Gas exchange - plants Flashcards
(8 cards)
Where does gas exchange occur in plants?
In the mesophyll cells
How does carbon dioxide reach the mesophyll cells?
Enters the leaf by the stomata (lower epidermis) which is opened by guard cells
It diffuses through air spaces down the diffusion gradient
How are plants adapted for gas exchange?
Large surface area of mesophyll cells means there’s a rapid rate of diffusion/gas exchange
Cells aren’t far away from the stomata so there’s a short diffusion pathway
Leaves are thin - short diffusion pathway
Numerous stomata - short diffusion pathway
Air spaces in lower mesophyll layer - rapid diffusion in the gas phase of oxygen and carbon dioxide
How is the gas exchange similar to insects?
In both diffusion is in gas phase which is quicker,
plants have stomata and insects have spiracles which control what’s entering/exiting the organism
no living cell is far from the external air and therefore the source of carbon dioxide/oxygen
How are plants adapted for water management?
Stomata can open and close to reduce dehydration in response to light intensity
Why isn’t the rate of water uptake by a plant not the same as the rate of transpiration?
Water is used for: support photosynthesis hydrolysis produced in respiration
What are xerophytic plants?
Plants specialised to dry habitats with low water availability
How are xerophytic plants adapted to reduce water loss?
Fewer stomata to avoid dehydration
Sunken stomata to trap moist air and decrease water potential between inside and outside of the leaves which slows rate of diffusion of water out of the stomata
Fine hairs covering the epidermis which traps moist air and decreases rate of water loss
Curled leaves - stomata are sheltered from winds so reduces rate of water loss
Waxy cuticle - waterproof so reduces rate of evaporation of water
Thick cuticle - reduces water loss
diffusion
