The second revision for Plant Growth Regulation (GROW-D-23-00091) sex-specific resource allocation in juvenile and adult salix myrtillacea

Key messageSex-specific trade-offs in resource allocation exist in juvenile and adult trees, which are likely regulated by phytohormones. Dioecious plants are ideal models for studying resource allocation. In Salicaceae, most previous studies have focused on juvenile trees, but it is questionable whether these results can be extrapolated to adult trees. In this study, we used juvenile cuttings and adult male and female willows to investigate changes in non-structural carbohydrates, secondary metabolites, amino acids, antioxidant enzymes and phytohormones over the growing season. We illustrated the differences in resource allocation between young cuttings and adult trees of each sex and the mechanisms involved. During vegetative growth, sucrose is transported from the leaves to the roots. Adult willows have reserved the allocation to starch and secondary leaf metabolites and are more resilient than young seedlings. Root starch and other nonstructural carbohydrates were consumed in adult females, but accumulated in adult males. The degradation of starch and carbon-containing secondary metabolites was enhanced in adult female willows, ensuring an adequate carbon supply for the rapid growth period after flowering. These sex differences were responsible for differential resource allocation and phytohormone regulation. These results suggest the occurrence of sex-specific trade-offs in resource allocation in juvenile and adult trees that are likely regulated by phytohormones. Therefore, future studies on sexual dimorphism should be carried out on adult trees and not only on juvenile cuttings.

Automated summary

This study investigated the differences in resource allocation between juvenile cuttings and adult trees of each sex in Salicaceae. Results showed that adult willows reserved the allocation to starch and secondary leaf metabolites, making them more resilient than young seedlings. Sex-specific differences in resource allocation and phytohormone regulation were observed, suggesting the occurrence of trade-offs in resource allocation in trees.