A type of secondary wall patterning in tracheary elements in which the secondary cell wall is more or less continuous, the continuity only broken by * pits and perforation plates (if present). The pits may be arranged in an opposite or alternate pattern. If the pits are greatly elongated transversely and parallel to each other, they are said to be scalariformly pitted. Like * reticulate and * scalariform thickenings , pitted thickening permits little further extension and is therefore found in tissues that have finished elongating at maturity, such as metaxylem and secondary xylem. Compare annular thickening , spiral thickening. |
