Difference between Protoxylem and Metaxylem: A Comparison Table

classification of xylem

Protoxylem vs Metaxylem
Similarities and Differences between Protoxylem and Metaxylem

Vascular bundles (fascicles) are the component of the stelar system in higher plants and their main function is the conduction of water, minerals and food materials. Typically the vascular bundle composed of xylem and phloem arranged together as bundles. In a young stem, both in dicots and monocots, the xylem of vascular bundles are differentiated into PROTOXYLEM and METAXYLEM based on the structural and functional difference of their elements.

The present post describes the similarities and differences between Protoxylem and Metaxylem in a primary vascular bundle of a young stem.

Similarities between Protoxylem and Metaxylem

Ø  Both protoxylem and metaxylem can conduct water and minerals.

Ø  Both components contain living and dead cells.

Ø  Both are developed from the primary meristem, the pro-cambium.

Ø  Both contain tracheids, vessels and parenchyma.

Ø  Protoxylem and metaxylem develop only in primary vascular bundles.

Differences between Protoxylem and Metaxylem

protoxylem and metaxylem

Sl. No.ProtoxylemMetaxylem
1First formed part of xylem in the vascular bundles.Metaxylem is the xylem part formed after the protoxylem.
2Matures before the plant organs have completed their elongation.Matures after the completion of growth of the plant organ.
3In the stem, protoxylem is arranged towards the centre.In stem, it is arranged towards the exterior
4In the root, it is arranged towards the periphery.In root, it is arranged towards the interior
5Composed of very less amount of tracheary elements.Composed of more tracheary elements then protoxylem.
6Contain large amounts of parenchyma.Contain less amount of parenchyma
7Tracheary elements are with a very narrow lumen.Cells of the tracheary elements are with large lumen than that of protoxylem.
8Show annular or spiral thickening in their secondary wall (primitive type).They show reticulate or pitted thickening (advanced type).
9Subjected to stress and strain during the maturation of the plantNot subjected to stress and strain
10In monocot stem, protoxylem elements fuse together to form a cavityMetaxylem elements do not form the lysigenous cavity
11Fibres absent in protoxylemFibres present in metaxylem
12Tyloses are not formed in protoxylemTyloses may present in metaxylem
13Less efficient in the conduction of water and mineralsMore efficient in the conduction of water and minerals

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