Model of Xylem and Phloem

To make models of xylem vessels and tracheids, phloem sieve tubes and companion cells use cardboard tubes from kitchen roll, cling film or aluminium foil and wrapping paper.

Materials

  • Cardboard tubes of varying sizes (kitchen roll and wrapping paper are best for xylem cells and sieve tubes whereas cling film rolls, which tend to be thinner are better for companion cells).
  • Scissors
  • Sellotape and wide brown packaging tape.
  • Thick-nib coloured marker (to draw on bands of lignin and mark dots to represent pits)
  • Paper punch (to form sieve plate holes)
  • Light card (to make sieve plates).

Xylem

Vessels: use the largest tubes or a number of kitchen roll tubes.

Mark bands of lignin of various types, e.g. spiral, reticulate or circular bands, using the marker pen.

Mark ‘pits’ on the wall of the vessel, using the marker pen.

The ‘cells’ can be stacked to show how they form a continuous column through the plant. Also holding a group of them together can be used to demonstrate how water can divert via the pits if a vessel gets blocked.

Tracheids.

Cut the top and bottom of a number of tubes at an angle to form tapered end, such that they can be stacked.

Cover the slanted end with the packaging tape and then use scissors to make visible slits in the end walls.

Draw on lignifications and pits as above.

These ‘cells’ can be stacked end on end and the presence of the ‘semi-blocked’ end walls shows how inefficient tracheids are used for transport.

Phloem

Sieve tubes.

Kitchen roll tubes are good here.

Fashion a flat end plate from the light card and then punch holes into it with the paper punch before attaching to the end space of the tube with sellotape  to represent the sieve plates.

You could put some light gauze or bubble wrap in the tube to represent the cytoplasm present.

Companion cells

Thinner tubes are best for this (cling film roll).

Use marker pen to mark a ‘nucleus’ on one wall.

Group a number of sieve tubes and one companion cell together to show arrangement.

With all the above if you arrange them in different ways and hold them under your arm with the end walls showing, you can show the idea of the TS of the cells and how sometimes you might see a sieve plate and other times not.

These models keep for years.