Influence Of Salt And Alkaline Stress On Germiantion And Physiology Of Legumes Seeds

To discuss the adaptability of Legumes seeds and their adaptive mechanism under salt and alkaline stress during germinating, in this study, we conducted germination tests of seeds of Medicago sativa L., Melilotoides ruthenicus L., Vicia cracca L. and Lathyrus quinquenervius in growth chambers, and treated seeds with varing 0-200 mM salt stress (NaCl) and 0-50 mM alkaline stress (Na2CO3).The results are as follows:(1) Germination beginning and medium germination time of four Legume species were delayed by salt stress and alkaline stress. Germinating rate and seed vigor indices decreased under both stresses. The elongations of radicals and embryos were inhibited by stresses. Inhibition of stresses on germination inceased with increasing salinity and alkalinity. Negative effects of alkaline stress were stronger than salt stress at the same Na+ concentration. High salinity and alkalinity signficantly affected germination percentage within the allotted time, but low salinity and alkalinity not.(2) The Na+contents and Na+/K+ ratio in radicals and embryos of four Legume species increased with stress intensifing, and the Na+ contents under alkaline stress were heaviver than those under salt stress. The initial Na+contents injuring germination and growth were different. The K+contents fluctuated under salt stress and alkaline stress. The Cl- contents incresed with stress intensifing under salt stress, but there was no change under alkaline stress. The proline contents in radicals and embryos of four Legume species increased with increasing salinity and alkalinity, and the proline contents under alkaline stress were heaviver than those under salt stress. The soluble sugar contents fluctuated under salt stress, and reduced under alkaline stress. For Legume seeds, proline plays a major role in resisting salt stress and alkailine stress at germination stage, but soluble sugar is of no effect.(3)Seed Priming phenomena appeared on cultivar M.sativa L.at low salinity (at 50 mM Na+ concentration), and it showed typical traits like halophyte species. Under the same stress, seed vigor indices and the length of radicals and embryos of M.sativa L. were signficantly bigger than those of other three wild Legume species. The Cl- and proline contents in radicals and embryos of M.sativa L were heaviver than those of the others. Cultivar M.sativa L. seeds are more preponderant than other three wild Legume seeds on germination.(4)Under the same stress, the small seeds M.sativa L.and M. ruthenicus L.germianted rapidly than the big seeds V. cracca L.and L. quinquenervius. Germination beginning and medium germination time of the small seeds were earlier than those of the big seeds, and seed vigor indices of the small seeds were bigger than those of the big seeds. The Na+contents and Na+/K+ ratio in radicals and embryos of the small seeds were signficantly heaviver than those of the big seeds. The small seeds resisted stronger ion toxicity. Under salt stress and alkali stress, the small seeds M.sativa L.and M. ruthenicus L.are more preponderant than the big seeds V. cracca L.and L. quinquenervius on germination.