Legume Genomics and Genetics 2025, Vol.16, No.6, 279-287 http://cropscipublisher.com/index.php/lgg 280 The higher the density, the taller the stems will grow in order to compete for light, and the area of leaves or cotyledons may decrease (Henry et al., 2019). Although the individual quality of each plant may decrease, the overall yield may still increase because there are more plants in the field (Daşgan and Balik, 2025; Filho et al., 2025). However, if the competition is too intense, the chlorophyll in the leaves may decrease, the vitality of the seeds will also weaken, and finally affect the yield and quality (Zucareli et al., 2021). 2.2 Influence on canopy structure and microclimate Planting density directly affects the structure of the crop canopy, which in turn affects the microclimate in the field (Figure 1). Generally speaking, high density makes the canopy thicker, so that sunlight cannot easily reach the leaves below, relative humidity will increase, and the temperature and carbon dioxide concentration in the canopy will decrease (Wu et al., 2023). These changes will affect the photosynthetic efficiency of the plant, the degree of leaf cover, and the distribution of nutrients, which may affect the effect of grain filling and yield performance (Bobrecka-Jamro et al., 2023; Błaszczyk et al., 2024). Therefore, in order to make the crop grow healthily and have high yields, the density must be selected to ensure that light can penetrate, air can circulate, and the humidity is not too high. Figure 1 Effect of plant distribution on canopy light interception rate of soybean under different planting densities. (A-D), the canopy light interception rate under Np-Nu, Hp-Nu, Np-U, and Hp-U treatments, respectively. Np, normal seeding density. Hp, high seeding density. Nu, non-uniform plant distribution. U, uniform plant distribution. The change from dark blue to deep red indicates that the canopy light interception rate gradually increases. The number represents the value of canopy light interception rate on the contour line (Adopted from Xu et al., 2021) 2.3 Root development and its effect on nutrient uptake Seeding density also affects how the roots of plants grow. When the density is relatively high, the roots in the topsoil will be more numerous and denser, because the plants will grow more fine roots, which can more
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