Vario el 3 model

The reagents employed for the present work were of analar grade obtained from commercial sources and used without further purifications. Percentage of carbon, hydrogen, nitrogen, and Sulphur in the ligand as well as complexes were determined using a CHNS analyser (Elementar Vario EL III Model). The percentage of metal in the complexes was determined by standard procedures [11 ]. The magnetic susceptibility studies were carried out in a Gouy balance (Sherwood Scientific Cambridge, UK) at room temperature using Hg[Co(SCN)₄] as calibrant. The Infra red spectra of the ligand as well as complexes were conducted using KBr pellet method on a JASCO FTIR-4100 instrument in 4000-400 cm^─1 region. The proton NMR spectra of ligand as well as its diamagnetic zinc complex was taken in solution front using DMSO 6d as the solvent in Bruker Avance III 400 MHz NMR instrument using TMS as the internal standard. The X band EPR spectra of the copper complex were recorded at 77 K in DMF with a JES-FA200 ESR spectrometer using Mn²⁺ as a marker. The electronic spectra of the ligand as well as paramagnetic metal complexes were recorded using JASCO-V-550 spectrophotometer both in diffused reflectance mode and in solution form.

The metabolite analyses were performed on the seedlings of 16‐day‐old plants grown hydroponically with different concentrations of nitrate. The per cent total N content in oven‐dried plant material was measured with an NC analyser (Vario EL III model, Elementar, Hanau, Germany) according to the manufacturer’s instructions. Nitrate was extracted in 50 mm HEPES–KOH (pH 7.4), and measured by the method based on the previous report (Cataldo et al., 1975). The maximum in vitro activity of NR was assayed as described previously (Sylvie et al., 1998). NiR, GS, GOGAT enzyme activities, glutamine and glutamate contents were measured using assay kits (Su Zhou Keming Bioengineer Company, China) following to the manufacturer’s instructions. All the materials analysed were whole plants.