Formation during glycine-nitrate combustion and magnetic properties of YFe1–xNixO3 nanoparticles

The synthesis of FeO3 and YFe1–xNixO3 (x = 0.1; 0.15; 0.2; 0.3; 0.5) nanocrystals was performed under the conditions of a self-propagating wave of glycine-nitrate combustion and their characterization and determination of the effect of Ni2+ doping of yttrium ferrite on the magnetic properties of nanopowders. The technology for the synthesis of yttrium orthoferrite nanoparticles (with and without doping with Ni2+ ions) by the glycine-nitrate combustion method at a ratio of G/N = 1 and 1.5 without adding a gelling agent to the reaction mixture and using ethylene glycol/glycerol is described. For the characterization of nanopowders based on YFeO3, the following were determined: phase composition and crystal structure (X-ray diffraction (XRD) method); size and structure of nanocrystal particles (transmission electron microscopy (TEM)); elemental composition of the samples (local X-ray spectral microanalysis (LXSMA)); magnetic characteristics (field dependences of specific magnetization). Thermal annealing of the synthesized samples at 800°C for 60 min led to the formation of the о-YFeO3 main phase. Undoped samples of yttrium orthoferrite were characterized by a particle diameter in the range of 5-185 nm, depending on the gelling agent used. YFe1-xNixO3 particles had a predominantly round shape with a size of 24 to 31 nm; the non-monotonic dependence of the average particle diameter on the dopant content was revealed: as the amount of dopant added increased, the average crystallite size tended to decrease. Nanopowders of undoped yttrium orthoferrite exhibit antiferromagnetic behaviour of magnetic susceptibility with temperature. The change in the magnetic properties of the nickel-doped YFeO3 nanocrystalline powders was due to the incorporation of Ni2+ into the Fe3+position, which led to the formation of a material with more pronounced soft magnetic properties at a substitution degree of 0.1. Samples with high degrees of substitution (x = 0.15 and 0.3) were also characterized by paramagnetic behaviour at temperatures above 100 K

Biotechnological Perspective of Reactive Oxygen Species (ROS)-Mediated Stress Tolerance in Plants

All environmental cues lead to develop secondary stress conditions like osmotic and oxidative stress conditions that reduces average crop yields by more than 50% every year. The univalent reduction of molecular oxygen (O2) in metabolic reactions consequently produces superoxide anions (O2•−) and other reactive oxygen species (ROS) ubiquitously in all compartments of the cell that disturbs redox potential and causes threat to cellular organelles. The production of ROS further increases under stress conditions and especially in combination with high light intensity. Plants have evolved different strategies to minimize the accumulation of excess ROS like avoidance mechanisms such as physiological adaptation, efficient photosystems such as C4 or CAM metabolism and scavenging mechanisms through production of antioxidants and antioxidative enzymes. Ascorbate-glutathione pathway plays an important role in detoxifying excess ROS in plant cells, which includes superoxide dismutase (SOD) and ascorbate peroxidase (APX) in detoxifying O2•−radical and hydrogen peroxide (H2O2) respectively, monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) involved in recycling of reduced substrates such as ascorbate and glutathione. Efficient ROS management is one of the strategies used by tolerant plants to survive and perform cellular activities under stress conditions. The present chapter describes different sites of ROS generation and and their consequences under abiotic stress conditions and also described the approaches to overcome oxidative stress through genomics and genetic engineering