In highly organized plants, the transport system is sophisticated and essential for distributing water, nutrients, and other substances throughout the plant. This system consists of two primary types of vascular tissues:
Function: The xylem is responsible for transporting water and dissolved minerals from the roots to the rest of the plant. This includes upward transport from the roots to the leaves, stems, and flowers.
Tracheids and Vessel Elements: These are the water-conducting cells in the xylem. Tracheids are long, thin cells that are found in all vascular plants, while vessel elements, which are shorter and wider, are found in most angiosperms (flowering plants) and a few other plant groups.
Xylem Fibers: These provide structural support.
Xylem Parenchyma: These cells are involved in the storage and lateral transport of water and nutrients within the xylem.
Function: The phloem transports organic nutrients, particularly sugar (sucrose), from the leaves to other parts of the plant. This process is known as translocation and can move substances in any direction, depending on the plant’s needs.
Sieve Tube Elements: These are the main conducting cells in the phloem, forming long tubes through which nutrients flow.
Companion Cells: These cells are closely associated with sieve tube elements and play a crucial role in loading and unloading sugars into and out of the sieve tubes.
Phloem Fibers: These provide structural support.
Phloem Parenchyma: These cells are involved in the storage and lateral transport of nutrients within the phloem.
Other parts of the plant transport system
Roots: Roots absorb water and minerals from the soil and transport them to the xylem.
Leaves: Leaves are the primary sites of photosynthesis and produce the sugars that are transported by the phloem.
Stems: Stems support the leaves and flowers and contain the vascular tissues (xylem and phloem) that connect the roots and leaves.
This transport system allows plants to move water, nutrients, and sugars to where they are needed, supporting growth, development, and reproduction. The efficiency and effectiveness of this system are crucial for the survival of the plant, especially in large and complex plants.