During photosynthesis, plants produce glucose from simple inorganic molecules - carbon dioxide and water - using light energy. Some of the glucose produced by photosynthesis is used for respiration. This releases energy for the seven life processes.
The phloem moves food substances that the plant has produced by photosynthesis to where they are needed for processes such as:
Transport in the phloem therefore takes place both up and down the stem - in contrast to transport in the xylem, which is just upwards.
Transport of substances in the phloem is called translocation.
Phloem consists of living cells. The cells that make up the phloem are adapted to their function:
|Type of transport||Physical process||Requires energy|
|Substances transported||Water and minerals||Products of photosynthesis; includes sugars and amino acids dissolved in water|
|Direction of transport||Upwards||Upwards and downwards|
The xylem and phloem are distributed differently in roots and stems. In the root, the xylem forms a central column. It forms a solid support. The phloem is towards the centre, outside the xylem.
In the stem, the transport tissues of the xylem and phloem are grouped into vascular bundles.