Phloem is mainly made of four kinds of cells: sieve tubes, companion cells, phloem parenchyma, and phloem fibres.

Quick Scoop: What are the constituents of phloem?

Think of phloem as the plant’s food-delivery network , carrying sugars from leaves to all other parts of the plant. To do this smoothly, it is built from several specialized cell types working together like a coordinated delivery team.

Main constituents of phloem

  • Sieve tubes – Long, tube-like cells arranged end to end that actually transport sugary sap through sieve plates.
  • Companion cells – Narrow, living cells attached to sieve tubes that manage and support their function, including loading and unloading sugars.
  • Phloem parenchyma – Living cells that store food (like starch) and help in side-ways transport within the phloem.
  • Phloem fibres (bast fibres) – Usually dead, thick-walled cells that give mechanical strength and support to the tissue.

Some references also mention sieve cells in addition to sieve tubes, especially in more general or older descriptions of phloem, but in standard school-level answers, the four key constituents listed above are usually expected.

Mini table for quick revision

[1][3][5] [3][4][9] [4][1][3] [5][7][4]
Constituent Main role
Sieve tubes Conduct food (sugars) through phloem.
Companion cells Control and support sieve tubes, help load/unload sugars.
Phloem parenchyma Store food and assist in lateral transport.
Phloem fibres Provide strength; only major dead element in phloem.

For typical exam questions like “what are the constituents of phloem,” you can safely answer: sieve tubes, companion cells, phloem parenchyma, and phloem fibres.

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Learn what the constituents of phloem are, with a simple explanation of sieve tubes, companion cells, phloem parenchyma, and phloem fibres for quick Class 9–10 biology revision.

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