Browsing by Author "Vijeta Singh"

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Carotenoids and pH of the culture medium play an important role in displaying metal stress in batch and semi-continuous cultures of Anabaena doliolum
(2009) Bhumi Nath Tripathi; Rohini Kasana; Vijeta Singh; Indu Bhatt; Ashutosh Singh; Vinay Sharma; Jai Prakash Gaur
We analysed the responses of Anabaena doliolum to elevated levels of copper and zinc in batch and semi-continuous cultures. Approximately 10, 4 and 8 and 5-times greater inhibition in final yield of A. doliolum occurred at 1, 2 μM Cu and 2.5 and 5 μM of Zn, respectively, in semi-continuous culture in comparison to batch culture. Protein, chlorophyl a and carotenoid contents of A. doliolum showed significantly (P<0.05) higher inhibition by test metals in semi-continuous culture than in batch culture. The greater sensitivity of different parameters of the test organism was related to the high metal content of the cells grown in semi-continuous system. Moreover, enhancement of pH of the culture suspension in batch culture showed a negative relationship with metal accumulation, and therefore with toxicity. This was due to decrease in free ionic concentrations of test metals. Carotenoids acted as a metal detoxifying agent by minimizing metal-induced inhibition in batch culture as was evident from its negative relationship with metal toxicity. © EDP Sciences, 2009.
Mechanism of Cu- and Cd-Induced Proline Hyperaccumulation in Triticum aestivum (Wheat)
(2013) Bhumi Nath Tripathi; Vijeta Singh; Bunichi Ezaki; Vinay Sharma; J.P. Gaur
Proline hyperaccumulation, a frequently reported phenomenon in the plant kingdom, is considered an adaptive strategy of plants to cope with a variety of stresses. The present study demonstrated the mechanism of proline hyperaccumulation in Triticum aestivum exposed to excess Cu and Cd. The intracellular level of proline was increased significantly in the plants treated with test metals. Enhanced proline accumulation due to Cu and Cd was negatively correlated with the growth of the treated plants, indicating that plants divert their resources toward induction of survival strategies rather than improving growth and development. The activities of pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) were increased immediately after metal treatment and remained higher through the end of the experiment, whereas ornithine amino transferase (OAT) activity of the treated plants was lower than P5CS and P5CR enzymes. The activity of proline dehydrogenase (PDH) was decreased sharply in the early phase of metal exposure (up to 12 h) but remained unchanged thereafter until the end of the experiment. Expression analysis of the transcripts of P5CS, OAT, and PDH also supports the above findings and indicates the tissue-specific expression of these genes. Based on these results, increased proline synthesis through the glutamate pathway involving the P5CS and P5CR enzymes is a major contributor to proline hyperaccumulation followed by decreased catabolism of proline. © 2013 Springer Science+Business Media New York.
Unexplored photoluminescence from bulk and mechanically exfoliated few layers of Bi2Te3
(Nature Publishing Group, 2018) Bipin Kumar Gupta; Rabia Sultana; Satbir Singh; Vijeta Singh; Geet Awana; Anurag Gupta; Bahadur Singh; A.K. Srivastava; O.N. Srivastava; S. Auluck; V.P.S. Awana
We report the exotic photoluminescence (PL) behaviour of 3D topological insulator Bi2Te3 single crystals grown by customized self-flux method and mechanically exfoliated few layers (18 ± 2 nm)/thin flakes obtained by standard scotch tape method from as grown Bi2Te3 crystals. The experimental PL studies on bulk single crystal and mechanically exfoliated few layers of Bi2Te3 evidenced a broad red emission in the visible region from 600-690 nm upon 375 nm excitation wavelength corresponding to optical band gap of 2 eV. These findings are in good agreement with our theoretical results obtained using the ab initio density functional theory framework. Interestingly, the observed optical band gap is several times larger than the known electronic band gap of ∼0.15 eV. The experimentally observed 2 eV optical band gap in the visible region for bulk as well as for mechanically exfoliated few layers Bi2Te3 single crystals clearly rules out the quantum confinement effects in the investigated samples which are well known in the 2D systems like MoS2,WS2, WSe2, and MoSe2 for 1-3 layers. © 2018 The Author(s).