Which tissue transports sugars from sources to sinks in a plant?

• A. Xylem
• B. Phloem
• C. Cambium
• D. Cortex

Answer: (B)

Sugar transport in plants happens through phloem, the vascular tissue that moves sugars from sources to sinks. Sources are tissues that produce or release sugar, like mature leaves, while sinks are tissues that consume or store sugar, such as growing roots, developing fruits, or young leaves. Phloem is made of sieve tube elements and companion cells and uses the pressure-flow mechanism: sugars are actively loaded into the phloem at the source, water follows by osmosis, creating positive turgor pressure that pushes the sap toward sinks. There, sugars are unloaded and taken up by cells for growth or storage. Xylem, in contrast, carries water and minerals upward from roots and isn’t used for sugar transport. Cambium is a growth tissue that generates new xylem and phloem, and cortex is outer ground tissue involved in storage and protection, not long-distance sugar movement.