CBSE Class 10 Answered

Phloem transports organic molecules such as the products of photosynthesis in a process called translocation. It requires energy to create a pressure difference and so is considered an active process. Sucrose molecules in the leaves enter the phloem cells by active transport. There is a concentration of sucrose in the phloem of the leaves. This creates a positive potential in the leaf phloem tissue. The phloem in the other parts of the plant have negative potential as food is continuously being used without being manufactured. Thus sucrose moves from the region of positive potential to the region of negative potential along the concentration gradient. The food moves from leaves to the other parts like the roots, young leaves, flowers and fruits.