The Effects Of NaCl Stress On Seed Germination And Physiological Indexes Of Seedlings Of Two Species Of Halophytes

In this paper, under different concentrations of NaCl stress, seed germination and seedling physiological indexes of two species of halophytes Atriplex centralasiatica and Suaeda salsa were studied and analyzed. And the differences of responses to salt stress and salt -tolerant mechanism and ability of two species of halophytes were discussed. The conclusions were as follows:(1) The results of the germination test showed that:under NaCl stress, with the growing of the concentration, all of germination percentage, germination energy, germination index and vigor index of these two species decreased in different degrees. Osmotic stress affected seed germination of these two halophytes under high concentrations of NaCl stress. Seed germination was inhibited. And germination process was delayed under NaCl stress. When stress was relieved, the seeds still have a high germination ability and vitality. For seed germination of Atriplex centralasiatica under NaCl stress, its fit value of salt-tolerant was 59.39mmol/L, critical value was 173.7mmol/L, and the maximum value is 288.01mmol/L. While for Suaeda salsa, the corresp-onding values were 83.67mmol/L,193.8mmol/L and 303.93mmol/L.Inhibition of root length inhibition index and shoot length inhibition index enhanced with the increasing of the concentration of NaCl solution. The radicals were more sensitive to NaCl stress than the germs. To some extent, Low concentrations of NaCl stress could promote seed germination and the growth of ridicules and germs.(2) The results of analysis on seedling physiological indexes showed that:With increasing of stress time and the concentration of NaCl solution, the relative conductivity of these two species showed a rising trend. There was a positive correlation between stress time, NaCl solution concentration and relative conductivity of these two halophytes.The changes of chlorophyll content of these two halophytes were different under NaCl stress. Chlorophyll content of Atriplex centralasiatica first increased and then decreased, while Suaeda salsa's showed a rising trend. There was a negative correlation between the chlorophyll content of Atriplex centralasiatica and NaCl concentration, while there was a positive correlation between the chlorophyll content of Suaeda salsa and NaCl concentration.SOD activity of Atriplex centralasiatica and Suaeda salsa was promoted in varying degrees during short-term and under low concentrations of NaCl stress. When NaCl stress increased, SOD activity declined. There was a negative correlation between SOD activity of these two halophytes and stress time.Under NaCl stress, soluble protein content of Atriplex centralasiatica increased slightly and then decreased. There was a positive correlation between stress time and it, while a negative correlation between NaCl concentration and it. For Suaeda salsa, there was a positive correlation between soluble protein content and NaCl concentration. Soluble protein content of Suaeda salsa decreased at first, then increased gradually.With increasing of the concentration of NaCl solution, proline content of these two halophytes raised constantly. It increased at first and then decreased, with the extension of stress time. During the NaCl stress, proline is not dominant in the osmotic adjustment of Suaeda salsa.