The food for plants is prepared by the green leaves by the process of photosynthesis. The leaves are the food production centres. Using the sunlight and Carbon dioxide they synthesize food through photosynthesis in the chloroplasts. Every part of plant body like the roots and stem also require food for its functioning so the food prepared by the leaves must be transported to different parts of the plant. All of this takes place through the vascular tissues of the plants. The process of transportation of carbohydrates (sugar) produced by the leaves to other parts of the plant is known as translocation. It is done through Phloem tissues. The movement of carbohydrates in phloem is bidirectional.