Difference between Protophloem and Metaphloem: A Comparison Table

Protophloem vs Metaphloem

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, a vascular bundle composed of xylem and phloem arranged together as bundles. In a young stem, both in dicots and monocots, Phloem, the food conducting tissue of vascular bundles, are differentiated into PROTOPHLOEM and METAPHLOEM based on the structural and functional modifications of their elements.

The present post describes the similarities and difference between Protophloem and Metaphloem in a primary vascular bundle of a young stem.

Similarities between Protophloem and Metaphloem

Ø  Both protophloem and metaphloem can conduct food materials.
Ø  Both are complex tissues, composed of many types of cells.
Ø  Both components contain living and dead cells.
Ø  Both are developed from the primary meristem, the pro-cambium.
Ø  Protophloem and metaphloem develop only in primary vascular bundles.

Difference between Protophloem and Metaphloem

Sl. No.ProtophloemMetaphloem
1Frist formed part of the phloem of vascular bundlesFormed after protophloem
2Mature before the plant organs have completed their elongationMature after the plant organs have completed their elongation
3Composed of sieve elements, phloem parenchyma and fibres.Composed of sieve elements, companion cells, phloem parenchyma and phloem fibres
4Companion cells usually absentCompanion cells are present
5In stem protophloem is arranged towards the peripheryIn stem metaphloem is arranged towards the inner side
6Protophloem is usually thinner and inconspicuousMetaphloem is usually with large and conspicuous sieve elements
7Sieve areas are indistinct in sieve tubes, Sieve areas absent in the phloem of GymnospermsSieve areas are well developed
8Protophloem is short lived, become non-functional when the plant maturesRemain functional for longer periods, in plants without secondary growth, the metaphloem survive till the end of the plant
9Specilized phloem fibres are sometimes presentPhloem fibres will be of normal type
10Subjected to stress during elongation and maturationNot subjected to stress during elongation and maturation, but with secondary growth

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