Photosynthesis is a process in which radiant energy, trapped by chlorophyll, combines
with water and carbon dioxide to form energy rich glucose.
• Products are glucose, stored in the plant a starch and oxygen, released into the atmosphere
via the stomata.
• Sunlight enters the leaves so the cuticle and epidermis.
• During photosynthesis various tissues in the leaf play a role to ensure food is manufactured
for the plant.
• Carbon dioxide enters the leaf via stomata.
• CO2 diffuses through the air spaces ne between the spongy mesophyll cells and enters all
the cells of the mesophyll layers.
• Water is transported from the roots to the leaves by specialised tissue known as xylem.
• The water then enters the mesophyll cells by osmosis.
Function of leaf :
• Manufacture food by photosynthesis (palisade mesophyll cells, spongy mesophyll cells,
guard cells)
• Trap sunlight for photosynthesis
• Allows gaseous exchange needed for photosynthesis and cellular respiration, occurs through
the stomata
• Stomata controls the process of transpiration by controlling the amount of water that is lost
to the leaves
Adaptations of leaf:
• To receive sunlight for photosynthesis
• To allow for gaseous exchanged for photosynthesis and cellular respiration
• To reduce water loss by transpiration
Adaptations for photosynthesis:
Absorption of light:
• Leaves contain chlorophyll to trap sunlight.
• They are broad and at to provide a large surface area for maximum absorption of sunlight.
• The epidermis and cuticle are transparent to allow sunlight to pass through to the mesophyll
tissue.
• Palisade cells are found directly below the epidermis allowing easy access to light.
• Palisade elongated for deep penetration of light.
Absorption of carbon dioxide:
• The upper and lower epidermis has stomata that allow carbon dioxide to enter.
• The spongy mesophyll has an irregular shape, which creates large intercellular spaces.
• These intercellular spaces allow for the easy and quick diffusion of carbon dioxide into the
cell.
• The palisade and spongy mesophyll have thin cell walls to allow for the easy fusion of
carbon dioxide into these cells.
Adaptations for gaseous exchange:
• These adaptations allow for the entry of oxygen and exit of carbon dioxide during cellular
respiration.
• The upper and lower epidermis has stomata that allow carbon dioxide to enter and oxygen
to leave.
• These intercellular spaces allow for the easy and quick diffusion of oxygen into the cell.
• The palisade and spongy mesophyll have thin cell walls to allow for the easy diffusion of
oxygen into these cells.
fl fi
, Adaptations to prevent water loss through evaporation:
• The epidermis has a transparent, waxy layer called the cuticle that reduces water lass through
transpiration.
• Fewer stomata are found on the upper epidermis to reduce the rate of transpiration.
• The stomata can close this reduces the rate of transpiration.
Adaptations for transport:
• These adaptations allow the leaf to transport water and mineral salts and manufactured food.
• Leaves have xylem to bring water from the roots to the leaves for photosynthesis.
• Leaves have phloem to transport the food that is made in the leaves to all parts of the plant.
Epidermis:
Covered by cuticle, waxy transparent layer that prevents water loss + allows for sunlight to past
through
Mesophyll tissue:
Found between epidermises (palisade + spongy)
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