Cadmium and lead interactive effects on oxidative stress and antioxidative responses in rice seedlings

Abstract

Interactive effects of two heavy metal pollutants Cd and Pb in the growth medium were examined on their uptake, production of reactive oxygen species (ROS), induction of oxidative stress and antioxidative defence responses in Indica rice (Oryza sativa L.) seedlings. When rice seedlings in sand culture were exposed to 150 μM Cd (NO3)2 or 600 μM Pb (CH3COO)2 individually or in combination for 8-16 days, a significant reduction in root/shoot length, fresh weight, relative water content, photosynthetic pigments and increased production of ROS (O2˙- and H2O2) was observed. Both Cd and Pb were readily taken up by rice roots and localisation of absorbed metals was greater in roots than in shoots. When present together in the growth medium, uptake of both the metals Cd and Pb declined by 25-40%. Scanning electron microscope (SEM) imaging of leaf stomata revealed that Pb caused more distortion in the shape of guard cells than Cd. Dithizone staining of roots showed localisation of absorbed Cd on root hairs and epidermal cells. Both Cd and Pb caused increased lipid peroxidation, protein carbonylation, decline in protein thiol and increase in non-protein thiol. The level of reduced forms of non-enzymic antioxidants glutathione (GSH) and ascorbate (AsA) and their redox ratios (GSH/AsA) declined, whereas the activities of antioxidative enzymes superoxide dismutase (SOD) and guaiacol peroxidase (GPX) increased in metal treated seedlings compared to controls. In-gel activity staining also revealed increased intensities of SOD and GPX isoforms with metal treatments. Catalase (CAT) activity increased during early days (8 days) of metal exposure and declined by 16 days. Results suggest that oxidative stress is an important component in expression of Cd and Pb toxicities in rice, though uptake of both metals gets reduced considerably when present together in the medium.

Cadmium Uptake and Distribution in Fragrant Rice Genotypes and Related Consequences on Yield and Grain Quality Traits

“…Heavy metals in paddy soils affect rice growth and performance; for instance, Cd stress has been proven to affect plants morphologically and physiologically as well as disrupting antioxidants enzymes in rice seedlings under polluted soils. Reports have shown reduction in rice growth and biomass, which might possibly be as a result of different Cd-mediated toxicity mechanisms in rice [10]. Various other studies have also reported that the toxic effects of Cd increased rice seedlings oxidative stress by releasing reactive oxygen species (ROS) like malondialdehyde (MDA) contents, hydrogen peroxide (H 2 O 2 ), and electrolyte leakage which affects rice growth and performance [10,11].…”

“…Reports have shown reduction in rice growth and biomass, which might possibly be as a result of different Cd-mediated toxicity mechanisms in rice [10]. Various other studies have also reported that the toxic effects of Cd increased rice seedlings oxidative stress by releasing reactive oxygen species (ROS) like malondialdehyde (MDA) contents, hydrogen peroxide (H 2 O 2 ), and electrolyte leakage which affects rice growth and performance [10,11]. Cadmium toxicity also altered leaf and root ultrastructure and caused structural damage to photosynthetic apparatus of rice [12].…”

Stress Response Monitoring of Photoautotrophic Higher Plant Suspension Cultures by Fluorescence Imaging for High-Throughput Toxic Compound Screening

“…[45]- [50]. This approach was successfully used with higher plants [41] [42] [51] however, loading of the dye into the leaf material is problematic as the procedure can cause additional stress and thus additional ROS formation as well as the distribution of the dye is rather heterogeneous.…”

Effects of Cadmium Stress on Antioxidant Enzymes and Osmolyte Accumulation in Aromatic Rice Seedlings

“…Cd stress has been proven to have some morpho-physiological and antioxidants effects in rice seedlings at the early growth stage (vegetative stage) especially in paddy polluted soils. Reports have shown reduction in rice growth and biomass, which might possibly be as a result of different Cd-mediated toxicity mechanisms in rice (Srivastava et al 2014). Other studies have reported that the toxic effects of Cd increased rice seedlings oxidative stress by releasing reactive oxygen species (ROS) like malondialdehyde (MDA) contents, hydrogen peroxide (H 2 O 2 ) and electrolyte leakage which affects rice growth and performance (Yu et al 2013;Srivastava et al 2014).…”

“…Reports have shown reduction in rice growth and biomass, which might possibly be as a result of different Cd-mediated toxicity mechanisms in rice (Srivastava et al 2014). Other studies have reported that the toxic effects of Cd increased rice seedlings oxidative stress by releasing reactive oxygen species (ROS) like malondialdehyde (MDA) contents, hydrogen peroxide (H 2 O 2 ) and electrolyte leakage which affects rice growth and performance (Yu et al 2013;Srivastava et al 2014). Cadmium toxicity also altered leaf and root ultrastructure and caused structural damages to photosynthetic apparatus of rice.…”