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-ring-porous 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.

Relationship between Vessel Formation and Seasonal Changes in Leaf Area of Evergreen and Deciduous Species with Different Vessel Arrangements

“…Twig vessel elements began to lignify prior to bud opening [14], and cell division at the bud bases began before or at the same time as bud break in both ring-and diffuse-porous trees [10]. Previous studies have shown that lignification of almost all of the first-formed vessels occurs within ±2 weeks of leaf appearance [7], e.g., 0 week and 0-3 weeks before leaf appearance in ring-porous Quercus serrata and diffuse-porous Liquidambar styraciflua, respectively [25]. In the present study, almost all of the first-formed vessels in twigs lignified during the period when leaf area was between 0% and 70% of the maximum, not only in deciduous species but also in evergreen species (Figures 1 and 2A), though evergreen species have perennial leaves.…”

“…The results of the present study are similar to these previous findings. Lignification of the first-formed trunk vessels occurred until full leaf expansion (71-84%LA) in ring-porous Q. serrata and after full leaf expansion in diffuse-porous L. styraciflua ( Figures 1A and 2B), i.e., 2-4 weeks before and more than 7 weeks after leaf appearance, respectively [25]. Previous studies have reported that the wide vessels of the inner ring in ring-porous species are not used for water transport [23,[36][37][38][39], and sap flow increases with the increase in leaf area index (LAI) [40].…”

“…A previous study has shown that different porosities may not affect the timing of vessel formation in trunks relative to leaf appearance in semi-ring-porous deciduous trees and in evergreen trees with various types of porosities [25]. The time lag between the firstformed vessel lignification of trunks and leaf appearance in ring-porous evergreen trees is not always short.…”

“…The time lag between the firstformed vessel lignification of trunks and leaf appearance in ring-porous evergreen trees is not always short. Furthermore, this time lag is not always long in diffuse-porous evergreen trees [25]. Similar to ring-porous and diffuse-porous deciduous trees, the first-formed vessel lignification of twigs is concurrent with leaf appearance in evergreen trees, irrespective of different vessel arrangements [25].…”

“…Furthermore, this time lag is not always long in diffuse-porous evergreen trees [25]. Similar to ring-porous and diffuse-porous deciduous trees, the first-formed vessel lignification of twigs is concurrent with leaf appearance in evergreen trees, irrespective of different vessel arrangements [25]. Nevertheless, the vessel formation pattern between leaf appearance and full leaf expansion in evergreen species and semi-ring-porous deciduous species remains unclear.…”