**3. Plant microbiome**

Plant microbial groups include microbial communities that generally interact with plants. They can survive within or outside plant tissues and carry out various beneficial activities, including inhibiting potential plant pathogens and promoting plant growth. Plant microflora mainly includes rhizosphere microbial community, leaf microbial community, and endogenous microbial community. The microbial community composition of different flora is complex, and its diversity, preference, and abundance are affected by host plants and environment, which is the medium of plant-soil-atmosphere interaction. They communicate material and energy through plant body and have formed a highly close symbiotic relationship in the long-term co-evolution [26]. During plant growth, microorganisms are actively recruited from the surrounding microbial pool. In soil, plant roots provide a unique niche for soil microbial communities in addition to fixing plants and as organs for absorbing water and nutrients, attracting various microbial communities to distribute in rhizosphere, root, and to a certain extent above ground parts [27].

Rhizosphere microbial communities can promote plant phenotypic plasticity, such as the flowering time of plants may be affected by them. Studies have found a molecular interaction network linking nitrogen cycle, tryptophan (Trp) synthesis of plant hormone IAA and flowering time, which is of great significance to the study of plant phenotype in climate change and the improvement of crop yield [28].

Endophytes and above-ground microbial communities are known for their potential to promote plant growth, improve disease resistance, and alleviate stress tolerance. Endophytes include fungi and bacteria, archaea, and the rarely explored viral world, among which there are abundant studies on endophytic fungi and their metabolites.
