Effects Of AMF (Arbuscular Mycorrhizal Fungi) On The Salt Tolerance Of Medicago Sativa L.

Salinized soil is a kind of stressful environment in natural ecosystem. It is urgent to restore salinized soil because salinized soil restricts agricultural production and the lasting development of resources and environment. Medicago sativa L. is a kind of important bird's-foot with great value for feeding. Also the leaves of M. sativa L. have mechanisms of ejecting salt ions so that M. sativa L. has the ability of salt resistance and exists almost everywhere in tidal land. Arbuscular mycorrhiza is a symbiosis which combines plants with arbuscular mycorrhizal fungi. It has been reported that ninety-seven percent of altitude plants in land ecosystem can form mycorrhizal symbiosis. AMF (arbuscular mycorrhizal fungi) plays an important role in plant growth, stress resistance and yields and quality of crops. More and more studies focus on the role of AMF in agricultural ecology as the fungi can act as latent biological fertilizer and biological pesticide. In order to enhance the yields of M. sativa L under salinized soil, many studies have already focused on the filter of breeds of M. sativa L. with character of salt resistance. However, whether AMF can enhance the salt-resistant ability of M. sativa L. is rarely reported. In our study, we conducted a mesocosm experiment to test the effects of arbuscular mycorrhizal fungi (AMF) on the growth and salinity resistance of M. sativa L. under salt stress. The main results were as follows:1. Salt stress reduced the colonization of AMF. In our study, the colonization rate of AMF decreased with increasing salinity, which corresponded with other studies.2. Salt stress restrained growth of M. sativa L. Salt stress significantly reduced the individual shoot and root biomass, total root biomass, growth rate, leaf area, canopy radius, number of branches, height and root/shoot ratio. Salt stress significantly enhanced mortality of M. sativa L. With salt stress increasing, the nitrogen content, phosphorus content, Mg²⁺ content, Ca²⁺ content decreased while Na+ content, the free proline content, malondialdehyd (MDA) content and membrane permeability in the leaves of M. sativa significantly increased.3. AMF enhanced growth of M. sativa L. AMF significantly increased the individual biomass of shoots, growth rate, number of leaves, canopy radius, number of branches. AMF significantly decreased mortality of M. sativa L. under severe salt stress.4. AMF enhanced the absorption and utilization of elements and ions. The contents of N, P, Mg²⁺, Ca²⁺ of M. sativa L. under higher AMF were higher than those under lower AMF.5. AMF can enhance the stress resistance of M. sativa L. Contents of free proline and malondialdehyd (MDA) and membrane permeability in the leaves were significantly lower under higher AMF than those under lower AMF. Besides, AMF can decrease individual root biomass, total root biomass and root/shoot ratio under no salt stress and slight salt stress while AMF can increase individual root biomass, total root biomass and root/shoot ratio under severe salt stress. So we could conclude that AMF can increase salt resistance of M. sativa L. by modulating the biomass which was distributed according to the change of environment.