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Mangrove speeies are growing in exposed areas whieh have heavy metal eontamination. The safeguard the mangrove eeosystem, it is important to understand their antioxidant responses to heavy metal toxieity. The goal of this study was to determine the effeet of multi-heavy metals i.e. (Pb, Cd, Cr and Hg) on two mangrove plants Avicennia marina and Rhizophora mucronata of Indus delta via investigating their antioxidative defenee meehanism of leaves and roots. In this regard mangrove seedlings of both speeies were treated with five different eoneentrations of four heavy metals and different time durations (15, 30, 45 and 60 days) for aseorbate peroxidase, eatalase and superoxide dismutase in leaves and root tissues. The findings indieate that the heavy metals have signifieantly altered the antioxidant enzyme aetivities with respeet of metals eoneentration and duration of exposure. With extended exposure higher antioxidant aetivities was observed in metal treated roots and leaves at higher eoneentrations. A pronouneed stimulation (P<0.001) of CAT aetivity in both roots and leaves of A. marina oeeurred after 15 days of stress (38.3 and 26.6 Limol/mg protein/min) at 1 MHM. Our analysis also found that roots have shown greater aetivity in proteeting against reaetive oxygen speeies (ROS). Among the roots of two mangroves SOD aetivity in A. marina showed better toleranee towards metals stress (9.26 U/mg protein at 15 MHM) eompare to R. mucronata (6.09 U/mg protein at10 MHM). APX showed maximum stimulation at 20 MHM in leaves (19.130 Limol/mg protein/min) and at 10 MHM in roots (19.02 Limol/mg protein/min) of A. marina after 30 days metals treated plant. Henee, it eonfirms that the antioxidative defenee system plays a eritieal role in A. marina and R. mucronata to tolerate the multiple heavy metals stress. However, A. marina showed greater antioxidant aetivity espeeially eatalyst enzyme aetivity as eompared to R. mucronata, whieh is well evident by its dominaney in the region. [ABSTRACT FROM AUTHOR]