Transport, Nutrition and Gas exchange in flowering plants Flashcards
4 materials transported in plants
H2O, minerals, CO2, photosynthetic products
where and how is absorption of H2O
root epidermal cells by osmosis
2 ways root epidermal cells ares are adapted for absorption
root hairs for surface area
the cytoplasm has low H2O concentration
how and where does water move along cells
by osmosis from cell to cell across the ground tissue into the xylem
where does H2O diffuse
into the spaces between the cells
how does H2O move in xylem vessels
upwards
how does water move upwards in plants 4
root pressure
transpiration
cohesion
adhesion
root pressure
the forced that pushes H2O up the xylem from root to stem. H2O enters root epidermal cells by osmosis and pushes H2O up the stem
can only push it up a few meters
transpiration
the loss of H2O vapour from a plant. It occurs through the stomata in the epidermis of leaves and stems, and through the lenticels of woody stems
How does transpiration occur?
H2O evaporates from cells in the ground tissue of the leaf into the air spaces, it then diffuses out through the stomata.
H2O is pulled out of the xylem vessels and up the stem to replace the H2O lost.
cohesion
the attractive force between similar molecules. H2O molecules are attracted to each other
adhesion
the attractive force between different molecules. H2O molecules are attracted to the walls of the xylem vessels.
what helps the cohesion
the never narrow diameter of xylem
transpiration stream
the flow of water up a plant from root to leaf
when is the rate of transpiration highest
in warm, bright breezy conditions when air humidity is low
how much water must a plant absorb
enough water to replace the water it loses by transpiration
the higher the rate of transpiration
the greater the amount of water that will be absorbed
if a plant loses more water than it can absorb from the soil
the cells lose their turgidity,the plant wilts and may die
3 ways plants reduce the rate of transpiration
leaves have a waxy cuticle
stomata on the undersurface of the leaf, less evaporation here
stomata can reduce in size and close together
stomata
pores in the epidermis of leaves that allow exchange of gases
what are each stoma surrounded by
a pair of guard cells
shape of guard cells
they change shape by taking in or losing water
what does the change in shape of the guard cells do?
opens and closes the stomata
what does the level of CO2 in the air spaces between the cells control
the opening and closing of the stomata
