Gas Exchange in the Leaf of a Plant Flashcards
How is gas exchange in plants different from animals?
Unlike animals, some plant cells carry out photosynthesis, meaning they both take in CO2 and release O2 during the day
How do respiration and photosynthesis affect gas exchange in plants
During photosynthesis: plants take in CO2 from the air, and oxygen produced is mostly released
During respiration: O2 diffuses in, and CO2 diffuses out as it is produced
How does photosynthesis reduce gas exchange with the external air?
Some gases produced in one process are used for the other, reducing the need for external gas exchange.
For example, oxygen produced in photosynthesis is mostly released but some is used within the plant cells
What determines the volume and type of gases exchanged by a plant leaf?
The balance between photosynthesis and respiration rates
Why is diffusion of gases in plants rapid?
1/ Diffusion takes place in the gas phase (air), which is faster than diffusion in water
2/ There is a short diffusion pathway as no living cell is far from external air
3/ There is a large surface area of air spaces inside the lear compared to living tissue
How do gases move through plants?
There is no specific transport system for gases; they move by diffusion
What are the adaptations of leaves for rapid gas exchange?
1/ There are many small stomata - ensuring no cell is far from a stoma keeping the diffusion pathway short
2/ Numerous interconnecting air spaces in the mesophyll - allow gases to easily contact mesophyll cells
3/ A large surface area of mesophyll cells - increasing the rate of diffusion
What are stomata and where are they found?
Stomata are minute pores, mainly found on the underside of leaves, allowing gas exchange
What are guard cells, and what is their function?
Each stoma is surrounded by two guard cells, which control the opening and closing of the stomatal pore to regulate gas exchange
Why is stomatal control important in plants?
It helps balance the conflicting needs of gas exchange and water conservation, preventing excessive water loss through evaporation
How do plants reduce water loss through stomata?
They close the stomata at times when water loss would be excessive, such as in hot or dry conditions
State two similarities between gas exchange in a plant leaf and gas exchange in a terrestrial insect?
1/ There is no transport system for gases, gases move by diffusion in both plants and insects
2/ Control of water loss - both have structures that open and close to reduce water loss (stomata in plants, spiracles in insects)
State two differences between gas exchange in a plant leaf and gas exchange in a terrestrial insect?
1/ Gas exchange surface
> Insects use an internal tracheals system, while plants use mesophyll cells and stomata
2/ Ventilation
> Insects use muscle contraction to create mass air flow, whereas plants rely solely on diffusion for gas movement
What is the advantage to a plant being able to control the opening and closing of stomata?
It helps reduce water loss by evaporation while still allowing gas exchange when needed
