Photosynthesis (leaf structure)
Leaf Structures
• To understand photosynthesis it is
important to understand the leaf structures
and functions.
• Leaves are the plants “food supply factory.”
– In higher plants the leaf structures is adapted
to maximize light absorption and carbon
dioxide diffusion.
Leaf structures
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Veins (xylem and phloem)
Mesophyll
Palisade layer (parenchyma cells)
Spongy Layer
Cuticle
Upper and Lower epidermis
Stomates
Guard cells
Veins (xylem and phloem)
• This is a network that acts like a plumbing system
that supplies water and minerals to the leaf and
that carries the products of photosynthesis away
to other parts of the plant.
• Xylem: carries water and dissolved minerals
from the roots to the leaves
• Phloem: carries the food made in the leaves to
the rest of the plant
Mesophyll
• The green leaf cells between the upper and
lower epidermis of a leaf which is loaded
with chloroplasts.
• The mesophyll consists of 2 layers:
– Palisade layer (parenchyma cells)
– Spongy Layer
Palisade layer (parenchyma cells)
• This layer is found right below the upper
epidermis, which is made of parenchyma cells.
• Most photosynthesis in plants takes place in
the palisade layer of the leaves
Spongy Layer
• This layer is found below the palisade layer and
above the lower epidermis, which contains many
air spaces.
• The spongy layer is involved in gas exchange.
Cuticle
• This is a thin non-living waxy substance that
covers leaves.
• The cuticle helps reduce water loss and
protection from most bacteria, fungi, and insects.
Upper and Lower epidermis
• This is a single layer of cells, which covers the
upper and lower surfaces of leaves.
• The epidermis also provides protection to the
leaves from most bacteria, fungi, and insects.
Stomates
• Are minute pores found in the epidermis of leaves,
which allows diffusion of gases in and out.
• During the day, stomata absorb carbon dioxide from
the air and release oxygen and water.
• Evaporation of water from the leaf is referred to as
transpiration, is the major source of water loss in
leaves.
Guard cells
• Are two bean-shaped cells that surround the
stomata.
• The guard cells control the size of the stomata.
• When the guard cells swell, the stomata open.
• When the guard cells shrink, the stomata close.
Chloroplast
Chloroplast- a organelle in plant cells and algae
that contain the chlorophyll pigments and the
enzyme systems for photosynthesis.
Diagram of A Chloroplast
Chlorophyll
Chlorophyll a light absorbing pigment that gives plants
their green color and converts the energy of sunlight to
food in the process known as photosynthesis.
Plant leaf pigments