Translocation
During photosynthesis, plants produce A simple sugar used by cells for respiration. from simple A compound that does not include carbon combined with hydrogen. molecules - A gaseous compound of carbon and oxygen, which is a by-product of respiration, and which is needed by plants for photosynthesis. and water - using light energy. Some of the glucose produced by photosynthesis is used for The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration.. This releases energy for the seven life processes.
The transport of dissolved material within a plant. is the movement of sugar produced in photosynthesis to all other parts of the plant for respiration and the other processes described above. This occurs in The tissue in plants that transports the products of photosynthesis, including sugars and amino acids. cells.
Phloem
The phloem moves food substances that the plant has produced by photosynthesis to where they are needed for processes such as:
- growing parts of the plant for immediate use
- storage organs such as An underground food store able to grow into a new plant. A natural method of asexual reproduction in plants. and A swollen, fleshy underground stem of a plant, such as the potato, bearing buds from which new plant shoots arise.
- developing seeds
Transport in the phloem therefore takes place both up and down the stem - in contrast to transport in the Narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants., 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:
- The conducting cells that, end to end, make up the phloem. - A cell that has become differentiated to carry out a particular function, eg red blood cell. for transport and have no The nucleus controls what happens inside the cell. Chromosomes are structures found in the nucleus of most cells. The plural of nucleus is nuclei.. Each sieve tube has a perforated end so its The living substance inside a cell (not including the nucleus). connects one cell to the next.
- The cell that lies alongside a sieve tube in the phloem, and provides the sieve tube with energy to tranpsort sugars and amino acids in solution. - transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy. A sieve tube is completely dependent on its companion cell(s).
Comparison of transport in the xylem and phloem
| Xylem | Phloem | |
| 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 |
| Type of transport | |
|---|---|
| Xylem | Physical process |
| Phloem | Requires energy |
| Substances transported | |
|---|---|
| Xylem | Water and minerals |
| Phloem | Products of photosynthesis; includes sugars and amino acids dissolved in water |
| Direction of transport | |
|---|---|
| Xylem | Upwards |
| Phloem | 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 Groups of xylem and phloem tissue in a plant..