Xylem transports water and minerals from the soil to various parts of the plant, while phloem moves products of photosynthesis from leaves, where they are synthesized, to other plant tissues.

Plants have low energy needs as they do not move and contain a significant proportion of dead cells. This allows them to use relatively slow transport systems.

In situations where the distance between roots and leaves is significant, a proper transportation system becomes essential because diffusion alone cannot efficiently provide raw materials to leaves and transport energy to roots.

The soil serves as a rich source of raw materials like nitrogen and phosphorus for plants. Roots are the plant organs primarily responsible for absorbing these substances from the soil.

Short distances between soil-contacting organs (roots) and chlorophyll-containing organs (leaves) allow easy diffusion of energy and raw materials throughout the plant body. However, if these distances increase due to changes in plant body design, diffusion becomes insufficient.