Bipasa Sarkar

Structural, physiological, and biochemical profiling of tea plantlets under zinc stress

Zinc is the most widespread deficient micronutrient in the tea growing soils of India which affects growth of the plants. In order to investigate the structural, physiological, and biochemical changes under Zn stress (i.e. both deficient and excess supply) of tea [Camellia sinensis (L.) O. Kuntze cv. T-78] plants, we treated young plants with ZnSO4 at 0 (deficiency), 0.3, 3 (optimum), and 30 μM (toxic) concentrations for 8 weeks. Zn deficiency and excess resulted in considerable decrease in shoot and root fresh and dry masses, and transmission electron microscopy (TEM) revealed disorganization of some cellular organelles. Further, Zn-stress decreased net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and content of chlorophylls a and b. On the other hand, content of superoxide anion, malondialdehyde, hydrogen peroxide, and phenols, and electrolyte leakage were elevated in stressed plants. The activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase as well as expression of respective genes were up-regulated under Zn-stress. Nevertheless, antioxidant system as a whole did not afford sufficient protection against oxidative damage.

Cellular differentiation, regeneration, and secondary metabolite production in medicinal Picrorhiza spp.

Picrorhiza kurroa and P. scrophulariiflora are two important endangered medicinal plant species of the Indo-China Himalayan region. These species contain several bioactive compounds that have therapeutic properties. In vitro culture studies have been conducted for developing protocols for shoot proliferation via apical/axillary meristem culture, rhizogenesis, acclimatization of plantlets, and nursery establishment. Moreover, successful efforts have been made to induce somatic embryogenesis from callus cultures as well as synchronous maturation of somatic embryos and plantlet conversion. In addition, regeneration has also been achieved via de novo shoot organogenesis, callus-mediated organogenesis, and from synthetic seeds following nutrient-alginate encapsulation. Factors impeding successful in vitro micropropagation have also been investigated. Clonal fidelity of micropropagated plants have been assessed using DNA markers. More recently, genetic transformation of P. kurroa has been reported via Agrobacterium tumefaciens or A. rhizogenes. Hairy root cultures (rhizoclones) containing higher levels of the bioactive compounds kutkoside and picroside I have also been identified. Two genes involved in picroside biosynthesis in P. kurroa have been identified, and these are found to be up-regulated under illumination and low temperature. High throughput de novo transcriptome sequencing has revealed abundance of trinucleotide simple sequence repeat markers associated with temperature-dependent biosynthesis of picrosides. Progress made in developing regeneration, transformation, as well as biochemical and molecular analysis of valuable bioactive compounds present in Picrorhiza species will be reviewed.

Potentiality of organotin(IV) compounds in the control of foliar blight disease of wheat (Triticum aestivum) caused by Bipolaris sorokiniana

Three different types of eight organotin(IV) compounds (of which four were newly synthesised) were screened against Bipolaris sorokiniana. The new compounds were characterised by elemental, IR, 1H and 13C NMR spectral analyses. The experiments were carried out in the field and laboratory between the months of November 2006 to March 2007 and November 2007 to March 2008 at Uttar Banga Krishi Viswavidyalaya, Cooch Bihar, W.B., India. All of the organotin(IV) compounds were tested for the toxicity assay against Indian wheat (Triticum aestivum L.), cv. Sonalika. The spore germination and growth of B. sorokiniana and the biochemical changes associated with the induction of resistance by these chemicals were also tested. The influence of the organic groups (attached to tin atom) of the three different types of compounds studied on the fungicidal activity is remarkably distinct. Some of the compounds tested are more active in controlling the fungus than a commonly used commercial product.

Poly[(μ3-3,5-di­nitro­benzoato-κ3O1:O1′:O3)(μ2-hydroxido-κ2O:O)copper(II)]

The title complex, [Cu{μ3-O2CC6H3(NO2)2-3,5}(μ-OH)]n, features zigzag chains in which successive pairs of CuII atoms are connected by OH bridges and bidentate carboxylate ligands, leading to six-membered Cu(O)(OCO)Cu rings. The zigzag chains are connected into a three-dimensional architecture by Cu—O(nitro) bonds. The coordination geometry of the CuII atom is square-pyramidal, with the axial position occupied by the nitro O atom, which forms the longer Cu—O bond. Bifurcated hydroxy–nitro O—H⋯O hydrogen bonds contribute to the stability of the crystal structure.

Bis(3,5-dinitro­benzoato-κO1)tetra­methano­lcobalt(II)

The CoII atom (site symmetry ) in the title complex, [Co(C7H3N2O6)2(CH3OH)4], exists within an octahedral O6 donor set defined by two O-monodentate 3,5-dinitrobenzoate anions and four methanol O atoms. An intramolecular Om—H⋯Oc (m = methanol and c = carbonyl) hydrogen bond leads to the formation of an S(6) ring. In the crystal, centrosymmetrically related molecules associate via further Om—H⋯Oc hydrogen bonds, leading to linear supramolecular chains propagating along the a-axis direction.

Bis(3,5-dinitrobenzoato-κO1)tetramethanolcobalt(II)

The CoII atom (site symmetry ) in the title complex, [Co(C7H3N2O6)2(CH3OH)4], exists within an octahedral O6 donor set defined by two O-monodentate 3,5-dinitrobenzoate anions and four methanol O atoms. An intramolecular Om—H⋯Oc (m = methanol and c = carbonyl) hydrogen bond leads to the formation of an S(6) ring. In the crystal, centrosymmetrically related molecules associate via further Om—H⋯Oc hydrogen bonds, leading to linear supramolecular chains propagating along the a-axis direction.

Bis(3,5-dinitro-benzoato-κO)tetra-methano-lcobalt(II).

The CoII atom (site symmetry ) in the title complex, [Co(C7H3N2O6)2(CH3OH)4], exists within an octahedral O6 donor set defined by two O-monodentate 3,5-dinitrobenzoate anions and four methanol O atoms. An intramolecular Om—H⋯Oc (m = methanol and c = carbonyl) hydrogen bond leads to the formation of an S(6) ring. In the crystal, centrosymmetrically related molecules associate via further Om—H⋯Oc hydrogen bonds, leading to linear supramolecular chains propagating along the a-axis direction.