Effects of humic acid fertilizer on the growth and microbial network stability of Panax notoginseng from the forest understorey.

Humic acid (HA) can substantially enhance plant growth and improve soil health. Currently, the impacts of HA concentrations variation on the development and soil quality of Panax notoginseng (Sanqi) from the forest understorey are still unclear. In this study, exogenous HA was administered to the roots of Sanqi at varying concentrations (2, 4, and 6 ml/L). Subsequently, the diversity and community structure of bacteria and fungi were assessed through high-throughput sequencing technology. The investigation further involved analyzing the interplay among the growth of sanqi, soil edaphic factors, and the microbial network stability. Our finding revealed that moderate concentrations (4 ml/L) of HA improved the fresh/dry weight of Sanqi and NO3--N levels. Compared with control, the moderate concentrations of HA had a notable impact on the bacterial and fungal communities compositions. However, there was no significant difference in the α and ß diversity of bacteria and fungi. Moreover, the abundance of beneficial bacteria (Bradyrhizobium) and harmful bacteria (Xanthobacteraceae) increased and decreased at 4 ml/L HA, respectively, while the bacterial and fungal network stability were enhanced. Structural equation model (SEM) revealed that the fresh weight of Sanqi and bacterial and fungal communities were the factors that directly affected the microbial network stability at moderate concentrations of HA. In conclusion, 4 ml/L of HA is beneficial for promoting Sanqi growth and soil quality. Our study provides a reference for increasing the yield of Sanqi and sustainable development of the Sanqi-pine agroforestry system.

The Relationship between Endophytic Fungi of Chimonanthus praecox and Volatile Metabolites under Different Circadian Rhythms and Blooming Stages.

Chimonanthus praecox is an aromatic plant that flowers in winter. The composition of the floral volatiles of C. praecox is influenced by different blooming stages, circadian rhythms and species. However, the relationship between floral volatiles and plant endophytic fungi has not received much research attention. Here, we used high-throughput sequencing technology to compare and analyze the changes in the structure and diversity of the endophytic fungal communities in C. praecox under different circadian rhythms (7:00 a.m., 1:00 p.m., and 7:00 p.m.) and in different blooming stages (unopened flowers and opened flowers). The endophytic fungi of C. praecox consisted of nine phyla, 34 classes, 79 orders, 181 families, 293 genera, and 397 species, and Ascomycota was the dominant phylum. Under a diurnal rhythm, the diversity (Chao1 and Shannon indices) of endophytic fungi gradually decreased in the unopened flowers, while an increasing and then decreasing trend was found for the opened flowers. In the different blooming stages, the endophytic fungal diversity was significantly higher at 7:00 a.m. in the unopened flowers compared to the opened flowers. Humidity was the key factors that significantly affected the endophytic fungal diversity and community. Moreover, 11 endophytic fungi were significantly positively or negatively correlated with seven floral volatiles. In conclusion, the community structure and diversity of endophytic fungi in C. praecox were affected by the different blooming stages and circadian rhythms, and a correlation effect related to floral volatiles was found, but there are other possible reasons that were not tested. This study provides a theoretical basis for elucidating the interrelationships between endophytic fungi, floral volatiles, and environmental factors in C. praecox.