Final answer:
Sucrose is used for phloem transport because it is easily broken down, stable, and has a lower osmotic potential than glucose.
Step-by-step explanation:
Sucrose is used for phloem transport because it provides several advantages over glucose. First, sucrose is a disaccharide made up of glucose and fructose molecules, so it is easily broken down into these simpler sugars to be used by the plant. Second, sucrose is less reactive and more stable than glucose, making it better suited for long-distance transport in the phloem. Finally, sucrose has a lower osmotic potential than glucose, which allows it to draw in water through osmosis, creating a positive pressure that drives the flow of phloem sap from source to sink.