Biochemical Adaptations in Zea mays Roots to Short-Term Pb2+ Exposure: ROS Generation and Metabolism
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The present study investigated the effect of lead (0, 16, 40 and 80 mg L−1 Pb2+) exposure for 3, 12 and 24 h on root biochemistry in hydroponically grown Zea mays (maize). Pb2+ exposure (80 mg L−1) enhanced malondialdehyde content (239 %–427 %), reactive carbonyl groups (425 %–512 %) and H2O2 (129 %–294 %) accumulation during 3–24 h of treatment, thereby indicating cellular peroxidation and oxidative damage. The quantitative estimations were in accordance with in situ detection of ROS generation (using 2′,7′-dichlorodihydrofluorescein diacetate dye) and H2O2 accumulation. Pb2+ treatment significantly reduced ascorbate and glutathione content during 3–24 h of exposure. On the contrary, levels of non-protein thiols were enhanced by 3–11.8 time over control in response to 16–80 mg L−1 Pb2+ treatment, after 24 h. A dose-dependent induction in ascorbate peroxidase and lipoxygenase enzyme activity was observed in Z. mays roots. The activities of ascorbate-recycling enzymes (dehydroascorbate reductase and monodehydroascorbate reductase) were significantly increased in relation to concentration and duration of Pb2+ treatment. The study concludes that Pb2+-exposure induces ROS-mediated oxidative damage during early period of exposure despite the upregulation of enzymes of ascorbate–glutathione cycle.
KeywordsCellular peroxidation ROS accumulation Cell death Defense mechanisms
GK is thankful to University Grants Commission (New Delhi, India) for research fellowship.
Conflict of interest
The authors declare that they have no conflict of interest.
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