Uploaded by adeyinka.banjo


2.1 – Plant Cells and Tissues
Many different types of plant cell
Each of these special types has a specific function
Three essential plant cells
Parenchyma Cells (Diagram labelling exercise) (Big table where they need to use word bank to connect
structure and function)
Structure: Thin walls; flexible; spherical shape; cell walls flatten when packed tightly together
Function: Storage; photosynthesis; gas exchange; protection
Special functions: Undergo mitosis when mature; when a plant is damaged, parenchyma cells
divide to repair it
Split into two broad groups: with and without chloroplasts
1) With chloroplasts: Photosynthesis; found in leaves and green stems
2) Without chloroplasts: Roots and fruits location; large central vacuoles which store starch,
water and oils
Found in Celery
Structure: Elongated (long); occur in long strands or cylinders; unevenly thickened cell walls (not
uniformly distributed)
Function: Provide support for surrounding cells
Growth abilities: As cell grows, thinner portions of the cell wall expand; allows collenchyma cells
to be flexible and stretch; which enables plants to bend without breaking
Cell division profile: can still undergo cell division when mature
Sclerenchyma cells
No cytoplasm and lacks organelles; only has thick, rigid cell walls
Function: Because of thickened cell walls Sclerenchyma cells are good at providing support for
plants; also transport material within the plant
Typically found in wood used for shelter, fuel and paper products
Comes in two distinct flavors:
1) Sclereid: Aka stone cells; what makes the outer skin of a pear rough; short and irregularly
shaped; makes the outer coat of seeds and nuts tough; contributes to transport
2) Fibers: Needle shaped with a thick cell wall and small interior space; stacking them end to
end creates a tough elastic tissue
Functions: to make ropes, linens, canvas, textiles
Plant Tissues [Diagram showing percentage composition of respective tissues and overall plant]
What is a tissue?
- A group of cells that work together to perform a specific function
- Can involve many copies of the same type or different cells coming together to contribute
towards a common goal
Meristematic tissue
- Equivalent of stem cell tissue
- Meristematic tissue  Meristems (regions of rapidly dividing cells)
- Structure: Large nuclei; small/no vacuoles
- Function: (plant) stem cells; can differentiate into any and all cells
- Found in 3 distinct locations:
1) Apical meristems
- Location: Tips of roots; stems of plants
- Function: Cell division at these locations leads to increases in length (primary growth)
2) Intercalary meristems
Location: Found along the stem of many monocots
Function: Cell division at these locations leads to increase in stem or leaf length
Lateral meristems
Facilitate an increase in root and stem diameters (widths)
This is secondary growth
Unique to a few plant types: non-flowering seed plants, eudicots, monocots
Two types:
1) Vascular cambium:
Thin cylinder of meristematic tissue and can run whole length of roots and stems
Function: produces new transport cells in some roots and stems
2) Cork cambium:
Function: Produces cells that develop tough cell walls; forms a protective outside layer on
stems and roots
Location: Outer bark on a woody plant like an oak tree
Dermal Tissue (Typically the surface of a leaf cell)
- Dermal tissue represents the layer of cells which make up the outer covering of a plant
- Jigsaw puzzle appearance; interlocking ridges and dips;
- Function? Creates waxy substances which go on to form the cuticle (reduces water loss by
slowing evaporation; also blocks entry of microbes)
- Interesting takes on the epidermis:
1) Stomata
Typically found on the epidermis of a leaf (sometimes green stems)
Structure: Small opening which has its size dictated by the opening and closing of guard cells
(shape changes)
Function: To allow carbon dioxide, water, oxygen and other gasses to pass
2) Trichomes
Hairlike projections; can leave a fuzzy appearance
Function? Protects from insects and animal predators; can also release toxic substances when
touched; also help to keep some plants cool by reflecting light
3) Root hairs
Fragile extensions of root epidermal cells
Increase surface area and enable the root to take in a greater volume of materials versus
Vascular tissue
Global function: Transport water, food, dissolved substances across the plant
What does it transport? Xylem carries water with dissolved minerals in it (vascular tissue)
Where does the transported substance come from? From the soil via the roots
Directionality? Away from the roots across the entire plant; one direction!
Remember! The xylem is a TISSUE: has two cell types within it – Vessel element; tracheids
At maturity these cell types only have a cell wall, allowing water to flow freely through them (no
Vessel elements
Tubular cells stacked end to end, forming vessels
Open at each end with barlike strips at each end (end walls)
In certain plants, these end walls (lids) are lost to allow the free movement of water and
dissolved substances across vessel elements without pause
Long cylindrical cells with pitted ends (end walls)
Cells are found end to end and form a tubelike strand
Even mature tracheids have end walls (unlike vessel elements which can lose theirs)
Less efficient
What does it transport? Food; dissolved sugars and other organic compounds
Directionality? Up and down the plant: from leaf/stems to root and from root to leaf/stem
Remember! The phloem is a TISSUE: has two cell types within it – sieve tube member;
companion cells
Sieve tube member
Has cytoplasm but no nucleus or ribosomes when mature
Has a sieve plate (end wall) with large pores to allow dissolved substances to flow
You find sieve plates at the end of each sieve tube member
2) Companion cells
- Has a nucleus
- Thought to support both cells
Special plant structures: The Sinks
Excess glucose can be converted to carbohydrates for use by the plant and stored in regions
called sinks
Parenchyma cells in the root cortex behave as sinks; they are storage cells
Transport of dissolved carbs from sources to sinks and other dissolved substances is called
Ground Tissue
Plant tissue which doesn’t belong to any of the three aforementioned categories
Consists of: parenchyma cells; collenchyma; sclerenchyma
Functions: Diverse – storage, support and photosynthesis
Forms most of the plant
Location specific roles
Leaves and green stems
- Ground tissue contains chloroplasts that produce glucose for the plant
Stems, roots and seeds
- Large vacuoles to store sugars, starch, oils and other substances