Biochemical and physiological adaptations of alfalfa to germination stresses imposed by sodium-chloride

摘要

Nine cycles of recurrent selection for germination salt tolerance in alfalfa (Medicago sativa L.) were compared with their parental cultivar, 'Mesa-Sirsa'. Test seeds were produced in the same season and locale. Cycle 9 and Mesa-Sirsa showed 90% and 2.5% germination, respectively, in a -1.7 MPa NaCl medium. Cycle 8 germinated more vigorously compared to Mesa-Sirsa in stressed and non-stressed environments. Selection also enhanced germination speed and radicle length. Fresh seed and one year old seed showed similar percent germination. Scarification decreased germination in a saline solution. Mesa-Sirsa and Cycle 8 displayed the same pattern of water uptake in a salt solution. Salinity decreased water uptake in Cycle 8 and Mesa-Sirsa compared to the control. Cycle 8 and Mesa-Sirsa contained 7% galactomannan and 3.2% stachyose. Galactomannan was not an important factor in seed salt tolerance. Seed protein content was stable throughout the cycles of selection. Selection for germination salt tolerance in alfalfa significantly affected the percentage of seed amino acids.