Osmotic stresses caused by reduced water availability or the accumulation of salts in the soil can be highly damaging to plants. The objective of this study was to investigate physiological responses and tolerance mechanisms of two turfgrass species (seashore paspalum and centipedegrass) with distinct differences in salinity tolerance exposed to osmotic and iso-osmotic salt stresses. Three turfgrass genotypes including seashore paspalums 'Seastar' and 'UGP113', and centipedegrass 'TifBlair' were grown in ½ strength Hoagland's solution with three different treatment conditions; control (no external addition), salt stress (-0.4 MPa by adding NaCl) and osmotic stress [-0.4 MPa by adding polyethylene glycol (PEG)]. Osmotic stress damages were more severe with greater reductions in turf quality, photochemical efficiency (Fv/Fm), relative water content (RWC) and leaf water potential (Ψw) compared to iso-osmotic salt stress in both seashore paspalum and centipedegrass. Greater osmotic adjustment (OA) with greater accumulation of metabolically inexpensive inorganic osmolytes (Na+) helped turfgrasses to lessen damages in salt stress compared to osmotic stress. However, such accumulation of Na+ resulted ion-toxicity and triggered some damages in terms of increased electrolyte leakage (EL) and reduced total protein in salt-sensitive centipedegrass. Seashore paspalum had better ion regulation and also maintained greater antioxidant enzyme activities compared to centipedegrass; therefore it was able to avoid ion-specific damages under salt stress. Differences in the utilization of specific solutes for osmotic adjustment and antioxidant metabolism are partially responsible for the differences in salt versus osmotic stress responses in these species; the regulation of these defense mechanisms requires further investigation.

中文翻译：

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海滨雀稗和蜈蚣在渗透和等渗盐胁迫下的生理反应和耐受机制

由可用水量减少或土壤中盐分积累引起的渗透胁迫会对植物造成高度破坏。本研究的目的是研究两种草坪草（海滨雀稗和蜈蚣草）在暴露于渗透和等渗盐胁迫下的盐度耐受性存在明显差异的生理反应和耐受机制。三种草坪草基因型，包括海滨雀稗 'Seastar' 和 'UGP113'，以及蜈蚣草 'TifBlair' 在 1/2 强度的 Hoagland 溶液中以三种不同的处理条件生长；控制（无外部添加）、盐胁迫（-0.4 MPa，添加 NaCl）和渗透压力 [-0.4 MPa，添加聚乙二醇 (PEG)]。渗透压力损害更严重，草坪质量下降幅度更大，与等渗盐胁迫相比，海滨雀稗和蜈蚣的光化学效率 (Fv/Fm)、相对含水量 (RWC) 和叶水势 (Ψw)。与渗透胁迫相比，随着代谢上廉价的无机渗透物 (Na+) 的更多积累，更大的渗透调节 (OA) 有助于草坪草减轻盐胁迫的损害。然而，这种 Na+ 的积累会导致离子毒性，并在电解质泄漏 (EL) 增加和盐敏感性蜈蚣总蛋白减少方面引发一些损害。与蜈蚣草相比，海滨雀稗具有更好的离子调节能力，并保持更高的抗氧化酶活性；因此它能够避免盐胁迫下的离子特异性损伤。特定溶质用于渗透调节和抗氧化代谢的差异是这些物种中盐与渗透应激反应差异的部分原因; 对这些防御机制的监管需要进一步调查。