Revisiting the Proliferated Seed Cones in Reveals a Growth Arrest Plasticity.

In angiosperms, such as , silique removal can reverse developmental arrest and reactivate inflorescence meristems, illustrating that post-fertilization growth cessation is a plastic process rather than terminal differentiation. However, it remains unclear whether a similar growth arrest plasticity occurs in conifers, where mature seed cones typically undergo terminal differentiation as determinate structures. In this study, we analyzed the proliferated seed cones of , which exhibited vegetative shoots sprouting from their central axes. We collected and examined both the proliferated and normal seed cones from a second-generation seed orchard. The proliferated seed cones were longer, produced more seeds, had a smaller seed scale spacing, and displayed enhanced secondary growth compared to normal seed cones. Our analysis suggested that the proliferated seed cones underwent a transition from reproductive to vegetative growth after seed production, indicating that proliferative arrest in these cones can be disrupted. Based on structural and developmental comparisons with , the proliferated seed cones exhibit unexpected plasticity: their growth arrest is reversible rather than terminal, similar to silique-removal-induced meristem reactivation in . This suggests that conifer cones retain the ability for delayed differentiation, not only offering new insights into conifer development but also a potential conifer model for studying reproductive-to-vegetative phase transition.