transport in plants Flashcards
what is the function of the xylem
transport water and minerals from the roots to the leaves
what is the function of the phloem
to transport sucrose and amino acids made by the plant through photosynthesis to photosynthesising regions in the roots and stem
what are root hair cells
single celled extensions of epidermis cells
what is the journey of water from the soil to the plant
soil -> root hair cell -> root cortex -> xylem vessel -> mesophyll cells
what is transpiration
Transpiration is the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
how is lost water recollected
Water travels up xylem from the roots into the leaves of the plant to replace the water that has been lost due to transpiration
how does transpiration occur
- Evaporation takes place from the surfaces of spongy mesophyll cells
- The many interconnecting air spaces between these cells and the stomata creates a large surface area
- This means evaporation can happen rapidly when stomata are open
how is the transpiration stream created
Water molecules are attracted to each other by cohesion - creating a continuous column of water up the plant
Water moves through the xylem vessels in a continuous transpiration stream from roots to leaves
Transpiration produces a tension or ‘pull’ on the water in the xylem vessels by the leaves
As water molecules are held together by cohesive forces (each individual molecule ‘pulls’ on the one below it), so water is pulled up through the plant
If the rate of transpiration from the leaves increases, water molecules are pulled up the xylem vessels quicker
what is cohesion force
force of attraction between molecules
what is wilting
If more water evaporates from the leaves of a plant than is available in the soil to move into the root by osmosis, then wilting will occur
This is when all the cells of the plant are not full of water, so the strength of the cell walls cannot support the plant and it starts to collapse
how does temperature affect rate of transpiration
increases with temprature
why does temperature increase rate of transpiration
as water evaporates more rapidly at higher temperatures
how does humidity affect rate of transpiration
as humidity increases rate of transpiration decreases
why does humidity decrease rate of transpiration
as the atmosphere/air around the plant will be having more water in it, the concentration gradient of water inside the plant and in the atmosphere is stopped, therefore water wont diffuse out of the plant as fast.
what does turgidity mean
how does it occur
the fact of being swollen or firm, usually because of being full of liquid: Water is essential to maintain the turgidity of cells. Cell membrane pushes up against cell wall
what is a flaccid cell
Flaccid corresponds to a cell lacking turgidity. cells are floppy and/or loose, and cells have drawn in and pulled away from the cell wall.
what is an isotonic solution
Isotonic solutions contain equal concentrations of impermeable solutes on either side of the membrane and so the cell neither swells nor shrinks.
what is a hypotonic solution
A hypotonic solution is one in which the concentration of solutes is greater inside the cell than outside of it.
solution has more water than the cell
what is a hypertonic solution
A hypertonic solution is one in which the concentration of the solute is higher outside the cell compared to inside the cell.
solution has less water than the cell
water will leave the cell leaving it flaccid
what happens to a cell which is placed in a isotonic solution
no change
what happens to a cell which is placed in a hypertonic solution
the cell becomes flaccid, as the water inside the cell is more dilute than the water outside, causing the water to flow down the potential gradient through a partially permeable membrane
what happens to a cell which is placed in a hypotonic solution
the cell becomes turgid as the solute is more dilute than the cell, causing the water to move down the potential gradient through a partially permeable membrane
what does concentration mean
the solute will have less water
what does dilute mean
the solute will have more water
where is the xylem
inside
where is the phloem
outside
what is translocation
The transport of sucrose and amino acids in the phloem, from regions of production to regions of storage or use.
what is the place food in the plant is made called
source
what is the place food in the plant reaches called
sink
how does the winter affect how the phloem transports food
During winter, when many plants have no leaves, the phloem tubes may transport dissolved sucrose and amino acids from the storage organs to other parts of the plant so that respiration can continue
how does the summer affect how the phloem transports food
the plant has grown, the leaves are photosynthesizing and producing large quantities of sugars; so they become the source and the roots become the sinks – storing sucrose as starch until it is needed again
how does the “growth period” affect how the phloem transports food
the storage organs (eg roots) would be the source and the many growing areas of the plant would be the sinks
aphids feed on the contents of the phloem tubes
what type of food is lacking in their diet
fat
what are the guard cells function
to open and close stomata
what are some adaptation of leaves for photosynthesis
thin, to reduce the diffusion distance
large surface area to absorb maximum sunlight
what is the order of the specific organs in the plant
waxy cuticle
upper epidermis
palisade mesophyll
spongy mesophyll-vascular bundle on same level
lower epidermis-guard cell with chloroplasts
stomata
water not lost in transpiration is used for what
photosynthesis
turgidity
explain how transpiration is responsible for the movement of water in the xylem
loss of water vapour through stomata in leaves
evaporation from surfaces of mesophyll cells into air spaces
loss of water from leaf cells lowers water potential
water moves into leafs from xylem
this pulls on water by cohesion forces and pulls water to the leaf cells
state three structural adaptations of plants living in hot dry environments
few stomata
hairs on the leaves
small leaf surface area
features of epidermis and its adaptation for photosynthesis
guard cells —– allows gas to enter/leave
thin/flat —– allows more light to pass through
no chloroplasts —– allows light to pass through
features of pallisade mesophyll cells and its adaptation for photosynthesis
contains many chloroplasts — traps light energy
air spaces —- for diffusion/ movement of gasses
tightly packed —– maximise light received
describe the pathway taken by co2 when entering a leaf to the spongy mesophyll cells
passes through stomata
moves through intracellular air spaces
