Notes

One-way molecules move is by diffusion but it alone cannot supply the need. It takes much time for materials in solution to diffuse even a few inches Diffusion can work only in unicellular and simple multicellular organisms because every corner of their body is in close and direct contact with the environment. In complex multicellular bodies, cells are far apart from the environment and such bodies need a comprehensive system for the transport of materials. 

Water is vital to plant life. It is necessary not just for photosynthesis and turgor, but much of the cellular activities occur in the presence of water molecules and the internal temperature of the plant is also regulated by water. Land plants get water and minerals from the soil. After absorption by the roots, these water and minerals have to be transported to the aerial parts of the body.

The function of Xylem Tissue:

Xylem tissue is responsible for the transport of water and dissolved substances from roots to the aerial parts. It consists of two types of cells i.e. vessel elements and tracheids.

The function of Phloem Tissue:

Phloem tissue is responsible for the conduction of dissolved organic matter (food) between different parts of the plant body. It consists of sieve tube cells and companion cells.