An Intro to Xylem and Phloem in Plants

Al Ardh Alkhadra > Blog > Agriculture > An Intro to Xylem and Phloem in Plants

Xylem and phloem 1

Xylem and phloem are complex tissues that perform the transportation of water and food in a plant. They are the vascular tissues of the plant. Xylem and phloem together form vascular bundles. They work together to bring about adequate transportation of nutrients, food, minerals, and water.

The plant tissue, xylem – transports and stores water and water-soluble nutrients in vascular plants. In contrast, plant tissue phloem is responsible for transporting sugars, proteins, and other organic molecules in different types of plants.

Xylem and phloem 6

Do you know that vascular plants can grow higher and taller than other plants due to the rigidity of xylem cells? It is the xylem cells that support the plant.

Vascular Tissue: Xylem and Phloem

You would be surprised to know that the first fossils that show the presence of vascular tissue dates back to the Silurian period. It was about 430 million years ago. 

The most straightforward arrangement of conductive cells shows a pattern of xylem cells at the center. These phloem cells surround the xylem cells. Both together, xylem and phloem tissues – from the vascular system in plants.

Xylem is the tissue solely responsible for supporting the plant. It is also responsible for the storage and long-distance transport of water and nutrients. Nutrients may include the transfer of water-soluble growth factors from the organs of synthesis to the target organs. 

Xylem and phloem 3

The xylem tissue consists of vessel elements or conducting cells. These conducting cells are known as tracheids. The supportive filler tissues are called parenchyma. These cells are generally joined end-to-end to form long tubes. 

Tracheids and vessels are dead at maturity. Tracheids usually have thick secondary cell walls. These cells taper at the ends. The thick walls of the tracheids provide support for the plant. They support the plant, thus allowing them to achieve impressive heights. 

Tall plants are always at an advantage. Probably because they are able to reach unfiltered sunlight and disperse their seeds or spores further away. These two features make tall plants expand their range and can quickly spread to other areas.

When tall plants grow higher than other plants, they cast their shadow on shorter plants. This process limits the  competition for water and precious nutrients in the soil. 

Note that the tracheids do not have end openings like the vessels do. But the ends of the tracheids overlap, with pairs of pits present. These pit pairs allow water to pass horizontally from one cell to the other easily. 

Key Terms

Xylem – It is a vascular tissue in land plants. These vascular tissues are primarily responsible for distributing water and minerals taken up by the roots. Xylem also forms the primary component of wood.

Xylem and phloem 2

Phloem: A vascular tissue in land plants which is primarily responsible for the distribution of sugars and nutrients manufactured in the shoot.

Tracheid: They are elongated cells in the xylem of vascular plants that serve to transport mineral salts and water.

The Function of Phloem Tissue

Phloem tissue is primarily responsible for translocation. It transports soluble organic substances, for example, sugar. These substances like sugar travel along with sieve elements. But these tissues also contain other types of cells like the companion cells, parenchyma cells, and fibers. 

Unlike vessel members in the xylem, the end walls of phloem tissue do not have large openings. The end walls are full of tiny pores where cytoplasm extends from cell to cell.

Xylem and phloem 4

These small porous connections are called sieve plates. Though their cytoplasm is actively involved in the conduction of food materials, these sieve-tube members lack nuclei at maturity. Companion cells control the activity of the sieve tubes through a plant process.

Both the xylem and phloem need to maintain a steady water and carbohydrates transport rate. It is necessary to match the exchange rates of these compounds at the leaves. 

You should note that a major proportion of the nitrogen and carbon assimilated by a tree is allocated to maintaining and constructing the xylem and phloem long-distance transport tissues. 

Importance of Xylem and Phloem

Both the xylem and phloem need to maintain a steady water and carbohydrates transport rate. It is necessary to match the exchange rates of these compounds at the leaves. 

Xylem and phloem 5

You should note that a major proportion of the nitrogen and carbon assimilated by a tree is allocated to maintaining and constructing the xylem and phloem long-distance transport tissues.

All the dissolved compounds are transferred from roots to stems in the xylem tissues. But in the phloem tissue, the food is transported from the plant’s leaves. It is in the leaves that photosynthesis process takes place. So the prepared food is transported to other parts like roots and stems. As the other parts of the plant are non-photosynthesis parts of the plant. Meaning the roots and stems of the plant cannot prepare food for the plant.

Xylem and phloem 7

Therefore these two vascular tissues are essential for the survival of the plant. Without these tissues, plants cannot live. Water and food are very important to live similarly to plants as human beings. Every part of the plant needs food and water. Each cell in the plant indeed needs food, without which survival is impossible.

Frequently Asked Questions

What are the functions of xylem and phloem?

Xylem and phloem facilitate the transportation of food, water, and minerals throughout the plant. Xylem carries water and minerals from the roots to the leaves. Meaning they carry the raw material required by the plant. On the other hand, phloem carries the prepared food by the leaves to different plant parts.

Are xylem cells dead?

Yes, xylem cells are made up of a long chain of dead cells often known as vessel elements. The vessel elements have no organelles. Meaning the components of xylem tissues are highly clarified and dignified. Hence, xylem cells are considered dead.

Why are the phloem cells alive?

The cells that make up the phloem tissues should be alive to facilitate the active transport of sucrose throughout the plant.

What are the differences between xylem and phloem?

Xylem is the permanent and dead tissue that tends to carry both water and essential substances inside the plant. The primary function of the xylem is known to be to transport water, minerals, inorganic ions, and soluble nutrients. All this transportation happens in an upward movement from the roots to the different parts of the plant.

Xylem and phloem 8

On the other hand, phloem is a complex tissue in the plant. These tissues help transport the soluble organic compounds throughout the different parts of the vascular plants. Phloem tends to use the energy for transporting the sugars and many other substances to several parts of the plant.

What are the similarities between xylem and phloem?

Xylem and phloem are complex tissues with more than one kind of cell.

  • Both of them are the components of the vascular tissues system in plants. 
  • Both of them contain fiber.
  • The xylem and phloem are differentiated into the proto and eta elements in the primary vascular bundles.
  • Both of them show direct as well as secondary growth.
  • Both xylem and phloem develop from the cambium.

Final Thoughts

Just like in animals, vascular tissue in plants transports substances throughout the plant body. But instead of a circulatory system that may circulate by a pump, the vascular tissue in plants does not circulate substances in a loop. But in plants, it transports from one extreme end of the plant to the other.

Vascular tissue in plants like xylem and phloem is made of two specialized conducting tissues. Xylem conducts water, and phloem, conducts sugars and other organic compounds. 

Note that a single vascular bundle always contains both xylem and phloem tissues. Unlike the animal circulatory system, where the vascular system is composed of tubes that are lined by a layer of cells. The vascular system in plants is made of cells – the substance (water or sugars) moves through individual cells to get from one end of the plant to the other.

Leave a Reply

Your email address will not be published.