AQA GCSE Translocation (Biology)
Translocation
Translocation is the movement of food molecules (sucrose and amino acids) through phloem tissue.
Phloem is composed of tubes of elongated cells, called sieve tube elements. Cell sap can move from one phloem cell to the next through pores in the end walls.
Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use in respiration or storage in the roots as starch.
When you are eating a potato, this is the root part of the potato plant, it contains starch.
1.The leaves of the potato plant produce glucose using photosynthesis
2.Cells will convert the glucose to sucrose, which is then transported in the phloem from the leaf cells to the root cells.
3.In the roots, the sucrose is converted to starch and then stored in the potato.
Phloem tissue
Phloem tissue is made up:
1.Sieve tube elements
2. Companion cells.
The sieve tube elements have pores to allow the free flow of substances up or down the phloem.
The companion cells have many mitochondria, which carry out aerobic respiration.
Bidirectional flow
Bidirectional flow can occur in the phloem. The direction of flow depends on supply and demand
During the summer days, where lots of sugars are being produced in the leaves, sucrose is transported from the leaves, down to the roots for storage as starch.
During the spring, the starch reserves in the roots are converted to sucrose. This sucrose is then transported up the phloem to the growing tips of the plant, such as the buds.
Practice Questions
1.State the definition of translocation
2.Sucrose is transported from the leaves to the root. Explain why
3. Explain what is meant by bidirectional flow.