Molecular Pathogens, 2025, Vol.16, No.5, 217-225 http://microbescipublisher.com/index.php/mp 218 2 Wheat Root System Structure and Functional Characteristics 2.1 Morphological structure and development characteristics of root system The wheat root system is a typical fibrous root system, composed of primary roots and secondary roots, showing a highly branched network structure. After seed germination, radicles are first produced, and then a large number of crown roots (adventitious roots) are formed at the tiller nodes of wheat seedlings, allowing the root system to continuously expand vertically and horizontally into the soil (Figure 1) (Li et al., 2021; Wang et al., 2023). The development of wheat root system has stage characteristics: in the seedling stage, the root system is mainly formed, and in the tillering stage, the root system enters a rapid growth period, continuously increasing root length and branch number, laying the foundation for absorbing water and mineral nutrients; from heading to filling stage, root activity gradually decreases, and some old roots become lignified and functionally decline (Paz-Vidal et al., 2023). The dense root hairs of wheat roots effectively expand the rhizosphere interface and accelerate the uptake of water and nutrients. The mucus continuously secreted by the root cap and root apical meristems and the shed root edge cells also attract and regulate rhizosphere microorganisms. Figure 1 TabHLH123 is a nuclear-localized transactivator (Adopted from Wang et al., 2023) Image caption: (A) TabHLH123-GFP was transiently co-expressed with the nuclear marker H2B-mCherry in leaf cells of Nicotiana benthamiana. (B) Yeast two-hybrid assays showing transactivation activity of TabHLH123 (Adopted from Wang et al., 2023) 2.2 Chemical composition of root exudates There are a wide variety of wheat root secretions, including low-molecular substances such as sugars, organic acids, and amino acids, as well as secondary metabolites such as phenolic acids and flavonoids, and high-molecular substances such as mucilaginous substances and extracellular enzymes. Low-molecular root exudates can provide carbon sources and energy for rhizosphere microorganisms and promote the colonization of beneficial microorganisms; secondary metabolites have allelopathic and antibacterial effects and help regulate the balance of the microbial community; high-molecular slimes and enzymes improve rhizosphere soil structure and nutrient acquisition (Tsang et al., 2024). 2.3 Formation and regulation of rhizosphere microenvironment The rhizosphere is a soil micro-environment that is significantly affected by the root system and is significantly different from the surrounding soil. Wheat roots release carbon sources and signaling molecules through secretions and absorb water nutrients, forming a unique chemical gradient in the rhizosphere, such as increased carbon dioxide concentration, decreased oxygen, and pH changes (Iannucci et al., 2021). Root mucus keeps the rhizosphere moist, which is beneficial to the survival of microorganisms; microorganisms improve the nutrient status of the rhizosphere by decomposing organic matter, fixing nitrogen and decomposing phosphorus, etc. Wheat can regulate exudate composition and root hair development to shape a suitable rhizosphere microenvironment and maintain the balance of root-microbe interactions (Parunandi et al., 2023).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==