PLANT STRUCTURE
AND FUNCTION
Part 3. Leaves and Transport Review
By Zamzam Nursani
Biology Class SMAK 1 BPK Penabur Bandung
LEAVES
• Main organs of photosynthesis
– Makes food for plants (glucose: C 6H12O2)
• Structure is optimized
for absorbing light and
carrying out
photosynthesis
Blades: thin, flattened to
increase surface area to
absorb sunlight
• Attached to stem by petiole
Epidermis: outer layer
Cuticle: waxy, protective
layer
• Protects tissues and limits
water loss
Photosynthesis Tissue
Most of photosynthesis
carried out in
MESOPHYLL layer
• Packed with
chloroplasts
Palisade Mesophyll:
column-shaped cells
just under epidermis
• Absorb most of light
coming into leaf
Spongy Mesophyll: loose tissue layer
beneath palisade with air spaces
between cells
• Air spaces connect with outside
through STOMATA
Monocot
VS Dicot
Stomata
• STOMATA: pores in underside of leaf that let
carbon dioxide and oxygen diffuse in and out of
the leaf
– Each stoma consists of two GUARD CELLS
• Guard Cells: cells in the epidermis that control the opening
and closing of the stomata by responding to water pressure
changes
Stomata and transpiration rate
Transpiration is water taken up from the soil and lost through the stomata in
the leaves. This loss of water as vapor through stomata is directly related to the
degree of stomatal opening, the supply of water to the leaves, and the evaporative
demand of the atmosphere surrounding the leaf
WATER TRANSPORT REVIEW
Water potential is
the potential of
water to move from
one area to
another due to
differences in
pressure, solutes
dissolved in the
water and other
factors.