International Journal of Horticulture, 2025, Vol.15, No.4, 162-170 http://hortherbpublisher.com/index.php/ijh 166 Figure 2 A and B - Hylocereus undatus and H. polyrhizus flowers respectively. C and D - Dissected flowers of pitaya H. polyrhizus showing bracts and reproductive parts. E - Stigma disposition just above stamens. F and G- Dissected flowers showing the arrangement, size and color of the bracts. H and I - Young fruit and fully-developed fruit of H. undatus respectively (Adopted from Muniz et al., 2019) 5.3 Pollen structure and fertility The structural characteristics of pitaya pollen can ensure the fertility and reproduction of the flowers. pitaya pollen can easily stick to the bodies of pollinating insects and effectively reach other flowers. It is crucial that such structures exist in species like H. polyrhizus. These plants rely on insect pollination and fruiting and can effectively cross-pollinate (Muniz et al., 2019). The fertility analysis of pitaya pollen indicates that H. undatus lacks biological pollination and can spontaneously bear fruit, while H. polyrhizus has limited self-pollination ability. To achieve a high fruit setting rate and form high-quality fruits, it depends on the activities of pollinators, such as Apis mellifera. The optimization of pollen structure for its adhesion and vitality is also an important factor affecting fruit yield and quality (Muniz et al., 2019). 6 Floral Scent Biosynthesis and Regulation 6.1 Main scent compounds pitaya flowers mainly produce a special odor called volatile organic compounds (VOCs). These volatile organic compounds help attract pollinating insects and animals, especially at night. pitaya flowers usually release their strongest scent at night, which matches the active time of night pollinators. In Petunia hybrida, there are the same characteristics as pitaya flowers. The release of volatile compounds follows a circadian rhythm pattern and emits a strong odor at night to attract pollinators (Patrick et al., 2023). In Pitaya flower, the main volatile organic compounds include benzene compounds and phenylpropanoid compounds, which are the products of floral volatile benzene/phenylpropane (FVBP) metabolic pathway. These compounds come from a special metabolic pathway called FVBP in flowers. Odor compounds attract pollinators, helping plants reproduce successfully and increase the pollination rate (Fenske et al., 2015).
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