A. LEAF STRUCTURE
Waxy cuticle
Upper epidermis
Palisade Chloroplasts
mesophyll cells
Xylem
Spongy
mesophyll cells Phloem
Lower epidermis
Air space Stomata Guard cell
WAXY • Waterproof and prevents water from evaporating
CUTICLE out of the leaf.
UPPER • Single layer of cells with no chloroplasts.
EPIDERMIS • Thin and transparent for maximum light penetration.
PALISADE • These cells contain many chloroplasts.
MESOPHYLL • They are near the leaf surface and are packed close
CELLS together to absorb more light.
• Where most photosynthesis takes place.
CHLOROPLASTS • These trap light energy and convert it into
chemical energy and make leaves look green.
SPONGY • Have air spaces between them.
MESOPHYLL • For fast diffusion of gases in and out of the leaf.
CELLS
XYLEM • Transports water and minerals to the leaf.
PHLOEM • Transports dissolved sugar/sucrose away from the leaf.
LOWER EPIDERMIS • The bottom layer of a leaf.
STOMATA • Holes that let gases in and out of the leaf.
• There are more stomata on the bottom surface of a leaf
than on the upper surface.
GUARD CELLS • These cells control the opening and closing of stomata
in the lower epidermis.
, B. TRANSPIRATION
• A three-part definition:
The LOSS of WATER VAPOUR from PLANT LEAVES by EVAPORATION of WATER
At the SURFACES of the MESOPHYLL CELLS
Followed by the DIFFUSION of WATER VAPOUR through the STOMATA
• Plants transport water from the roots to the leaves in xylem vessels, to replace losses from
transpiration.
C. HOW WATER MOVES UP THE XYLEM TO THE LEAVES
• Light causes stomata to open;
• (Causing) evaporation of water molecules in
mesophyll cells (of leaf);
• (And) diffusion of water vapour through the
stomata;
• (This) lowers the water potential at the top of
the
plant (leaves);
• (So) water moves up the xylem by
transpiration pull;
• Water molecules are attracted to each other
by the force of cohesion;
• (So) a continuous column of water moves up
the xylem;
Waxy cuticle
Upper epidermis
Palisade Chloroplasts
mesophyll cells
Xylem
Spongy
mesophyll cells Phloem
Lower epidermis
Air space Stomata Guard cell
WAXY • Waterproof and prevents water from evaporating
CUTICLE out of the leaf.
UPPER • Single layer of cells with no chloroplasts.
EPIDERMIS • Thin and transparent for maximum light penetration.
PALISADE • These cells contain many chloroplasts.
MESOPHYLL • They are near the leaf surface and are packed close
CELLS together to absorb more light.
• Where most photosynthesis takes place.
CHLOROPLASTS • These trap light energy and convert it into
chemical energy and make leaves look green.
SPONGY • Have air spaces between them.
MESOPHYLL • For fast diffusion of gases in and out of the leaf.
CELLS
XYLEM • Transports water and minerals to the leaf.
PHLOEM • Transports dissolved sugar/sucrose away from the leaf.
LOWER EPIDERMIS • The bottom layer of a leaf.
STOMATA • Holes that let gases in and out of the leaf.
• There are more stomata on the bottom surface of a leaf
than on the upper surface.
GUARD CELLS • These cells control the opening and closing of stomata
in the lower epidermis.
, B. TRANSPIRATION
• A three-part definition:
The LOSS of WATER VAPOUR from PLANT LEAVES by EVAPORATION of WATER
At the SURFACES of the MESOPHYLL CELLS
Followed by the DIFFUSION of WATER VAPOUR through the STOMATA
• Plants transport water from the roots to the leaves in xylem vessels, to replace losses from
transpiration.
C. HOW WATER MOVES UP THE XYLEM TO THE LEAVES
• Light causes stomata to open;
• (Causing) evaporation of water molecules in
mesophyll cells (of leaf);
• (And) diffusion of water vapour through the
stomata;
• (This) lowers the water potential at the top of
the
plant (leaves);
• (So) water moves up the xylem by
transpiration pull;
• Water molecules are attracted to each other
by the force of cohesion;
• (So) a continuous column of water moves up
the xylem;
