Pretilachlor is a systemic, pre-emergence herbicide applied in the paddy fields to kill narrow and broadleaf weeds. The present study evaluates the toxicity of pretilachlor on the non-target diazotrophic free-living cyanobacterium Anabaena doliolum, commonly found in the paddy fields of eastern Uttar Pradesh (India) and used as a biofertilizer. A.doliolum was subjected to several doses (0, 2, 5, 7, 10, 20 and 40 μg/ml) of pretilachlor and its effects were examined in terms of alterations in cellular morphology, ultrastructure, physiology, and biochemical attributes. The treatment of pretilachlor decreased the growth, total pigment content and photosynthetic efficiency of the test organism in a dose-dependent manner. The decline in growth was observed on 20th day at 2, 5, 7, 10, 20 and 40 μg/ml of pretilachlor concentration by 4, 9, 26, 47, 71 and 92%, respectively. Furthermore, Chlorophyll a and phycocyanin levels were noticeably declined. As a result, the photosynthetic performance also registered a similar decline as measured by chlorophyll fluorescence. However, carotenoid content increased by 13%, 41% and 53% at 5, 10 and 20 μg/ml on 5th day reflecting its protective property. A marked increase in fluorescence intensity and malondialdehyde content by 2.65 and 2.45 folds at 10 and 20 μg/ml on 7th day was registered^. The enzymatic antioxidants (SOD and CAT) and a concurrent increase in glutathione reductase activity were registered (1.75 and 2.11-fold at 20 and 40 μg/ml on 5th day), indicating pretilachlor mediated ROS generation. Moreover, ultrastructural studies done by SEM and TEM revealed plasma membrane and thylakoid membrane damage and fragmentation. These findings have contributed to the broader comprehension of the stress responses triggered by pretilachlor in cyanobacteria. Moreover, they can aid in the evaluation of the detrimental impact of pretilachlor on A. doliolum, given their crucial function as a nitrogen contributor in paddy fields.

丙草胺是一种内吸性芽前除草剂，用于稻田杀灭窄叶杂草和阔叶杂草。本研究评估了丙草胺对非目标固氮自由生活蓝细菌Anabaena doliolum的毒性，这种细菌常见于印度北方邦东部的稻田，用作生物肥料。向A.doliolum施用多个剂量（0、2、5、7、10、20 和 40 μg/ml）的丙草胺，并在细胞形态、超微结构、生理学和生化属性的改变方面检查其效果。丙草胺的处理以剂量依赖的方式降低了测试生物体的生长、总色素含量和光合效率。第20天，丙草胺浓度为2、5、7、10、20和40μg/ml时，生长下降分别为4%、9%、26%、47%、71%和92%。此外，叶绿素a和藻蓝蛋白水平显着下降。结果，通过叶绿素荧光测量，光合作用性能也出现了类似的下降。然而，第 5 天，5、10 和 20 μg/ml 下的类胡萝卜素含量分别增加了 13%、41% 和 53%，反映了其保护性能。在第 7 天，10 和 20 μg/ml 的荧光强度和丙二醛含量显着增加了 2.65 和 2.45 倍^。酶抗氧化剂（SOD 和 CAT）和谷胱甘肽还原酶活性同时增加（第 5 天，20 和 40 μg/ml 分别增加 1.75 和 2.11 倍），表明丙草胺介导 ROS生成。此外，通过 SEM 和 TEM 进行的超微结构研究揭示了质膜和类囊体膜的损伤和破碎。这些发现有助于更广泛地理解蓝藻中丙草胺引发的应激反应。此外，鉴于丙草胺在稻田中作为氮素贡献者的重要作用，它们可以帮助评估丙草胺对多利草的有害影响。