Plant Gene and Trait 2025, Vol.16, No.4, 162-172 http://genbreedpublisher.com/index.php/pgt 162 Feature Review Open Access Regulation of Light Environment and Growth Response of Understory Crops in Mulberry-Based Vertical Systems Kaiwen Liang Agri-Products Application Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, Hainan, China Corresponding email: kaiwen.liang@hitar.com Plant Gene and Trait, 2025, Vol.16, No.4 doi: 10.5376/pgt.2025.16.0018 Received: 03 Jul., 2025 Accepted: 10 Aug., 2025 Published: 19 Aug., 2025 Copyright © 2025 Liang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liang K.W., 2025, Regulation of light environment and growth response of understory crops in mulberry-based vertical systems, Plant Gene and Trait, 16(4): 162-172 (doi: 10.5376/pgt.2025.16.0018) Abstract This study collates relevant research on the impact of light regulation on the growth of understory crops in mulberry three-dimensional planting systems. Starting from aspects such as the structural design of mulberry planting and the changing characteristics of light distribution, it examines how understory crops adapt to different light conditions and summarizes some key factors affecting the shade tolerance of crops. Several simple and effective methods to improve the lighting environment under the forest are introduced, such as appropriate pruning of mulberry trees, adjusting the planting orientation, and laying reflective films. The example of “intercropping mulberry trees and soybeans” is also used to illustrate that by improving the lighting conditions, not only can the yield of soybeans be increased, but also their quality can be enhanced. This study aims to provide some theoretical and practical operation suggestions for the efficient planting of lower layer crops in the three-dimensional mulberry planting system. Keywords Mulberry-based vertical planting; Understory crops; Light environment regulation; Shade response; Resource use efficiency 1 Introduction The agroforestry system is a planting method that groups different plant species together and arranges them in layers. This can make better use of the land and also enhance ecological benefits. Mulberry (Morus spp.) are often selected as upper-layer tree species due to their strong adaptability and high economic value. Its leaves can be used to feed silkworms and can also be grown together with many crops to increase the output rate and resource utilization rate of each plot (Chanotra et al., 2024). In recent years, mulberry has also begun to appear in vertical agriculture and controlled environment planting systems, and are regarded as a good idea for developing sustainable agriculture (Baciu et al., 2023). However, under the shade of tall crops like mulberry, the crops planted below often do not receive enough sunlight. The shape of the canopy and the seasonal variation of mulberry leaves can directly affect the light conditions under the canopy, which may limit the growth and yield of crops (De Pauw et al., 2021; Kara, 2022). Studies have found that the intensity and variation of light under the forest can affect the growth rate, photosynthetic efficiency and nutrient absorption capacity of crops (Baligar et al., 2020; Modolo et al., 2021; Xu et al., 2023). Therefore, how to adjust the canopy structure or adopt a more reasonable planting method to improve the light conditions below is a key issue that needs to be solved in current three-dimensional planting (Su et al., 2023). This study reviews the research progress on how to regulate light in the three-dimensional planting system of mulberry and what impact this has on the crops under the forest. We also analyzed the physiological and ecological responses of undergrowth crops under different lighting conditions. This study hopes that these contents can provide some theoretical references and practical suggestions for the design and management of mulberry planting systems. 2 Characteristics of Mulberry-Based Vertical Planting Systems 2.1 Structural configurations of mulberry-based systems Several common layout methods are often used in the three-dimensional planting system of mulberry, such as pit type, row type and double-row type. The pit type (90×90 cm) is generally used for growing one-year-old mulberry
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