Difference Between Protoxylem and Metaxylem (Protoxylem vs Metaxylem)

Xylem is a conducting tissue in plants that is meant to conduct water and minerals upwards from the roots to the leaf. It is a complex tissue composed of different types of cells. Xylem consists of xylem tracheids, vessels or tracheae, xylem fibers/xylem sclerenchyma (wood fibres) and xylem parenchyma (wood parenchyma). Secondary function of xylem is mechanical support to the plant body.

Protoxylem vs Metaxylem

Protoxylem

1. It is the first formed primary xylem

2. It matures much before the plant organs has completed their elongation.

3. It is smaller in diameter or smaller lumen.

4. No tylosis* formation

5. Annular and spiral thickening

Metaxylem

1. It is the later formed primary xylem

2. It matures after the plant organs has completed their elongation.

3. It is larger in diameter or large lumen compared to protoxylem.

4. Tylosis formation is very common

5. Pitted thickening

* Tylosis: Bubble like outgrowth of parenchyma cells into the lumen of a vessel through a pit cavity.
Related: Difference between Primary Xylem and Secondary Xylem

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