Potential biochemical indicators of salinity tolerance in Prosopis strombulifera

LUNA, MARIA VIRGINIA; LLANES, ANALIA SUSANA; REGINATO , MARIANA ANDREA; BERTAZZA, GIANPAOLO

Gammarth, Tunisia

Congreso; INTERNATIONAL CONFERENCE ON BIOSALINE AGRICULTURE & HIGH SALINITY TOLERANCE; 2006

P. strombulifera is an interesting model plant to study mechanisms involved in plant tolerance to extreme salinity conditions. Growth parameters, pigments and ions content were diferentially affected by iso-osmotic concentrations of NaCl, Na2SO4 and their combination. A possible explanation for the adaptive success of this species when growing in high NaCl concentrations could involve a delicate balance between an effective Na+ and K+ compartmentation in vacuoles, Cl- exclusion and osmotic adjustment through production of high endogenous levels of specific compatible solutes for cytoplasm protection under high internal Na+ concentrations. Aminoacids, proteins, polyamines, sugars and polyalcohols were determined. Total aminoacids showed no quantitative but qualitative differences within treatments, with proline accumulation 200% higher than controls from the beginning of the experiments independently of the medium composition, showing a direct correlation between proline content and stress intensity. Contrarily, there was no increase in glycinbethaine levels in response to any salt. Total proteins content was no modified in treated plants at o ?1.0 MPa salt, accumulated considerably at o ?1.9 MPa with all treatments, and at ψo -2.6 MPa only NaCl caused extra total protein synthesis; SO4= treated plants had reduced protein content while bisaline treated plants had and intermediate value. Total soluble carbohydrates increased proportionally to salinity increase with changes in the partitioning root/shoot; glucose and fructose accumulated mainly in SO4= treated plants roots with a notable decrease in sucrose content. Polyols content had a particular profile, showing mannitol accumulation in moderate and high salinity only in leaves of NaCl treated plants while in SO4= and bisaline treated plants mannitol content was lower than in control plants. Inversely, sorbitol accumulated in leaves of SO4= and bisaline treated plants while in the presence NaCl there was no sorbitol production. Inositol was not detected with any treatment suggesting a rapid conversion to pinitol which accumulated near 280% more than in controls with all treatments. Nevertheless, pinitol syntheis would not be enough to assure cell protection again salt stress taking into account that SO4= treated plants were seriously injured and few of them survived. Their high endogenous levels of sorbitol maybe a manifestation of carbon metabolism disorder, being the combination of mannitol together with pinitol a potential biochemical marker formula of salt tolerance in this species. According to our results, proline could be considered a stress metabolic signal not necessarily indicating salt tolerance. Putresine content in leaves increased considerably in all salinity treatments, being noticeable that cadaverine and 1,3-diaminopropane, uncommon polyamines, were detected in leaves and roots exposed to the highest salinities.