Nodal Anatomy of Plants with Diagram
(Leaf Gap, Leaf Trace: Unilacunar, Trilacunar and Multilacunar Nodes in Angiosperms)
Anatomy of Nodal and Inter-nodal Region are Different:
The stem of plants is differentiated into nodes and internodes. The anatomical features of the nodal region are quite different from that of the inter-nodal region. This anatomical difference is due to the presence of Vascular Supply to the leaves and branches from the main vascular cylinder of the stem.
Nodal Region of Higher Plants Posses Leaf Gaps and Leaf Traces
Each leaf that originates from the node, of higher plants possesses vascular tissue and these vascular tissues of the leaves are connected to that of the stem. A vascular strand that extends between the vascular cylinder of stem and the base of the leaf is called Leaf Trace or Foliar Trace.
Even if the leaf trace possesses both xylem and phloem, the relative amount of xylem will be more in the leaf trace than phloem. Moreover, the proximal portion, (portion near the vascular cylinder of the stem) contains only the xylem. Whereas, the distal end of the leaf trace (near to the leaf base) contains both xylem and phloem.
Leaf trace helps to transport water and minerals from the xylem to the leaf lamina for photosynthesis. The circulation of photosynthetic products from the leaf lamina to the phloem of the stem is also facilitated by the phloem strands in the leaf traces.