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Plants
A study of
multicellular organisms
Cell Specialization
• Why do cells specialize?
– Increase efficiency
• Division of labor
– What does efficiency look like?
• Special cell shapes, sizes, type and
number of organelles, and locations in
the organism
Cell Specialization
• The cell is the basic unit of life
• In multicellular organisms cells take on
specialized roles to perform a
specialized function.
– Tissues: Groups of cells that perform the
same function are called tissues
– Organ: Different types of tissues can
combine together to form an organ
– System: Different organs can also
work together to form a system
What are some functions done
by different parts of a plant?
Shoot
System
Root
System
Specialized cells
in a leaf
Tissue Types in the Leaf
• Dermal Tissue
– Thin protective outer layer
• Ground Tissue
– Middle layers
• Vascular Tissue
– Cells specialized in transport
Dermal Tissue
Epidermal Cells
• Like skin cells, they form a
protective layer on the upper and
lower surface of the leaf
– one cell layer thick
– Arranged in a flat tightly knit sheet
– Transparent to allow sunlight to pass
through to cells that specialize in
photosynthesis layer
Cuticle
• Covers the epidermis to prevent
water loss
– Waxy substance secreted by the leaf
cells
– Also protects from disease causing
micro-organisms
Stomata and Guard Cells
• Small openings in the epidermal
layer
– Allow gasses and water to enter
and leave the leaf
– Mostly found on the underside
of the leaf
– Each stoma has 2 guard cells that
regulate the stoma’s size
Micrographs of Stomata
Ground Tissue
Ground Tissue
• The majority of the plant
• Located under the epidermis
– In the stem
• Provides strength, support
– In the roots
• Food and water storage
– In the leaves
• Where photosynthesis occurs
What functions occurs
inside a leaf?
• Photosynthesis!!!
– Leaves are flat and have a lot of
surface area so that they can absorb
the suns rays and use the energy to
create glucose.
• What is the chemical formula for
photosynthesis?
– CO2 + H2O
C6H12O6 + O2
Where does
photosynthesis occur?
• Chloroplasts
– Contain special pigments that capture
light energy
• Therefore, leaf cells contain
a lot of chloroplasts
Palisade
Tissue Cells
• Cells that are structured and arranged
to maximize efficiency for
photosynthesis
–
–
–
–
Form a distinct layer in the leaf
Long, and narrow (look like columns)
Tightly packed
Contain many chloroplasts
Spongy Tissue Cells
• Located below palisade tissue cells
• Round and loosely packed, lots of
air spaces
– Helps exchange gasses and water
with the environment
• Contain some chloroplasts (thus,
perform photosynthesis)