Effects of gender and developmental stages on carbohydrate allocation in leaves of Fraxinus velutina

To explore the differential mechanisms of carbohydrates in dioecious plants, this study took Fraxinus velutina as the research object. It aimed to analyze the differences in carbohydrate allocation patterns between male and female plants at different developmental stages, thereby providing a scientific basis for the regulation of carbon metabolism in sexually dimorphic plants and the management of urban forests.

Specimens were gathered during the fruiting phase (S1), fruit expansion period (S2), and fruit ripening stage (S3). Branches in the upper southern section of the trees were tested to determine the levels of non-structural and structural carbohydrates.

Growth stages and their combined effect with gender notably affect structural carbohydrates and some non-structural carbohydrates (P<0.05). In both genders of F. velutina, leaf cellulose content first increases and then decreases, with females showing significantly lower levels than males at S1. Lignin content declines steadily, and females have lower levels in all stages, with a marked difference at S2 (P<0.05). Regarding non-structural carbohydrates: female starch content drops dramatically from S1 to S2 and is significantly lower than that of males at S2 (P<0.05); fructose content first decreases and then increases, with females were significantly lower at S2; sucrose content follows a similar trend, with females showing significantly lower levels at S2 (P<0.05). Correlation analysis indicates that in females, cellulose is mostly negatively associated with non-structural carbohydrates (such as starch and soluble sugars), while in males, starch is mostly positively associated with soluble sugars and their components. This reflects gender-specific coordination in carbon metabolism and trade-off strategies in carbon allocation.

Owing to distinct life history strategies, male and female F. velutina exhibit differences in carbohydrate allocation during development: males retain higher levels of structural carbohydrates in leaves, relying on the advantages of cellulose and lignin to support vegetative growth; females display more adaptable mobilization of non-structural carbohydrates, adjusting starch and soluble sugars dynamically to meet reproductive needs.