Knot (botany)

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A knot in a young ash tree

The area of ​​the stem axis to which one or more leaves attach is referred to as a node ( Latin nodus ) or shoot node . The nodes or Nodi (colloquially Nodien ) can be hairy depending on the plant species or bald. The stem axis area between two nodes is called the internode . The term knot refers to the frequent thickening of the stem axis at the point of the leaf base.

The term nodus was already used by Albertus Magnus (1192–1280) in his work De Vegetabilismus .

Nodal anatomy

The vascular bundles branching off into the leaves (leaf traces) leave gaps, the lacunae , in the axial vascular bundle of the stem axis. The number of lacunae and leaf traces is variable and of systematic interest. The most common types are:

  • single-track / unilacunar: only one leaf track branches off at a node and leaves a gap.
  • two-lane / dilacunar: two leaf traces branch off at a node and leave a common gap.
  • three-lane / trilacunar: three leaf traces branch off at a node, each of which leaves a gap.
  • multi-lane / multi-lane: more than three leaf tracks branch off at a node, each of which leaves a gap. This case often occurs in plants that form a basal leaf sheath, such as the umbelliferae or knotweed plants .