B4a Leaves
Adaptations for Photosynthesis
Air spaces in spongy layer allow diffusion af gasses
Transparent epidermis allows most light through to palisade layer
Stomata allow gas exchange to take place. When leaf is photosynthesising, CO2 diffuses in and Os out
Network of veins transport water to leaf and sucrose around plant. Veins also support leaf
Chloroplasts absorb sunlight
Thin, so sunlight reaches most cells in the mesophyll - also, less distanced for diffusion
Leaves are broad, so more sunlight absorbed by chloroplasts
Leaf Structure
Each stomata surounded by two guard cells, which open or close stomata
Pores between some cells in lower epidermis
Veins
Phloum tubes
Living cells carry sucrose down plant by diffusion
xylem vessels
Dead cells carry water up plant by cappilary action
Veins lie between palisade and spongey layer
Mesophyll layer
Spongey layer
Big air spaces between cells for reactions
Contains cells with some chloroplasts
Palisade layer
Contain lots of chloroplasts
Tall and thin, stacked close together.
Epidermis
Thin layer of cells that completely covers the leaf, top and bottom
Secretes wax to protect leaf and stop from drying out (wax - Cuticle)
Stomata and guard cells
No chloroplasts
Diagram
