Dehydration Responsive Element Binding (DREB) gene is one of the essential transcription factors plants use for responding to stress conditions including salinity, drought, and cold stress. The purpose of this study was to isolate the full length and characterize the DREB gene from three different genotypes of sugarcane, wild, commercial cultivar, and interspecific hybrid sugarcane. The length of the gene, designated ScDREB was 789 bp, and coding for a putative polypeptide of 262 amino acid residues. Sequences of the gene were submitted to the GenBank database with accession numbers of KX280722.1, KX280721.1, and KX280719.1 for wild sugarcane, commercial cultivar (KPS94-13), and interspecific hybrid (Biotec2), respectively. In silico characterization indicated that the deduced polypeptide contains a putative nuclear localization signal (NLS) sequence, and a conserved AP2/ERF domain of the DREB family, at 82-140 amino residues. Based on multiple sequence alignment, sequences of the gene from the three sugarcane genotypes were classified in the DREB2 group. Gene expression analysis indicated, that ScDREB2 expression pattern in tested sugarcane was up-regulated by salt stress. When the plants were under 100 mM NaCl stress, relative expressions of the gene in leaves was higher than those in roots. In contrast, under 200 mM NaCl stress, relative expressions of the gene in roots was higher than those in leaves. This is the first report on cloning the full length and characterization, of ScDREB2 gene of sugarcane. Results indicate that ScDREB2 is highly responsive to salt stress.
In this study, Fe loaded zeolite NaY with varying iron contents was prepared and used as glyphosate adsorbents. A hydrothermal method was used to synthesize the zeolite NaY from bagasse ash derived silica (Si-BA). Various Fe contents (1.75 - 7.66 %w/w) were impregnated onto the zeolite. Several techniques were used to examine the physicochemical properties of adsorbents, including X-ray diffraction (XRD), energy dispersive X-ray fluorescence (ED-XRF), N2 adsorption-desorption, field emission scanning electron microscopy (FE-SEM), pH drift method, and zeta potential. In a batch adsorption process with an initial glyphosate concentration of 50 mg/L at pH 4, the effect of contact time was investigated. The pseudo second order kinetic model fitted the experimental data well, indicating that chemisorption controlled the rate determining step for all adsorbents. The Fe loaded zeolite NaY outperformed the bare zeolite NaY in terms of adsorption capacity. The rate constant (K2) and adsorption capacity at equilibrium time (qe) increased when the adsorbents were used in the following order: 1.75 < 5.11 < 7.66 %Fe/NaY. Furthermore, the intra-particle diffusion model was fitted to the experimental data, with a correlation coefficient R2 greater than 0.95. The findings demonstrated that both internal and external diffusion contributed to the rate-determining step. The Langmuir and Freundlich adsorption isotherm models were used to depict the glyphosate adsorption mechanism by the adsorbents. The Freundlich adsorption isotherm best explained all of the data. Glyphosate was thus multilayer adsorbed on the heterogeneous surfaced adsorbents. The adsorption of glyphosate increased as the Fe content, which is primarily due to complexation between Fe and the glyphosate molecule. HIGHLIGHTS A novel Fe loaded zeolite NaY effectively improves the glyphosate adsorption as compared to the bare zeolite The faster adsorption kinetics, stronger adsorbate-adsorbent attraction and higher glyphosate adsorption capacity have been obtained from the adsorbents with a higher Fe content The main adsorption mechanisms are following of electrostatic interaction and Fe-complexation GRAPHICAL ABSTRACT
Amorphous silica from sugarcane bagasse ash (Si-BA) was extracted and used as a support for iron (Fe). The FeSO4 was loaded onto the Si-BA by 3 different methods consisting of refluxing (RF), incipient wetness impregnation (IWI) and physical mixing (PM) methods. The prepared materials used as glyphosate adsorbents were Fe/Si-BA-RF, Fe/Si-BA-IWI and Fe/SI-BA-PM. All adsorbents were further studied by several techniques. There were X-ray diffraction (XRD), energy dispersive X-ray fluorescence (ED-XRF), N2 adsorption-desorption, diffused reflected UV-Visible (DR-UV-Vis) techniques and pH Drift method. The Fe was highly dispersed onto the Si-BA with Fe loading of approximately 2.36-2.55%wt. The Fe/Si-BA-IWI and Fe/Si-BA-PM exhibited a large amount of FexOy oligomer and Fe2O3 species as compared to the Fe/Si-BA-RF. Then, the glyphosate adsorption kinetic was further studied over the Si-BA and all Fe loaded Si-BA. The adsorption kinetic of glyphosate could be described by pseudo-second order kinetic model for all adsorbents. Moreover, the Langmuir and Freundlich isotherm models were applied to study the adsorption isotherms. All adsorbents were fitted well with the Freundlich isotherm model. Based on the Freundlich isotherm, the relative adsorption capacity of the adsorbents could be determined from the Freundlich isotherm constant (KF). The Fe/Si-BA-IWI provided a higher KF value than Fe/Si-BA-PM, Fe/Si-BA-RF and Si-BA, respectively. As the results, the synthesis method of Fe loaded amorphous silica affected the glyphosate adsorption capacity. The highest capacity of Fe/Si-BA-IWI was attributed to its predominately observed FexOy oligomer and Fe2O3 species.
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