Tissues in flowering plants Flashcards
What does dermal tissue form?
It forms the covering on a plant
Name an example of dermal tissue
epidermis
What is the main function of dermal tissue?
To protect the plant
Dermal tissue may have secondary functions, depending on its location.
Give two examples.
- Root hairs are extensions of the epidermis near the tip of the root and are designed to absorb water and minerals.
- The epidermis of leaves and most stems are coated with a way cuticle to prevent water loss from the plant.
Where is ground tissue found?
It occupies the area between the dermal and vascular tissues in a plant
List 3 functions of ground tissue.
It carries out a range of functions such as:
- photosynthesis
- Storage of food and wastes
- gives strength and support to a plant
What does vascular tissue consist of?
Xylem and phloem
What is the main function of vascular tissue?
To transport materials throughout the plant
Name the types of cells that xylem is made up of
Xylem is made up of two types of cells: vessels and tracheids
What happens to the living contents of tracheids and vessels before they reach maturity?
They die
When do the living contents of tracheids and vessels die?
before they reach maturity
Why is xylem a dead cell?
As the living contents of tracheids and vessels die before they reach maturity
Describe the appearance of xylem tracheids (4)
- They are long, sloping or tapering cells
- whose insides are hollow at maturity.
- They overlap and
- allow water to pass from tracheid to tracheid through thin parts of the wall called pits.
How do xylem tracheids pass water to each other?
They overlap and allow water to pass from tracheid to tracheid through thin parts of the wall called pits.
Where are xylem tracheids found?
They are the only type of xylem found in coniferous trees such as pine trees.
Define lignin
Lignin is a strengthening material found in some plant cell walls
Describe the structure of xylem vessels
They are tubular structures formed when a number of cells join end-to-end.
How do xylem vessels differ from tracheids?
They are wider than tracheids and their end walls break down to form a continuous tube.
What do xylem vessels have in their walls? What is their purpose?
They have pits in their walls to allow water to pass from one vessel to another.
How are vessels better than tracheids?
They are more efficient at transporting water than tracheids
Where are xylem vessels commonly found?
They are very common in flowering plants
What are cells that contain lignin said to be?
Lignified
What do tracheids and vessels have in common in terms of their structure?
They both have thick, lignified cell walls that gives them strength
What definite pattern is most common for lignin?
spiral
Give the functions of xylem (2)
- It transports water and mineral salts from the roots to the leaves.
- It also gives mechanical support to the plant (due to lignin)
Where is xylem found in plants?
It is found in roots, stems, leaves and flowers. It is often found in vascular bundles.
What is phloem composed of?
Sieve tubes and companion cells
How is phloem a living cell?
As companion cells are alive, phloem is a living cell
describe the structure of sieve tubes
They are long, tubular structures.
When do sieve tubes form?
when individual cells, called sieve-tube elements, join end-to-end.
Why do the end walls develop pores?
The end walls develop pores, which allow the passage of materials from one element to another.
Why are end walls called sieve plates?
The end walls are called sieve plates because they resemble plates with numerous pores in them.
The end walls develop pores, which allow the passage of materials from one element to another.
What happens to these elements?
The cytoplasm of each element remains, although the nucleus degenerates.
What are the cell walls of sieve tubes made of?
cellulose but lignin is not present
What does each sieve tube element have accompanying it?
Each sieve tube element has an accompanying companion cell on its outside.
What do companion cells contain?
These have a nucleus and dense cytoplasm
Where is phloem located?
Found in the roots, stems, leaves and flowers
Summarise all 4 differences between xylem and phloem
Xylem:
- Carries water and minerals
- Is dead
- Has lignin
- has no companion cells
Phloem:
- Carries food
- Is living
- Has no lignin
- Has companion cells
What must be labelled on a diagram for vessels? (5)
cell wall, lignin, pit, remains of old end wall, hollow lumen
What must be labelled on a diagram for tracheids? (4)
Lignin, cell wall, pit and hollow lumen
What must be labelled on a diagram for LS of phloem? (6)
Companion cell, sieve tube element, hollow lumen, cell wall, sieve plate, sieve tube
What must be labelled on a diagram for the TS (transverse section) of phloem? (3)
Companion cell, sieve tube (element) and sieve plate
