In a plant, translocation in the xylem

The vascular bundle, phloem is responsible for conducting the food from the source to the sink. But the process is reversed during seasons like spring because during

that term the food which is stored in the sink is then supplied to the growing parts of the plant. The source and sink relation are hence variable so the direction of

movement of food via the phloem can be either upwards or downwards i.e. bidirectional.