Transcript Leaf structure - Teaching Biology Project

Plant Tissues and Organs
Plant Tissues
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All plants are made up roots, stems, leaves and
flowers. These structures are made up of cells
These cells are not always the same in structure.
They differ depending on what function they perform
Some groups of cells have a supportive function.
Others may be involved in photosynthesis.
Cells which have a similar function, are similar in
structure and form tissues.
Examples of some Plant Tissues
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Epidermal tissue – a single layer of cells found
covering the surface of the plant
Some epidermal cells are specialised for
perform a certain function. Examples:
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Guard cells in leaves
Roots hairs in roots
Vascular Tissue: Two types:Xylem – transports water
from the roots via the
stems to the leaves. The
cells are elongated and
hollow with thickened,
lignified cell walls. They
are arranged end-to-end.
They also have a
supportive function.
Vascular Tissue:
Phloem – transports
food made in the
leaves to the rest of
the plant. Cells are
also elongated and
arranged end-toend.
Supportive Tissues
Supportive tissues – collenchyma and sclerenchyma
Other Plant Tissues
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Photosynthetic Tissue – found in the leaves –
the cells contain many chloroplasts.
Storage and packing tissues called
parenchyma. This tissue is the most common
plant tissue found in plants.
Plant Organs
Tissues are grouped
together to form a
structure with a special
function. This structure is
called an organ.
Examples of plant organs
are:
– Roots
– Stems
– Leaves
– Flowers
Function of the Root
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To anchor the plant in the soil
To absorb water and nutrients from the soil
for photosynthesis in the leaves
Some roots store extra food – e.g. carrot
Function of the Stem
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Support the plant
Conduct water and nutrients from the roots to
the leaves
Conduct food (glucose) manufactured in the
leaves to rest of plant
Structure and Functions of a Plant
Leaf
Function of the Leaf
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Photosynthesis
Gaseous exchange
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take in O2 and release CO2 during respiration
take in CO2 and release O2 during photosynthesis
Water Vapour can be lost from the surface of
the leaf in a process known as Transpiration.
Photosynthesis
Energy
(Sun)
+ CO2
(from
air)
+ H20
(from
roots)
Glucose
In chloroplast
(chlorophyll)
(Stored as
starch)
+ O2
(Released
into air)
Structure of the Leaf
Transverse section of a leaf
phloem
xylem
Water-carrying cell
Leaf vein
Opening for CO2
and O2 and water
vapour
Transverse section of a leaf at cellular level
Stomata: Functions
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The stomata are
responsible for the
interchange of gases for
respiration and
photosynthesis.
The stomata allow for
the loss of excess water
in the form of water
vapour, which also
allows for cooling.
Quiz: Label the parts of the leaf
Stoma
cuticle
Palisade mesophyll
Spongy mesophyll
Upper epidermis
Air spaces
A
B
C
D
E
F
Brainstorm
How are leaves adapted to
their functions of
photosynthesis and gaseous
exchange? - Try to think of 7
adaptations
How is the Leaf adapted to its function?
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Broad, flat-shape – large surface area for absorption of sunlight
and carbon dioxide
Thin – gases have a short distance to travel (Epidermis – 1 cell
layer thick)
Large air spaces between the cells of the spongy mesophyll –
allow for easy passage of carbon dioxide and oxygen
Waxy Cuticle (reduces water loss)
Many stomata in the lower surface allow for the exchange of carbon
dioxide and oxygen with the air outside (open during day, close at
night)
More chloroplasts in upper palisade than spongy mesophyll cells
where they receive the most sunlight
Branching network of veins which provide a good water supply to
the cells for photosynthesis.