Acetic acid modulates rhizosphere microbial communities to improve temperature stress resistance in dioecious Salix myrtillacea

Dioecious plants show sexual dimorphism in responses to abiotic stresses. However, the effects of temperature stresses on the growth of female and male plants, as well as on their rhizospheric microbiomes, along with the mechanisms through which exogenous acetic acid (AA) application alleviates stress, remain unclear. Our study aimed to investigate the impact of high temperature and low temperature stresses on the growth, physiological traits, and rhizosphere microbial communities of dioecious Salix myrtillacea. We also explored how AA application mitigate stresses. Female willows demonstrated greater resistance to both high and low temperature stresses when compared with males, as evident in plant growth (phenotype, leaf anatomy and photosynthesis), and leaf physiology (antioxidant enzyme activity, hormone accumulation, and nutrient uptake). Furthermore, the addition of AA had a significant alleviating effect on stress in both sexes. Compared with high temperatures, plants showed better adaptation to low temperatures, as the stress intensity significantly decreased. Sex-specific differences were also observed in the composition of rhizosphere microbial communities. Particularly, with the application of AA, the relative abundance of microorganisms at phylum level (eg. Bacteroidetes, Chloroflexi and Acidobacteria) changed to support carbon uptake and storage and enhance stress tolerance in females. In contrast, males exhibited a strongly association with fungi to maintain stability. This study provides novel insights into how plant physiological plasticity and soil microbial interactions mediate sex-specific responses to temperature stresses. Additionally, it highlights that AA application can enhance temperature tolerance.

雌雄异株植物（dioecious plants）在非生物胁迫（abiotic stresses）响应中存在性别二态性。然而，温度胁迫对雌雄株生长及其根际微生物组（rhizospheric microbiomes）的影响，以及外源乙酸（acetic acid, AA）缓解胁迫的具体机制，目前仍不明确。本研究以雌雄异株的越橘柳（Salix myrtillacea）为研究对象，探究高低温胁迫对其生长、生理特性及根际微生物群落的影响，并解析外源乙酸施加对胁迫的缓解作用机制。与雄株相比，雌株对高低温胁迫均表现出更强的抗性，该抗性可通过植株生长（表型、叶片解剖结构与光合能力）及叶片生理指标（抗氧化酶活性、激素积累与养分吸收）得到印证。此外，施加外源乙酸对两个性别的植株均具有显著的胁迫缓解效果。相较于高温胁迫，植株对低温胁迫的适应性更佳，这是因为低温胁迫的强度显著更低。根际微生物群落的组成同样存在性别特异性差异。尤为关键的是，施加外源乙酸后，雌株根际微生物的门水平相对丰度（例如拟杆菌门（Bacteroidetes）、绿弯菌门（Chloroflexi）与酸杆菌门（Acidobacteria））发生适应性改变，以促进碳吸收与储存并增强雌株的胁迫耐受性。与之相反，雄株则与真菌形成紧密关联，以此维持根际微生物群落的稳定性。本研究揭示了植物生理可塑性与土壤微生物互作如何介导植株对温度胁迫的性别特异性响应，为该领域提供了全新的研究视角；同时证实外源乙酸施加可有效提升植株的温度胁迫耐受性。