Answer;
Transport of substances
Step-by-step explanation;
-Veins have vascular tissues, that is the xylem and the phloem. Xylem tissue transports water and mineral salts to the leaf, while phloem transports manufactured food from the leaf to other parts of the plant.
-Leaves need water for photosynthesis and the water is transported from roots to leaves through xylem.
-Veins are spread all over the leaves ,so they can easily transport water to all the cells of leaves.
-After the completion of photosynthesis in a chloroplasts, glucose is formed which may be used for cellular respiration or stored in form of starch. Phloem transports the glucose to other parts of the plant for cellular respiration;