4.1 - Vascular Tissues

The Necessity of Transport in Plants

Due to the larger size of the plants, the total surface area is not enough for the absorption of organic and non-organic substances from the environment. Thankfully, the presence of vascular tissues can help to solve this problem. Vascular tissues are transport system in plants that transports nutrients, water and mineral salts to all parts of the plants. Vacular tissues consist of xylem and phloem.

• Xylem
  • Transport water and minerals from the roots to the stems and leaves of plants.
• Phloem
  • Transport organic compounds produced during photosynthesis from the leaves to the stems and roots.

Plants that have vascular tissues are called vascular plants. On the other hand, non-vascular plants are those without vascular tissues. Examples of non-vascular plants are alga and moss.

Structural Adaptations of Xylem Vessels and Tracheids to Transport Water and Mineral Salts

Other than transporting water and mineral salts, xylem also provides mechanical support to the plants.

Structures, Characteristics and its' functions

Xylem vessel

• Consist of dead cells upon maturation.
• Cells do not contain cytoplasm and are arranged continuously from end to end to allow transport of water efficiently.
• Cell walls are thickened with lignin to strengthen xylem vessel so that they will not rupture due to tension force and water pressure when water flows through.
• Lignin also prevents the plants from bending.

Figure 1 - Xylem vessel.

Tracheid

• Cell walls are also thickened with lignin and contain pores that enable water movement to the neighboring tracheids.

Figure 2 - Tracheids.

Structural Adaptations of Sieve Tubes and Companion Cells to the Transport of Organic Substances

Figure 3 - Structure of phloem.