Exchange in leaves Flashcards
What is water used for in plants
Photosynthesis
growth and elongation of cell
keeping cell turgid
carries minerals up the plant, and sucrose in solution around the plant
evaporation of water keeps the plant cool
Give general basic characteristics of the leaf structure
Many stomata, Interconnecting air spaces in spongy mesophyll, large surface area of mesophyll cells
What does the leaf having many stomata mean
Diffusion pathway is reduced, as particles don’t have to travel as far to reach stoma
What does interconnecting air spaces in spongy mesophyll allow for
gases to readily come into contact with all mesophyll cells
What does a large surface area of mesophyll cells allow for
rapid diffusion
What are stomata
Pores that occur mainly on the under side of leaf
What are stomata surrounded by
guard cells
What can guard cells do
open and close the stoma to control gas exchange.
How do plants balance the conflicting needs of gas exchange and water loss
By opening and closing the guard cells
When might stomata need to close to prevent water loss?
When photosynthesis is not taking place e.g. over night
Where does the majority of carbon dioxide used in photosynthesis come from
The external air, but some comes from respiration
What happens to oxygen produced in photosynthesis
Some is used in respiration but most is lost through stomata by diffusion.
What happens with oxygen when photosynthesis is not occurring
Oxygen diffuses into and out of the leaf through stomata
What happens to guard cells to allow stoma to open
They become swollen/turgid -> ()
What happens to guard cells to close the stoma
they become shrunken /flaccid -> II
Where is marram grass found
Found on windy sand dunes, water drains away easily
What are xerophytes
Plants that are able to grow in very dry or arid conditions e.g. Cacti, Succulents
What’s the order of the different plant structures in a section of plant from top to bottom
Cuticle
Upper Epidermis
Palisade Mesophyll
Spongy Mesophyll
Lower Epidermis
Cuticle
How does water move up the stem through the xylem
Water is pulled along the xylem,
water moves into cells down water potential gradient by osmosis,
water evaporates from the spongy mesophyll cell surface lowering cell water potential,
lowest water potential in the air,
water vapour diffuses into the air down water potential gradient
How does leaves being rolled up support the plant
Traps air inside reducing water vapour potential concentration gradient for osmosis of water
List adaptations of xerophytes
reduced leaf surface area
reduced number of stomata
stomata in pits or depressions
thicker (waxy) cuticle
hairs
succulence
stomata close during the day.
How does leaves having a thick waxy cuticle support the plant
Reduces water loss by evaporation from surface
How does trapped air inside the role of the plants leaf support the plant
Creates high water vapour potential, reducing vapour potential gradient
How do hairs in lower surface of the plant support the plant
Reduce air movement so water vapour potential can increase, reducing the gradient.
How does the stomata being in pits support the plant
Trap air with moisture close to stomata reducing and sometimes stopping all together the water vapour potential gradient .
How does the reduced surface area to volume ratio support the plant
Slows the rate of diffusion. This has to be balanced against the need for sufficient area for photosynthesis to meet the needs of the plant
