Title: Pretilachlor-induced physiological, biochemical and morphological changes in indian paddy field agroecosystem inhabited anabaena doliolum
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.
Audience Take Away Notes:
- The repeated use of the herbicide pretilachlor can have detrimental effects on environment-friendly paddy field N2-fixing cyanobacteria in higher concentration environments than on those growing in sufficient lower herbicide concentration environments, indirectly affecting paddy production and endangering global food security.
- The adverse effect observed including inhibition of growth, distruption of cellular morphology and potential alteration in metabolic process on cyanobacterium Anaaena doilolum, emphasize the vulnerability of aquatic organism to this herbicide.
- As we navigate the intricate balance between agricultural practice and environmental preservation, it is imperative to consider the potential repercussions on other non target species.
- Ultimately, fostering a sustainable coexistence between agriculture and food security demands a thoughtful and science driven approach to herbicide management.