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Regulation of Osmolytes Syntheses and Improvement of Abiotic Stress Tolerance in Plants
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Ambuj Bhushan Jha, Pallavi Sharma
Several osmolytes accumulate in plants when exposed to abiotic stresses. These osmolytes can be classified into four chemical classes: (i) sugars (e.g. trehalose and sucrose), (ii) sugar alcohols or polyols (sorbitol, glycerol, mannitol etc.), (iii) amino acids (proline, glutamate etc.) and (iv) quaternary and tertiary sulfonium compounds (e.g. glycine betaine (GB), alanine betaine, dimethylsulfoniopropionate; Delauney and Verma, 1993). Figure 17.2 shows the various classes of osmolytes. Initially, osmolytes were believed to be involved in the osmotic adjustment and protection of subcellular structure. Later, their absolute concentrations suggested a reassessment of their functional significance. Osmolytes are now known to maintain cell turgor and osmotic balance, protect membranes, proteins, enzymes and other subcellular structures and act as metal chelators, antioxidants and signaling molecules (Murmu et al., 2017). Various roles of osmolytes in plants under abiotic stresses are depicted in Figure 17.3.
Nitric oxide mediated regulation of ascorbate-glutathione pathway alleviates mitotic aberrations and DNA damage in Allium cepa L. under salinity stress
Published in International Journal of Phytoremediation, 2023
Priyanka Prajapati, Praveen Gupta, Ravindra Nath Kharwar, Chandra Shekhar Seth
Compatible osmolytes prevent stress-induced damage by protecting enzyme functioning, membrane structures, and maintaining hydration status of cells (Ahanger et al. 2019). Proline acts as molecular chaperone, preserve the structure of cellular enzymes and proteins from toxic effects of ROS (Gupta et al. 2017). In present study, dose-dependent proline content enhancement was observed, but its level may not be adequate to alleviate oxidative damage (Figure 5B). However, noticeable increment in proline accumulation under NO supplementation indicated NO importance in maintaining hydration under salinity stress. This could be attributed to changes in activities of proline synthesizing (Δ′-pyrroline-5-carboxylate synthase or γ-glutamyl kinase) and degrading enzymes (proline oxidase or proline dehydrogenase) as reported in Brassica juncea (Gupta et al. 2017) and Triticum aestivum (Sehar et al. 2019) under salinity stress.
Preparation and characterization of W/O/W double emulsions containing MgCl2
Published in Journal of Dispersion Science and Technology, 2018
Qiaomei Zhu, Liping Feng, Masayoshi Saito, Lijun Yin
Generally, the diffusion process would result in the breakdown of swelling emulsion droplets. It is difficult to determine the exact diffusion rate. Schmidts et al.[12] reported that storage of multiple emulsions led to the viscosity changes caused by the migration of water or electrolytes between comparted aqueous phases. Therefore, the viscosity changes over time could be used as an indicator of water transfer extent. The viscosity values of all the prepared W/O/W emulsions increased within 12 hours, while the increasing extent varied with MgCl2 concentrations. After 4 hours’ storage time, the increased viscosity value of double emulsion without encapsulated Mg2+ was 1.43 mPa.s. When the concentration of MgCl2 increased from 0.1 M to 2.0 M, the increasing viscosity values of double emulsion varied from 5.97 to 26.42 mPa.s. The increasing viscosity of multiple emulsions had a decreasing trend over time and had a negative correlation with MgCl2 concentration, suggesting that these emulsions exhibited different swelling rates. A higher concentration of osmolytes would promote the water transport quickly from W2 to W1 and therefore change the ratio of dispersed–continuous phases, inducing a fast change in viscosity. Then the diffusion process began to slow down as the osmotic pressure gradients between two aqueous phases tended to be smaller. Eventually, the water transfer stopped when the osmotic pressure reached equilibrium. The rupture of interfacial film or breakdown would take place and this would result in the phase separation as well as a decrease in viscosity of multiple emulsion.
Cotyledonary leaves effectively shield the true leaves in Ricinus communis L. from copper toxicity
Published in International Journal of Phytoremediation, 2021
Due to the accumulation/deposition of metals inside the xylem vessels and other spaces, the water transport from the external environment to the shoot system is highly obstructed, which will lead to the decreased availability of water in the plant and therefore plants experience high osmotic stress (Shackira 2017). During osmotic stress, lowering of the solute potential is stimulated by the synthesis of osmolytes, and the process is termed as osmotic adjustment. The accumulation of the low molecular weight compatible solutes assists in lowering osmotic potential to maintain the osmotic balance of the cell and keeps the cell active under various stress conditions including heavy metal stress (Mirshad and Puthur 2017). These osmolytes protect the cellular structures and scavenge reactive oxygen species. Ricinus communis seedlings subjected to different concentrations of CuSO4 resulted in enhanced osmolality in both cotyledonary and true leaves, but the enhancement was higher in the former (Figure 4). In the case of cotyledonary leaves, the increase in osmolality was 110–132% upon exposure to CuSO4 on the 6th day of treatment with a 10–19% increase in true leaves. But in the case of true leaves with excised cotyledonary leaves, a 10–30% increase in osmolality was recorded at various concentrations of CuSO4 between 2nd and 6th day of the exposure period. The osmolalities of the cell sap were found to be increased with an increase in CuSO4 concentrations and this increase was mainly due to the accumulation of various metabolites such as sugars, free amino acids, etc. both in the cotyledonary and true leaves under Cu toxicity. Enhanced accumulation of various osmolytes helps to maintain a better osmotic adjustment so as to cope up with the osmotic stress (Lintunen et al. 2016), and the reserve metabolites in cotyledonary leaves provide a conducive situation for the accumulation of specific compatible solutes contributing toward osmolality due to conversion from one form to other.