Molecular Soil Biology 2025, Vol.16, No.6, 297-305 http://bioscipublisher.com/index.php/msb 298 includes primary roots (also called seminal roots), adventitious roots such as crown roots and brace roots, and many lateral roots. This root structure is different from that of typical taproot crops. Even so, maize still depends on both axial roots and a large number of lateral roots to take up water and nutrients from both deep and shallow soil layers (Hochholdinger et al., 2018; Jiang and Whalen, 2025). The root system architecture (RSA) of maize is affected by time and planting density. When maize is planted at high density in the field, the total root biomass usually becomes smaller as density increases. However, the length of axial roots does not change much. Maize adapts to this situation by reducing the number of root nodes and limiting the length and density of lateral roots. In this way, roots grow less within the row but spread more between rows (Shao et al., 2018). In most cases, the highest root length density is found in the topsoil layer, mainly within 0~36 cm. When soil nutrients or water are limited, or when fertilizers are placed deeper in the soil, maize roots can grow further downward. Under these conditions, roots may extend into soil layers deeper than 36 cm (Chen et al., 2022; Zhang et al., 2023). 2.2 Key root traits influencing nutrient uptake Under low nitrogen and salt stress, root traits change in obvious ways. When roots become longer and the total root surface area increases, shoots usually grow better. Aboveground biomass often goes up, and root and stem mass increase at the same time. These changes are closely linked to each other. However, thicker roots do not always mean better performance. When the average root diameter increases, specific root length often drops. This suggests that plants may be changing how they get nutrients, rather than simply trying to absorb more (Guo et al., 2025; Jiang and Whalen, 2025; Keerthi et al., 2025). Root hairs are especially important for phosphorus uptake, because phosphorus moves very slowly in soil. In field experiments, plants without root hairs absorbed much less P and K than normal plants. Their aboveground growth was also clearly weaker, especially in soils with high adsorption. Simply increasing root length could not fully solve this problem (Lippold et al., 2022; Vetterlein et al., 2022). Lateral roots also matter for nutrient use. When plants have more lateral roots or longer lateral roots, they can better explore small nutrient-rich areas in the soil. This includes local high-P zones or areas around soil aggregates, which helps improve nutrient use efficiency (Zhang et al., 2023). 2.3 Interactions between root architecture and soil nutrient availability Root morphology is influenced by various environmental conditions, such as gravity, soil compaction, water content, soil texture, aeration, and nutrient supply levels. When the supply of nitrogen and phosphorus is insufficient, crops usually adjust their root system structure. A common change is an increase in the "ratio of root length to aboveground biomass" (Lopez et al., 2023). In the comparative experiments of sandy soil and loam soil, the influence of soil texture on root traits was significant, especially in terms of root hair quantity and root diameter (Vetterlein et al., 2022). When large aggregates of loam are distributed in sandy soil, local areas often have both high nutrient content and greater soil resistance simultaneously. The root system of corn does not enter the interior of the aggregates in large quantities, but rather grows more along the surface of the aggregates. The root system significantly increased root length density and the number of branches at these positions. The application of nitrogen and phosphorus fertilizers at different depths will form band-shaped regions with high contents of NO3 - and available phosphorus within the soil layer of 16~32 cm, which will stimulate root growth and increase the expression levels of genes related to nitrogen and phosphorus absorption and transport (Chen et al., 2022; Zhang et al., 2023). 3. Mechanisms of Root Architecture Modifications for Enhanced Nutrient Uptake 3.1 Genetic approaches to modifying root architecture After conducting an integrated analysis of 917 QTLS, 68 root meta-Qtls were identified. Thirty-six results are consistent with the markers reported in previous GWAS studies. Traits such as root length, root Angle, root volume and root enzyme activity are not controlled by a single gene (Karnatam et al., 2023). Wang et al. (2021) conducted a GWAS analysis on the Angle, diameter and quantity of coronal roots, identified 38 QTLS and predicted 113 candidate genes. The AUX/IAA gene, heat shock protein and genes related to cytokinin are all involved in the development process of the coronal root. Li et al. (2024a) conducted GWAS and linkage analyses on 14 traits and identified hundreds of QTLS. Genes related to hormone signaling pathways such as IAA26, ARF2,
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