AP BIOLOGY

Detailed explanation-1: -Sucrose, RFOs and polyols are transported in the sieve tubes to the sink organs in the transport phloem. All along the path, they can be leaked from and reloaded into the phloem via the same mechanism (not shown). Sucrose is unloaded into the release phloem where the hydrostatic pressure is supposed to be lower.

Detailed explanation-2: -The glucose prepared in the leaves is converted into sugar. 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-3: -The sugar and other organic molecules are transported through the plant by means of a special layer of tissue called phloem. Phloem is composed of living cells that transport a water solution of sugars that we commonly call sap.

Detailed explanation-4: -There has been a consensus in the phloem transport field for over 50 years that sucrose is the predominant sugar carried in the sieve tubes of most species.

Detailed explanation-5: -Sucrose transport is favorable for the following reasons: (i) 1 mol sucrose contains more energy than 1 mol of a monosaccharide such as glucose or fructose, thus using the disaccharide is more energy efficient for transport and storage.