adaptation for gas exchange in plants unit 2

Waxy transparent layer
Allows light thru to palisade mesophyll
Reduces water loss by evaporation on top of leaf

Main photosynthetic layer packed with chloroplasts

Surrounded by air spaces for easy diffusion
Mesophyll cell membranes=site of gas exchange

Stomatal pores- allow gas exchange down conc gradient
Gases diffuse thru intracellular spaces to and from photosynthetic cells
Gases then diffuse in the moist lining and into the cells
Pores opened and closed during day / night

Guard cells

Allows CO2 to enter the air spaces and cells to be used for photosynthesis
Sunlight= photosynthesis

Reduces water loss
No sunlight= no photosynthesis

Transparent layer
Light can easily penetrate photosynthetic layers

Xylem- carry water from roots
Phloem- carry sucrose to other parts of
plant
Bundle sheath parenchyma

Large SA
Thin with transparent cuticle and upper epidermis
Palisade cells packed with chloroplasts

In light- chloroplasts in guard cells photosynthesise, produce ATP
ATP used for active transport of K+ ions to guard cells
Starch converted to malate
Malate and K+ ions lower WP of g cells, water drawn in by osmosis
G cell inner wall thickens unevenly causing to bend as swell..
..Stomatal pore opens