Question Video: Describing the Transport Vessels for Water in the Plant | Nagwa Question Video: Describing the Transport Vessels for Water in the Plant | Nagwa

Question Video: Describing the Transport Vessels for Water in the Plant Biology • Second Year of Secondary School

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The diagram provided shows a simplified outline of the movement of water through a plant. Through what transport vessel does the majority of water move? [A] Vein [B] Phloem [C] Cell walls [D] Xylem

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Video Transcript

The diagram provided shows a simplified outline of the movement of water through a plant. Through what transport vessel does the majority of water move? (A) Vein, (B) phloem, (C) cell walls, or (D) xylem.

To answer this question, let’s go through the different answer options and discuss what the purpose of each of the different mentioned structures is.

A vein, when used in the context of transport vessels, is a type of blood vessel that’s found in animals like humans. Veins form part of the human circulatory system that are responsible for transporting blood back toward the heart from the body tissues. A different sort of vein can also be found in leaves. While leaf veins do play a role in transport, they are not transport vessels themselves. As the question is specifically asking us the transport vessel through which water moves, we can eliminate option (A).

While the phloem and the xylem are both transport vessels that are found in plants, the cell wall is a rigid structural layer that surrounds plant cells. Cell walls are responsible for providing structural support and protection to plant cells, but cell walls are not a transport vessel. So this option can also be eliminated.

As we mentioned, the phloem and the xylem are both transport vessels, but they differ in their structure and function. The phloem transports substances like sugars and amino acids both up and down the plant stem. While these sugars and amino acids will be dissolved in water, so some water will be involved in phloem transport, it is not the main function of the phloem to transport water.

The xylem, on the other hand, is responsible for transporting the majority of water molecules in a plant. It also transports dissolved mineral ions. The water molecules and ions are generally absorbed from soil into the roots of a plant and then are transported from the roots into the plant stem. Unlike in the phloem, where substances can move both up and down the plant, the xylem only transports water and mineral ions up the plant from the roots to the leaves and flowers and any other organs that might require them.

If we take a look back at the diagram provided by the question, we can see that water is only moving up the plant from the roots to the leaves. This helps us to confirm that the phloem is not the vessel through which the majority of water moves, as it transports sugars and amino acids both up and down the plant stem. Instead, the role of the xylem is to move the majority of water through the plant.

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