Research progress in in situ visualization of biochemical processes at rhizosphere microhabitat

Material exchange and energy flow are active in the rhizosphere and the adjacent area within several millimeters. The cycling of critical biogenic elements, including carbon, oxygen, and mineral elements in terrestrial ecosystems, predominantly occurs within this rhizosphere microhabitat. Visualizing the dynamic processes in the rhizosphere microhabitat can facilitate the capture and quantification of the process and function of material migration and transformation. Over the past few decades, two-dimensional imaging techniques have been developed for realizing in situ visualization. This article provides a systematic overview of the latest methods and research advancements in in situ visualization of rhizosphere chemicals, microbial environments, and metabolites, with an emphasis on the application prospects of multi-parameter imaging technology in studying the rhizosphere process. The future development direction and unsolved issues of in situ visualization of biochemical processes at rhizosphere microhabitat are also discussed. For more practical use of in situ visualization technology of rhizosphere in the researches of biochemical processes and mechanisms within microhabitats, researches should target on: 1) developing straightforward, time-efficient, and cost-effective visualization technologies and performing compatibility assessments for multi-parameter and multi-method integration; 2) advancing three-dimensional and four-dimensional visualization techniques for the rhizosphere, encompassing sample preparation and data synthesis, to investigate the spatio-temporal dynamics of the rhizosphere microhabitats; 3) creating portable instrumentation to facilitate the field application of rhizosphere in situ visualization technology.