Translocation of Organic Solutes

Movement of organic and inorganic solutes from one part of the plant to another is known as translocation. For example, transport of sugar in sieve tubes of leaves to stem or fruit.

There are experimental evidences to suggest that phloem is the tissue involved in translocation of products of photosynthesis i.e. sugars. Sugar is produced in photosynthesis in the leaves and then sent to all part of the plants for the growth and development of the plant.

Leaf is known as the source, where the food is produced and all other parts of the plant which receive this food is known as the sink. Sink can be root, stem, fruits and storage organs like tuber, bulbs and, rhizomes.

Thus, unlike conduction of water in xylem which takes place in one direction from the root to upwards in the aerial parts of the plant, phloem translocation from a leaf takes place in all directions.

Mechanism of Translocation

Sugar solution in the phloem sieve tube moves along the water potential gradient created between the source (leaf) and sink (storage) cells.