Plant Gene and Trait 2025, Vol.16, No.3, 123-132 http://genbreedpublisher.com/index.php/pgt 125 2.3 Role of pollinators and environmental influences Bees (such as Apis mellifera) and some wild sweat bees (Lasioglossum spp.) are the main pollinators of cucumbers. The more types and quantities of pollinators there are, the higher the yields of fruits and seeds will be (Lowenstein et al., 2015; Hall et al., 2022). Whether these pollinators frequently visit the flowers is influenced by “rewards” such as nectar and pollen as well as environmental conditions. If the ratio of nitrogen to phosphorus in the soil is inappropriate, fewer flowers will bloom, the rewards will be less, the attractiveness of pollinators will decline, and the yield will also decrease accordingly (Patch et al., 2022). In addition, pests such as cucumber beetles can interfere with pollination, reduce the stay time of bees, and thereby affect pollination efficiency and fruit quantity (Kaplan and Leach, 2024). Even in urban or greenhouse cultivation environments, wild bees and honeybees remain the main pollinators, while some thornless bees offer relatively limited assistance for cucumber pollination (Hall et al., 2022). 3 Plant Density Strategies in Cucumber Cultivation 3.1 Definitions and categories of planting density Planting density refers to the number of cucumber plants per square meter, which is an important factor affecting whether cucumbers grow well, have a high yield and good quality. Generally speaking, density can be classified into low density (such as 2.25 plants /m²), medium density (3.0 plants /m²) and high density (3.75 plants /m²) (Ayala-Tafoya et al., 2019; Ding et al., 2022; Babatunde et al., 2023) Under different planting methods, such as greenhouse, open-air, hydroponics or hydroponics, the selection of density should also be adjusted according to the characteristics of the variety (Ayala-Tafoya et al., 2019; Ding et al., 2022; Babatunde et al., 2023) 3.2 Effects on canopy architecture and microclimate Whether cucumbers are planted densely or not will directly affect the leaf structure and microclimate conditions of cucumbers. When the density is high, the competition among plants is fierce. The leaves grow densely and overlap a lot. Light cannot enter, and the lower leaves are not easy to carry out photosynthesis (Ayala-Tafoya et al., 2019). When the density is a little lower, sunlight can reach more evenly, leaves can absorb light better, and dry matter accumulates more (Ding et al., 2022). Planting too densely will also affect the temperature, humidity and carbon dioxide distribution in the greenhouse, thereby influencing the growth and yield of cucumbers (Shen and Tao, 2024; Guo et al., 2025). If the density is appropriate, not only will the ventilation be better, but also the occurrence of diseases can be reduced. 3.3 Impact on flower distribution and access to pollinators Planting density also affects the position of flowers and the activities of pollinators, such as bees. When the density is too high, the flowers are mostly concentrated in the upper layer and block each other, making it difficult for pollinating insects to find the flowers and the access efficiency will also decrease (Tscharntke et al., 2015). If the density is appropriately reduced, the flower distribution will be more uniform, the activity space of bees will be larger, the number of visits to flowers will increase, and the pollination efficiency and fruit setting rate can be improved. Studies have also found that the quantity and distribution of flowers directly affect the number and activity level of pollinating insects, ultimately influencing the yield and fruit commercialization rate of cucumbers (Tscharntke et al., 2015; Stein et al., 2020). 4 Vertical Trellis Systems: Structures and Agronomic Roles 4.1 Common trellis configurations in protected and open fields In cucumber cultivation, common vertical trellis methods include high rope type, umbrella type, modified umbrella type, inclined plane type, T type and inverted Y type, etc. These structures can be used in greenhouse and open-field cultivation (Berghage et al., 2024; Jamil et al., 2023). Among them, the high-rope system is the most common in greenhouse hydroponics. It not only facilitates the management of cucumber plants but also makes fruit picking convenient (Berghage et al., 2024). These trellis can not only support cucumbers to grow upwards, but also cooperate with the irrigation and fertilization systems to improve the overall planting efficiency (Jamil et al., 2023).
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