Relationship between formation of earlywood vessels and leaf phenology in two ring-porous hardwoods, Quercus serrata and Robinia pseudoacacia, in early spring

In deciduous ring-porous hardwoods, three-dimensional networks of the current year's earlywood vessels play an important role in the movement of water. In the present study, we analyzed the formation of earlywood vessels along the main stem and leaf phenology in two deciduous ring-porous hardwoods, Quercus serrata and Robinia pseudoacacia. We introduced a dye in an effort to monitor the timing of initial water conduction through the network of the current year's earlywood vessels. The formation of earlywood vessels began before bud break. At bud break, perforation of the first earlywood vessels was evident at the top of the stem but not at other positions within the stem. Perforations were observed along the entire stem when small leaves became visible and then leaves continued to develop. These results suggest that conduction of water via the network of the first earlywood vessels of the current year might not contribute to the initial growth of buds but might play an important role in the development of the current year's leaves and shoots.