Plant Gene and Trait 2025, Vol.16, No.5, 234-241 http://genbreedpublisher.com/index.php/pgt 236 3.3 Flowering dynamics, sex ratio, and fruit set characteristics Flowering time, the ratio of male to female flowers and fruit setting rate are the key reproductive traits that affect yield. The groups with early flowering, high proportion of female flowers and high fruit setting rate tend to have higher yield per plant (Moharana et al., 2022; Srinivasulu and Singh, 2024). QTL mapping and genetic analysis indicated that female flower nodes, the number of male and female flowers, and fruit setting were closely related to yield and controlled by multiple genes (Rao et al., 2021; Kaur et al., 2022). High-density planting combined with drip irrigation helps regulate the flowering rhythm and increase the fruit setting rate, thereby enhancing the total yield (Alhariri et al., 2021). 4 Influence of High-Density Planting on Morphology 4.1 Changes in plant height, internode length, and leaf arrangement Under high-density planting conditions, bitter gourd plants will show obvious morphological changes. As the density increases, the competition among plants intensifies, their height will rise, and the internodes will become longer. This is to compete for more light resources. The leaves will be arranged more densely, and some leaves will overlap, thereby reducing the light-receiving area of a single leaf and lowering the photosynthetic efficiency (Seong et al., 2015). These changes are the adaptive responses of bitter gourd under limited light and space conditions. 4.2 Canopy closure effects on light penetration and air circulation High density will cause the canopy of bitter gourd to close more quickly, and the light inside the canopy will be significantly reduced. Studies have found that under high-density conditions, the light intensity at the bottom of the canopy decreases significantly, and the net photosynthetic rate of leaves drops by 41% to 71%, affecting the photosynthesis of lower leaves (Seong et al., 2015). The closure of the canopy will also reduce air circulation and increase humidity, thereby raising the risk of diseases. Therefore, appropriately pruning low and weak branches can improve the ventilation of the canopy and the distribution of light. 4.3 Morphological adaptations to inter-plant competition In high-density environments, bitter gourds will adopt various morphological adaptation strategies to cope with competition. The plants will exhibit characteristics such as longer main vines, fewer lateral vines, and reduced root weight in order to prioritize growth and obtain light and nutrients (Seong et al., 2015). At the same time, the leaf area index will increase, with more leaves concentrated at the top to better utilize the light from the top. Moderate dense planting combined with reasonable pruning can not only increase the yield per unit area, but also improve the commercial fruit rate. 5 Influence of Drip Irrigation on Morphology 5.1 Effects on root architecture and distribution Drip irrigation can provide precise water supply, keep the moisture in the soil of the root zone evenly distributed, help the root system of bitter gourd expand to the surface and middle layers, and enhance the water and nutrient absorption capacity (Mali et al., 2017). Compared with traditional irrigation, drip irrigation reduces deep water seepage and surface evaporation. The root system will be concentrated in the water and fertilizer supply area, making it easier to efficiently utilize nutrients and water (Turkar and Deshmukh, 2018). If combined with bio-organic fertilizer or biostimulants, the root morphology and rhizosphere environment can be further improved (Wang et al., 2024). 5.2 Influence on vine vigor, leaf turgidity, and fruit development Drip irrigation can significantly increase the vine length, branch number and dry matter accumulation of leaves of bitter gourd, making the plants grow more vigorously (Bahadur et al., 2021). When there is sufficient and uniform moisture, the turgor pressure of leaves is better, the photosynthetic efficiency is higher, the leaves will be thicker, and the chlorophyll content will also increase (Dolatmand-Shahri et al., 2024). In terms of fruit growth, drip irrigation can promote fruit enlargement, increase weight and uniformity, thereby improving the commercial fruit rate and total yield (Samad, 2018). High-frequency and moderate drip irrigation combined with reasonable fertilization can also enable fruits to ripen earlier and achieve high yields.
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