Protoxylem vs Metaxylem

Xylem is a conducting vascular tissue, which helps in the transport of water and minerals from roots to other parts of the plant. A xylem consists of four elements – tracheids, parenchyma, vessel elements and fibres. A xylem undergoes primary and secondary growth. During primary growth, the xylem forms protoxylem and metaxylem from the procambium. Let us look at their differences:

Protoxylem

Metaxylem

Definition

Protoxylem is the primary xylem that develops first during primary growth.

Metaxylem is formed after the protoxylem during primary growth in the xylem.

Growth

It grows before the maturation of other plant organs.

It grows after the maturation of all plant organs.

Size of Cells

The cells are smaller in size, and hence the whole protoxylem is less prominent.

The cells are bigger in size, and the metaxylem is much more prominent.

Lumen

The lumen is narrow.

The lumen is wider.

Xylem Parenchyma

Contains xylem parenchyma in large amounts.

Less amount of parenchyma is present.

Lignification

It does not have much lignifications.

It has extensive lignifications.

Thickenings

It has annular or spiral thickenings around the vessels.

It has reticulate, scalariform or pitted thickenings around the vessels.

Location

It is present on the periphery of the stem and inside of the root.

It is present on the inside of the stem and periphery of the roots.

Efficiency

It is less efficient in water transportation.

It is more efficient in water transportation.

Explore BYJU’S Biology for more.

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FAQs

Does protoxylem become metaxylem?

No, metaxylem develops after the formation of protoxylem.

Which is more mature, protoxylem or metaxylem?

Since the metaxylem is formed at later stages, it is more mature.

How do you identify a protoxylem?

A protoxylem can be identified by smaller cells with narrow lumen. It has less lignifications, and the vessels contain simple thickenings.

Which thickening is found in protoxylem?

Annular and spiral thickenings are found in protoxylem.

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