Transport in Plants Flashcards
What is transpiration?
movement of water through a plant from roots to leaves
How does transpiration work?
- water evaporates from leaves through stomata
- draws up more water through xylem in vein & stem
- which draws water from roots
- water potential in root cell decreases
- causes water to move into root cell from soil by osmosis
What are stomata?
pores on underside of leaf, surrounded by guard cells
What are stomata used for?
gas exchange, control rate of evaporation/transpiration
When are stomata open?
during day - allows gas exchange for photosynthesis
When are stomata closed?
night - conserve water
What are the parts of the stomata?
nucleus
thinner cell wall
thickened cell wall
lower epidermis
stoma
guard cells
chloroplasts
vacuole
What factors affect the rate of transpiration?
- temp - increased temp, increases kinetic energy of water so increases rate of evaporation & transpiration
- light intensity - increased light sensitivity increases opening of stomata so more places for water to evaporate from - faster rate
- wind speed - wind removes water vapour from outside stomata, increases difference in water vapour & concentration between inside & outside of leaf, increasing rate of water vapour diffusing it of leaf, increasing rate of transpiration
- humidity - higher humidity decreases concentration gradient & so decreases rate of diffusion of water out the leaf & so transpiration decreases
What are potometer?
equipment that measures the rate of transpiration
What are the 2 types of potometers?
- bubble - rate of transpiration is rate of movement of bubble
- weight - rate of transpiration is rate of change of mass
Why do plants need water?
- cooling - evaporation from leaves
- reactant for photosynthesis
- to make cells turgid to provide support
- transport of mineral ion from soil
What is the xylem?
- dead tubes of living cells
- 1 way (roots to leaves)
- transports water & mineral ions
What is the phloem?
- made of living cells
- 2 way
- transports sucrose & amino acids
What is the lower epidermis?
single layer of flat cells, covering bottom of surface of leaf
What are palisade cells?
layer of long cylindrical cells just under the upper epidermis
What is the waxy cuticle?
transparent layer on top of leaf
What is the upper epidermis?
single layer of flat cells, covering top surface of leaf
What is the spongy mesophyll?
layer of cells with air spaces between them
What is the vein of plants?
contains tissue that transports food & water
