Interesting how Oak trees hold onto their leaves

[Jovary]

Abscission tissues pump enzymes into the the abscission zone and it "unglues" the the lamela between the node and petiole. It doesn't effect the vascular bundle though but the loss of the glue makes it easier for the wind to blow the leaf off the tree and rip the bundle. My guess is that trees in the Beech family have stronger vascular bundles than most other trees