Relationship between the timing of vessel formation and leaf phenology in ten ring‐porous and diffuse‐porous deciduous tree species

Abstract The goal of this study is to clarify how different aspects of plant function are coordinated developmentally for species of ring‐porous versus diffuse‐porous deciduous trees, comparing the timing of leaf phenology and vessel formation in twigs and stems from an ecophysiological viewpoint. Cylindrical stem cores and twigs were collected at intervals from early spring through summer from five ring‐porous and five diffuse‐porous species in a cool temperate forest, and leaf and vessel formation were observed simultaneously. We found that the first‐formed vessels of the year were lignified in twigs around the time of leaf appearance and at or before full leaf expansion of each tree in both groups of species with flush‐leaves. Vessels in stems were lignified 2 weeks before to 4 weeks after leaf appearance and before or around full leaf expansion of the tree in ring‐porous species. This was significantly earlier than in diffuse‐porous species, in which stem vessel lignification was 2–8 weeks after leaf appearance and at or after full leaf expansion of the tree. The timing of vessel formation in twigs compared to stems was significantly earlier in ring‐porous species than in diffuse‐porous species. Lignification of vessels in stems occurred within 2 weeks of lignification in the twigs of ring‐porous species and 2–8 weeks after lignification in twigs of diffuse‐porous species. These results indicate the order and time‐lag of leaf and vessel formation. Ring‐porous species showed intensive leaf/vessel production, whereas diffuse‐porous species showed less intensive leaf/vessel production.