GAS EXCHANGE AND XEROPHYTES Flashcards
adaptations for gas exchange in leaves
thin so a short diffusion pathway
not far from external environment so have a good supply of o2 and co2
leaves large SA:V so absorb more sunlight
leaves arranged in a manner to prevent shadows
leaves have stomata allowing for gases to enter sand exit also preventing water loss
leaves have numerous air spaces within which gases can be exchanged
leaves contain a large network of xylem and phloem
what is the gas exchange surfaces in leaves
surfaces of mesophyll cells in contact with air spaces on the leaf
stomata
only epidermal cells with chloroplasts
pores in the epidermis of leaves
most found on the undersides of leaves
cells are near stomata providing a short diffusion pathway
what are guard cells
control opening and closing of stomate and so controlling the diffusion of gases
only epidermal cells with chloroplast within it
guard cells actively pump K+ ions in
causes osmosis to occur so when water moves into the cells the cells are turgid so stomata opens
what are the 2 types of plant
monocots - grasses and related species
dicots - most other familiar groups
what are xerophytes
adapted to living in dry places and have evolved a range of adaptations to limit water loss through transpiration
normally found in warm , dry or windy environments
rolled up leaves - xerophytes
traps moist air near stomata
reduce water potential gradient between leaf and air reducing transpiration
reduces movement of air near the stomata
thick cuticle - xerophyte
some transpiration occurs through waxy cuticle as its impermeable to water
hairy leaves - xerophytes
hair traps moist air near leaf surface
reduces water potential gradient
sunken stomata - xerophytes
traps moist air near leaf surface
reduce water potential gradient
reduces air movement near stomata
