Phloem

Definition

Phloem is a type of vascular tissue in plants responsible for the transport of nutrients, particularly sugars produced through photosynthesis, from the leaves to other parts of the plant. This tissue plays a critical role in the plant's overall nutrition and growth, connecting leaves with stems and roots. Phloem is essential for maintaining energy balance and supporting metabolic processes throughout the plant.

5 Must Know Facts For Your Next Test

1. Phloem transports organic compounds, primarily sucrose, from source tissues (like leaves) to sink tissues (such as roots and fruits) where they are needed or stored.
2. The flow in phloem is bidirectional, allowing for nutrient distribution both upwards and downwards within the plant.
3. Phloem consists of living cells, which differentiates it from xylem that mainly consists of dead cells when mature.
4. The movement of substances in phloem is driven by a pressure flow mechanism, where sugars are actively transported into the sieve tubes, leading to water influx and increased pressure.
5. Damage to phloem can disrupt nutrient transport, leading to stunted growth or even death in plants, showcasing its vital role in plant health.

Review Questions

• How does phloem contribute to the overall nutrition of a plant?
  • Phloem is crucial for the distribution of nutrients throughout a plant. It primarily transports sugars produced in the leaves during photosynthesis to various parts of the plant, including stems, roots, and fruits. This transportation supports cellular respiration and energy storage, ensuring that all parts of the plant receive the necessary compounds for growth and maintenance.
• What are the key structural components of phloem, and how do they function together to transport nutrients?
  • Phloem is made up of several types of cells, including sieve tube elements and companion cells. Sieve tube elements form long tubes that facilitate the movement of sugars and other nutrients. Companion cells are closely associated with sieve tube elements and play a vital role in loading sugars into the phloem. Together, these components ensure efficient nutrient transport throughout the plant.
• Evaluate the importance of phloem in plant health and its impact on overall plant functioning.
  • Phloem plays a fundamental role in maintaining plant health by facilitating nutrient transport necessary for growth and development. Without proper phloem function, plants cannot distribute vital sugars and organic compounds effectively, leading to nutrient deficiencies that can stifle growth or result in death. The pressure flow mechanism within phloem is critical for responding to varying environmental conditions and internal needs, showcasing its adaptability and importance in overall plant functioning.

Related terms

Xylem: Another type of vascular tissue that transports water and dissolved minerals from the roots to the rest of the plant.

Sieve Tube Elements: The main conductive cells in phloem that facilitate the transport of sugars and other organic nutrients.

Companion Cells: Specialized cells associated with sieve tube elements that help in the transport process and maintain the function of phloem.