PHLOEM tubes are made of columns of elongated living cells with porous ends, this allows the cell sap (water and other substances) to be transported. The substances transported are usually dissolved sugars acting as foodstuffs for the plant and these can be used either for growth or for storage. This transport takes place in both directions (from the leaves down to the roots and vice versa) and is called TRANSLOCATION.


XYLEM tubes are, in contrast made up of dead cells which are joined end to end but which have a hole down the middle.These choose a strengthened with a substance called LIGNIN and are used to transport water and mineral ions from the roots up to the stem and leaves. This is called the TRANSPIRATION STREAM.