key term - Xylem

Definition

Xylem is a type of vascular tissue in plants responsible for the transport of water and dissolved minerals from the roots to the rest of the plant. It plays a crucial role in plant physiology, contributing to water relations, mineral nutrition, and overall plant structure and function.

5 Must Know Facts For Your Next Test

1. Xylem consists of two main types of cells: tracheids and vessel elements, which work together to transport water efficiently.
2. Water movement through xylem occurs primarily through capillary action and negative pressure generated by transpiration from leaves.
3. Xylem also provides structural support to the plant, allowing it to grow tall and maintain rigidity.
4. Unlike phloem, xylem is composed of dead cells at maturity, making it an efficient conductor of water.
5. Xylem tissues can vary in structure between different plant species, reflecting adaptations to their environments.

Review Questions

• How does the structure of xylem contribute to its function in water transport within plants?
  • The structure of xylem, which includes tracheids and vessel elements, is specifically designed to facilitate efficient water transport. Tracheids are long and narrow, allowing for minimal resistance as water moves through them, while vessel elements are wider and enable rapid flow. The combination of these cell types allows plants to transport water over long distances effectively, which is essential for their growth and survival.
• Discuss the role of xylem in maintaining plant structure and how this relates to overall plant health.
  • Xylem plays a critical role in maintaining plant structure due to its lignified walls, which provide rigidity and support. This structural integrity allows plants to grow taller and withstand various environmental stresses. A healthy xylem system ensures adequate water transport, which is vital for photosynthesis and nutrient uptake; any disruption in xylem function can lead to wilting or decreased growth, affecting overall plant health.
• Evaluate the significance of the cohesion-tension theory in understanding how xylem operates within plants under varying environmental conditions.
  • The cohesion-tension theory is fundamental in explaining xylem function, particularly how it operates under different environmental conditions. This theory posits that water molecules exhibit cohesion, creating a continuous column of water within xylem vessels. When transpiration occurs at the leaf surface, it generates negative pressure that pulls water upward through the xylem. Understanding this mechanism is crucial as it highlights how factors like humidity, temperature, and soil moisture can impact water transport efficiency in plants, revealing their adaptability to changing environments.

Related terms

Phloem:

Another type of vascular tissue that transports sugars and other metabolic products downward from the leaves.

Tracheids: Long, narrow cells in xylem that facilitate water transport and provide structural support; they are found in all vascular plants.

Cohesion-Tension Theory: A theory that explains how water moves through plants due to the combined effects of water cohesion and the tension created by evaporation from leaves.