Unveiling the Impact of Thiophanate-Methyl on Arthrospira platensis: Growth, Photosynthetic Pigments, Biomolecules, and Detoxification Enzyme Activities.

BACKGROUND: The intensive and injudicious use of pesticides in agriculture has emerged as a major concern due to its detrimental impact on aquatic ecosystems. However, the specific impact of broad-spectrum fungicides, such as Thiophanate-methyl (TM), on cyanobacteria remains a subject of ongoing research and debate. METHODS: In order to fill this knowledge gap, The present study aimed to comprehensively investigate the toxicological effects of TM (10-30 µg/L) on the growth, photosynthetic pigments, oxidative stress, and biochemical composition of the non-nitrogen-fixing cyanobacterium Arthrospira platensis. RESULTS: Our findings unequivocally demonstrated that TM exposure significantly inhibited the growth of A. platensis. Moreover, the decrease in chlorophyll content indicated a pronounced negative impact on the photosynthetic system of A. platensis caused by TM exposure. Notably, TM induced oxidative stress in A. platensis, as substantiated by a significant increase in lipid peroxidation (MDA) within the culture. Furthermore, the intracellular generation of hydrogen peroxide (H2O2) exhibited a positive correlation with higher TM dosages, while the levels of vital antioxidant enzymes, such as catalase (CAT) and ascorbate peroxidase (APX), exhibited a discernible decrease. This suggests that TM compromises the antioxidant defense mechanisms of A. platensis. Additionally, TM was found to enhance the activity of a plethora of enzymes involved in the detoxification of pesticides, including peroxidase (POD) and glutathione-S-transferase (GST), thereby indicating a robust detoxification response by A. platensis. Interestingly, exposure to TM resulted in a general suppression of biocomponent production, such as total proteins and total carbohydrates, which exhibited a diminishing trend with increasing TM concentration. Conversely, the lipid content witnessed a significant increase, possibly as an adaptive response to TM-induced stress. CONCLUSIONS: These findings contribute to a deeper understanding of the ecological implications of pesticide usage and emphasize the urgent need for the adoption of sustainable and environmentally-friendly agricultural practices to safeguard aquatic ecosystems.

Phytotoxic evaluation of neonicotinoid imidacloprid and cadmium alone and in combination on tomato (Solanum lycopersicum L.).

Neonicotinoids and heavy metals pollution exist simultaneously in agro ecosystem. However, little is known about their combined ecotoxicological effects on non-target crop plants. We have selected imidacloprid (IMI) and cadmium (Cd), applied alone and in combination, to evaluate their effect on growth, physiological and biochemical parameters of tomato. Results showed that the single application of contaminants (IMI and/or Cd) adversely affected both the growth and chlorophyll pigment, and Cd alone application was more phytotoxic than IMI. However, their combined action aggravated the inhibitory effect and indicate a synergistic effect, but it exerted antagonistic effects on chlorophyll pigment inhibition compared with IMI and Cd alone treatments. Both chemicals increased hydrogen peroxide level and generated lipid peroxidation, and the co-contamination exacerbates oxidative stress by their synergistic effect. Those results implicate that disturbance of cellular redox status is the plausible mechanism for IMI and Cd induced toxicity. In conclusion, the single or combined IMI and Cd cause negative effects on tomatoes.