Final answer:
Translocation is the transport of photosynthates via the phloem from sources to sinks within a plant; phloem sap is the medium that carries these substances, rich in sugar and other nutrients.
Step-by-step explanation:
Translocation refers to the process of transporting photosynthates, like sucrose, from where they are synthesized in the plant (sources) to where they are needed or stored (sinks). The synthesized sugars, or other organic molecules, are moved through the plant's phloem tissue. During translocation, the phloem sap, which is an aqueous solution containing up to 30 percent sugar along with minerals, amino acids, and plant growth regulators, plays a crucial role. This sap moves from the sources, such as the leaves where photosynthesis occurs, to the sinks, such as roots, young shoots, and developing seeds, for use in growth, storage, or structural integrity.
The phloem transportation is made possible by a difference in pressure that is created by the active transport of sugars into the phloem, followed by osmotic movement of water. This generates a flow from the high-pressure sources to the low-pressure sinks. The direction and destination of the phloem sap can vary depending on the plant's needs; for example, in different stages of growth or in different seasons, the roles of source and sink may change, with structures like seeds, tubers, and bulbs being sources at some times and sinks at others.