Effeets Of AMF On Salt Tolerance Of Sedum Aizoon L Under NaCl Stress

Sedum aizoon L, the perennial herbs of the genus Sedum, has the ornamental, medicinal and edible values. In recent years, it is accepted with unanimous approval in the fields of garden, food and environmental protection etc.. Arable land area is decreasing, as the salinization of soil gets worse. Thus, saline-alkali land reform has become the focus of national agricultural development. Under the new situation, improving saline-alkali soil should follow the sustainable development principle, that is, improve the soil with plants instead of pesticides and fertilizers to achieve the goal of improving the ecosystem.In this experiment, we firstly evaluated the salt tolerance of Sedum aizoon L by determining the salt injury index, shape index, chlorophyll, proline, soluble sugar and activity of antioxidant enzymes, MDA, chlorophyll fluorescence parameters (Fo, Fm, Fv/Fo, Fv/Fm, Y (Ⅱ), NPQ, qP, ETR). The vegetables were watered NaCl with different concentrations (0,8,12,16,20g/kg) before the determination. In order to explore physiological mechanisms of salt tolerance of Sedum aizoon L, we tried to exaggerate Sedum aizoon L’s vis under NaCl stress by inoculating the vegetables with GMH and GMA, two kinds of arbuscular mycorrhizal fungi (AMF). It is expected that the study can provide a reference for improving saline-alkali land by the utilization of such special wild vegetable. The main results are as follows:1.Under salt stress, the root activity of Sedum aizoon L, with the prolonging of treatment time, increased firstly and then decreased. It showed a similar trend with increasing concentrations of NaCl, and the root activity reached the peak at 8g/kg. Indicating that Sedum aizoon L could improved the metabolic ability of root in response to salt stress, this ability under high salt concentration decreased gradually.2.Under salt stress, the change trend of SOD, POD, CAT activity of the leaves of Sedum aizoon L are increasing first and then decreasing, and the peak value appeared at the concentration of 8g/kg. Whereas the content of MDA increased with the increasing of NaCl concentration. It indicated that low salt stress caused the increase of antioxidant enzyme activity of Sedum aizoon L, the function of antioxidant enzyme impairment occurred in high salt concentration.3. With prolonged NaCl treatment time and the increasing of NaCl concentration, the content of proline and soluble sugar in the Sedum aizoon L increased in different degrees, and it was positively correlated with salt injury index. It indicated that Sedum aizoon L could through the synthesis of organic osmolytes to relieve stress.4. Compared with the control group, chlorophyll a and total chlorophyll content was significantly higher but chlorophyll b was significantly lower in NaCl 12g/kg group, indicating that this treatment may hinder the synthesis of chlorophyll b and limit the ability of the light harvesting protein to capture light energy.5. In the NaCl concentration of 8g/kg group, Sedum aizoon L showed certain adaptability, andthey can guarantee a certain growth through the antioxidant system, spontaneous osmotic adjustment mechanism and protective mechanism. However, when the concentration of NaCl was higher than 8 g/kg it affected normal growth of the plants. Thus tolerance concentration of Sedum aizoon L to continuous NaCl stress was 8g/kg.6. When NaCl concentration reached 20g/kg, Sedum aizoon L was wilt on the 21st day.7. Infection rate of GMA on Sedum aizoon L was significantly higher than that of GMH and AMF, After inoculation with different AMF, the root length, plant height, dry root weight and shoot dry weight were significantly increased compared with the control group.8. Compared with the control group, inoculation of AMF could induce the generation of soluble protein and proline, reduce water loss, maintain cell turgor, be conducive to plant growth and development, and reduce the damage to cells induced by salt stress.9.Inoculation with mycorrhiza can improve the activity of protective enzymes in plants of Sedum aizoon L, effectively eliminate active oxygen, reduce the extent of lipid peroxidation, and eventually enhance plant resistance to salt stress.10.Under NaCl stress, the PSII reaction centers of Sedum aizoon L plants in the control group were damaged, but inoculation with AMF increased the salt tolerance concentration and reduced the damages to these centers. However, when the concentration exceeded 12g/kg, PSII also suffered from damages.11.NaCl stress could lead to a decrease of Fv/Fm, while Fv/Fm was significantly increased under the stress if plants were inoculated with AMF. Inoculation with AMF can reduce the damage of electron transfer rate and light energy conversion efficiency, and improve the photosynthetic ability of Sedum aizoon L.12.Under low salt concentration, inoculation of GMA compared with GMH can better improve the ability of the plant to convert light energy, reduce the damage to PSII resulted from the excess excitation energy by increasing thermal dissipation, and maintain as much as energy to participate in photochemical reactions.13.Sedum aizoon L inoculated with GMH, under the NaCl concentration of 8g/kg, showed a stronger salt tolerance than that in the control group, but when the salt concentration reached 12g/kg, the performance of physiological indexes of the plants were not as good as those of plants inoculated with GMA so we infer that GMA, compared with GMH, can better improve the salt tolerance of Sedum aizoon L.