Investigating the regulatory role of seasonal changes in soil and microbial communities on Codonopsis pilosula physiology

Abstract

Seasonal variations significantly shape soil-microbe-plant interactions, thereby influencing plant growth and metabolic adaptations. Understanding these dynamics is crucial, particularly for medicinal plants like Codonopsis pilosula. This study explored the seasonal links between soil physicochemical properties, C. pilosula physiological traits, and its root-associated microbiome (bacteria via 16S rRNA, fungi via ITS) across four seasons. Distinct seasonal patterns emerged: the growth rate of roots (length and diameter) was significantly higher in autumn and winter, whereas sugar content was highest in spring and summer. Microbial diversity also shifted seasonally; endophytic bacterial diversity was greater in autumn/winter, while rhizosphere fungal diversity peaked in spring/summer. Correlation analyses revealed that key soil properties (e.g., pH, EC, OM), likely driven by seasonal climate shifts, significantly structured the root microbiome and influenced plant physiology. Specifically, certain endophytic bacteria (Exiguobacterium, Bacillus, Acinetobacter) positively correlated with root growth, while the rhizosphere fungus Mortierella correlated positively with sugar content. These findings suggest a seasonal resource allocation strategy in C. pilosula: spring/summer conditions favor sugar accumulation, potentially linked to Mortierella activity, whereas autumn/winter conditions promote accelerated root development, possibly mediated by beneficial endophytic bacteria. Overall, this research elucidates the adaptive physiological strategies of C. pilosula driven by seasonal variations in the soil-microbiome environment.