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The SpAHA1 gene, encoding a plasma membrane (PM) H+-ATPase (AHA) in Sesuvium portulacastrum, was transformed into Arabidopsis plants, and its expression increased salinity tolerance of transgenic Arabidopsis plants: seed germination ratio, root growth, and biomass of transgenic plants were greater compared to wild-type plants under NaCl treatment condition. Upon salinity stress, both Na+ and H+ effluxes in the roots of SpAHA1 expressing plants were faster than those of untransformed plants. Transformed plants with SpAHA1 had lower Na+ and higher K+ contents relative to wild-type plants when treated with NaCl, resulting in greater K+/Na+ ratio in transgenic plants than in wild-type plants under salt stress. Extent of oxidative stress increased in both transgenic and wild-type plants exposed to salinity stress, but overexpression of SpAHA1 could alleviate the accumulation of hydrogen peroxide (H2O2) induced by NaCl treatment in transgenic plants relative to wild-type plants; the content of malondialdehyde (MDA) was lower in transgenic plants than that in wild-type plants under salinity stress. These results suggest that the higher H+-pumping activity generated by SpAHA1 improved the growth of transgenic plants via regulating ion and reactive oxygen species (ROS) homeostasis in plant cells under salinity stress. [ABSTRACT FROM AUTHOR]

The plasma membrane (PM) Na+/H+ antiporter SOS1 (salt overly sensitive 1) has emerged as a key factor in regulating plant salt tolerance. The SpSOS1 gene, which encodes a PM Na+/H+ antiporter, was cloned from the halophyte Sesuvium portulacastrum and transformed into Arabidopsis sos1 mutant plants. As shown from the results, the SpSOS1 expression complemented the salt sensitivity of the sos1 mutant plants. Upon salinity stress, SpSOS1-transgenic Arabidopsis sos1 mutant seeds displayed higher germination ratio compared to the sos1 mutant. The sos1 mutant plants expressing SpSOS1 grew better and had a lower Na+/K+ ratio than that of the sos1 mutant and wild-type (WT) plants when they were treated with NaCl. In addition, SpSOS1-overexpressed Arabidopsis accumulated less malondialdehyde (MDA) and had a lower level of electrolyte leakage than that in the sos1 mutant and WT plants under salt stress. Furthermore, the SpSOS1 expression in transgenic sos1 mutant plants also increased the transcript levels of some salt stress-related genes, such as AtHKT1;1 (high-affinity K+ transporter 1;1), AtSOS2 (salt overly sensitive 2), AtSCABP8 (SOS3-like calcium binding protein 8), and AtNHX1 (Na+/H+ exchanger 1). These results suggested that SpSOS1 improved the plant salt tolerance by regulating ion homeostasis and protecting the plasma membrane against oxidative damage under salt stress. [ABSTRACT FROM AUTHOR]

Fiber-reinforced ceramic matrix composite (FRCMC) have been widely used in aerospace and other high-technology fields due to their excellent mechanical and physical properties. However, FRCMC is a kind of typical material with anisotropic and inhomogeneous structure; thus, it is difficult to guarantee the precision and surface quality using traditional machining. The present paper employed ultrasonic vibration-assisted grinding (UAG) to machine 2.5D woven SiO2f/SiO2composites. By comparing the grinding force, surface microstructure, chip formation, surface topography and surface roughness with and without ultrasonic vibration for the machining of SiO2f/SiO2composites, the feasibility of UAG on FRCMC was investigated experimentally. In addition, the effects of the process parameters (including spindle speed, feed rate, grinding depth, grain mesh size and ultrasonic power) on grinding force and surface roughness were studied through an orthogonal experiment. The research obtained can be a useful technical support for the development of UAG in the machining of FRCMC. [ABSTRACT FROM AUTHOR]