AP BIOLOGY

Detailed explanation-1: -Xylem tissue transports water and dissolved minerals from roots to leaves, using some active transport, but mostly passive processes. Phloem tissue transports dissolved sugars up or down a plant, using active transport and osmosis.

Detailed explanation-2: -Phloem transport is called active because phloem loading at the source and unloading at the sink are both done by active transport. This is a biological process in which molecules move against a concentration gradient, requiring chemical energy to transport biochemical substances from a lower to a higher concentration.

Detailed explanation-3: -Once the sucrose reaches the phloem tissue in a source, it needs to be actively transported into the companion cells and sieve tube members. This process does require energy, and this is why the companion cells must have many mitochondria to release this energy through cellular respiration.