Salinity and water deficit effects on seed germination and recovery of Lotus populations from Northern Tunisia

摘要

Trials were set to assess salinity and water deficit effects on seed germination and recovery of populations of Lotus creticus L. and Lotus ornithopodioides L. species collected from different bioclimatic regions in northern Tunisia. Salinity treatments used were 0, 50, 100, 150, 200 and 250 mM of NaCl whereas water deficits of 0, -0.2, -0.6, -0.8 and 1.0 MPa were induced using polyethylene glycol 8000 (PEG-8000). Seeds of L. creticus L. collected from Tabarka region weighted 3.39 g/1000 seeds which were less than half of this weight for all other Lotus populations but having no effect on seeds germination capacity. Lotus creticus L. seeds collected from Seddine region showed 80% germination at 250 mM of NaCl compared to 55.7% for Tabarka populations. Seed germination of L. ornithopodioides L. was not affected by salinity regardless of population provenance indicating species tolerance to salinity. At -0.4 MPa water potential deficit, seed germination of L. creticus L. collected from Seddine region was reduced by 14% compared to 48.5% reduction for seeds from Tabarka provenance which would indicate its tolerance to water stress. Lotus ornithopodioides L. seed germination was reduced by 47% at -0.2 MPa and almost inhibited at -0.6 MPa water potential indicating species low tolerance to water deficit. Ungerminated seeds of Lotus species due to salinity and PEG-8000 treatments recovered their germination capacity when they were transferred to distilled water regardless of species and provenances indicating osmotic inhibition of seed germination for these two Lotus species.