Tracheid

Angiosperms also use another type of conductive cell, called vessel elements, to transport water through the xylem.

The main functions of tracheid cells are to transport water and inorganic salts, and to provide structural support for trees.

[6] The fossil record shows three different types of tracheid cells found in early plants, which were classified as S-type, G-type and P-type.

As tracheids evolved along with secondary xylem tissues, specialized inter-tracheid pits appeared.

[7] Tracheids then evolved into the vessel elements and structural fibers that make up angiosperm wood.

In radial section, two tracheids of a coniferous wood species are shown. A series of bordered pits are also appearing in each tracheid.
A tracheid of oak shows pits along the walls. It has no perforation plates . Angiosperms have both tracheids and vessel elements. [ 1 ]