## 5 Role of Root Exudations in Rhizospheric Microbial Interactions
Fast-growing-stage exudates enhanced nutrient mineralization and microbial functional potential more than slow-stage exudates, suggesting plants actively modulate exudates to recruit beneficial microbes that meet their nutrient needs during rapid growth. The concentration of specific compounds, such as sugars and jasmonic acid, has been shown to significantly affect rhizosphere bacterial communities at various plant developmental stages of maize, with different sugars influencing community composition at different times [119]. Root exudates also facilitate microbial succession, where early colonizers modify the rhizosphere environment, paving the way for secondary colonizers with complementary functions [120]. The study in [120] reveals that _Avena barbata_ follows a developmental program of root exudation, releasing aromatic organic acids, like nicotinic, shikimic, salicylic, cinnamic, and indole-3-acetic, that selectively recruit microbes with matching substrate preferences. This chemically driven interaction guides predictable microbial community assembly, highlighting a plant-regulated mechanism to shape beneficial rhizosphere microbiomes for enhanced fitness. Moreover, through plant-microbe feedback loops systematically alter root exudation patterns through mechanisms such as Systemically Induced Root Exudation of Metabolites (SIREM), where local microbial colonization triggers changes in exudate composition elsewhere in the root system, further influencing microbial assembly and soil conditioning [101]. Understanding how root exudates influence microbial assembly and function is crucial for developing strategies to enhance plant health and productivity, such as breeding/engineering crops with optimized exudate profiles or manipulating exudate chemistry to promote beneficial microbial consortia and suppress disease. Chemoattraction is a fundamental mechanism by which root exudates shape rhizosphere microbial communities, as many beneficial microbes use chemotaxis to move toward specific root-derived compounds such as sugars, organic acids, amino acids, and nucleosides, enabling efficient colonization and the establishment of mutualistic interactions [121; 122; 123; 124]. For instance, nucleosides in root exudates have been shown to induce strong chemotactic responses in both beneficial bacteria like _Bacillus_ and _Pseudomonas_ and certain pathogens, highlighting the double edge of chemoattraction in recruiting both helpful and harmful microbes [121]. The specific composition of root exudates, which varies among plant species and even within different root regions, acts as a selective force, guiding the assembly and spatial distribution of microbial communities in the rhizosphere [125; 120]. Key attractants such as arginine and other amino acids can be particularly important in establishing microbial community structure, as demonstrated in _Casuarina equisietifolia_, where arginine attracted beneficial strains that closely resembled the natural forest community [122]. Advanced experimental approaches, such as the real-time monitoring of chemotaxis and high-throughput sequencing, have revealed that the interplay between chemoattraction, microbial colonization, and plant signaling is central to the dynamic assembly and function of rhizospheric microbial communities, ultimately impacting plant health and ecosystem stability [114; 126].