15 Major Difference between Protoxylem and Metaxylem with Table

What is the difference between protoxylem and metaxylem?

Xylem is a complex tissue comprising of different cells. Xylem tissue is responsible for conducting water and minerals from the roots to the other parts of the plant.

Xylem consists of xylem tracheid, vessels, xylem fibers, and xylem parenchyma. The secondary function of the xylem is to offer mechanical support to the plant.

The core difference between protoxylem and metaxylem is that protoxylem is the first formed part of the xylem while metaxylem is the second part of the xylem.

Difference between Protoxylem and Metaxylem

What Is Protoxylem?

Protoxylem is the primary part of the xylem that develops first during primary growth. The part tends to mature faster than the other parts of the plant.

Young stems have protoxylem on the outside and tend to have smaller cells. The protoxylem has narrow lumen since it contains narrow vessel elements and tracheid.

The protoxylem cells do not experience lignification but show annular and spiral thickening. It also contains a large amount of parenchyma.

What Is Metaxylem?

Metaxylem is part of the primary xylem that develops after protoxylem. The part tends to mature after the completion of major plant organs.

It occurs inside the plant stem and it is marked with the wider lumen. Besides that, it has wider tracheid and vessel elements.

The metaxylem show lignification and the vessel show scalariform, reticulate, and pitted thickenings in their secondary cell walls.

The tissue is quite efficient in the conduction of water and minerals. It has more of xylem fibers and less of parenchyma cells.

Comparison Chart: Protoxylem Vs Metaxylem

Basic TermsProtoxylem Metaxylem
MeaningRefer to the first-formed xylem part during primary growthRefer to the second formed part of the xylem after protoxylem
FormationFormed firstFormed after completion of protoxylem
DifferentiationProcambiumFascicular cambium
Significance in MaturationMature before other plant organsMature after completion of other plant organs
In the Stems of Seed PlantsOccur close to the centerOccur on the periphery of the stem
In the Root of Vascular PlantOccur on the periphery of the rootOccur on the closet of the center
Tracheids and ParenchymaHas a large amount of parenchyma and less of tracheidHas a large amount of tracheid and fewer parenchyma cells
Size of TracheidsTracheid and vessel elements have a narrow lumenTracheid and vessel elements have a wider lumen
Secondary Wall Thickening of TracheidsEither annular or spiralEither reticulate or pitted
TylosesAbsentPresent
Water Conduction efficiencyLess efficientMore efficient
Xylem FibersAbsentPresent
Subjection to the Stress and StrainHighly susceptibleLess susceptible
Formation of Lysigenous CavityInvolve in the formation of a lysigenous cavityDoes not get involved in the formation of a lysigenous cavity
FlexibilityTend to stretchNot able to stretch

Core Differences between Protoxylem and Metaxylem In Point Form

  1. Protoxylem is the first formed part of the vascular bundle while metaxylem is the part of xylem formed after protoxylem
  2. Protoxylem mature before other plant organs while metaxylem mature after completion of other plant organs
  3. Protoxylem is arranged towards the center in the stems while metaxylem is arranged on the periphery of the stem
  4. Protoxylem is arranged towards the periphery in the roots while metaxylem is arranged around the center of the root
  5. Protoxylem contain less amount of treachery elements while metaxylem contain more of treachery elements
  6. Protoxylem contain more of parenchyma cells while metaxylem contain less amount of parenchyma cells
  7. The tracheary elements in protoxylem have narrow lumen while in metaxylem have a wider lumen
  8. The cell thickening of protoxylem either show annular or spiral thickening while metaxylem show either reticulate or pitted thickening
  9. Protoxylem is prone to stress and strain while metaxylem is not prone to strain or stress
  10. Protoxylem are fused together in monocot to form cavity while metaxylem does not form any cavity
  11. Metaxylem have tracheid fibers while protoxylem do not have fibers
  12. Metaxylem have tylose while protoxylem do not have tylose
  13. Protoxylem is less efficient in water and mineral transport while metaxylem is quite efficient in water conduction
  14. Protoxylem have comparatively smaller cells while metaxylem have comparatively larger cells
  15. Lignification is less extensive in protoxylem while more extensive in metaxylem

Similarities between Protoxylem and Metaxylem

  1. Both are responsible for water and mineral conduction
  2. Both contain living and dead cells
  3. Both develop primary meristem
  4. Both contain tracheid, vessels, and parenchyma
  5. Both develop in primary vascular bundles

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Comparison Video

Summary

The core difference between metaxylem and protoxylem is the morphological orientation. Metaxylem has wider lumen while protoxylem has a narrower lumen. But both are responsible for mineral and water conduction.

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