Nitrogen absorption efficiency and mechanism in Arbuscular mycorrhizal fungi - Canna indica symbiosis

Arbuscular mycorrhizal fungi (AMF) and its symbiosis with Canna indica on nitrogen (N) absorption was investigated for the remediation of contaminated soil. Canna indica plants with rhizome and leaf integrity intact were collected in spring and autumn seasons. To maintain the ideal nutrient composition, Hoagland concentrated nutrient solution was diluted with deionized water and additional nutrient solution was added periodically. Treated root samples were observed with an optical microscope and the number of hyphae and intersections as well as inoculation status were examined. High-throughput sequencing experiment was conducted to quantify AMF inoculation. Alpha diversity study was used to characterize abundance and diversity of the symbiosis. Hydroponic experiments were conducted to explore the absorption effectiveness of AMF-Canna symbiosis under different NH₄⁺-N and NO₃^--N combinations. Hyphal colonization rate was only about 5.66 ± 1.08% in seedling stage in spring, but enhanced in the adult stage in autumn (53.89 ± 1.43%). Results revealed that AMF had no significant impact on NO₃^--N absorption by Canna roots, however, absorption of NH₄⁺-N was improved by 63% under low concentration. Results revealed that when NH₄⁺-N and NO₃^--N were applied combinedly in a 1:1 ratio, their respective absorption rates were enhanced to 99.63% and 99.50%. Compared with the case of NH₄⁺-N as N source alone, synergistic effect of NH₄⁺-N and NO₃^--N significantly changed the absorption of NH₄⁺-N by C. indica, but its correlation with AMF inoculation was still not significant. Current findings could enhance understanding for effective N uptake and resource recovery.