OCR AS Biology

Revision Notes

3.3.3 The Xylem

Xylem Vessel Elements: Structure & Function

  • The functions of xylem tissue in a plant are:
    • Vascular tissue that transports dissolved minerals and water around the plant
    • Structural support
    • Food storage
  • Xylem tissue is made up of four cell types that function together:
  1. Tracheids (long, narrow tapered cells with pits)
  2. Vessel elements (large with thickened cell walls and no end plates when mature)
  3. Xylem parenchyma
  4. Sclerenchyma cells (fibres and sclereids)
  • Most of the xylem tissue is made up of tracheids and vessel elements, which are both types of water-conducting cell

Xylem vessel elements, downloadable AS & A Level Biology revision notes

Images of xylem vessel elements, (a) photomicrograph in longitudinal section (lignin is stained red), (b) scanning electron micrograph in transverse section and (c) microscope image in transverse section and drawing (lignin is stained red)

Relating structure & function in xylem vessel elements table

Relating structure & function in xylem vessel elements table, downloadable AS & A Level Biology revision notes

  • Also see Comparison of xylem & phloem tissue table in Phloem Sieve Tube Elements

Exam Tip

You must be able to recognise the xylem vessel elements in images so look for the thicker cell walls and the larger diameter. You also need to know the difference between xylem and phloem tissue.

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