Phloem
Food-conducting tissue composed of sieve tube elements, companion cells, phloem parenchyma, and phloem fibres, transports organic nutrients.
What is Phloem?
The movement of sugars and other organic nutrients from the site of synthesis or storage to other parts of the plant where they are needed for growth or storage.
Key points
- Identify the components of phloem.
- Explain the function of phloem in translocation.
- Differentiate between the roles of sieve tube elements and companion cells.
- Understand the bidirectional nature of phloem transport.
Common exam trap
Confusing phloem with xylem in terms of function (food vs. water transport).
Definitions
- Term
Translocation
- Meaning
The movement of sugars and other organic nutrients from the site of synthesis or storage to other parts of the plant where they are needed for growth or storage.
- Term
Sieve Tube Elements
- Meaning
Elongated, living cells that form the sieve tubes; they are the primary conducting cells of the phloem but lack a nucleus and other major organelles at maturity.
- Term
Companion Cells
- Meaning
Specialized parenchyma cells closely associated with sieve tube elements, providing metabolic and functional support.
- Term
Source
- Meaning
A region in the plant where organic nutrients (like sugars) are produced or stored, typically mature leaves during photosynthesis.
- Term
Sink
- Meaning
A region in the plant where organic nutrients are utilized or stored, such as roots, fruits, seeds, or growing points.
Learning objectives
Identify the components of phloem.
Explain the function of phloem in translocation.
Differentiate between the roles of sieve tube elements and companion cells.
Understand the bidirectional nature of phloem transport.
Prerequisites
Plant Anatomy
Photosynthesis
Vascular Tissues (Xylem)
Common mistakes
Confusing phloem with xylem in terms of function (food vs. water transport).
Assuming sieve tube elements have a nucleus.
Forgetting the bidirectional nature of phloem transport.
Not distinguishing between the different cell types within phloem.
Keywords
Phloem
Translocation
Sucrose
Sieve Tube Elements
Companion Cells
Phloem Parenchyma
Phloem Fibres
Vascular Tissue
Source
Sink
Bidirectional Transport
Practice preview
Sieve tube elements are characterized by:…
medium
In a plant, if the phloem is removed from a stem in a ring (girdling), what is the most likely immediate consequence observed above the removed region?…
hard
Which of the following is NOT a component of phloem tissue in plants?…
easy