Osmotic Stress Regulation Research Articles

Effect of osmotic stress and sodium nitroprusside pretreatment on proline metabolism of wheat seedlings

Effect of osmotic stress and sodium nitroprusside (SNP, NO donor) pretreatment on growth and proline metabolism of wheat seedlings was investigated. Polyethylene glycol 6000 treatment for 2, 4 and 6 d could be termed as mild, moderate and severe stress, respectively, according to decrease in the relative water content. Severe osmotic stress significantly decreased the growth and photochemical efficiency, and increased proline content due to activation of its synthesis. 0.2 mM SNP pretreatment enhanced growth of wheat seedlings, increased variable to maximum fluorescence ratio (Fv/Fm) and fluorescence yield, while decreased proline content. However, 2 mM SNP retarded the seedlings growth and chlorophyll a fluorescence, and increased proline accumulation. Our results showed that NO might be involved in the regulation of osmotic stress in a concentration-dependent manner.

Lipids as energy source during salinity acclimation in the euryhaline crab Chasmagnathus granulata dana, 1851 (crustacea-grapsidae).

Lipids seem to be the major energy store in crustaceans. Moreover, they are extremely important in maintaining structural and physiological integrity of cellular and sub cellular membranes. During salinity adaptation, energy-demanding mechanisms for hemolymph osmotic and ionic regulation are activated. Thus, the main goal of this work was to verify the possible involvement of lipids as an energy source in the osmotic adaptation process. The estuarine crab Chasmagnathus granulata was captured and acclimated to salt water at 20 per thousand salinity and 20 +/- 2 degrees C, for 30 days. After acclimation, crabs were divided into groups of ten and transferred to fresh water (0 per thousand ), salt water at 40 per thousand salinity, or maintained in salt water at 20 per thousand salinity (control group), without feeding. Before and seven days after the salinity change, wet weight and lipid concentration in gills, muscle, hepatopancreas, and hemolymph were determined according to the colorimetric assay of sulphophosphovanilin. Results show that hepatopancreas lipids were not mobilized during osmotic stress regulation. Gill and muscle lipids were significantly lower in crabs subjected to hypo-osmotic stress than those subjected to the hyper-osmotic stress or maintained at the control salinity. Our results point to the occurrence of lipid mobilization and involvement of these compounds in the osmotic acclimation process in C. granulata, but with differences between tissues and the osmotic shock (hypo or hyper) considered.