Xylem is a conducting vascular tissue, which helps in the transport of water and minerals from roots to other parts of the plant. The xylem tissue consists of four elements – tracheids, xylem parenchyma, vessel elements and fibres. The xylem tissue undergoes primary and secondary growth. During primary growth, the xylem forms protoxylem and metaxylem from the procambium. Let us look at their differences:
| Protoxylem is the primary xylem that develops first during primary growth. | Metaxylem is formed after the protoxylem during primary growth in the xylem. |
| It grows before the maturation of other plant organs. | It grows after the maturation of all plant organs. |
| 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. |
| The lumen is narrow. | The lumen is wider. |
| Contains xylem parenchyma in large amounts. | Less amount of parenchyma is present. |
| It has fewer lignifications. | It has extensive lignifications. |
| It has annular or spiral thickenings around the vessels. | It has reticulate, scalariform or pitted thickenings around the vessels. |
| 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. |
| It is less efficient in water transportation. | It is more efficient in water transportation. |
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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 the narrow lumen. It has fewer 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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