Plant Gene and Trait 2025, Vol.16, No.4, 162-172 http://genbreedpublisher.com/index.php/pgt 166 5.3 Screening and breeding of shade-compatible cultivars To ensure that the under-forest crops in the mulber-based three-dimensional planting system grow better, it is crucial to select and breed varieties suitable for shady environments. Studies have found that different crop varieties perform differently under different shading conditions. For example, cocoa and some coniferous trees have significant differences in physiological responses when the light is different (Ávila-Lovera et al., 2020; Schmiege et al., 2020; García-Pérez et al., 2021). Nowadays, molecular biology and genetics studies have also identified many genes and pathways related to shade tolerance, providing a basis for future molecular breeding (Martinez-Garcia and Rodriguez‐Concepcion, 2023). In addition, the use of quantitative indicators such as "low light abundance index" can more accurately select varieties suitable for weak light (Feng et al., 2018). 6 Regulation of the Light Environment for Optimized Growth 6.1 Pruning and canopy management of mulberry The canopy of a mulberry can affect whether the crops beneath it can be exposed to sunlight. Pruning, rotation and shaping can help us control the tree canopy, allowing more sunlight to reach the understory of the forest and enhancing the photosynthesis and growth of crops. For instance, rotational cutting, top pruning or cutting off some branches can not only reduce soil erosion and improve the soil, but also open the tree canopy, allowing sunlight to penetrate more easily, resulting in better crop growth and increased yield and quality (Kaushal et al., 2024). In some places, mixed forests or multi-layer planting systems are used. Under such structures, sunlight varies greatly, especially during seasonal changes. Regular pruning is very useful as it can increase light gaps and help the crops below grow better (Kara, 2022). 6.2 Use of reflective materials and row orientation In addition to pruning, we can also use some simple tools to enhance sunlight, such as laying reflective film, white ground film, etc. These things can reflect sunlight to the understory of the forest, especially scattered light, which enables the lower leaves to absorb more light and enhance photosynthesis. In addition, when planting mulberry, if the rows face north and south, the sunlight will be more evenly distributed and it is less likely that there will be too much shadow covering the crops below. Studies have found that using LED for supplementary lighting, adjusting the intensity or color of the light (such as supplementing blue or white light) can also make undergrowth crops grow better and accumulate more nutrients (Win et al., 2022; Paponov, 2025). 6.3 Controlled intercropping and spacing adjustments The planting layout is also very important. By changing the types, densities or arrangements of intercropping crops, they can be made to compete for less light and cooperate more. For instance, when mulberry is planted together with turmeric and vegetables, if the row spacing and plant spacing are designed reasonably, sunlight can be distributed better, the yield and quality of under-forest crops can be improved, and the land can be used more efficiently (Kaushal et al., 2024). Moreover, different planting methods, such as pit planting, single-row planting, and double-row planting, will cause the crops below to receive different amounts of light. The appropriate approach should be selected based on the actual situation (Chanotra et al., 2024). 7 Interactions Between Light, Microclimate, and Soil Factors 7.1 Light-mediated effects on temperature and humidity In vertical planting systems, light not only has a direct effect on the photosynthesis of crops but also indirectly affects their growth conditions. For instance, after the lights are turned on, the LED lights will make the surrounding area warmer, which will change the air humidity and also accelerate the evaporation rate of soil moisture (Kamenchuk et al., 2023). Moreover, different combinations of light intensity and spectra can also cause changes in temperature and humidity. Therefore, when designing vertical systems, one cannot only consider whether the light intensity is strong or not, but also find ways to make the microclimate suitable for crop growth. 7.2 Effects on soil moisture retention and microbial activity In mulber-based composite systems, soil moisture can be maintained, rainwater erosion can be reduced, soil loss can be decreased, and the organic carbon and moisture content in the soil can also be increased by managing the tree canopy and reasonable intercropping (Kaushal et al., 2024). If planting is reasonable and fertilization is
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