林木根际微生态过程与细根寿命调控机制研究进展

Review on micro-ecological processes in rhizosphere soils of trees and the modulation mechanisms of fine roots lifespan

细根在森林生态系统中具有重要的生物学和生态学地位。细根寿命取决于树种本身,也受控于环境条件。根际作为植物、土壤与微生物三者交互作用的区域,其中的微生态过程对细根寿命的调控具有决定意义。笔者基于当前国内外细根寿命调控的主要因素,分别从根际碳沉积与根际微生态过程、根系对根际微生物群落构建的影响、根际微生物对细根寿命调控的可能机制3个方面对根际微生物与根系的互作效应,及其对细根寿命调控机制的相关研究进展进行综述。在此基础上,提出了:①酚酸介导的植物-微生物化学对话机制是未来根土互作研究的重要领域;②根系与微生物互作主要以光合产物碳作为枢纽,根际碳沉积促进了土壤微生物在根际的定殖,进而导致根际的微生物群落在组成和结构上与非根际土壤的呈现显著差异;③根土互作过程中由根系和根际微生物产生的信号物质可能对根系的生长发育产生显著影响;④作为细菌的主要群感信号分子,酰化高丝氨酸内脂(AHLs)可参与调控根系细胞的凋亡;真菌侵染根系后也可能导致根内活性氧(ROS)累积,进而调控根系细胞凋亡。目前未见根际微生物参与根系寿命调控的研究报道。建议进一步构建细菌群落演变-群感信号表达-细根寿命关系模型,以及真菌侵染-活性氧信号内稳态调控-细根寿命关系模型,这些对深入揭示林木细根衰老和凋亡的微生态调控机制具有重要理论意义。

Fine roots play important roles in biological and ecological processes of the forest ecosystem.The lifespans of fine roots are controlled by tree species genetics and environmental factors.Rhizosphere serves as an interaction zone among plant,soil and microbes,in which the biological and ecological processes demonstrate decisive significances on root lifespans.Based on the dominant factors controlling root lifespans,this review focuses on three topics about the effects of plant roots and microbes interaction on root lifespans(i.e,the carbon rhizo-deposition and micro-ecological processes in rhizosphere,the effects of roots on microbial communities assembly in rhizosphere soils,the potential mechanisms of microbial communities modulating fine root lifespan).In the review,the chemical cross-talk between plant and microbes is considered to be very important in the future studies about the relationship between roots and soils.The photosynthetic carbon provides the connection between roots and soil microbes.The carbon accumulation in rhizosphere soils promotes the colonization of microbes around the roots,leading to the significant differences of microbial communities between rhizosphere and bulk soils.The signal substances from roots and microbes might affect root growth and development during the root-soil interaction.As the important quorum sensing signal among bacteria,Acyl-homoserine lactones(AHLs)could attend the modulation of root cell apoptosis.The reactive oxygen species(ROS)was observed to be accumulated in the roots after being infected by fungi,which also modulated the root cell apoptosis;however,the study about microbes attending the modulation of root lifespan is still not reported.Two models should be established in the future,one is about the relationships between bacterial communities succession,quorum sensing signals expression,and fine root longevity,another is about the relationships between fungal infection,ROS homeostasis modulation,and fine root longevity.The models would provide insights into the micro-ecological modulation mechanism of fine roots senescence and apoptosis in trees,and also be helpful to reveal the effects of root-soil interaction on fine root lifespans.