Antioxidant metabolism in forage cactus genotypes intercropped with Gliricidia sepium in a semi-arid environment

Although forage cactus is a CAM plant capable of adjusting to adverse conditions, little is known about the regulation of the antioxidant defense system under typical growth conditions and even less under competitive environment such as intercropping system. Therefore, this study aimed to investigate the regulation of the antioxidant defense system in three forage cactus genotypes grown in intercropping. The experimental design was in randomized blocks set up in a 3 × 2 factorial with three replications, consisting of three forage cactus genotypes (‘Orelha de Elefante Mexicana’—Opuntia stricta (Haw.), ‘Miúda’—Nopalea cochenillifera (L.) Salm. Dyck, and ‘Baiana’ – N. cochenillifera (L.) Salm. Dyck) and two cropping systems (monocropping and intercropping with Gliricidia sepium). Intercropping significantly affected the antioxidant metabolism of forage cactus genotypes. ‘Orelha de Elefante Mexicana’ in intercropping showed higher contents of photosynthetic pigments and H₂O₂, and activities of SOD (EC 1.15.1.1) and CAT (EC 1.11.1.6), and lower contents fresh mass, dry mass, and MDA, and activity of APX (EC 1.11.1.11), than under monocropping. ‘Miúda’ showed similar results except for dry mass, which was the same in both cropping systems. In turn, ‘Baiana’ in intercropping showed higher contents of fresh and dry mass, water, photosynthetic pigments, and H₂O₂, activities of SOD, CAT, and APX, and lower lipid peroxidation than under monocropping. Thus, intercropping favored the ‘Baiana’ as a function of the effective role of the antioxidant enzyme system, reducing lipid peroxidation, maintaining the stability of the photosynthetic process, and increasing growth.