The food is transported in plants both in upward and downward direction through phloem tissues, which consist of sieve tubes and companion cells. The translocation in phloem occurs with the expenditure of energy. Sucrose is the main form of carbohydrate which is transferred into the phloem tissues using energy from ATP. When sucrose is synthesised in the leaf cells, the osmotic pressure of the cells increases causing water to move into it. This causes translocation of sucrose in the form of solution from the point of synthesis to the points having less pressure. This allows the phloem to move material according to the plants needs.