Explain the transportation of water and minerals by xylem tissues.
Plants have two systems for the transportation of substances - using two different types of transport tissue. Xylem transports water and solutes from the roots to the leaves, while phloem transports food from the leaves to the rest of the plant. Transpiration is the process by which water evaporates from the leaves, which results in more water being drawn up from the roots. Plants have adaptations to reduce excessive water loss. Phloem transports synthesized food from the leaves to the rest of the plant body.
Water from the roots is pulled up by this tension. At night, when stomata close and transpiration stops, the water is held in the stem and leaf by the cohesion of water molecules and the adhesion of water to the cell walls of the xylem vessels and tracheids.
Transportation in Plants
Transportation is the process which involves the movement of water and necessary nutrients to all parts of the plant for its survival.
There are two kind transport systems found in plant - xylem and phloem.
Transport of water
Xylem
The xylem transports mainly water and minerals from the roots up the plant stem and into the leaves.
Most of the cells that make up the xylem in a mature flowering plant or tree are specialized cells called vessels.
Transportation in the xylem is a physical process. It does not require energy.
The water is absorbed by the root hair and that undergoes cell to cell movement by osmosis until it reaches the xylem.
This water is then transported through the xylem vessels to the leaves and is evaporated by the process of transpiration.
Transport of food and other substances
Phloem
Phloem is a special tissue that moves sugar shich the plant has produced by the process of photosynthesis to other parts of where it is needed for processes such as:
• growth parts of the plant for immediate use.
• storage organs such as bulbs and tubers
• developing seeds
• respiration
Transport in the phloem is therefore both upwards and downward the stem.
The process of transportation of substances in the phloem is called translocation.
Phloem consists of living cells.