Investigation Of The Mechanism Of Arbuscular Mycorrhizal Fungi Enhancing Maize Cadmium Tolerance By The Split-root Technique

Arbuscular mycorrhizal fungi（AMF）is an important functional component of roots,which plays an important role in enhancing host plants to deal with biological and abiotic stresses.However,the relationship between the degree of colonization and the tolerance of host plants is not clear.Due to the distribution of arbuscular mycorrhizal fungi in natural soil is uneven,it is not clear whether the mycorrhizal fungi enhance the tolerance of heavy metals systematically or locally.In this study,maize is cultivated in greenhouse in split-root method which roots are split into two compartments,and 50 mg kg^-1 Cd is added externally to simulate soil heavy metal pollution.Without Cd addition as control,two chambers without inoculation,single chamber inoculation and two chambers with the same dose of AMF inoculant（with the same amount of inactivated inoculant in the control）.The functional effects and physiological responses of different levels of AMF colonization on Cd tolerance of maize are studied.Our results and conclusions are as follows:1.50 mg kg^-1 Cd stress significantly inhibit maize growth,and significantly decrease maize height,dry weight and chlorophyll content compared with 0 mg kg^-1 Cd.However,compared with the control,single chamber or double chambers inoculated with AMF both significantly alleviate Cd stress on maize growth and significantly promote maize growth.In contrast,AMF inoculation can inhibit plant growth in the absence of Cd treatment,that is,two chambers inoculation significantly reduce aboveground and underground biomass and chlorophyll content of maize.2.Our analysis also show that AMF inoculation effectively inhibit the accumulation of Cd in maize aboveground,especially in the two chambers inoculation group.Accordingly,compared with the control,AMF inoculation inhibit Cd uptake by maize roots,but there is no statistical significance（p>0.05）.At the same time,under Cd stress,for single chamber inoculation group,there is no significant difference in root biomass and cadmium concentration between the AMF inoculation chamber and the control chamber.Preliminary results suggest that AMF may play a systemic role in regulating Cd uptake by maize roots.3.Study on antioxidant capacity and antioxidant enzyme activity of maize in different treatments:for single chamber inoculation group,MDA,H₂O₂,OFR,POD and CAT show no significant differences between the two chambers.These results also suggest the systematic regulation of AMF inoculation on host plant maize.4.Our results show that the degree of AMF colonization is significantly correlated with its function of alleviating heavy metal Cd stress,that is,under Cd stress,the stronger the degree of AMF colonization,the better the growth,the higher the biomass and chlorophyll content,and the lower Cd concentration of maize,which is two chambers inoculation>single chamber inoculation>two chambers without inoculation.