Ontogeny of the proventitious epicormic buds in Quercus petraea. II. From 6 to 40 years of the tree's life

In the present work, we described the fate of proventitious epicormic buds on the trunks of 40-year-old Quercus petraea trees and in parallel the vasc ular trace they produced in the wood. Our results show that small and large individual epicormic buds can survive as buds for 40 years and that both a re composed of a terminal meristem and scales. Meristematic areas are detec ted in the scale axils of small buds; in addition to these meristems the la rge buds also have secondary bud primordia. The small buds are connected to the pith of the main stem by a unique trace, whereas the large buds are co nnected by one or multiple traces. A single trace might imply that the whol e bud is still alive and multiple traces might indicate that the terminal m eristem has died. In the latter case, each trace is connected to a secondar y bud of the large bud. The buds found in a cluster are composed of a termi nal meristem and scales with axillary meristems in the scale axils. A clust er is connected to the pith of a stem either by a unique trace when it seem s to be the result of partial abscission of an epicormic shoot or multiple traces when it might have originated from an epicormic bud in which the ter minal meristem has died. Whatever the type of the bud, the vascular trace i n the bark is composed of a cambium, secondary xylem and parenchyma cells a nd the trace present in the wood had parenchyma cells with vestiges of seco ndary xylem. Each year, the vascular trace should be produced in the bark b y the cambium of the tree but not by the bud itself. On 40-year-old Q. petr aea, we observed a proliferation of epicormic buds and in parallel a multip lication of the number of vascular traces in the trunk, but the knots cause d by the traces of epicormic buds in the wood, either as individuals or in clusters, are minor since their colours are only slightly darker than those of woody rays and they are less than 2 mm in diameter. The knots will appe ar when epicormic buds develop into shoots.