Question

Why is long distance transport important for vascular plants?

Answer 1

There are principally two ways by which plants absorb and transport nutrients and food materials across its body. One is the short distance transport which includes processes like diffusion and osmosis, active and passive transport, and facilitated diffusion. And the other one is long distance transport which includes the usage of conduction vessels (xylem and phloem).

Complete answer:
We are well-known the fact that from the root region, the minerals and water are absorbed through diffusion. But the point to be noted is that diffusion is a slow process. Long distance transport like from the roots to the leaves or vice-versa cannot be done through diffusion alone. This would take years for the nutrients to reach the leaves!
In the larger complex plants, substances have to be moved covering large distances. Sometimes the sites of production or absorption and sites of storage are too far from each other. Diffusion and active transport are not the methods of choice to serve this purpose. They are the only okay to be used for short distances like one cell to the adjacent cell or situations like this.
So, in order to transport substances at a faster pace and in an efficient manner, special mechanisms involving long distance transport were to be evolved. Thus, in vascular plants evolved the xylem and phloem to conduct transport of substances efficiently and faster.

Note:
In the vascular plants, water, minerals and food are generally moved by a mass or bulk flow system. Mass flow is the movement of substances in bulk from one point to another as a result of pressure differences between the two.
This bulk movement of substances through the conducting and vascular tissues of plants is known as translocation.
This differs from diffusion where the substances flow independently and the only governing factor is the concentration gradient.