| Populus euphratica is a constructive species of desert riparian forest in the lower reaches of Tarim River.It is also the most typical and important mycorrhizal dependent plant in the lower reaches of Tarim River.However,its seedling growth is stressed by salt stress at the early stage,and its seedling regeneration is difficult.Populus euphratica seedlings were used as materials in this study.Four Na Cl treatments(CK,0.3%(S1),0.6%(S2)and 1.2%(S3)were set.Arbuscular mycorrhizal fungi(AMF)inoculation and no AMF inoculation were set as controls under each salt treatment level.A total of 8 treatments were set,and each treatment was divided into two groups Three replicates.A pot experiment was conducted to study the effects of AMF on the growth of Populus euphratica seedlings under salt stress.The results show that:(1)Soil salt content can affect AMF infection in plant roots,and salt stress can reduce its infection rate.AMF infection rate is closely related to salt concentration.With the increase of salt concentration,mycorrhizal infection rate decreased rapidly.The results showed that the root infection rate of Populus euphratica seedlings by AMF decreased significantly with the aggravation of salt stress,indicating that salt stress had an inhibitory effect on arbuscular mycorrhiza,especially under high salt stress.With the increase of salt concentration,the relative height growth rate,relative basal diameter growth rate,root length,root surface area and biomass of seedlings decreased.The root shoot ratio was significantly different between inoculated and non inoculated groups under S2 treatment(P < 0.05).(2)The maximum photochemical quantum yield Fv / Fm,potential photochemical efficiency Fv / F0 and photochemical quenching coefficient QP decreased under salt stress.Inoculation with AMF could increase the Fv / Fm,Fv / F0 and QP decreased under salt stress.There were significant differences in chlorophyll content between inoculated and non inoculated groups under medium(S2)and high(S3)salt stress(P < 0.05),and there were significant differences in chlorophyll content between inoculated and non inoculated groups under S3treatment(P < 0.05),AMF inoculation could improve chlorophyll fluorescence and chlorophyll content of seedlings to some extent.(3)With the increase of salt concentration,leaf relative water content and salt damage index increased,but water saturation deficit decreased.There was a positive correlation between salt injury index and salt concentration,and the difference was significant under S2 and S3treatments(P < 0.05).The relative water content of leaves in S2 and S3 treatments increased by1.1% and 4.1%,the salt damage index decreased by 16.8% and 11.2%,and the water saturation deficit of leaves decreased by 9.1% and 66.7% compared with the non inoculation group.The results showed that AMF inhibited water loss and alleviated the damage of salt stress to seedlings.In conclusion,although the seedlings infected with AMF were affected to some extent under salt stress,from the growth index and chlorophyll fluorescence parameters of Populus euphratica,mycorrhizal inoculation can improve the salt tolerance of Populus euphratica seedlings,and AMF can effectively help Populus euphratica seedlings pass through the fragile growth period,thus playing a positive role in the population regeneration. |
