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Osmotic and Ionic Regulation
Published in Alan G. Heath, Water Pollution and Fish Physiology, 2018
Osmoregulation refers to the processes by which the osmotic pressure of the body fluids and the water volume in an animal are held relatively constant. The osmotic pressure of fish blood is mostly provided by inorganic salts and is approximately one third that of seawater, with marine fish having slightly more salt in their blood than freshwater species. Because gills are permeable to water as well as oxygen, CO2, etc., there is an osmotic flow of water out of the marine fish because the salt concentration of its blood is less than that of the ocean, and into the freshwater fish because of an opposite osmotic gradient. The diffusion gradient for sodium chloride (the primary salt) is in the direction opposite to the osmotic diffusion of water across the gill epithelium. Figure 1 illustrates these major ion and water fluxes in typical teleost fish.
Trehalose Metabolism in Plants under Abiotic Stresses
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Qasim Ali, Sumreena Shahid, Shafaqat Ali, Muhammad Tariq Javed, Naeem Iqbal, Noman Habib, Syed Makhdoom Hussain, Shahzad Ali Shahid, Zahra Noreen, Abdullah Ijaz Hussain, Muhammad Zulqurnain Haider
A stressful environment adversely affects crop plant biomass production and final yield by causing decreased tissue water status and turgor as a function of inadequate water supply. (Kiani et al., 2007; Hussain et al., 2009). To maintain cellular water content under limited soil water supply, plants have developed mechanisms of osmoregulation to lower cellular osmotic potential by accumulating organic and inorganic solutes without decreasing the actual cellular water content (Serraj and Sinclair, 2002). Even so, even in high concentration, these solutes have no recorded injurious effect on macro-organic molecules, whether metabolic enzymes or membranes. These organic solutes are referred as compatible solutes (Cechin et al., 2006; Kiani et al., 2007). The major and important ones include the sugar alcohols, glycine betaine (GB), soluble sugars, proline, organic acids and trehalose (Cechin et al., 2006; Kiani et al., 2007; Farooq et al., 2008, 2009a, b). In parallel with the maintenance of cellular turgor pressure, they act as molecule chaperones to protect macromolecules, including metabolic enzymes, and cells from the damaging effects of ROS (Farooq et al., 2009a, b). To minimize the adverse effects of stress-induced damage in crop plants, the key adaptation of plants is cellular osmotic adjustment (Blum, 2005). First, it plays a significant role in maintenance of leaf turgor to improve stomatal opening for efficient CO2 intake (Kiani et al., 2007). Second, it increases the ability of roots to uptake water (Chimenti et al., 2006). Compatible solutes that accumulate under different stresses include free proline, free amino acids, GB and sugars (Manivannan et al., 2007; Farooq et al., 2008). Osmotic adjustment by accumulating a variety of organic and inorganic solutes, along with higher activity from antioxidant enzymes in leaves, is among the most important physiological adaptations of plants grown in drought-prone environments (Lei et al., 2006). Among others, sugars also play a significant role, not only in non-stress conditions but importantly under varying stress conditions (Huang et al., 2006; Rollandet al., 2006; Grigston et al., 2008).
Comparative analysis of remediation efficiency and ultrastructural translocalization of polycyclic aromatic hydrocarbons in Medicago sativa, Helianthus annuus, and Tagetes erecta
Published in International Journal of Phytoremediation, 2023
An increase in proline content was observed with increasing concentration of hydrocarbons as represented in Figure 4d. The highest proline contents (31.865 ± 1.007 µmol g−1) were recorded for Medicago sativa at 700 mg kg−1 in all the treatments. The proline content in Medicago > Helianthus > Tagetes increased significantly (p ≤ 0.05) as presented in Figure 4d. The concentration of proline in phenanthrene-treated plants was the highest and lowest level observed in pyrene-treated plants at 700 mg kg−1, respectively. With increasing concentrations of PAH, proline content in the leaves increased significantly. Increasing proline levels in plants shows a protective response toward stress and protects them from oxidative damage. The metabolism of proline has a regulatory function in osmoregulation, homeostasis, cell survival, and oxidation-reduction in plants (Liang et al.2013; Molina and Segura 2021). Under stress conditions, the electron transport chain causes an increase in mitochondrial reactive oxygen species (ROS) production (Jalal et al.2021).
Effects of sublethal concentrations of cypermethrin on the gills of Lake Van Fish (Alburnus tarichi)
Published in Chemistry and Ecology, 2022
Gills are vital organs in fish that serve functions such as acid–base regulation, osmoregulation, respiration, and excretion of nitrogenous compounds [14,15]. Gills, like skin, comprise tissues with a large surface area. Therefore, they act as a barrier between the internal and external environment. All physicochemical changes and parasitic and bacterial infections occurring in the external environment directly affect the gill tissue. This tissue consists of four pairs of lamellae and secondary filaments emerging from those lamellae. The cells that make up the tissue include pavement, mucous, chloride, blood, and neuroepithelial cells [15,16]. Mucous cells protect the gills from the harmful effects of pollutants, parasites, and microbial contamination by covering the tissue like a barrier due to the mucus they secrete [17]. Mitochondria-rich cells (MRCs) play a role in osmoregulation as a result of the Na,K-ATPase (NKA) transmembrane protein. Environmental pollutants and many physicochemical changes in the water affect both the numbers and cell contents of mucous cells and MRCs [18,19].
Exogenous melatonin improves cadmium tolerance in Solanum nigrum L. without affecting its remediation potential
Published in International Journal of Phytoremediation, 2022
Yue Teng, Wenjie Guan, An Yu, Zhishuai Li, Zhenjun Wang, Hongyan Yu, Luyi Zou
Solanum nigrum L. showed limited tolerance to Cd, and treatment of Cd at 25 or 50 µM resulted in disrupted cellular redox homeostasis, elevated membrane lipid peroxidation, and permeability, decreased water, and photosynthetic pigment content, and reduced shoot and root growth. However, pretreatment with melatonin before Cd exposure consistently decreased the total accumulated concentration of cadmium, increased the chlorophyll content, membrane integrity, and biomass accumulations. These results highlight the important role of melatonin in detoxification, osmoregulation, and water balance. Moreover, and from a remediation-related perspective, this induced protection did not affect the uptake and accumulation of Cd by this plant species, suggesting that melatonin can be regarded as an efficient tool to promote plant phytoremediation potential. Further studies might be needed to explore the signaling roles of melatonin and its interactions with other molecules, such as nitric oxide (NO), H2S, polyamines, and phytohormones.