Gas exchange in leaf of plant Flashcards
what is the difference between animal cells and some plant cells?
some plant cells carry out photosynthesis
what is an advantage of plant cells carrying out photosynthesis?
at times the gas produced in one process can be used in the other, reducing the need for gas exchange with the external air
what does photosynthesis of a plant mean to they volume and type of gas exchanged?
the volumes and types of gases that are being exchanged by a plant leaf CHANGE
what happens to gas exchange when photosynthesis is taking place?
- some CO2 from respiration, most from external air
- some O2 from photosynthesis used in respiration, MOST diffuses out
what happens to gas exchange when photosynthesis is not taking place?
- O2 diffuses into leaves CONSTANTLY- being used by cells during respiration
- CO2 diffuses out
how is gas exchange in plants similar to insects?
- no living cell is FAR from external air
- diffusion takes place in gas phase- more rapid than in water
why is no specialised transport system needed for gases in plants?
there is a short, fast diffusion pathway
- no living cell far from external air + diffusion takes place in gas phase
the plant leaf has a very large SURFACE AREA to volume ratio
where does most gaseous exchange occur?
in the leaves
how are leaves adapted for rapid diffusion?
- thin, flat shape
- many small pores (STOMATA)
- lots of interconnecting air spaces in mesophyll
what are stomata?
minute pores that occur mainly on the leafs underside.
what is each stroma surrounded by?
guard cells
what do guard cells do?
open and close the stomatal pore and control the rate of gaseous exchange
how do guard cells control water loss?
completely or partly close stomata at times when water loss would be excessive
how do guard cells open stomata?
- light causes guard cells chloroplasts to PHOTOSYNTHESIS
- photosynthesis produces glucose
- lowers WATER POTENTIAL- water moves by osmosis into cells
- guard cells turgid + are pulled apart- OPEN STOMATA
how do guard cells close stomata?
they lose water and the inner walls move together- closing the stomata
