Field Crop 2025, Vol.8, No.6, 265-273 http://cropscipublisher.com/index.php/fc 266 lodging under dense planting conditions, assess the latest progress in enhancing lodging resistance breeding and management practices, and explore its significance for sustainable yield increase and large-scale mechanized production. By integrating existing knowledge and highlighting practical strategies, this study aims to provide references for breeding programs and field management, and promote the development of high-yield and lodging resistant maize systems. 2 Genetic and Physiological Basis of Lodging Resistance in Maize 2.1 Stem strength and the development mechanism of mechanical tissue Not all corn lodging problems lie in the roots; the strength of the stems is often the key. Physical indicators such as stem diameter, bending resistance, and cortical puncture resistance are basically inversely proportional to the lodging rate (Manga-Robles et al., 2021). However, when it comes to what can enhance these strengths, the core lies in the development of mechanical tissues, such as the condition of thick-walled tissues and vascular bundles. Especially the thickness of the cell wall, the amount of cellulose content, the arrangement structure of the cell wall, etc., will all affect whether the stem has a "waist" or not. The lower internodes are a key area. If the lignin accumulates insufficiently here, the stem bark's resistance to penetration will be poor, and problems are more likely to occur in stronger winds (Li et al., 2022). Nowadays, many breeding and management techniques are targeting this point, with the aim of rapidly depositing dry matter and synthesizing more lignin in the internodes at the base, making the stems more "tough". 2.2 Influence of root architecture and rooting depth on lodging resistance Ultimately, whether corn can stand steadily or not, its roots also account for half of the sky. Especially in a densely planted environment, if the roots are not firm, it will be troublesome if they fall over during wind and rain (Zheng et al., 2023). Some traits stand out in this regard, such as a wide enough root crown, a large root Angle, thick pillar roots, and deep roots. All these help the roots to better "grasp the ground". Some studies have specifically evaluated the stability of roots by the ratio of superweight to vertical tensile strength (Xue et al., 2020). However, it is not the case that being thick and strong is necessarily good. Some detailed traits, such as root hair density and the distribution hierarchy of roots, also have an impact on lodging resistance, and these characteristics cannot be easily observed with the naked eye. Now that the planting density has increased, it is even more necessary to consider how to adjust the structure of the roots, such as strengthening the embryo roots and increasing the dry matter in the underground part. Only in this way can the plants be stabilized without affecting nutrient absorption (Zhang et al., 2023). 2.3 Advances in the identification of key lodging-resistance genes and QTLs Research has been conducted for many years, and many QTLS and candidate genes related to lodging resistance have been located (Sun et al., 2020). On the stem side, it is mainly the mechanism of cell wall biosynthesis at work, such as genes involving membrane steroid-binding proteins, pectin methylesterase, and cell cycle regulation, which all have regulatory effects on how cells grow and divide (Yang et al., 2024). In terms of roots, the sites that regulate the number of root nodes, root angles and support root development have also been identified. Quite a few genes have "part-time" roles both above and below ground, that is, they are pleiotropy. However, the genetic structure of these traits is complex, with many superior interactions, and they are quite sensitive to the environment. Ultimately, integrating those alleles that are conducive to strong stems and stable roots is still the most direct breeding breakthrough to achieve lodging resistance under close planting conditions. 3 Effects of High-Density Planting on Maize Physiological and Ecological Traits 3.1 Changes in canopy structure and photosynthetic efficiency A closed canopy is not necessarily a bad thing. Once the planting density is increased, indicators like LAI naturally follow suit, the interception of photosynthetically active radiation (PAR) also increases, and the overall biomass of the population increases (Figure 1) (Tian et al., 2022). However, the lower leaves were not so lucky. The shading problem was obvious. Light couldn't penetrate and the photosynthetic efficiency dropped sharply. Some modern breeding ideas are quite interesting, such as the "intelligent canopy" approach, where the upper leaves stand upright and the lower leaves spread flat, allowing light to penetrate more reasonably. The effect is
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