Abstract
The present study was conducted to evaluate the physiological and biochemical responses of vegetables (garlic, tomato and okra) grown at Jurma, Canal Road, Hangu Road and Kharmatu, District Kohat under wastewater irrigation. Crops at Jurma were irrigated with tube-well water, whereas those at Canal Road, Hangu Road and Kharmatu were irrigated with wastewater. Vegetable samples were analyzed for heavy metal accumulation, antioxidant enzyme activities and morphological attributes using RCBD. The results revealed that the highest Pb concentrations were recorded in Kharmatu for garlic (1.97 mg kg⁻¹), tomato (1.31 mg kg⁻¹) and okra (1.21 mg kg⁻¹). Similarly, the maximum Cd concentration was observed in garlic (0.107 mg kg⁻¹) at Kharmatu, while tomato (0.095 mg kg⁻¹) and okra (0.087 mg kg⁻¹) showed the highest Cd levels at Hangu Road. Chromium concentration was highest in garlic (2.40 mg kg⁻¹) at Hangu Road, whereas tomato (2.52 mg kg⁻¹) and okra (2.37 mg kg⁻¹) exhibited maximum Cr accumulation at Kharmatu. In contrast, Jarma consistently showed the lowest heavy metal concentrations. Antioxidant enzyme activities increased markedly in wastewater-irrigated sites, with the highest APX activity recorded in Kharmatu for garlic (2.25 min⁻¹ g⁻¹ F. wt), tomato (3.77 min⁻¹ g⁻¹ F. wt) and okra (2.34 min⁻¹ g⁻¹ F. wt). The highest CAT activity was observed in garlic (32.40 min⁻¹ g⁻¹ F. wt) and tomato (69.95 min⁻¹ g⁻¹ F. wt) at Kharmatu and in okra (54.14 min⁻¹ g⁻¹ F. wt) at Hangu Road. Likewise, maximum POD activity was noted in garlic (19.06 min⁻¹ g⁻¹ F. wt) and okra (25.40 min⁻¹ g⁻¹ F. wt) at Hangu Road and in tomato (30.49 min⁻¹ g⁻¹ F. wt) at Kharmatu, while the highest SOD activity was recorded in garlic (64.03 min⁻¹ g⁻¹ F. wt), tomato (97.35 min⁻¹ g⁻¹ F. wt) and okra (89.39 min⁻¹ g⁻¹ F. wt) at Kharmatu. Overall, the lowest antioxidant enzyme activities were observed in Jarma. Morphological assessment showed superior growth performance under tube-well irrigation, where the highest fresh weight of garlic (149 g), tomato (721 g) and okra (444 g), as well as the highest dry weight of garlic (42 g), tomato (135 g) and okra (94 g) were recorded at Jarma. Similarly, maximum root length of garlic (8.13 cm), tomato (25 cm) and okra (22 cm) along with the highest shoot length of garlic (62 cm), tomato (63 cm) and okra (75 cm) were observed at Jarma, whereas the lowest values were recorded at Kharmatu and Hangu Road. The study revealed that wastewater irrigation, particularly at Kharmatu and Hangu Road, significantly increased heavy metal accumulation and induced oxidative stress in vegetables, leading to reduced growth and biomass. Therefore, alternative irrigation sources should be adopted to minimize heavy metal contamination and ensure the production of safe and healthy vegetables