Xylem

Definition

Xylem is a type of vascular tissue in plants that is responsible for the transport of water and dissolved nutrients from the roots to the leaves and other parts of the plant. It is a key component in the overall process of chemical bonding and energy production within the plant.

5 Must Know Facts For Your Next Test

1. Xylem vessels are made up of dead, hollow cells that are reinforced with the carbohydrate polymer cellulose, providing structural support for the plant.
2. The movement of water and nutrients through the xylem is driven by the process of transpiration, which creates a negative pressure (or tension) that pulls the water upwards.
3. Xylem also plays a role in the transport of some plant hormones, such as auxin, which are important for growth and development.
4. The walls of xylem vessels are often lignified, making them rigid and resistant to compression, which is important for the plant's ability to transport water against gravity.
5. Xylem tissue is typically found in the vascular bundles of the plant, alongside the phloem, and is arranged in a way that allows for efficient transport of water and nutrients.

Review Questions

• Explain the role of xylem in the overall process of chemical bonding and energy production within a plant.
  • Xylem is responsible for the transport of water and dissolved nutrients, such as minerals, from the roots to the leaves and other parts of the plant. This water and nutrient transport is essential for the plant's metabolic processes, including photosynthesis, which is the primary source of energy production. The water and nutrients transported by the xylem provide the raw materials needed for the chemical reactions that occur during photosynthesis and other metabolic pathways, ultimately supporting the plant's growth and development.
• Describe how the structure of xylem vessels contributes to their function in the plant.
  • Xylem vessels are composed of dead, hollow cells that are reinforced with the carbohydrate polymer cellulose. This structure provides the necessary rigidity and support for the xylem to effectively transport water and nutrients against the force of gravity. The lignified walls of the xylem vessels also help to resist compression, which is crucial for maintaining the continuous column of water that is drawn up through the plant via the process of transpiration. Additionally, the arrangement of xylem tissue within the vascular bundles, alongside the phloem, allows for the efficient and coordinated transport of water, nutrients, and other essential compounds throughout the plant.
• Analyze the relationship between xylem function and the cohesion-tension theory, and explain how this theory helps to explain the mechanism of water transport in plants.
  • The cohesion-tension theory provides a comprehensive explanation for how the continuous column of water in the xylem is able to be drawn up through the plant against the force of gravity. This theory states that the process of transpiration, which occurs in the leaves, creates a negative pressure (or tension) that pulls the water upwards through the xylem. The cohesive properties of water molecules, combined with the adhesive forces between the water and the walls of the xylem vessels, allow for the unbroken column of water to be maintained despite the pull of gravity. This efficient water transport system, facilitated by the xylem, is essential for the plant's overall metabolic processes, including the production of energy through photosynthesis. Understanding the relationship between xylem function and the cohesion-tension theory is crucial for comprehending the fundamental mechanisms underlying a plant's ability to transport and utilize water and nutrients.

Related terms

Phloem: Phloem is another type of vascular tissue in plants that transports organic nutrients, primarily sucrose, from the leaves to the rest of the plant.

Transpiration: Transpiration is the process by which water is lost from the leaves of a plant, creating a pull that draws water up through the xylem from the roots.

Cohesion-Tension Theory: The cohesion-tension theory explains how the continuous column of water in the xylem is able to be drawn up through the plant against the force of gravity.