Why is translocation important to plants?

The transportation of the substances are  carried out by the vascular system of the plant and that constitute xylem and phloem. Translocation is an important phenomenon that can be seen in the plants through which the various substances are transported from one part of the plant to the different parts in the plants. 

Xylem carries a water and nutrients from the roots to the shoots and the leaves. 

Phloem carries the food derived from the photosynthesis and other nutrients from the leaves to down to the roots and other parts.