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28-Winter stem features

[FMP-field: image]

This photo, representing winter twigs of white, black, and red oaks, points out some features of stems:

  • nodes are the positions on the stem where leaves and buds arise. Note here how the buds are crowded at the tip of the twigs
  • an internode is a region of the stem between two nodes
  • a bud is an external meristem. A bud may give rise to a leafy stem, a flower, or both. A bud may be naked or protected by bud scales or stipules.
  • the axil is the upper angle between a leaf stalk (or any lateral structure) and the stem to which it is attached.
  • an axillary bud is a bud borne in the axil of a leaf. It is also called lateral bud.
  • bud scales are scale-like modified leaves that protect the lateral and terminal buds (better view on next photo).
  • bud scale scars are the scars remaining after the bud scales fall off.
  • a leaf scar is the scar remaining after the leaf falls off.
  • Bundle scars are the broken ends of the vascular bundles passing from the stem into the leaves. They are identified as small dots, discolorations, or raised bumps on the surface of the leaf scar ( not very visible here).

Photo of white, black, and red oak species by K. R. Robertson of trees cultivated at the University of Illinois.

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