Difference between Protoxylem and Metaxylem

The difference between protoxylem and metaxylem lies in their developmental stages within the plant’s vascular system. Protoxylem and metaxylem are types of plant tissues that help in transport as well as growth in plants. The protoxylem is the primary xylem that develops during the early stages of a plant’s development whereas the metaxylem is later formed xylem in mature plants.

Both of these forms are of xylem tissue that is mainly responsible for the conduction of water and minerals in the plant. In this article, we will differentiate between protoxylem and metaxylem and also discuss some similarities as well.

What is Protoxylem?

Protoxylem is the primary form of xylem that is seen in plants during their early stage of growth. It forms the foundation of the xylem system of vascular plants. The xylem is a component of vascular tissues that are responsible for the transport of water and minerals. The characteristic feature of protoxylem is its smaller diameter and thinner cell walls. When plants mature the protoxylem further differentiates to give rise to tracheids, and vessel elements due to the deposition of lignin.

Features of Protoxylem

Some of the characteristic features of protoxylem are:

• It is the first formed xylem tissue during the initial stage of plant growth.
• The vessels have a smaller diameter.
• They have a thinner cell wall.
• They consist of tracheids.
• Due to the lack of lignin deposits, these cells are less rigid and more flexible.
• During primary growth, the protoxylem is located towards the centre of the vascular bundle, adjacent to the pith

What is Metaxylem?

Metaxylem is the secondary form of xylem that is seen during the later stages of the plant’s life cycle. Metaxylem plays an important role in the later stages of a plant’s life by providing structural support as well as transport of water and minerals throughout the plant’s body. These cells have a comparatively larger diameter than protoxylem. These cells have lignin deposits in their cell wall that result in the formation of rigid tracheids, and vessel elements.

Features of Metaxylem

Some of the most common features of metaxylem are;

• It is the mature form of the xylem in the later stages of the plant’s life.
• They have a characteristic feature of a larger diameter.
• They have a thicker cell wall due to the lignin deposits providing structural strength.
• Their unique structure enables efficient water and mineral transport.
• During growth, the metaxylem forms towards the outer region of the vascular bundle, opposite to the position of the protoxylem.

Difference Between Protoxylem and Metaxylem

Some of the differences between protoxylem and metaxylem are given below:

Features	Protoxylem	Metaxylem
Definition	Primary xylem that develops during primary growth.	Secondary form of xylem that develop during later stages of plant growth.
Cell Diameter/ Lumen	Small	Large
Size of Cells	Smaller size, hence protoxylem less prominent	Larger in size making metaxylem more prominent
Cell Wall Thickness	Thin	Thick
Growth	Grows and matures before other plant organs.	Grows and matures after other plant organs.
Location	Located towards the center of the vascular bundle; on the periphery of stem and inside of root	Forms towards the periphery of the vascular bundle; on the inside of the stem and periphery of the roots.
Visibility	Less prominent among other plant cell structures.	More prominent among other plant cell structures.
Lignin	Absent	Present
Vascular Bundle	Located towards the centre of primary growth.	Forms towards the periphery in primary growth.
Xylem Parenchyma	Present in huge numbers.	Present in less numbers.
Efficiency	Less efficient in water transport	More efficient in water transport

Similarities Between Protoxylem and Metaxylem

Some of the most common similarities between protoxylem and metaxylem are:

• Both are types of xylem tissue.
• They are involved in water and mineral transport within the plant.
• Both are composed of specialized cells such as vessel elements and tracheids.

Conclusion – Difference Between Protoxylem and Metaxylem

In conclusion, protoxylem and metaxylem represent distinct stages in the development of xylem tissue within plants. Protoxylem emerges early in the plant’s growth, characterized by smaller diameter and thinner cell walls, while metaxylem appears later, featuring larger diameter and thicker cell walls due to lignin deposition. Both types of xylem play crucial roles in water and mineral transport, with protoxylem maturing before other plant organs and metaxylem forming later, towards the outer region of the vascular bundle. Despite the many differences between protoxylem and metaxylem, they share some similarities as well.

Difference Between Related Links

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FAQs – Difference Between Protoxylem and Metaxylem

What is the Difference Between Protoxylem and Metaxylem in Terms of Types of Secondary Wall Thickenings?

Protoxylem has annular or spiral thickening. whereas the metaxylem has pitted thickening in the secondary wall and elongated ends.

What is the Position of Protoxylem and Metaxylem?

The protoxylem is located towards the center in primary growth whereas the metaxylem forms towards the periphery in primary growth.

What is the Difference Between Secondary Xylem and Metaxylem?

Secondary xylem includes both protoxylem and metaxylem whereas metaxylem is a specific part of the secondary xylem.

Which is the Bigger Protoxylem or Metaxylem?

Metaxylem has a larger diameter as compared to protoxylem due to which it is bigger in structure.

What is the Arrangement of Protoxylem and Metaxylem in Monocot Root?

The xylem shows an exarch arrangement in which the protoxylem lies towards the periphery and the metaxylem toward the centre.

What is the Arrangement of Protoxylem and Metaxylem in Monocot Root?

In monocot roots, protoxylem is located towards the center of the vascular bundle, while metaxylem is positioned towards the periphery.