Abiotic stress is known to influence the synthesis of secondary metabolites in plants, particularly flavonoids, which play a vital role in antioxidant defence. This study investigated the effects of various abiotic stressors: UV radiation, drought, salinity, mechanical stress, high temperature, high light intensity, high blue light, and elevated electrical conductivity on flavonoid accumulation and antioxidant capacity in three medicinal plant varieties (A25, T25, and B25) cultivated in a controlled vertical farming system. Flavonoid levels were measured using the aluminium chloride colorimetric method, while antioxidant activity was assessed through the DPPH radical scavenging assay.
The results revealed distinct responses among the plant varieties and treatments. In plant A25, several stress conditions led to a notable decline in flavonoid content, suggesting that certain stressors may interfere with biosynthetic pathways. T25 showed increased flavonoid levels under high EC, high temperature, and mechanical stress, though the changes were not statistically significant. In B25, no significant changes in flavonoid content were observed across treatments.
Interestingly, antioxidant activity in A25 increased under UV, high EC, and high light treatments, indicating a defence response triggered by reactive oxygen species. However, antioxidant activity did not consistently align with flavonoid levels, suggesting the involvement of other antioxidant mechanisms. Salinity and high temperature stress led to negative inhibition values, possibly due to oxidative damage exceeding the plant’s defence capacity.
Overall, the study highlights that abiotic stress can both enhance and suppress flavonoid production and antioxidant activity. Further research is needed to clarify the interplay between flavonoid and enzymatic antioxidant responses under different stress conditions.
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