• For the first time, systematically revealed the sexual dimorphism characteristics of Kmeria septentrionalis , the only dioecious plant in the Magnoliaceae family. • Clarified the morphological differences between male and female plants of K.septentrionalis and the specificity of physiological indicators in different seasons. • A gender identification model based on multiple leaf indicators has been constructed, breaking through the traditional limitation of relying on flowering. Kmeria septentrionalis , the only dioecious species in the family Magnoliaceae, has natural populations scattered sporadically in localized areas of China, Thailand and Cambodia. As a multifunctional tree valued for landscaping, ornamentation, timber, and industrial uses, K. septentrionalis offers important scientific, economic, and ecological benefits. Recently, it has been introduced and cultivated as a valuable ornamental and timber tree in regions such as Guangxi and Guizhou, China. However, the absence of reliable sex identification technology has severely hindered its conservation and sustainable utilization. In this study, we systematically investigated sexual dimorphism in K. septentrionalis by integrating morphological and anatomical analyses with cross-seasonal dynamic monitoring of physiological and biochemical traits. The results showed that the leaf length of female plants was significantly smaller than that of males ( P < 0.05, the same below), and the ratio of leaf length to width was even more significantly smaller than that of males ( P < 0.01, the same below). In contrast, the leaf width at 1 cm and 3 cm from the leaf base was significantly larger than that of males. Leaf thickness, lower epidermis thickness, palisade tissue thickness, and the palisade-spongy tissue ratio were significantly greater than those of males, whereas upper epidermis thickness was significantly smaller than that of males. The pith on the transverse section of branches was narrower and more compact than that of males, and the xylem was wider than that of males. Marked differences were also observed in reproductive organ differentiation: female flower buds were gradually pointed and smaller in size, with 8–10 linear lanceolate inner perianth segments; male flower buds were sharp, with oval inner perianth segments, and the stamens were separated by a 2–3 mm tongue-shaped tip. Physiological indicators exhibited clear seasonal specificity. The SOD activity of female plants was extremely significantly lower than that of males in spring. Sexual differences in POD activity showed pronounced seasonal variation, with female plants exhibiting significantly lower POD activity than males in spring, extremely significantly lower activity in autumn, but significantly higher activity in winter. PPO activity in female plants was significantly higher than that of males only in midsummer. For nutrient indicators, soluble sugar content in female plants was significantly higher than in males in spring and autumn, but significantly lower in early summer, whereas soluble protein content in female plants was extremely significantly lower than in males in winter. In this study, an innovative sex identification model was established by integrating leaf morphological and anatomical characteristics, supplemented by flower bud traits and key seasonal physiological indicators. This model overcomes the limitations of traditional identification methods that rely on flowering periods and provides a practical strategy for conservation and sex-directed breeding of this endangered species.
Ma et al. (Sun,) studied this question.