14天相对于第14至28天的茎长和茎干重生长速率的x%影响率（ERx）和NOER值的比较，卷心菜茎长生长速率以及番茄茎长和茎干重生长速率明显恢复。为其余8个物种选择的试验施用量要么显示出微弱响应，无法明确评估恢复情况，要么根本没有响应。对于营养活力研究，在测试的10个物种中，有9个在试验1（第0 - 21天）中表现出明显的比率响应；玉米在测试的最高施用量28,000克a.i./公顷下未表现出任何除草响应。基于第0至21天（试验1）相对于第21至42天（试验2）的茎长ERx和NOER值的比较，平均生长速率表明9个物种中有8个在2个或更多指标上明显增加（卷心菜基于茎长未表现出响应）。9个物种中有7个的茎干重平均生长速率从试验1到试验2的ERx和/或NOER值增加也表明明显恢复（玉米未表现出响应，燕麦和大豆表现出可变响应）。因此，在大多数观察到初始除草效果的物种中，随着时间的推移，这些影响在很大程度上得到缓解。
