Abstract:
Plant immunity is the defense mechanism that plants use to protect themselves from harmful effects caused by other organisms and abiotic stress conditions such as salinity, drought, and high light intensity. The antioxidant enzyme activities of catalase (CAT) and ascorbate peroxidase (APX) are two indicators of strong plant immunity. Plant immunity inducers activate or prime plant immunity, and seaweeds are known to enhance this process. The present experiment was conducted to evaluate the effect of seaweed extracts on the growth and yield of Capsicum annuum L. (green chili) in relation to CAT and APX activities. Three different foliar applications were prepared by mixing varying ratios of green algae (Ulva lactuca) and brown algae (Stoechospermum marginatum) extracts: T1 (2:1), T2 (1:1), and T3 (1:2). T4 was a commercialized product (Cropmaster©), and T5 was deionized water. Treatments were arranged in a completely randomized design with three replicates. Results indicated significant differences in CAT and APX activity among treatments. CAT and APX activities were measured using a spectrophotometric method. The highest CAT activity (30.53 μM/min/g FW) was recorded in T2, whereas the lowest (20.39 μM/min/g FW) was observed in T5. Similarly, the highest APX activity (464.06 μM/min/g FW) was recorded in T2, followed by T5 (335.63 μM/min/g FW), while the lowest activity was observed in T4 (65.13 μM/min/g FW). Significant differences were also observed in fruit yield parameters. The highest number of fruits per plant (53) and the lowest (33) were recorded in T2 and T5, respectively. Likewise, the highest fresh fruit weight per plant was in T2 (299 g), while the lowest was in T5 (172 g). The seaweed-based foliar spray prepared with equal proportions of green and brown algae (T2) significantly improved growth and yield parameters in green chili. The results suggest that the enhancement of antioxidant enzyme activity through seaweed extract application may contribute to improved plant resilience, stress tolerance, and productivity.
