Antioxidant responses and isoenzyme activity of hydroponically grown safflower seedlings under copper stress

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Safflower is an oilseed rabi crop. Continuous use of use of copper (Cu) containing fungicides and pesticides, due to high susceptibility of this crop of fungal attack has increased the accumulation of Cu in the soil. To investigate the effect of extra accumulated Cu on this particular crop, safflower seeds were germinated on different concentration of Cu (25, 50 and 100 µM) present in Hoagland’s solution (hydroponic) along with control (0.5 µM of Cu) and seedlings were harvested after 10 and 20 days of Cu treatment. The concentration of alpha-tocopherol was high in leaves as compared to roots in presence of Cu stress. The content of vitamin C was increased in both leaves and roots. In 10 and 20 day leaves, the CAT activity has been decreased in all the treatments. In 10 day roots, the CAT activity was increased but decreased abruptly in 20 day harvested roots. Isoenzymatic pattern of CAT showed three bands of CAT (CAT 1, CAT 2 and CAT 3) in control in 10 day leaves while CAT 1 was diminished in lane 2, 3 and 4. In 20 day leaves, we observed only one bands of CAT (CAT 2) in lane 1 (control) while CAT 1 was appeared at high concentration of Cu. We observed no more significant changes in the CAT isoforms in 10 and 20 day roots. The GPX activity was increased in both the day’s collected samples (leaves and roots). The analysis of GPX isoenzymes revealed no significant changes in isoenzymatic pattern but their band’s intensity was increased with an elevated metal treatment. In 20 day harvested leaves, we observed two bands of isoenzyme in lane 1 and four bands of GPX in lane 2, 3, 4 along with their increased intensities. In 10 day roots, we observed two band of GPX in all the treatment with elevated intensities as compared to control (lane 1). Similarly we observed two bands of GPX in all the treatments and control. But the intensity of bands was increased till lane 3 but in 20 day rootsat highest treatment (100 µM) the intensity of bands was decreased. The SOD activity was reduced in 10 and 20 day leaves. In 10 day roots, it was augmented but reduced at 100 µM as compared to control (100%). In 20 day harvested roots, the activity was decreased by 1.30, 11.11 and 15.68% with increased Cu concentration than control (100%). Three isoenzymes of SOD were appeared in 10 day leaves with more or less same intensity. While in 20 day leaves ex-plant has shown SOD 1, 2 and 3 activities. In 10 day treated roots SOD 1 with increasing intensity was appeared in lane 3 and 4 than control (lane 1) while SOD 2 was almost constantly present in all four lanes. Similarly in 20 day root ex-plant, SOD 1 has been observed with decreasing intensity in lane 2, 3 and 4 than control (lane 1). To cope up with the Cu stress, the antioxidant enzymes such as GPX and SOD were actively involved in safflower seedlings.