AP BIOLOGY

Detailed explanation-1: -The sugar in the form of sucrose is moved into the companion cells and then into the living phloem sieve tube cells by active transport. This creates a hypertonic condition in the phloem. Water in xylem vessels adjacent to phloem moves through endosmosis.

Detailed explanation-2: -The photosynthates from the source are usually translocated to the nearest sink through the phloem sieve tube elements. For example, the highest leaves will send sugars upward to the growing shoot tip, whereas lower leaves will direct sugars downward to the roots.

Detailed explanation-3: -Sucrose, which is formed by the plant during photosynthesis, is a sugar transported through the phloem of the plant.

Detailed explanation-4: -These compounds are transported by the phloem tissue, which allows them to go both up and down within the plant, unlike sap which moves through the xylem. Phloem cells are tailored to perform certain functions: Sieve tubes lack a nucleus and are designed for transfer.

Detailed explanation-5: -Pressure Flow Water follows the sugar molecules into the sieve elements through osmosis (since water passively diffuses into regions of higher solute concentration). This water creates turgor pressure in the sieve elements, which forces the sugars and fluids down the phloem tubes toward the sinks.