Plants normally absorb carbon dioxide through their leaves and water through the roots.

The movement of substances through the plant is called translocation. The plumbing system involves two systems, xylem (pronounced "zylem") and phloem.

The xylem moves water and fertiliser up from the roots to the leaves. Sugars move down through the phloem. Sometimes the two systems can go into reverse.


It is possible to apply certain organic chemicals to the leaves where they will be translocated to the roots and soil. Anyone who has used a systemic insecticide or weedkiller has seen this in action.


Indoor plants absorb pollutants from the air and move them to the root zone or rhizosphere where they are broken down by benefical soil bacteria. Some chemicals are destroyed internally by the plant.


The plant secretes "food" into the soil for use by bacteria. This promotes large populations of benefical bacteria which protect the plant from harmful organisms, helps the plant absorb fertiliser, breakdown minerals and breakdown pollutants. This relationship is called symbiosis.