Browsing by Author "Riti Thapar"

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A comparative study of antioxidative defense system in the copper and temperature acclimated strains of Anabaena doliolum
(2008) Yogesh Mishra; Poonam Bhargava; Riti Thapar; Ashish Kumar Srivastava; Lal Chand Rai
This study provides first hand comparative account of growth and antioxidative defense system of the wild type, Cu2+ and temperature treated wild type and acclimated strains of Anabaena doliolum Bharadwaja against Cu2+ and high temperature. The acclimated strains showed perceptible growth at 250 μM Cu2+ and 47°C temperatures, respectively. In contrast to this the wild type strain on exposure to 50 μM Cu2+ and 47°C temperature depicted almost complete inhibition of growth. However, the peroxide content was significantly higher in the acclimated strains than the wild type. Superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) showed maximum activity at high temperature followed by Cu2+ acclimated and minimum in the wild type strains. The ascorbate (ASC) and glutathione (GSH) contents were increased by 2.3 and 43.3, and 15.5 and 36.5-fold in Cu2+ and 47°C acclimated strains, respectively. However, when the wild type strain was subjected to Cu2+ and temperature all antioxidative enzymes except SOD showed inhibition of their activity. In case of wild type the GSH content was inhibited by 0.39-fold at 50 μM Cu2+ but the ASC content registered increase by 2 and 2.7-fold on subjecting to Cu2+ and temperature, respectively. Thus increased activity of enzymatic antioxidants as well as accumulation of ascorbate and glutathione in both the acclimated strains suggests that enzymatic and non-enzymatic antioxidants help in the acclimation of A. doliolum Bharadwaja against Cu2+ and high temperature. However, inhibition of antioxidative defense system of wild type under Cu2+ and heat stress appears to be the reason for its non survival. In view of the appreciable increase in the level of antioxidants as well as greater inhibition of specific growth rate in temperature than Cu2+ acclimated strains, temperature (47°C) is proposed to be is more deleterious to the organism than copper (250 μM). © 2008 Springer Science+Business Media B.V.
Differential response of antioxidative defense system of Anabaena doliolum under arsenite and arsenate stress
(2009) Ashish Kumar Srivastava; Poonam Bhargava; Riti Thapar; Lal Chand Rai
This study offers first hand information on the arsenite (As(III)) and arsenate (As(V))-induced oxidative tress and changes in antioxidative defense system of Anabaena doliolum. A requirement of 58 mM As(V) as compared to only 11 mM As(III) to cause 50% reduction in growth rate suggests that As(III) is more toxic than As(V) in the test cyanobacterium. In contrast to above, oxidative damage measured in terms of lipid peroxidation, electrolyte leakage and peroxide content were significantly higher after As(V) than As(III) treatment as compared to control. Similarly all the studied enzymatic parameters of antioxidative defense system except glutathione reductase (GR) and non-enzymatic parameters except glutathione reduced (GSH) showed greater induction against As(V) than As(III). Interestingly, higher increase in non-enzymatic counterpart than enzymatic in both the stresses suggests that detoxification is mainly managed by former than the later. This confirms the belief of pronounced stimulation of the antioxidative defense system by As(V) than As(III). In conclusion, the cyanobacterium may survive better in As(V) than As(III) contaminated fields because of its low toxicity and pronounced induction of antioxidative defense system. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Impact of different abiotic stresses on growth, photosynthetic electron transport chain, nutrient uptake and enzyme activities of Cu-acclimated Anabaena doliolum
(Elsevier GmbH, 2008) Riti Thapar; Ashish Kumar Srivastava; Poonam Bhargava; Yogesh Mishra; Lal Chand Rai
This study provides a comparative account of the effects of cadmium, temperature, ultraviolet-B and sodium chloride on the growth, photosynthesis, nutrient uptake and enzyme activities of untreated control and copper-acclimated Anabaena doliolum. Reduction in all the studied parameters, except carotenoids, was maximum for sodium chloride followed by ultraviolet-B, temperature and cadmium treatments, the reduction being greater in control than acclimated A. doliolum. Among the various parameters, photosystem II was most sensitive for all the stresses in both control and acclimated A. doliolum. Likewise, O2 evolution was more susceptible to various stressors than 14C uptake. Ammonium uptake and glutamine synthetase (GS, EC 6.3.1.2) were the least affected parameters. As compared to control, acclimated Anabaena exhibited higher ATP content under normal conditions. These results attest our hypotheses that acclimated Anabaena was physiologically more robust than control and that salinity was more injurious to the test organism than other abiotic stresses investigated. © 2007 Elsevier GmbH. All rights reserved.