Question

Explain why xylem transport is unidirectional and phloem transport bi-directional?

Answer 1

Hint: Plants do not have a fully organized circulatory system like the higher animal. They have some slightly different processes of transport of the material. Xylem and phloem are the vascular tissue for transport of the material from a long distance. Cell to cell movement of material occurs for short distances.

Complete Answer:
- The leaves of the plant are the main source of food because they play a main role in photosynthesis.
- Roots absorb water from soil and transport to the tip of stem and this process is known as water uptake.
- Water uptake into the plants is carried out by three mechanisms that are diffusion, osmosis, and water potential gradients.
- Xylem transports the minerals with water and columns in the xylem flow the water in upward direction. Movement of water takes place from roots to leaves only.
- Phloem transports the organic solute in the various parts of the plant as well as store the food from various parts of the body so that movement of food in phloem is upward and downward. So, phloem transports bi- directional.
- Xylem transport the water from roots to various parts of the plant like stem, leaves, flowers and fruits that are unidirectional.
- Food synthesized in one part of the plant and transported to all parts including storage units by phloem.

Note: The nutrients transported by xylem are inorganic nutrients whereas phloem transport the organic solute.