4.3 - Translocation

Definition of Translocation

Translocation refers to the process of transporting organic substances like sucrose, amino acids and hormones from the leaves to other parts of the plants. The word translocation comes from the Greek words 'trans' and 'locus'. 'Trans' means crossing while 'locus' means site or place.

The Necessity of Translocation in Plants

• Transport product of photosynthesis from the leaves to other parts of the plants which are still growing for growth and respiration.
• Transport excess product of photosynthesis to rhizomes, tubers and bulbs.

Pathways of Translocation in Plants

Figure 8 -

1. The product of photosynthesis such as sucrose is transported into the sieve tubes via active transport.
2. The transportation of sucrose to the sieve tubes reduces the water potential in the sieve tubes. This causes water to diffuse into the sieve tubes from the xylem via osmosis.
3. The diffusion of water increases the hydrostatic pressure within the sieve tubes.
4. The increased hydrostatic pressure pushes the sucrose along the sieve tubes to other organs of the plants.
5. Sucrose will be transported actively from the sieve tubes to other parts of the plants such as the stems, roots, shoots, fruits and tubers.
6. The higher water potential in the phloem causes the diffusion of water back into the xylem via osmosis.
7. Transpiration pulls the water along the xylem vessels against gravitational pull.