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Reactive oxygen species (ROS) are endogenously produced by several plant organelles and compartments, particularly those with high electron transport rates, such as chloroplasts, mitochondria and peroxisomes as metabolic by-products that act as cellular messengers and redox regulators of several plant biological processes. Excessive accumulation of ROS causes oxidative stress leading to protein denaturation, lipids peroxidation, and nucleotides degradation, which results in cellular damage and ultimately cell death. Functional approaches have provided evidence of the convergence of signaling pathways regulating plant responses to developmental cues and abiotic and biotic stress factors. They have highlighted the role of phytohormones and redox signaling, and identified key regulatory elements – molecular hubs – where multiple signaling cascades converge. The integration of multiple signals through these hubs allows the plant to fine-tune its response to particular conditions. In this regard, growing evidence shows that the generation of ROS is one of the most common plant responses to different stresses, representing a point at which various signaling pathways come together to modulate the plant response to environmental cues. Redox regulation of integral pathway proteins provides a rapid and simple mechanism for the regulation of plant development and defence pathways. MAPK pathways are common and versatile signaling components that lie downstream of second messengers and hormones, and play central roles in plant responses to various stresses. In this review, the complex nature of plant stress signaling network is discussed. An emphasis on different signaling players with a specific attention to ROS as the primary source of the signaling battery in plants is presented. The interaction between ROS and other signaling components, e.g., redox homeostasis, MAPKs, and plant hormones has also been assessed.

Nano-sized CuO particles were prepared insitu via “one-pot, solvent-less” microwave-induced synthesis, by environmentally benign polyol process using polyol obtained from Linseed oil by (non-aqueous) condensation reaction, for the first time. Linseed polyol acts as solvent, base matrix providing functional groups, and stabilizer; the reaction is devoid of any additive, catalyst or solvent. In the prepared nanocomposites [LPE-CuO], CuO nanoparticles shaped somewhat like rods, assembled themselves in a “T-fashion”. The antifungal effects of synthesized particles were investigated against four clinical isolates of different Candida species. Results showed that the synthesized compound LPE-0.06 was found to be most effective, followed by LPE-0.05 and LPE-0.04. The rapid actions of the synthesized compounds on fungal cells suggested membrane-located targets. We investigated the effect of MIC90 values of these compounds on H+-ATPase mediated proton pumping by different Candida species. In the absence of glucose, the mean inhibition rate of H+ extrusion caused by MIC of LP was 28.09%, LPE: 33.04%, CuAc: 36.86%, LPE-0.04: 58.54%, LPE-0.05: 69.82% and LPE-0.06: 78.07%, respectively. Antifungal mechanism of action suggested that the synthesized compounds exert their antifungal activity by targeting H+-ATPase mediated proton pumping. Inhibition of H+-ATPase activity leads to intracellular acidification and consequently cell death. Results obtained in this study indicated strong antifungal activity of synthesized compounds against all the Candida species and suggest that the inhibition of fungal H+ ATPase is responsible for the antifungal activity of the test compounds. LPE-CuO can be employed as antifungal polyester and polyurethane coatings. The present work is consistent with the Principles (Principle 1,2,3,4,5,6,7,8, 12) of Green Chemistry.

The foliar and biochemical traits of Azadirachta indica A. Juss from fly ash (FA) dumping site in Badarpur thermal power plant (BTPP) New Delhi, India was studied. Three different experimental sites were selected at different distances from the thermal power plant. Ambient suspended particulate matter (SPM) and plant responses such as leaf pigments (chlorophyll a, chlorophyll b, and carotenoids), total chlorophyll, net photosynthetic rate, stomatal index (SI), stomatal conductance (SC), intercellular carbon dioxide concentration [CO2]i, net photosynthetic rate (NPR), nitrogen, nitrate, nitrate reductase activity, proline, protein, reducing sugar and sulphur content were measured. Considerable reduction in pigments (chlorophyll a, chlorophyll b and carotenoids), and total chlorophyll was observed at fly ash dumping site. Fly ash stress revealed the inhibitory effect on Nitrate reductase activity (NRA), Nitrate, soluble protein, and reducing sugar content, whereas stimulatory effect was found for the stomatal index, nitrogen, proline, antioxidants and sulphur content in the leaves. Under fly ash stress, stomatal conductance was low, leading to declining in photosynthetic rate and increase in the internal CO2 concentration of leaf. Single leaf area (SLA), leaf length and leaf width also showed a declining trend from control to the polluted site. Antioxidant enzymes increased in leaves reflecting stress and extenuation of reactive oxygen species (ROS).

In this study, we have used aldehyde function of cinnamaldehyde to synthesize N, N'-Bis (cinnamaldehyde) ethylenediimine [C20H20N2] and Co(II) complex of the type [Co(C40H40N4)Cl2]. The structures of the synthesized compounds were determined on the basis of physiochemical analysis and spectroscopic data ((1)H NMR, FTIR, UV-visible and mass spectra) along with molar conductivity measurements. Anticandidal activity of cinnamaldehyde its ligand [L] and Co(II) complex was investigated by determining MIC80, time-kill kinetics, disc diffusion assay and ergosterol extraction and estimation assay. Ligand [L] and Co(II) complex are found to be 4.55 and 21.0 folds more efficient than cinnamaldehyde in a liquid medium. MIC80 of Co(II) complex correlated well with ergosterol inhibition suggesting ergosterol biosynthesis to be the primary site of action. In comparison to fluconazole, the test compounds showed limited toxicity against H9c2 rat cardiac myoblasts. In confocal microscopy propidium iodide (PI) penetrates the yeast cells when treated with MIC of metal complex, indicating a disruption of cell membrane that results in imbibition of dye. TEM analysis of metal complex treated cells exhibited notable alterations or damage to the cell membrane and the cell wall. The structural disorganization within the cell cytoplasm was noted. It was concluded that fungicidal activity of Co(II) complex originated from loss of membrane integrity and a decrease in ergosterol content is only one consequence of this.