Plant Tissues Flashcards
What are the two main types of plant tissues?
Meristematic
Permanent
What is a tissue?
A group of similarly differentiated cells that group together to perform a common function
What is meristematic tissue?
Those that can divide
Not specialised
What is permanent tissue?
Those that have become completely differentiated to perform a common function
What are the two types of meristematic tissue?
Apical meristem
Lateral meristem
What is apical meristem?
Tissues that grow in height and length
What is lateral meristem?
Tissue that grows in width
What are the three types of permanent tissue?
Dermal
Ground
Vascular
Where can the dermal tissue be found?
In the epidermis
What is the function of the dermal tissue?
For protection
Prevention of water loss
Where are four places where ground tissue is found?
Parenchyma
Collenchyma
Chlorenchyma
Sclerenchyma
What are the five main functions of ground tissue?
Regeneration Protection Food storage Support Photosynthesis
Where are two places where vascular tissue can be found?
Phloem
Xylem
What does xylem carry?
Water
What does phloem carry?
Food
What is the function of vascular tissue?
To transport water, mineral salts and food
What does meristematic tissue do?
The cells are constantly dividing through mitosis
They produce new cells for growth and to replace damaged cells
Where can apical meristem be found?
In the tips of roots and stems
What kind of growth is apical meristem needed for?
Primary growth
Length of roots and stems
What is another name for lateral meristem?
Cambium
Where can cambium be found?
In the stems of flowering plants
Between xylem and phloem in vascular bundles
What kind of growth is cambium necessary for?
For growth in the width of the stem
Lateral roots
What are lateral roots?
In the tap root system, they are the roots that spread out from the tap root
What is the structure of meristematic cells?
Small Brick shaped Thin cell wall Large round nucleus (for active cell division) Dense cytoplasm No vacuoles No intracellular airspaces
How does meristematic tissue act as a lubricant?
The cells on the tips of the roots burst
The dense cytoplasm in them acts as a lubricant to allow the roots to grow further
What happens to meristematic tissue after a while?
It will turn into permanent tissue through the process of differentiation
How does differentiation occur?
Cells undergo chemical and structural changes
What is the general function of parenchyma?
Packaging material
What is the general function of collenchyma?
Structure and support
What is the general function of sclerenchyma?
Strength and protection
What is the general function of the epidermis?
Protection
What is the general structure of permanent tissue?
Has a specific function Cells are larger The cell walls are thicker The cytoplasm is not as dense Large vacuoles are common Shapes and sizes differ according to function
Where can the dermal tissue be found?
Surrounding the outside of the plant
What does the epidermis prevent?
Drying out
Mechanical injury
Which is the most abundant tissue?
Ground tissue
What does ground tissue do?
Fills spaces between other tissues
Is used for mechanical support
What is the structure of the epidermis like?
Brick shaped
No intercellular airspaces
Cells walls are strengthened with cellulose and lignin
Transparent to allow sunlight to reach the cells beneath
These plant cells have no chloroplasts
Waxy cuticles on the stems and leaves
Why are the cuticles on the epidermal cells necessary on the stems and leaves, but not on the roots?
The cuticle reduces water loss, but on the roots water needs to be able to pass easily through the roots
What are three types of specialised epidermal cells?
Stomata
Root hair
Trichomes
What kind of cell is a guard cell?
An epidermal cell
Where can a guard cell be found?
On the leaf epidermis
On the underside of the leaf
What is the structure of the guard cell like?
Kidney shaped
The only epidermal cells with chloroplasts
Unevenly thickened cell wall (thin outer, thick inner)
What does a turgid guard cell create?
A stomata
What is a stomata?
A hole between guard cells that allows for gaseous exchange
What happens when guard cells become flaccid?
The stomata closes
What are trichomes?
Epidermal hairs
They are small outgrowths on the surface of a plant
They are multicellular
What is the size of trichomes?
They are microscopic
Where can trichomes be found?
On the stems of some plants
What is a root hair?
Also an epidermal outgrowth
They are unicellular
It does not have a cuticle
Where can root hairs be found?
On the roots of cells
Why can chlorenchyma not be considered its own type of ground tissue?
It is a specialised parenchyma
Where can parenchyma be found?
In the spaces between other tissues
What is the basic structure of parenchyma?
Living Round Thin cell walls Large vacuoles Large intercellular spaces
Why are large vacuoles in parenchyma important?
They store water
They control turgor pressure
They provide internal support for young plants
Why are the large intercellular spaces necessary in parenchyma?
Allows gases to move between cells
What else does parenchyma do?
Stores sugar and starch for the plant Used as packaging tissue Provided carbohydrates through photosynthesis Gaseous exchange Rigidity (turgor pressure)
Why is chlorenchyma different from ordinary parenchyma?
It contains chloroplasts
Where are chlorenchyma found?
In herbaceous leaves and stems
What is the general structure of chlorenchyma?
Thin walls for gaseous diffusion
Plenty of chloroplasts for maximum photosynthesis
What is the function of a root hair?
To increase the surface area
To help absorb water and mineral salts
Where can palisade chlorenchyma be found?
Underneath the epidermis
Where can spongy chlorenchyma be found?
Underneath the palisade chlorenchyma
What is the structure of palisade chlorenchyma?
Rectangular
Vertical to intercept maximum sunlight
Tightly packed
What is the structure of spongy parenchyma?
Round
Large intercellular airspaces for movement of gasses
How does being vertical help palisade chlorenchyma absorb more sunlight?
Having a short side on the bottom as opposed to having along side in the bottom means that the surface area exposed to the sun is increased
Where can collenchyma be found?
In young stems just beneath the epidermis
What is the structure of collenchyma?
Living
Unevenly thickened cell walls
No intercellular spaces (filled with pectin and cellulose)
Often have chloroplasts
What is the function of collenchyma?
For structure and support
For photosynthesis
What is the difference between collenchyma and parenchyma?
The collenchyma has cellulose where parenchyma has intercellular air spaces
Where is sclerenchyma found?
Leaves
Stems
Fruits
What is the structure of sclerenchyma?
Dead cells
Evenly thickened cell walls (lignin and cellulose)
Pits in walls (allow water to move)
At the centre is a lumen (empty space)
What are the two types of sclerenchyma?
Sclereids
Firbres
Where can sclereids be found?
Stone in peach
Gritty part of a pear
Where can fibres be found?
Rope
Twine
Linen
Where can xylem be found?
Leaves
Stem
Roots
What is the general structure for xylem?
Walls contain lignin
Mature cells are dead
Large lumen present (to carry the water)
What are the two kinds of xylem?
Vessels
Tracheids
Where do vessels occur?
In older plants
Where do tracheids occur?
In younger plants
What is the structure of vessels?
Elongated
Arranged end-to-end
Form a long continuous tube
What is the structure of tracheids?
Long, narrow cells
Taper at ends
Form a tube
Apart from carrying water, what function does xylem have?
Strengthening component (dead cells) and lignin Lignin is waterproof (does not collapse)
Where can phloem be found?
Roots
Stems
Leaves
What are the two types of cells that form phloem?
Sieve cell
Companion cell
What is the structure of a sieve cell?
Forms a tube with sieve plates
Has a large vacuole
Has a thin layer of cytoplasm
Has no nucleus
What is the function of the companion cell?
It is attached to the sieve cell
Has a nucleus for communication
Controls the sieve cell
What are the phloem cells like when mature?
Living
What does T/S mean?
Transection
What does a transection mean?
The diagram shows the cell when it has been cut across itself
What are the two types of chlorenchyma?
Palisade chlorenchyma
Spongy chlorenchyma
How does the structure of lateral meristem differ from apical meristem?
They are flatter and slightly elongated
The cell walls are slightly thicker
What is secondary meristematic tissue?
When a group of cells divides actively for a particular function (replace damaged and worn-out cells)
How many layers does the epidermis form?
Usually a single layer
What is the biological word for drying out?
Dessication
What is the structure of sclereids?
Rounder than fibres
What is the structure of fibres?
More elongated
Where is the cell wall in collenchyma thickest?
In the corners
What are vessel elements?
The individual cells composing the xylem vessels
What are transverse walls?
The walls between vascular cells
What is another name for a transverse wall?
A cross-wall
What three patterns does lignin form in xylem cells?
Spiral
Annular
Pitted
What do pits in xylem cell walls do?
Enable lateral transport between the xylem vessels
What is xylem like in a cross section?
Round
Which kind of xylem transports water faster?
Vessels
Why does xylem need to be so strong?
If it was weak, the water pressure would crush the xylem and it wouldn’t work
What are sieve plates?
Cross-walls between sieve cells
What do sieve plates do?
They are perforated and serve to filter the substances that travel through the phloem
Why do sieve tubes need companion cells?
The companion cells have nuclei, which instruct the sieve tube’s metabolic processes
Where does phloem transport food to and from?
From the leaves to the rest of the plant
Where does xylem transport water to and from?
From the roots to the rest of the plant
How do you identify parenchyma?
Air spaces
Large vacuoles
Thin cell walls
How do you tell the difference between collenchyma and sclerenchyma?
Sclerenchyma: cell walls are thickened evenly
Collenchyma: cell walls are unevenly thickened (most thickened around the corners
