The change of bacterial community structure helped Salvia miltiorrhiza alleviate the pressure of drought stress

Abstract

Introduction: Drought stress poses a significant threat to plant growth and development, thereby adversely impacting agricultural productivity and ecosystem stability. In recent years, increasing attention has been given to plant-microorganism interactions as a promising strategy to enhance plant resistance to abiotic stresses.

Methods: In this study, we evaluated the effects of microbial inoculation on the growth, photosynthetic performance, nutrient uptake, and root morphology of Salvia miltiorrhiza under drought stress. Microbial community composition was also analyzed to explore the interaction between drought stress and rhizosphere microbiota.

Results: Our results demonstrated that microbial inoculation significantly alleviated the adverse effects of drought stress on S. miltiorrhiza. Inoculated plants exhibited a 3.61-fold increase in biomass compared to the uninoculated controls. Chlorophyll content increased by approximately 85.45%, while nitrogen and potassium contents rose by 27.77% and 33.27%, respectively. Furthermore, microbial inoculation improved root system architecture. Drought stress altered the rhizosphere microbial community, with the relative abundance of Enterobacteriaceae increasing by 5.50% and Brucellaceae decreasing by 2.76%.

Discussion: These findings suggest that microorganisms can enhance plant drought resistance through multiple mechanisms, including the promotion of growth, nutrient absorption, and root development, as well as modulation of microbial community structure. This study provides a theoretical foundation and practical insights for the development of microbial-based strategies to improve plant resilience under drought conditions.

Keywords: PGPR; S.miltiorrhiza; drought stress; plant resistance; plant-microorganism interaction.

Figure 1

Phylogenetic trees of tested and treated bacterial strains annotated at the species level. CK was the blank group and D was the drought treatment. (A) The phylogenetic tree of all tested strains; (B) The heatmap of the relative abundance of bacterial species under drought stress.

Figure 2

Changes of biomass and photosynthetic parameters of S. miltiorrhiza under drought stress. CK and B-CK were respectively the uninoculated group and the inoculated blank group, while D and B-D were respectively the uninoculated group and the inoculated drought stress group. (A) The growth status of S. miltiorrhiza under stress for 15 days; (B) The state of S. miltiorrhiza at the time of sample collection; (C) The changes of physiological and biochemical indicators of S. miltiorrhiza under drought stress: (a) TW is the total fresh weight; (b) root: shoot ratio; (c) The content of chlorophyll; (d) Net photosynthesis (μmolCO₂·m^-2·s ^-1); (e) stomatal conductance (mmolH₂O·m^-2·s^-1); (f) Transpiration rate (mmolH₂O·m^-2·s^-2); (g) Intercellular CO₂ concentration (μmolCO₂·mol^-1). Different lowercase letters indicate significant differences (p<0.05).

Figure 3

Changes of nitrogen, phosphorus and potassium in S. miltiorrhiza leaves under drought stress. CK and B-CK were respectively the uninoculated group and the inoculated blank group, while D and B-D were respectively the uninoculated group and the inoculated drought stress group. (a) N content in the leaves; (b) P content in the leaves; (c) K content in the leaves. Different lowercase letters indicate significant differences (p<0.05).

Figure 4

Changes in the root morphology of S. miltiorrhiza under drought stress. CK and B-CK were respectively the uninoculated group and the inoculated blank group, while D and B-D were respectively the uninoculated group and the inoculated drought stress group. (a) root length (cm); (b) root surface area (cm²); (c) number of root tips; (d) root volume (cm³). Different lowercase letters indicate significant differences (p<0.05).

Figure 5

Changes at the family and genus levels of bacteria under drought stress. B-CK was the blank group and B-D was the drought treatment. (A) Changes in the relative abundance of bacteria at the family level; (B) Changes in the relative abundance of bacteria at the genus level.

Figure 6

Microbial co-occurrence networks under different treatments. (A) Microbial co-occurrence network in the CK group; (B) Microbial co-occurrence network in Group (D) The size of each node is proportional to the degree and is colored at the family level of the microorganisms.

Figure 7

Changes of microbial co-occurrence network topology index and microbial function under different treatments. (A) Microbial co-occurrence network topology indexes; (B) Changes in microbial function.