Effects of treated wastewater reuse in irrigation on germination, biomass, and antioxidant enzyme response of onion (Allium cepa)

The present study was conducted on a variety of onion (<i>Allium cepa</i>) to evaluate the effects of treated wastewater on various physiological, biochemical, and enzymatic parameters. The experiment involved planting seeds in pots and irrigating them with either treated wastewater from the Guelma city treatment plant (Algeria) or regular water as a control (Ctrl). Samples were collected at three stages: Cotyledon Drop (CD), five Leaves (5-L), and Bulb Formation ((BF). The parameters measured included germination rate, biomass of leaves and roots, total protein, and proline levels in roots, stems, and leaves, as well as the enzymatic activity of catalase (CAT) and guaiacol peroxidase (GPX). Results showed that treated wastewater irrigation led to an increase in biomass. Germination rates were positively impacted, with a prolonged germination period observed. Proline and total protein levels were higher in treated plants, indicating an adaptation to abiotic stress. Additionally, enhanced specific activities of guaiacol peroxidase and catalase suggested a high antioxidative capacity in onions.