Timing of vessel formation in twigs and trunks in relation to porosity and leaf flushing

Abstract

In order to understand the coordination of leaf phenology and functional xylem anatomy, the timing of vessel wall lignification in twigs and stems in relation to leaf appearance was studied in nine species with different porosity patterns. Cylindrical stem cores and twigs were collected from early spring through late summer from deciduous (Quercus serrata, Liquidambar styraciflua, and Acanthopanax sciadophylloides), and evergreen (Castanopsis cuspidata; Cinnamomum camphora, Ilex pedunculosa, Symplocos prunifolia, Quercus glauca and Quercus myrsinifolia) species in a temperate forest. The first-formed twig vessels lignified at the time of leaf appearance or before in all species. The timing of stem vessel lignification in relation to leaf appearance in semi-ringporous deciduous species was overlapping with that of ring-porous deciduous species and diffuse-porous deciduous species. Evergreen species showed a great variation in the timing of stem vessel lignification, relative to leaf flushing. The main conclusions are that 1) Vessel lignification occurs much earlier in twigs than in trunks of the same trees, with hardly any overlap between the two; 2) Deciduous trees do not differ much from evergreen species, but there is a weak tendency for evergreen species to have later vessel differentiation than deciduous species; 3) The timing of vessel formation shows little relation with porosity patterns and overlaps between diffuse-porous and ring-porous species. This suggests a much greater intergradation of timing of vessel formation in species of different porosity pattern in evergreen and deciduous species than recognized in the literature.