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Specialized Plant Cells:
Transport in Leaves
9 Bio
Leaf Structure- Overview
• Leaf structure is arranged in
layers:
– 1. Upper epidermis
• Waxy cuticle prevents water
loss
– 2. Pallisade layer
• Chloroplasts – photosynthesis
(glucose production)
– 3. Spongy pallisade layer
• Storage of H2O, CO2 and O2
– 4. Lower epidermis
• Stomata and guard cells
regulate the passage of water
vapor( transpiration), intake of
CO2, output of O2
Palisade Mesophyll Layer
• Contains chloroplasts:
– Outer membrane
– Granum- stack of
thylakoids
– Thylakoids- contain
chlorophyll, catch
photons of light
photosynthesis
glucose
– Stroma- fluid filled space
Spongy Mesophyll Layer
• Open space to store
gases ( CO2 and O2) and
H2O molecules for
exchange in
atmosphere
– CO2 needed for
photosynthesis
– O2- by-product of
photosynthesis
– H2O- transpiration
Lower Epidermis
• Has guard cells
surrounding stomata
– Stomate (singular)
– Opening and closing of
stomata regulated by
plant hormone abscisic
acid
• Abscisic acid present: K+
leaves, H2O leaves,
stomata close
• Abscisic acid absent: K+
stays, H2O stays, stomata
open
Regulation of Transport
• Lower Epidermis:
– Takes in CO2 for
photosynthesis
– Releases O2 from
photosynthesis
– Releases H2O
(Transpiration)
• Why would stomata
remain closed in arid
conditions?
• When might plants lose
the most H2O?
• When might plants
produce a high level of
O2?
• When might plants need
a greater amount of CO2?